Constantina (Tina) Lekakou

Dr Constantina (Tina) Lekakou


Professor in Energy, Multiphase and Multifunctional Materials and Devices
PhD (Imperial College), Dipl. Chemical Eng. (NTUA), CEng, MIMechE

Academic and research departments

Department of Mechanical Engineering Sciences.

Biography

Areas of specialism

Energy materials, devices and systems; Functional and biomedical materials; Smart and actuating materials and their modelling for robotic applications; Multiphase and composite materials science and engineering

University roles and responsibilities

  • Organiser of the Individual Final Year Projects (BEng and MEng)
  • Member of the Academic Misconduct Panels

    Affiliations and memberships

    Chartered Engineer, UK
    CEng
    Institute of Mechanical Engineers, UK
    Member
    Technical Chamber of Greece (TEE-TCG)
    Member
    Institute of Chemical Engineers, Greece
    Member
    European Society of Composite Materials (ESCM)
    Member
    International Association of Engineers (IAENG)
    Member
    Materials KTN
    Member
    EPSRC UK-RAS Network
    Member
    Energy Storage Research Network, UK
    Member

    News

    In the media

    Research

    Research interests

    Research projects

    Indicators of esteem

    • IOM3 AWARDS 2020: AWARDS FOR PUBLISHED WORK - Composite Award: Mathew Rutt, Constantina (Tina) Lekakou, Paul A Smith, Alessandro Sordon and Ian Hamerton received the Composite Award from IoM3 for their published paper: "Methods for process-related resin selection and optimisation in high-pressure resin transfer moulding" published in Materials Science and Technology, 35(3), 2018, pp.327-335.

    • Invited Keynote Speaker at 3rd International Conference on Materials Science and Materials Chemistry (ICMSMC19), Vienna, 14-15 Oct 2019, Talk titled: “Materials for post Li-ion batteries”

    • As overall coordinator of the EC-funded research project AUTOSUPERCAP, C.Lekakou received Best Prize in the FP7 NMP projects (2007-2014) ongoing category, awarded by the European Community (EC)  (April 2014).

    • Patent GB201509870D0 “Composite Supercapacitor”, Assignee University of Surrey, 2015-07-22 Grant.

    • Best Paper Award at the 2007 International Conference of Mechanical Engineering in World Congress of Engineering WCE 2007 for the paper: U. Vidyarthi, P. Zhdan, C. Gravanis and C. Lekakou "Gelatine-hydroxyapatite nanocomposites for orthopaedic applications".

    • Panellist in Panel Discussion at TAROS2017 (18th Annual Conference Towards Autonomous Robotic Systems, 2017, Guildford) with Professor Yang Gao, Surrey Space Centre, Professor Alan Winfield, UWE Bristol, Dr Alexander Thorn, University of Sheffield.

    • Invited Speaker at NARA Institute of Science and Technology (NAIST), Japan, Summer 2016.

    • Panellist in Panel Discussion at ICRA 2014 Workshop: Soft and stiffness-controllable robots for MIS, 1st June 2014, Hong Kong, IEEE Robotics and Automation Society.

    • Invited Speaker to Experts Workshops of ICT4EV in Brussels (Nov 2010), Berlin (June 2011), Brussels (April 2013; December 2014).

    • Invited Speaker/Plenary Session at IEEE-NANO: C. Lekakou, C. Lei, F. Markoulidis, A. Sorniotti “Nanomaterials and Nanocomposites for High Energy/High Power Supercapacitors” IEEE 12th International Conference on Nanotechnology (IEEE-NANO), August 2012.

    • Editor of Lecture Notes in Computer Science book series (LNCS, volume 10454), 2017, Editors: Y. Gao, S. Fallah, Y. Jin, C. Lekakou, Publisher: Springer.

    • Member of the Editorial Board of Advances in Mechanical Engineering, Publisher: SAGE (2018-present)

    • Member of the Editorial Board of the Journal of Composites Science, Publisher: MDPI (2016-present).

    • Member of the Editorial Board for the SF Journal of Biotechnology and Biomedical Engineering (2018-present).

    • Associate Editor for journal: Advances in Renewable Energy, Avestia Publishers (2013-2017).

    Courses I teach on

    Undergraduate

    Postgraduate taught

    My publications

    Highlights

    Selected publications from the last 10 years

    R. Reece, C. Lekakou, P.A. Smith ""A High-Performance Structural Supercapacitor""  ACS Appl. Mater. Interfaces 2020, 12, 23, 25683–25692

    F. Markoulidis, J. Bates, C. Lekakou, R. Slade, G.M. Laudone “Supercapacitors with lithium-ion electrolyte: An experimental study and design of the activated carbon electrodes via modelling and simulations” Carbon, 2020, online: https://doi.org/10.1016/j.carbon.2020.04.017

    R. Reece, C. Lekakou, P.A. Smith, R. Grilli, C. Trapalis “Sulphur-linked graphitic and graphene oxide platelet-based electrodes for electrochemical double layer capacitors” Journal of Alloys and Compounds, 792, 2019, pp.582-593

    Jonathan Pope and Constantina (Tina) Lekakou “Thermoelectric polymer composite yarns and an energy harvesting wearable textile” Smart Materials and Structures, published online 2019

    Y. Elsayed  C. Lekakou  P. Tomlins “Modeling, simulations, and optimization of smooth muscle cell tissue engineering for the production of vascular grafts” Biotechnology and Bioengineering, online 2019, https://doi.org/10.1002/bit.26955

    S.Mastura Mustaza, Y.Elsayed, C.Lekakou , C.Saaj, J.Fras “Dynamic modeling of fiber-reinforced soft manipulator: A Visco-hyperelastic material-based continuum mechanics approach” Soft Robotics, online March 2019, https://doi.org/10.1089/soro.2018.0032

    M.Rutt, C.Lekakou, P.A.Smith, A.Sordon, C.Santoni, G.Meeks & I.Hamerton “Methods for process-related resin selection and optimisation in high-pressure resin transfer moulding” Materials Science and Technology, 35(3), 2018, pp.327-335. IoM3 Composite Award

    R.Reece, C.Lekakou, P.A.Smith “A structural supercapacitor based on activated carbon fabric and a solid electrolyte” Materials Science and Technology, 35(3), 2018, pp.368-375

    E. Shumbayawonda, A.A.Salifu, C.Lekakou, J.P.Cosmas “Numerical and Experimental Simulations of the Wireless Energy Transmission and Harvesting by a Camera Pill” ASME Transactions - Journal of Medical Devices, 12, 2018, doi:10.1115/1.4039390, 9pp.

    E.C. Vermisoglou, T. Giannakopoulou, G. Romanos, N. Boukos, V. Psycharis, C. Lei, C. Lekakou, D. Petridis and C. Trapalis “Graphene-based materials via benzidine-assisted exfoliation and reduction of graphite oxide and their electrochemical properties” Applied Surface Science, 392, 2017, 244-255

    N. Todorova, T. Giannakopoulou, N. Boukos, E. Vermisoglou, C. Lekakou, C. Trapalis “Self-propagating solar light reduction of graphite oxide in water” Applied Surface Science, Part B, 391, 2017, pp.601-608

    R.Fields, C.Lei, F.Markoulidis and C.Lekakou “The Composite Supercapacitor” Energy Technology, 4(4), 2016, pp. 517–525

    A.A. Salifu, C. Lekakou, F. Labeed “Multilayer cellular stacks of gelatin-hydroxyapatite fiber scaffolds for bone tissue engineering”, Journal of Biomedical Materials Research Part A, 105(3), 2017, pp. 779-789

    A.A. Salifu, C. Lekakou, F.H. Labeed “Electrospun oriented gelatin-hydroxyapatite fiber scaffolds for bone tissue engineering”, Journal of Biomedical Materials Research Part A, 105(7), 2017, pp. 1911–1926

    Y.Elsayed,  C.Lekakou, F.Labeed, and P.Tomlins “Fabrication and characterisation of biomimetic, electrospun gelatin fibre scaffolds for tunica media-equivalent, tissue engineered vascular grafts” Materials Science & Engineering C-Materials For Biological Applications, 61, 2016, pp. 473-483

    Y.Elsayed,  C.Lekakou, F.Labeed, and P.Tomlins “Smooth muscle tissue engineering in crosslinked electrospun gelatin scaffolds” Journal of Biomedical Materials Research Part A, 104(1), 2016, pp.313–321

    C.Lei, F.Markoulidis, P.Wilson and C.Lekakou “Phenolic Carbon Cloth-Based Electric Double-Layer Capacitors with Conductive Interlayers and Graphene Coating” Journal of Applied Electrochemistry, 46(2), 2016, pp.251–258

    E.C.Vermisoglou, T.Giannakopoulou, G.E.Romanos, N.Boukos, M.Giannouri, C.Lei, C. Lekakou and C.Trapalis “Non-Activated High Surface Area Expanded Graphite Oxide for Supercapacitors” Applied Surface Science, Part A, 358, 2015, pp.110-121

    E.C. Vermisoglou, T. Giannakopoulou, G. Romanos, M. Giannouri, N. Boukos, C. Lei,C. Lekakou, C. Trapalis “Effect of hydrothermal reaction time and alkaline conditions on the electrochemical properties of reduced graphene oxide” Applied Surface Science, Part A, 358, 2015, pp.100-109

    I.Papailias, M. Giannouri, A. Trapalis, N.Todorova, T. Giannakopoulou, N. Boukos, C. Lekakou “Decoration of crumpled rGO sheets with Ag nanoparticles by spray pyrolysis” Applied Surface Science, Part A, 358,  2015, pp.84-90

    C.Lekakou, Y. Elsayed, T. Geng and C.M. Saaj “Skins and Sleeves for Soft Robotics: Inspiration from Nature and Architecture” Advanced Engineering Materials, 17(8), 2015, pp. 1180-1188

    Y.Elsayed, C.Lekakou, T. Ranzani, M.Cianchetti, M Morino, A.Arezzo, A.Menciassi, T.Geng and C.M.Saaj “Crimped braided sleeves for soft, actuating arm in robotic abdominal surgery”, Minimally Invasive Therapy & Allied Technologies, 24(4), 2015, pp. 204-210

    Y Elsayed,  A Vincensi, C Lekakou, T Geng,, C. M. Saaj, T Ranzani, M Cianchetti,and A Menciassi “Finite Element Analysis and Design Optimization of a Pneumatically Actuating Silicone Module for Robotic Surgery Applications”, Soft Robotics, 1(4), 2014, pp. 255-262

    F.Markoulidis, C.Lei, C. Lekakou, D.Duff, S.Khalil, B.Martorana and I.Cannavaro “A Method to Increase the Energy Density of Supercapacitor Cells by the Addition of Multiwall Carbon Nanotubes into Activated Carbon Electrodes” Carbon, 68, 2014, pp.58–66

    E.C.Vermisoglou, E.Devlin, T.Giannakopoulou, G.Romanos, N.Boukos, V.Psycharis, C.Lei, C.Lekakou, D.Petridis and C. Trapalis “Reduced Graphene Oxide/Iron Carbide Nanocomposites for Magnetic and Supercapacitor Applications” Journal of Alloys and Compounds, 590, 2014, pp.102-109

    A. Santucci, A. Sorniotti and C. Lekakou “Power split strategies for hybrid energy storage systems for vehicular applications” Journal of Power Sources, 258, 2014, pp.395-407

    P Wilson, C.Lei, C Lekakou, JF Watts “Transverse charge transport in inkjet printed poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)”, Organic Electronics, 15(9), 2014, pp. 2043-2051

    P.Wilson, C.Lekakou and J.F.Watts “In-plane conduction characterisation and charge transport model of DMSO co-doped, inkjet printed Poly(3,4-ethylenedioxythiophene): Polystyrene sulfonate (PEDOT:PSS)”, Organic Electronics, 14, 2013, pp.3277–3285

    Y.Elsayed,  C.Lekakou, P.Tomlins “Monitoring and modelling of oxygen transport through un-crosslinked and crosslinked gelatine gels”, Polymer Testing, 40, 2014, pp.106-115

    F.Markoulidis, C.Lei, C.Lekakou “Fabrication of high-performance supercapacitors based on transversely oriented carbon nanotubes”. Applied Physics A: Materials Science and Processing, 111 (1), 2013, pp. 227-236

    C. Lei, F. Markoulidis, Z. Ashitaka and C. Lekakou “Reduction of porous carbon/Al contact resistance for an electric double-layer capacitor (EDLC)” Electrochimica Acta, 92, 2013, pp.183– 187

    C. Lei, N. Amini, F. Markoulidis, P. Wilson, S. Tennison and C. Lekakou “Activated carbon from phenolic resin with controlled mesoporosity for an electric double-layer capacitor (EDLC)” Journal of Materials Chemistry A, 1(19), 2013, pp. 6037-6042

    P.Wilson, C.Lekakou, J.F.Watts “A comparative assessment of surface microstructure and electrical conductivity dependence on co-solvent addition in spin coated and inkjet printed poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), Organic Electronics, 13 (3), 2012, pp.409 – 418

    C.Lei, P.Wilson, C.Lekakou “Effect of poly(3,4-ethylenedioxythiophene) (PEDOT) in carbon-based composite electrodes for electrochemical supercapacitors” Journal of Power Sources, 196 (18), 2011, pp. 7823-7827

    A.A.Salifu, B.D.Nury and C.Lekakou "Electrospinning of nanocomposite fibrillar tubular and flat scaffolds with controlled fiber orientation" Annals of Biomedical Engineering, 39(10), 2011, 2510-2520

    A.K.Murugesh, A.Uthayanan and C.Lekakou "Electrophoresis and orientation of multiple wall carbon nanotubes in polymer solution", Applied Physics A:  Materials Science and Processing, 100(1), 2010, pp.135-144

    C.Lekakou, D.Lamprou, U.Vidyarthi, E.Karopoulou and P.Zhdan "Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopaedic grafts" Journal of Biomedical Materials Research Part B-Applied Biomaterials Volume: 85B   Issue: 2   Pages: 461-468   Published: 2008, pp.461-468 

    Publications

    Lekakou C, Cook S, Deng Y, Ang TW, Reed GT (2006) Optical fibre sensor for monitoring flow and resin curing in composites manufacturing, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING37(6)pp. 934-938 ELSEVIER SCI LTD
    Kanas K, Lekakou C, Vrellos N (2007) FEA and experimental studies of adaptive composite materials with SMA wires,World Congress on Engineering 2007, Vols 1 and 2pp. 1329-1334 INT ASSOC ENGINEERS-IAENG
    Kanas K, Lekakou C, Vrellos N (2008) FEA and Experimental Studies of Adaptive Composite Materials with SMA Wires,CURRENT THEMES IN ENGINEERING SCIENCE 20071045pp. 101-110 AMER INST PHYSICS
    Lei C, Markoulidis F, Wilson P, Lekakou C (2016) Phenolic carbon cloth-based electric double-layer capacitors with conductive interlayers and graphene coating, JOURNAL OF APPLIED ELECTROCHEMISTRY46(2)pp. 251-258 SPRINGER
    Phenolic resin-derived activated carbon (AC) cloths are used as electrodes for large-scale electric double-layer capacitors or supercapacitors. To increase the energy and power density of the supercapacitor, the contact resistance between the carbon cloth and the aluminium foil current collector is reduced by modifying the Al current collectors. Different modified Al current collectors, including Toyal-Carbo®(surface-modified Al), DAG® (deflocculated Acheson" graphite) coating and poly(3,4-ethylenedioxythiophene) (PEDOT) coating, have been tested and compared. The use of modified Al current collectors are shown to greatly reduce the contact resistance between the AC cloth and the Al foil. Another solution investigated in this study is to coat AC cloth with graphene through electrophoretic deposition (EPD). The graphene coated AC cloth is shown increased the capacitance and greatly reduced internal resistance.
    Lekakou C, Elsayed Y, Geng T, Saaj CM (2015) Skins and Sleeves for Soft Robotics: Inspiration from Nature and Architecture, ADVANCED ENGINEERING MATERIALS17(8)pp. 1180-1188 WILEY-V C H VERLAG GMBH
    Vermisoglou EC, Giannakopoulou T, Giannouri M, Boukos N, Lekakou C, Trapalis C (2014) Single-step hydrothermal synthesis of reduced graphene oxide (rGO) and Fe2O3/rGO composites for supercapacitor applications,16th European Conference on Composite Materials, ECCM 2014
    Reduced graphene oxide sheets were prepared by hydrothermal method. IR and XRD data revealed that both reduction and exfoliation occur during hydrothermal process of graphite oxide (GtO) aqueous dispersions. The concentration of GtO dispersion, process duration and alkali conditions e.g. presence of K2CO3 influence quality characteristics of the produced materials as it was emerged by Raman spectroscopy. Hydrothermal process allows in parallel with reduction and exfoliation the intercalation with nanoparticles (NPs). By using FeCl3.6H2O in presence of NaAc as a precursor, a composite of reduced graphene oxide (rGO) intercalated with iron oxide NPs (Fe2O3/rGO) was synthesized. Electrochemical measurements indicated that the sample treated with K2CO3 had the best performance in terms of capacitance. Both rGO and Fe2O3/rGO are materials of particular interest for supercapacitor applications.
    Lekakou CN, Richardson SM (1986) SIMULATION OF REACTING FLOW DURING FILLING IN REACTION INJECTION MOLDING (RIM)., Polymer Engineering and Science26(18)pp. 1264-1275
    This paper deals with computer simulation of the filling stage of the Reaction Injection Molding (RIM) process for cavities of rectangular, cylindrical, and disc shapes. The computer model is in two parts: the main flow and the flow by the moving front. In the main flow part, the transient equations of axial momentum, energy and species conservation and also the continuity equation are solved numerically by finite-difference methods using a moving, changing mesh. In the flow front part, which is quite novel, the transient (parabolic) vorticity, energy and species conservation equations and the elliptic stream function equation are again solved by finite-difference methods. Results are presented for all three cavity shapes and those for rectangular cavities are compared with the experimental results of previous investigators.
    Vidyarthi U, Zhdan P, Gravanis C, Lekakou C (2008) Gelatine-Hydroxyapatite Nano-composites for Orthopaedic Applications, CURRENT THEMES IN ENGINEERING SCIENCE 20071045pp. 81-90 AMER INST PHYSICS
    Lekakou C, Edwards S, Bell G, Amico SC (2006) Computer modelling for the prediction of the in-plane permeability of non-crimp stitch bonded fabrics, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING37(6)pp. 820-825 ELSEVIER SCI LTD
    DEAZLE AS, HOWLIN BJ, LEKAKOU C, BUIST GJ, JONES J, BARTON JM (1994) MODELING OF THE STRUCTURE AND PHYSICAL-PROPERTIES OF POLYMERS, JOURNAL OF CHEMICAL CRYSTALLOGRAPHY24(1)pp. 17-20 PLENUM PUBL CORP
    Papailias I, Giannouri M, Trapalis A, Todorova N, Giannakopoulou T, Boukos N, Lekakou C (2015) Decoration of crumpled rGO sheets with Ag nanoparticles by spray pyrolysis,APPLIED SURFACE SCIENCE358pp. 84-90 ELSEVIER SCIENCE BV
    Wilson P, Lekakou C, Watts J (2012) Electrical, Morphological and Electronic Properties of Inkjet Printed PEDOT:PSS, 2012 12TH IEEE CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO) IEEE
    Vidyarthi U, Zhdan P, Gravanis C, Lekakou C (2007) Gelatine-hydroxyapatite nanocomposites for orthopaedic applications, World Congress on Engineering 2007, Vols 1 and 2pp. 1251-1256 INT ASSOC ENGINEERS-IAENG
    Mohammed U, Lekakou C, Bader MG (2000) Experimental studies and analysis of the draping of woven fabrics, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING31(12)pp. 1409-1420 ELSEVIER SCI LTD
    Markoulidis F, Lei C, Lekakou C, Duff D, Khalil S, Martorana B, Cannavaro I (2013) A method to increase the energy density of supercapacitor cells by the addition of multiwall carbon nanotubes into activated carbon electrodes, Carbon
    The performance of supercapacitor cells with activated carbon (AC) electrodes was improved by adding a small amount of multiwall carbon nanotubes (MWCNTs). The electrode structure investigated comprised AC, four different types of MWCNTs and two polymer binders, polyvinylidene fluoride or polyvinyl alcohol. All fabricated devices were of the electrochemical double layer capacitor type. The organic electrolyte used was tetraethyl ammonium tetrafluoroborate (TEABF) in two different solvents: propylene carbonate or acetonitrile (AN). The electrodes were characterised with scanning electron microscopy and tested for their specific surface area and pore size distribution. The electrode fabrication process was fine-tuned by investigating the effect of the coating thickness on the supercapacitor cell performance. It was established that an AC/MWCNT-based supercapacitor with 30 ¼m thick roll-coated, composite electrodes of just 0.15%w/w MWCNT content provided superior tested power and energy densities of 38 kW/kg and 28 W h/kg, respectively, compared to 18 kW/kg and 17 W h/kg for AC only-based cells in a 1.5 TEABF/AN electrolyte. The increased energy density was attributed to a fine lace of MWCNTs covering the AC microparticles with visible 20-30 nm lace pores and to the high specific area of micropores. © 2013 Elsevier Ltd. All rights reserved.
    Lei C, Lekakou C (2013) Activated carbon-carbon nanotube nanocomposite coatings for supercapacitor applications, Surface and Coatings Technology
    Electrochemical double layer capacitor cells were fabricated based on electrodes with activated carbon (AC) coating as the host material, targeting large energy storage. Highly dispersed multiwall carbon nanotubes (MWNTs) were added to form nanocomposite coatings, used as electrodes targeting high-power performance for very low content of MWNTs. 1 M tetraethylammonium tetrafluoroborate-propylene carbonate solution was used as organic electrolyte. The resulting cells were characterized using impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge tests. It was concluded that at optimum composition of AC-MWNT coatings both power and energy densities are raised whereas further increase of the MWNT content would increase the power density but decrease the energy density. © 2013 Elsevier B.V. All rights reserved.
    Amico S, Lekakou C (2001) An experimental study of the permeability and capillary pressure in resin-transfer moulding, COMPOSITES SCIENCE AND TECHNOLOGY61(13)pp. 1945-1959 ELSEVIER SCI LTD
    Vermisoglou EC, Giannouri M, Todorova N, Giannakopoulou T, Lekakou C, Trapalis C (2016) Recycling of typical supercapacitor materials., Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA34(4)pp. 337-344 Sage
    A simple, facile and low-cost method for recycling of supercapacitor materials is proposed. This process aims to recover some fundamental components of a used supercapacitor, namely the electrolyte salt tetraethyl ammonium tetrafluoroborate (TEABF4) dissolved in an aprotic organic solvent such as acetonitrile (ACN), the carbonaceous material (activated charcoal, carbon nanotubes) purified, the current collector (aluminium foil) and the separator (paper) for further utilization. The method includes mechanical shredding of the supercapacitor in order to reduce its size, and separation of aluminium foil and paper from the carbonaceous resources containing TEABF4by sieving. The extraction of TEABF4from the carbonaceous material was based on its solubility in water and subsequent separation through filtering and distillation. A cyclic voltammetry curve of the recycled carbonaceous material revealed supercapacitor behaviour allowing a potential reutilization. Furthermore, as BF4 (-)stemming from TEABF4can be slowly hydrolysed in an aqueous environment, thus releasing F(-)anions, which are hazardous, we went on to their gradual trapping with calcium acetate and conversion to non-hazardous CaF2.
    Amico SC, Lekakou C (2002) Axial impregnation of a fiber bundle. Part 2: Theoretical analysis, POLYMER COMPOSITES23(2)pp. 264-273 SOC PLASTICS ENG INC
    Lekakou C, Markoulidis F, Lei C, Sorniotti A, Perry J, Hoy C, Martorana B, Cannavaro I, Gosso M (2012) Meso-nano and micro-nano ion transport in porous carbon composite electrodes for energy storage applications, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
    In energy storage devices carbonaceous composite electrodes are a popular choice, consisting of activated carbon (ac), conductive additives and a polymeric binder matrix. The active electrode components are in the form of ac particles, ac fibres, or ac monolith combined with conductive additives such as carbon black. Activated carbon plays the most important role for storing a large amount of energy in the form of ions contained in the carbon nanopores. This study considers a modelling approach to the meso-nano and micro-nano infiltration of ions into the porous carbon structure during the operation of the energy storage device. Depending on the pore size, ion size and solvent molecule size, ions may be solvated or unsolvated as they move, where ions are solvated in meso-pores for most cases. Molecular model simulations have been performed to determine the values of the geometrical parameters of different ions, solvated and unsolvated in various solvents. A meso-nano and micro-nano ion infiltration model has been developed in this study under both steady state and dynamic conditions.
    Lekakou C, Wilson P, Craggs D, Chau YC, Salifu AA, Chen YL, Watts JF (2009) Electrospinning of polymer nanocomposites, Proceedings of 17th International Conference on Composite Materials
    Dong L, Lekakou C, Bader MG (2001) Processing of composites: Simulations of the draping of fabrics with updated material behaviour law, JOURNAL OF COMPOSITE MATERIALS35(2)pp. 138-163 TECHNOMIC PUBL CO INC
    Fields R, Lei C, Markoulidis F, Lekakou C (2016) The Composite Supercapacitor,ENERGY TECHNOLOGY4(4)pp. 517-525 WILEY-V C H VERLAG GMBH
    Saunders RA, Lekakou C, Bader MG (1999) Compression in the processing of polymer composites 1. A mechanical and microstructural study for different glass fabrics and resins, COMPOSITES SCIENCE AND TECHNOLOGY59(7)pp. 983-993 ELSEVIER SCI LTD
    Lekakou C, Dickinson CE (1996) Self-reinforcing polymer blends containing a liquid crystalline polymer: Processing, microstructure and properties, HIGH PERFORMANCE POLYMERS8(1)pp. 109-118 IOP PUBLISHING LTD
    Rios CR, Ogin SL, Lekakou C, Leong KH (2003) Study of progressive damage in a knitted fabric reinforced composite, Annual Technical Conference - ANTEC, Conference Proceedings2pp. 2188-2192
    Model sandwich laminates were manufactured by orienting the knitted cloth at a range of angles to the loading direction using a single Milano weft knitted layer sandwiched between outer plies of unidirectional glass reinforced epoxy resin in order to be able to observe progressive damage accumulation along the sample. By this way, the relationship between fibre architecture and damage accumulation under tensile loading, as well as the sequence of damage accumulation has been investigated. Damage has been found to initiate at the loop cross-over points of the knitted fabric structure for all orientations, although the further development of the damage depends on the orientation of the fabric to the applied load. The resultant transparent laminates provide a novel method of monitoring the damage development in a knitted-fabric composite as a function of increasing strain by allowing direct observation of the sequence of damage.
    This study focuses on the fabrication of poly(3,4-ethylenedioxythiophene): polystyrene sulphonate (PEDOT:PSS) thin films by inkjet printing and investigates the developed surface morphology and electrical conductivity of the printed films as a function of the concentration of dimethyl sulfoxide (DMSO), added as conduction enhancing co-solvent, and Surfynol, added as a surfactant. The printed films are compared with PEDOT:PSS films fabricated by the traditional spin coating technique. Measurements of the surface tension justify including surfactant as a processing additive, where addition of 1% Surfynol results in substantial decrease of the surface tension of the PEDOT:PSS solution, whilst it also increases film surface roughness by an order of magnitude for both fabrication methods. The addition of 5 wt% DMSO is shown to result in a 10 3 decrease in sheet resistance for both spin coated and inkjet printed films with both processing routes demonstrating decrease in surface roughness and coarsening of PEDOT grains as a function of the co-solvent concentration, whilst X-ray photon spectroscopy showed an increase in the surface PEDOT to PSS ratio from 0.4 to 0.5. Inkjet printed films have lower sheet resistance than the corresponding spin coated films, whilst atomic force microscopy reveals a coarser surface morphology for the inkjet printed films. The findings in this work point out at the decrease of sheet resistance due to coarsening of PEDOT grains which is linked to a decrease of surface roughness for small RMS values associated with the PEDOT grains. However, the higher surface roughness generated when Surfynol surfactant was added was not detrimental to the film's in-plane conductivity due to the fact that these higher roughness values were unrelated to the PEDOT grains. © 2011 Elsevier B.V. All rights reserved.
    Amico SC, Lekakou C (1999) Predictions and measurement of the permeability and capillary pressure in capillary flows through woven fabrics, PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON FLOW PROCESSES IN COMPOSITE MATERIALSpp. 311-318 ADVANCED COMPOSITES MANUFACTURING CENTRE
    Amico S, Lekakou C (2000) Mathematical modelling of capillary micro-flow through woven fabrics, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING31(12)pp. 1331-1344 ELSEVIER SCI LTD
    Lei C, Lekakou C (2010) Carbon-based nanocomposite EDLC supercapacitors,Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites1pp. 176-179 Nano Science and Technology Institute
    Wang X, Geng T, Elsayed Y, Saaj C, Lekakou C (2015) A unified system identification approach for a class of pneumatically-driven soft actuators,ROBOTICS AND AUTONOMOUS SYSTEMS63(P1)pp. 136-149 ELSEVIER SCIENCE BV
    The class of Pneumatically-driven Low-pressure Soft Actuators (PLSA) is a popular choice potentially used in the surgical robotic applications. One fundamental problem lying in the PLSA research is the lack of a generally validated model for the complex nonlinear dynamic behaviours. In this paper, a unified identification approach for the general PLSAs is proposed. It is a parameter-independent way directly used to identify the dynamical relation between the actuating pressures and the principal degrees of freedom of a PLSA, the bending and the steering. The approach is based on a modified auxiliary kinematic setting and a newly developed identification model structure, named DIO-PWL-OBF. Following the concluded identification procedure, the implementations for the single chamber bending and the double chamber bending and steering are demonstrated separately. The results show that the proposed approach can accurately capture the nonlinear pressure-shape dynamical relation. The approach is also efficient in real-time applications. It can be further used to improve the current control design for the PLSAs in robotic applications.
    Todorova N, Giannakopoulou T, Boukos N, Vermisoglou E, Lekakou C, Trapalis C (2016) Self-propagating solar light reduction of graphite oxide in water,Applied Surface Science.391(Part B)pp. 601-608 Elsevier
    Graphite Oxide (GtO) is commonly used as an intermediate material for preparation of graphene in the form of reduced graphene oxide (rGO). Being a semiconductor with tunable band gap rGO is often coupled with various photocatalysts to enhance their visible light activity. The behavior of such rGO-based composites could be affected after prolonged exposure to solar light. In the present work, the alteration of the GtO properties under solar light irradiation is investigated. Water dispersions of GtO manufactured by oxidation of natural graphite via Hummers method were irradiated into solar light simulator for different periods of time without addition of catalysts or reductive agent. The FT-IR analysis of the treated dispersions revealed gradual reduction of the GtO with the increase of the irradiation time. The XRD, FT-IR and XPS analyses of the obtained solid materials confirmed the transition of GtO to rGO under solar light irradiation. The reduction of the GtO was also manifested by the CV measurements that revealed stepwise increase of the specific capacitance connected with the restoration of the sp2 domains. Photothermal self-propagating reduction of graphene oxide in aqueous media under solar light irradiation is suggested as a possible mechanism. The self-photoreduction of GtO utilizing solar light provides a green, sustainable route towards preparation of reduced graphene oxide. However, the instability of the GtO and partially reduced GO under irradiation should be considered when choosing the field of its application.
    Electrospinning was used in innovative electrospinning rigs to obtain tubular and flat fibrous structures with controlled fiber orientation with the aim to be used as scaffolds for biomedical applications, more specifically in the tissue engineering of vascular and orthopedic grafts. Gelatine and hydroxyapatite (HA)-gelatine solutions of various compositions were tried and electrospinning of continuous fibers was maintained for gelatine and up to 0.30 g/g HA-gelatine solutions in 2,2,2-trifluoroethanol (TFE). Small diameter tubular scaffolds were electrospun with axial fiber orientation and flat scaffolds were cut from fiber mats electrospun around a wired drum substrate. The fibrous mats were crosslinked using a glutaraldehyde solution and subjected to image analysis of SEM micrographs, water swelling tests, and mechanical testing. Fiber diameter in the electrospun scaffolds could be varied depending on the feed solution concentration and composition whereas fiber orientation was affected by the processing conditions. After crosslinking, the 0.30 g/g HA-gelatine scaffolds absorbed the minimum amount of water after 48 h soaking and they had the highest Young's modulus, 60 MPa, and highest strength, 3.9 MPa.
    LEKAKOU CN, RICHARDSON SM (1990) SIMULATION OF REACTION INJECTION-MOLDING IN MOLD CAVITIES OF COMPLEX GEOMETRIES, PLASTICS AND RUBBER PROCESSING AND APPLICATIONS13(2)pp. 129-137 ELSEVIER SCI LTD
    Schmidt TM, Goss TM, Amico SC, Lekakou C (2009) Permeability of Hybrid Reinforcements and Mechanical Properties of their Composites Molded by Resin Transfer Molding, JOURNAL OF REINFORCED PLASTICS AND COMPOSITES28(23)pp. 2839-2850 SAGE PUBLICATIONS LTD
    Duncan R, Stolojan V, Lekakou C (2007) Manufacture of carbon multi-walled nanotubes by the arc discharge technique, World Congress on Engineering 2007, Vols 1 and 2pp. 1391-1395 INT ASSOC ENGINEERS-IAENG
    Saunders RA, Lekakou C, Bader MG (1999) Compression in the processing of polymer composites 2. Modelling of the viscoelastic compression of resin-impregnated fibre networks, COMPOSITES SCIENCE AND TECHNOLOGY59(10)pp. 1483-1494 ELSEVIER SCI LTD
    Kampouris EM, Papaspyrides CD, Lekakou CN (1988) MODEL PROCESS FOR THE SOLVENT RECYCLING OF POLYSTYRENE., Polymer Engineering and Science28(8)pp. 534-537
    A model solvent technique is presented according to which polystyrene (PS) foam scrap is recovered in the form of small grains. The process mainly comprises dissolution of the waste into benzene or toluene, filtering, dispersion of the solution into water, and subsequent distillation. The alternative solvent/non-solvent systems have been studied on the basis of solution rheology, operating conditions during the recycling procedure, and extents of recovery of PS and solvent. Eventually, the toluene/water system has been chosen for a larger scale experiment (LSE), the product of which was used for characterization work. No influence on critical properties was detected due to the solvent technique followed.
    Kampouris EM, Papaspyrides CD, Lekakou CN (1987) A model recovery process for scrap polystyrene foam by means of solvent systems, Conservation and Recycling10(4)pp. 315-319
    A solvent technique is studied for the recovery of polystyrene (PS) foam waste. The model process proposed ensures removal of any impurities present and comprises dissolution of the starting material, filtering, reprecipitation, thorough washing of the polymer grains obtained and drying. The solvent mixtures involved are separated by distillation for re-use. The following criteria are considered: (a) the rheological behaviour of the PS solutions prepared, (b) the yield of the process of polymer of acceptable grain size and (c) sufficient solvent/non-solvent separation. On the basis of these criteria, methyl ethyl ketone/n-hexane or methanol and p-xylene/n-heptane are suggested as effective solvent/non-solvent systems. © 1988.
    Vermisoglou EC, Devlin E, Giannakopoulou T, Romanos G, Boukos N, Psycharis V, Lei C, Lekakou C, Petridis D, Trapalis C (2014) Reduced graphene oxide/iron carbide nanocomposites for magnetic and supercapacitor applications, Journal of Alloys and Compounds590pp. 102-109
    Reduced graphene oxide/Fe3C hybrids were prepared through Fe-based intercalation of graphite oxide (GtO). Altering pH (acidic to basic) of aqueous GtO dispersion, the immobilization of Fe-based intercalant bearing amino benzoate groups (IFe) was strongly affected following either the nucleophilic substitution (sample: IGO) or ion exchange path (sample: IGO/b). Subsequent pyrolysis of the intercalated materials provided magnetic hybrid materials (samples: r-IGO and r-IGO/b), differing in terms of BET surface area (87 and 163 m2/g), magnetization (70 and 43 J/T/kg), resistance (3 and 3.7 Ohm) and capacitance (5 and 17 F/g) correspondingly, displaying both magnetic and supercapacitor behavior. IFe triggered after thermal treatment in vacuum the formation of Fe3C nanoparticles encapsulated in a graphite shell whose incorporation into the multi-layer reduced graphene oxide (GO) matrix provided multi-functional materials. In these materials, aggregation is prevented in two directions: (a) between adjacent Fe3C nanoparticles, since the graphitic shell offers isolation, and (b) between bundles of neighboring multi-layer graphenes, due to Fe3C nanoparticle interference. The graphitic shell assists cohesion of encapsulated Fe 3C nanoparticles with the graphene matrix as well as chemical stability, affording thus materials appropriate for a variety of applications. © 2013 Elsevier B.V. All rights reserved.
    Moudam O, Andrews T, Lekakou C, Watts JF, Reed G (2013) Carbon Nanotube-Epoxy Nanocomposites: Correlation and Integration of Dynamic Impedance, Dielectric, and Mechanical Analyses, JOURNAL OF NANOMATERIALSARTN 801850 HINDAWI PUBLISHING CORP
    Vermisoglou EC, Giannakopoulou T, Romanos G, Giannouri M, Boukos N, Lei C, Lekakou C, Trapalis C (2015) Effect of hydrothermal reaction time and alkaline conditions on the electrochemical properties of reduced graphene oxide,APPLIED SURFACE SCIENCE358pp. 100-109 ELSEVIER SCIENCE BV
    Lekakou C, Bader MG (1998) Mathematical modelling of macro- and micro-infiltration in resin transfer moulding (RTM), COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING29(1-2)pp. 29-37 ELSEVIER SCI LTD
    Heardman E, Lekakou C, Bader MG (1999) Measurement of the principal components of the in-plane permeability of woven fabrics, PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON FLOW PROCESSES IN COMPOSITE MATERIALSpp. 153-159 ADVANCED COMPOSITES MANUFACTURING CENTRE
    Santucci A, Sorniotti A, Lekakou C (2013) Model predictive control for the power-split between supercapacitor and battery for automotive applications, 2013 IEEE International Electric Vehicle Conference, IEVC 2013
    Research and development of energy storage systems are almost entirely dominated by the need for continuously increasing their performance, reducing weight, cost, and increasing efficiency. The combination of battery and supercapacitor within the hybrid energy storage system (HESS) involves the management of the power between the two devices. The objective of this study is to develop a novel model predictive controller for the HESS of a through-the- road-parallel hybrid electric vehicle, which aims to extend the battery life. Results in terms of battery life expectancy and HESS energy efficiency are presented and discussed. © 2013 IEEE.
    Wilson P, Lekakou C, Watts JF (2013) In-plane conduction characterisation and charge transport model of DMSO co-doped, inkjet printed Poly(3,4-ethylenedioxythiophene): Polystyrene sulfonate (PEDOT:PSS), Organic Electronics: physics, materials, applications14(12)pp. 3277-3285
    The technologically important inkjet printed poly(3,4- ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) films, at different extents of co-doping with dimethyl sulfoxide DMSO, have been studied in terms of in-plane charge transport and electric field force microscopy (EFM). Similarly to past studies of spin coated PEDOT:PSS films, room temperature conductivity is enhanced by a factor of 103 to 130 S cm-1 on the addition of 5% DMSO, Hall probe analysis demonstrated a decrease in contact resistance from 106 © to 104 © whilst variable-temperature conductivity analysis shows an increase in the VRH exponent from 0.25 to 0.5 signifying a charge transport evolution from Mott Variable Range Hopping in 3-dimensions to a pseudo 1-dimensional Variable Range Hopping. In addition, electric field force microscopy (EFM) showed a corresponding threefold increase in PEDOT grain size. Further analysis was conducted to determine the hopping length and the ratio of the hopping length versus localization length in the electron transport model. © 2013 Elsevier B.V. All rights reserved.
    Lekakou C, Foderingham M, Abbas MK, Sorniotti A, Cosmas JP (2014) Photovoltaic energy source, Battery-supercapacitor energy storage/power system, electric vehicle charge station, in the grid, WIT Transactions on Engineering Sciences88pp. 305-310
    A system of photovoltaic (PV)-supercapacitor battery is outlined in this study for the charging of a battery for a mid-power electric vehicle (EV) or hybrid vehicle, in conjunction with charging contributions from the grid. Computational models have been developed for each component of the system, namely the PV, supercapacitor, and battery. Model predictions are presented for each system component and validated with experimental data. The required PV area for the charging of the battery of a mid-range EV or hybrid vehicle has also been estimated. © 2014 WIT Press.
    Wilson P, Lei C, Lekakou C, Watts JF (2014) Transverse charge transport in inkjet printed poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), Organic Electronics: physics, materials, applications15(9)pp. 2043-2051
    Transverse (z) alignment of PEDOT grains was demonstrated in inkjet printed PEDOT:PSS. This explained the superior transverse charge conduction mode in inkjet printed PEDOT:PSS films, best fitted by the Efros-Shklovskii 1D-VRH (variable range hopping) model in this study compared with spin coated PEDOT:PSS films, which have demonstrated layers of generally in-plane aligned PEDOT:PSS grains. The findings of this study, regarding the microstructure of inkjet printed PEDOT:PSS films and their transverse charge transport model, justify measurements of the transverse conductivity of inkjet printed films in this study being 600 times higher than that of spin coated films. In addition, it was found that the addition of 5 wt% DMSO in the printing PEDOT:PSS ink lowers the workfunction by 3% approximately. © 2014 Elsevier Ltd. All rights reserved.
    Antipas GSE, Lekakou C, Tsakiropoulos P (2011) Microstructural characterisation of Al - Hf and Al - Li - Hf spray deposits, Materials Characterization62(4)pp. 402-408
    Salifu AA, Nury BD, Lekakou C (2011) Electrospinning of Nanocomposite Fibrillar Tubular and Flat Scaffolds with Controlled Fiber Orientation, Annals of Biomedical Engineeringpp. 1-11
    Vermisoglou EC, Giannakopoulou T, Romanos GE, Boukos N, Giannouri M, Lei C, Lekakou C, Trapalis C (2015) Non-activated high surface area expanded graphite oxide for supercapacitors,APPLIED SURFACE SCIENCE358pp. 110-121 ELSEVIER SCIENCE BV
    Amico SC, Lekakou C (2002) Axial impregnation of a fiber bundle. Part 1: Capillary experiments, POLYMER COMPOSITES23(2)pp. 249-263 SOC PLASTICS ENG INC
    Heardman E, Lekakou C, Bader MG (2001) In-plane permeability of sheared fabrics, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING32(7)pp. 933-940 ELSEVIER SCI LTD
    Lekakou C, Brandao J (1996) Extrusion of polypropylene .2. Process analysis of the metering zone, POLYMER ENGINEERING AND SCIENCE36(1)pp. 56-64 SOC PLASTICS ENG INC
    Lekakou C (1997) Mathematical modeling and computer simulations of the flow, nematic phase orientation, and heat transfer in thermotropic liquid crystalline polymers, POLYMER ENGINEERING AND SCIENCE37(3)pp. 529-540 SOC PLASTICS ENG INC
    Elsayed Y, Lekakou C, Tomlins P (2014) Monitoring and modelling of oxygen transport through un-crosslinked and crosslinked gelatine gels, Polymer Testing40pp. 106-115
    © 2014 Elsevier Ltd. All rights reserved.A non-invasive, luminescence quenching technique is developed for continuous monitoring of oxygen spatial-temporal concentration distribution in fully hydrated gelatine gels, intended for use as scaffolds in tissue engineering. Two mass transfer-diffusion models were used to simulate the unsteady-state oxygen mass transport in the system. Oxygen diffusion coefficient and mass transfer coefficient at the water-gel interface were determined for un-crosslinked gelatine, as well as gelatine crosslinked with 1 and 1.5% w/v glutaraldehyde. While crosslinking and increased concentration of the crosslinking agent reduced oxygen mass transfer across the gel surface, both factors increased the diffusion coefficient of oxygen in the bulk of the gel. Voids in the gelatine's microstructure, which were generated during the crosslinking process due to shrinkage and associated internal stresses, were associated with both increasing the diffusion coefficient within the gel, as well as inhomogeneous diffusion of oxygen within the gel.
    Lekakou CN, Richardson SM (1988) Computer simulation of the filling and curing stages in RIM: Sensitivity analysis on reaction kinetics, Plastics and Rubber Processing and Applications10(1)pp. 17-25
    This work presents results obtained using a computer model of the filling and curing stages in reaction injection moulding (RIM), the main emphasis being given to the rheology and reaction kinetics. Three types of viscosity relation and four types of reaction kinetics are included so that the computer code can be applied to a wide range of RIM materials. Comparisons of computational results with experimental ones are made for a polyurethane system. A sensitivity analysis, mainly on reaction kinetics, is performed for three types of chemical system. The variables which govern the RIM process are combined in three main dimensionless groups, namely the Reynolds, Graetz and Damkohler numbers. The effect of changes in each of these numbers on the gelling time, reaction time and maximum temperature is studied.
    Rios CR, Ogin SL, Lekakou C, Leong KH (2007) A study of damage development in a weft knitted fabric reinforced composite. Part 1: Experiments using model sandwich laminates, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING38(7)pp. 1773-1793 ELSEVIER SCI LTD
    Saunders RA, Lekakou C, Bader MG (1998) Compression and microstructure of fibre plain woven cloths in the processing of polymer composites, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING29(4)pp. 443-454 ELSEVIER SCI LTD
    Markoulidis F, Lei C, Lekakou C, Figgemeier E, Duff D, Khalil S, Martorana B, Cannavaro I (2012) High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes, IOP Conf.Series:MaterialsScienceandEngineering 40 (2012) 01202140 IOP Publishing
    The purpose of this work was to investigate and improve the performance of supercapacitor cells with carbon-based nanocomposite electrodes. The electrode structure comprised activated carbon (AC), four types of multi-wall nanotubes (MWNTs) and two alternative polymer binders, Polyvinyl alcohol (PVA) or Polyvinylidene fluoride (PVDF). Electrode fabrication involved various stages of mixing and dispersion of the AC powder and carbon nanotubes, rolling and coating of the AC/MWNT/binder paste on an aluminium substrate which also served as current collector. The organic electrolyte utilised was 1M tetraethylammonium tetrafluoroborate (TEABF4) fully dissolved in propylene carbonate (PC). All devices were of the electrochemical double layer capacitor (EDLC) type, incorporating four layers of tissue paper as separator material. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Each supercapacitor cell was subjected to Cyclic Voltammetry (CV) at various scan rates from 0.01 V/s to 1 V/s, Charge-Discharge at a fixed current steps (2 mA) and Electrochemical Impedance Spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz. It was established that an AC-based supercapacitor with 0.15%w/w MWNT content and 30 ¼m roll-coated, nanocomposite electrodes provided superior energy and power and energy densities while the cells was immersed in the electrolyte; well above those generated by the AC-based EDLC cells.
    LEKAKOU C, BADER MG, TONKIN JD (1993) MODELING OF FIBER NETWORK DEFORMATION DURING PROCESSING OF CONTINUOUS FIBER-REINFORCED POLYMER COMPOSITES, COMPUTER AIDED INNOVATION OF NEW MATERIALS II, PTS 1 AND 2pp. 1511-1514 ELSEVIER SCIENCE PUBL B V
    Lei C, Lekakou C (2013) Activated carbon-carbon nanotube nanocomposite coatings for supercapacitor applications, Surface and Coatings Technology232pp. 326-330
    Electrochemical double layer capacitor cells were fabricated based on electrodes with activated carbon (AC) coating as the host material, targeting large energy storage. Highly dispersed multiwall carbon nanotubes (MWNTs) were added to form nanocomposite coatings, used as electrodes targeting high-power performance for very low content of MWNTs. 1. M tetraethylammonium tetrafluoroborate-propylene carbonate solution was used as organic electrolyte. The resulting cells were characterized using impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge tests. It was concluded that at optimum composition of AC-MWNT coatings both power and energy densities are raised whereas further increase of the MWNT content would increase the power density but decrease the energy density. © 2013 Elsevier B.V.
    Santucci A, Sorniotti A, Lekakou C (2014) Power split strategies for hybrid energy storage systems for vehicular applications, Journal of Power Sources258pp. 395-407
    This paper deals with the control system development for a hybrid energy storage system, consisting of a battery and a supercapacitor, for a through-the-road-parallel hybrid electric vehicle. One of the main advantages deriving from the coupling of a battery and a supercapacitor is the possibility of reducing battery ageing, in addition to energy efficiency improvements when the system operates in critical climate conditions. At the moment, no specific controller has been proposed with the aim of directly reducing battery wear. This paper presents a novel model predictive controller and a dynamic programming algorithm including a simplified battery ageing model in their formulations. The simulation results of the model predictive controller and dynamic programming algorithm are compared with the results deriving from a rule-based strategy. The rule-based controller achieves a 67% reduction of the root mean square values of battery current along a selection of driving cycles in comparison with the same vehicle equipped with battery only. In the same conditions the battery peak current is reduced by 38%. The model predictive controller and the dynamic programming algorithm further reduce the root mean square value by 6% and 10% respectively, whilst the peak values are additionally decreased by 17% and 45%. © 2014 The Authors. Published by Elsevier B.V.
    Salifu AA, Lekakou C (2012) Electrospinning of hydroxyapatite-gelatine scaffolds: Physical characterisation and process optimisation, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
    Electrospun scaffolds of hydroxyapatite-gelatine nanocomposites were fabricated, crosslinked and subjected to image analysis, water swelling and mechanical testing. Fibre diameter and pore size of scaffolds increased with the applied voltage and the hydroxyapatite (HA) content. The scaffolds were stable in water for up to three weeks and there was a positive correlation between their mechanical properties and the applied voltage and the HA content. Maximum Young's modulus and tensile strength of 925 MPa and 9.75 MPa, respectively, were recorded for 25% HA scaffold.
    Lekakou C, Hearn A, Murugesh AK, Le Page B (2007) Liquid composite moulding of fibre nanocomposites,MATERIALS SCIENCE AND TECHNOLOGY23(4)pp. 487-491 MANEY PUBLISHING
    Rios CR, Ogin SL, Lekakou C, Leong KH (2004) Study of the mechanisms of fracture and mechanical properties of an engineering knitted fabric reinforced composite, Annual Technical Conference - ANTEC, Conference Proceedings2pp. 1384-1389
    In this work the tensile properties and failure mechanisms for a knitted fabric reinforced composite has been investigated. Two commercial composites manufactured with Milano 2×68 tex knitted fabric as a reinforcement and Derakane vinyl ester resin as matrix were analysed. The quasi-static behaviour of the materials has been analysed as a function of tested direction, including an investigation of the damage accumulation. Characterization of these materials under tensile loading has been carried out for monotonic and cyclic loading and the results have been compared with those found earlier for a single layer and the sandwich model material with epoxy resin as matrix1. Various failure mechanisms such as cracking at loop cross-over points, resin matrix cracking, fibre bundle debonding and tensile fracture of fibre bundles in failed specimens were observed.
    Lamprou D, Zhdan P, Labeed F, Lekakou C (2011) Gelatine and gelatine/elastin nanocomposites for vascular grafts: processing and characterization.,J Biomater Appl26(2)pp. 209-226
    This study involves the preparation, microstructural, physical, mechanical, and biological characterization of novel gelatine and gelatine/elastin gels for their use in the tissue engineering of vascular grafts. Gelatine and gelatine/elastin nanocomposite gels were prepared via a sol-gel process, using soluble gelatine. Gelatine was subsequently cross-linked by leaving the gels in 1% glutaraldehyde. The cross-linking time was optimized by assessing the mass loss of the cross-linked gels in water and examining their mechanical properties in dynamic mechanical tests. Atomic force microscopy (AFM) studies revealed elastin nanodomains, homogeneously distributed and embedded in a bed of gelatine nanofibrils in the 30/70 elastin/gelatine gel. It was concluded that the manufactured nanocomposite gels resembled natural arteries in terms of microstructure and stiffness. The biological characterization involved the culture of rat smooth muscle cells (SMCs) on tubular gelatine and gelatine/ elastin nanocomposite gels, and measurements of the scaffold diameter and the cell density as a function of time.
    Rios CR, Ogin SL, Lekakou C, Leong KH (2007) Study of damage development in a weft knitted fabric reinforced composite. Part 2: Stress-strain and early cyclic behaviour of composite laminates with realistic fabric layups, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING38(7)pp. 1794-1808 ELSEVIER SCI LTD
    Mustaza SM, Mahdi D, Saaj C, Albukhanajer WA, Lekakou C, Elsayed Y, Fras J (2015) Tuneable Stiffness Design of Soft Continuum Manipulator, INTELLIGENT ROBOTICS AND APPLICATIONS (ICIRA 2015), PT III9246pp. 152-163 SPRINGER-VERLAG BERLIN
    Heardman E, Lekakou C, Bader MG (2004) Flow monitoring and permeability measurement under constant and transient flow conditions, COMPOSITES SCIENCE AND TECHNOLOGY64(9)pp. 1239-1249 ELSEVIER SCI LTD
    Lekakou C, Lei C, Markoulidis F, Sorniotti A (2012) Nanomaterials and Nanocomposites for High Energy/High Power Supercapacitors, 2012 12TH IEEE CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO) IEEE
    Mohammed U, Lekakou C, Dong L, Bader MG (2000) Shear deformation and micromechanics of woven fabrics, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING31(4)pp. 299-308 ELSEVIER SCI LTD
    Lekakou C, Johari MAK, Norman D, Bader MG (1996) Measurement techniques and effects on in-plane permeability of woven cloths in resin transfer moulding, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING27(5)pp. 401-408 ELSEVIER SCI LTD
    Lei C, Markoulidis F, Ashitaka Z, Lekakou C (2013) Reduction of porous carbon/Al contact resistance for an electric double-layer capacitor (EDLC), Electrochimica Acta92pp. 183-187
    Carbonaceous materials are commonly used to fabricate electrodes for electric double-layer capacitors (EDLCs) or supercapacitors. The high contact resistance between the carbon active layer and the Al current collector can decrease capacitor energy and power performance, and shorten the lifetime of the capacitor. In this report, the sources of carbon based EDLC internal resistance were explored using electrochemical impedance spectroscopy (EIS). An equivalent circuit model was coupled with the EIS data for the analyses. The EDLC cells were made from symmetric carbon/Al electrodes and operated in organic electrolyte. The analysis results showed the effects of pressure and modified Al on the contact resistance, where a novel, carbon modified Al collector with Al4C3 nano whiskers greatly reduced the contact resistance. Finally the effect of scale-up on the internal resistance was discussed. © 2013 Elsevier Ltd.
    Dong L, Lekakou C, Bader MG (2000) Solid-mechanics finite element simulations of the draping of fabrics: a sensitivity analysis, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING31(7)pp. 639-652 ELSEVIER SCI LTD
    Lekakou C, Cowley J, Dickinson CE (1997) Injection moulding of self-reinforcing polymers and polymer blends, JOURNAL OF MATERIALS SCIENCE32(5)pp. 1319-1324 CHAPMAN HALL LTD
    Markoulidis F, Lei C, Lekakou C (2013) Fabrication of high-performance supercapacitors based on transversely oriented carbon nanotubes, Applied Physics A: Materials Science and Processing111(1)pp. 227-236
    High-performance supercapacitors with organic electrolyte 1 M TEABF 4 (tetraethyl ammonium tetrafluoroborate) in PC (propylene carbonate) were fabricated and tested, based on multiwall carbon nanotubes (MWNTs) deposited by electrophoresis on three types of alternative substrates: aluminium foil, ITO (indium tin oxide) coated PET (polyethylene terephthalate) film and PET film. In all cases, SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy) micrographs demonstrated that protruding, transversely oriented MWNT structures were formed, which should increase the transverse conductivity of these MWNT electrodes. The best supercapacitor cell of MWNT electrodes deposited on aluminium foil displayed good transverse orientation of the MWNT structures as well as an in-plane MWNT network at the feet of the protruding structures, which ensured good in-plane conductivity. Capacitor cells with MWNT electrodes deposited either on ITO-coated PET film or on PET film demonstrated lower but still very good performance due to the high density of transversely oriented MWNT structures (good transverse conductivity) but some in-plane inhomogeneities. Capacitor cells with drop-printed MWNTs on aluminium foil, without any transverse orientation, had 16-30 times lower specific capacitance and 5-40 times lower power density than the capacitor cells with the electrophoretically deposited MWNT electrodes. © 2012 Springer-Verlag Berlin Heidelberg.
    Lekakou C, Moudam O, Markoulidis F, Andrews T, Watts JF, Reed GT (2011) Carbon-based fibrous EDLC capacitors and supercapacitors,Journal of Nanotechnology2011409382
    This paper investigates electrochemical double-layer capacitors (EDLCs) including two alternative types of carbon-based fibrous electrodes, a carbon fibre woven fabric (CWF) and a multiwall carbon nanotube (CNT) electrode, as well as hybrid CWF-CNT electrodes. Two types of separator membranes were also considered. An organic gel electrolyte PEO-LiCIO4-EC-THF was used to maintain a high working voltage. The capacitor cells were tested in cyclic voltammetry, charge-discharge, and impedance tests. The best separator was a glass fibre-fine pore filter. The carbon woven fabric electrode and the corresponding supercapacitor exhibited superior performance per unit area, whereas the multiwall carbon nanotube electrode and corresponding supercapacitor demonstrated excellent specific properties. The hybrid CWF-CNT electrodes did not show a combined improved performance due to the lack of carbon nanotube penetration into the carbon fibre fabric.
    Lekakou C, Kontodimopoulos I, Murugesh AK, Chen YL, Jesson DA, Watts JF, Smith PA (2008) Processability studies of silica-thermoset polymer matrix nanocomposites,POLYMER ENGINEERING AND SCIENCE48(2)pp. 216-222 JOHN WILEY & SONS INC
    Markoulidis F, Lei C, Lekakou C (2012) Fabrication of high-performance supercapacitors based on transversely oriented carbon nanotubes, Applied Physics A: Materials Science and Processingpp. 1-10
    High-performance supercapacitors with organic electrolyte 1 M TEABF (tetraethyl ammonium tetrafluoroborate) in PC (propylene carbonate) were fabricated and tested, based on multiwall carbon nanotubes (MWNTs) deposited by electrophoresis on three types of alternative substrates: aluminium foil, ITO (indium tin oxide) coated PET (polyethylene terephthalate) film and PET film. In all cases, SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy) micrographs demonstrated that protruding, transversely oriented MWNT structures were formed, which should increase the transverse conductivity of these MWNT electrodes. The best supercapacitor cell of MWNT electrodes deposited on aluminium foil displayed good transverse orientation of the MWNT structures as well as an in-plane MWNT network at the feet of the protruding structures, which ensured good in-plane conductivity. Capacitor cells with MWNT electrodes deposited either on ITO-coated PET film or on PET film demonstrated lower but still very good performance due to the high density of transversely oriented MWNT structures (good transverse conductivity) but some in-plane inhomogeneities. Capacitor cells with drop-printed MWNTs on aluminium foil, without any transverse orientation, had 16-30 times lower specific capacitance and 5-40 times lower power density than the capacitor cells with the electrophoretically deposited MWNT electrodes. © 2012 Springer-Verlag Berlin Heidelberg.
    Markoulidis F, Lei C, Lekakou C, Duff D, Khalil S, Martorana B, Cannavaro I (2014) A method to increase the energy density of supercapacitor cells by the addition of multiwall carbon nanotubes into activated carbon electrodes, Carbon68pp. 58-66
    The performance of supercapacitor cells with activated carbon (AC) electrodes was improved by adding a small amount of multiwall carbon nanotubes (MWCNTs). The electrode structure investigated comprised AC, four different types of MWCNTs and two polymer binders, polyvinylidene fluoride or polyvinyl alcohol. All fabricated devices were of the electrochemical double layer capacitor type. The organic electrolyte used was tetraethyl ammonium tetrafluoroborate (TEABF4) in two different solvents: propylene carbonate or acetonitrile (AN). The electrodes were characterised with scanning electron microscopy and tested for their specific surface area and pore size distribution. The electrode fabrication process was fine-tuned by investigating the effect of the coating thickness on the supercapacitor cell performance. It was established that an AC/MWCNT-based supercapacitor with 30 ¼m thick roll-coated, composite electrodes of just 0.15%w/w MWCNT content provided superior tested power and energy densities of 38 kW/kg and 28 W h/kg, respectively, compared to 18 kW/kg and 17 W h/kg for AC only-based cells in a 1.5 TEABF4/AN electrolyte. The increased energy density was attributed to a fine lace of MWCNTs covering the AC microparticles with visible 20-30 nm lace pores and to the high specific area of micropores. © 2013 Elsevier Ltd. All rights reserved.
    Lekakou C, Lamprou D, Vidyarthi U, Karopoulou E, Zhdan P (2008) Structural hierarchy of biomimetic materials for tissue engineered vascular and orthopedic grafts,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS85B(2)pp. 461-468 WILEY-LISS
    Vermisoglou E, Todorova N, Pilatos G, Romanos G, Likodimos V, Boukos N, Lei C, Markoulidis F, Lekakou C, Trapalis C (2012) Few layer graphenes decorated with silver nanoparticles, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
    Graphite oxide (GO) powder was irradiated in a microwave oven and lightweight expanded graphite oxide (EGO) powder with high BET surface area 1316 m2/g was obtained. Activation of EGO was performed by impregnation in KOH solution and high temperature treatment under Ar flow, followed by annealing in vacuum (t-EGO). KOH acted more as a reducing agent diminishing the defects than as a surface modifier for high porosity. EGO and t-EGO were further decorated with Ag nanoparticles (<40 nm) applying solar light irradiation. Along with Ag deposition the structural defects of the graphene were reduced upon photo-irradiation. It was established that among the bare graphenes the EGO exhibited the highest capacitance. From the Ag-containing composites, the KOH activated EGO acted as a supercapacitor, while the non-activated EGO as a resistant.
    Lekakou Constantina, Elsayed Y, Geng T, Saaj Chakravarthini (2015) Skins and Sleeves for Soft Robotics: Inspiration from Nature and Architecture,Advanced Engineering Materials17(8)pp. 1180-1188
    © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. This paper is on the design, fabrication, and testing of skins and sleeves for soft robotics with the focus on the mechanical features of the microstructure of these skins, drawing inspiration from nature and architecture. Biological inspirations drawn from animals are used for designing skin membranes or skin structures for soft robotic actuators, in particular pneumatic actuators that protect, guide, and contribute to the development of the actuated shape. The results presented in this paper will be a new step toward advancing the state-of-the-art of biologically inspired soft robots for minimally invasive surgery. Inspirations from architecture are of particular interest in the areas of formability of design and continuous flow. The report presents a trade-off study using various skin and sleeve technologies of innovative fiber structures and combinations of different materials in different innovative designs, surrounding a pneumatically actuated, soft robot of variable stiffness.
    Elsayed Y, Lekakou C, Labeed F, Tomlins P (2016) Fabrication and characterisation of biomimetic, electrospun gelatin fibre scaffolds for tunica media-equivalent, tissue engineered vascular grafts,MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS61pp. 473-483 ELSEVIER SCIENCE BV
    It is increasingly recognised that biomimetic, natural polymers mimicking the extracellular matrix (ECM) have low thrombogenicity and functional motifs that regulate cell?matrix interactions, with these factors being critical for tissue engineered vascular grafts especially grafts of small diameter. Gelatin constitutes a low cost substitute of soluble collagen but gelatin scaffolds so far have shown generally low strength and suture retention strength. In this study, we have devised the fabrication of novel, electrospun, multilayer, gelatin fibre scaffolds, with controlled fibre layer orientation, and optimised gelatin crosslinking to achieve not only compliance equivalent to that of coronary artery but also for the first time strength of the wet tubular acellular scaffold (swollen with absorbed water) same as that of the tunica media of coronary artery in both circumferential and axial directions. Most importantly, for the first time for natural scaffolds and in particular gelatin, high suture retention strength was achieved in the range of 1.8?1.94 N for wet acellular scaffolds, same or better than that for fresh saphenous vein. The study presents the investigations to relate the electrospinning process parameters to the microstructural parameters of the scaffold, which are further related to the mechanical performance data of wet, crosslinked, electrospun scaffolds in both circumferential and axial tubular directions. The scaffolds exhibited excellent performance in human smooth muscle cell (SMC) proliferation, with SMCs seeded on the top surface adhering, elongating and aligning along the local fibres, migrating through the scaffold thickness and populating a transverse distance of 186 ¼m and 240 ¼m 9 days post-seeding for scaffolds of initial dry porosity of 74 and 83%, respectively.
    Lekakou C, Cook S, Ang TW, Reed GT (2003) Optical fibre flow-sensor for composites manufacturing, Advanced Composites Letters12(5)pp. 211-215
    An optical fibre has been used as an intensity-based sensor for the monitoring of the fluid front infiltrating a reinforcing fibre mat in composites manufacturing. The sensor length comprised the fibre core, initially surrounded by air or vacuum and subsequently covered by the infiltrating fluid. Two configurations were tested where a step-change or a continual output signal was obtained, respectively. In the latter case, the sensor used in this study demonstrates an improvement of up to two orders of magnitude over conventional monitoring techniques used for this application. This performance is coupled with more obvious advantages of low cost, compatibility with composite fabrication, and ease of use.
    Brandao J, Spieth E, Lekakou C (1996) Extrusion of polypropylene .1. Melt rheology, POLYMER ENGINEERING AND SCIENCE36(1)pp. 49-55 SOC PLASTICS ENG INC
    Lei C, Amini N, Markoulidis F, Wilson P, Tennison S, Lekakou C (2013) Activated carbon from phenolic resin with controlled mesoporosity for an electric double-layer capacitor (EDLC), Journal of Materials Chemistry A1(19)pp. 6037-6042
    Activated carbon materials are prepared from phenolic resin precursors by physical activation to fabricate electrodes for electric double-layer capacitors (EDLCs). Pore size and surface area of the carbon materials are controlled during the synthesizing process and after the carbonization through activation in a CO2 atmosphere to different levels of burn-off. The resultant carbon materials were evaluated as EDLC electrodes, using electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD) measurements with the organic electrolyte of spiro-(1,12)-bipyrrolidinium tetrafluoroborate in propylene carbonate, SBPBF4/PC. The results of the study showed that the capacitance of carbon materials, as well as energy density of the EDLC cells, increased by increasing the level of burn-off (activation). The 46% activated carbon gave a capacitance of <160 F g -1 and an energy density of <35 W h kg-1, at a current density of 1 mA cm-2. The long term cycling tests showed high cycling stability of these carbon materials. © The Royal Society of Chemistry 2013.
    Salifu AA, Nury BD, Lekakou C (2011) Electrospinning of nanocomposite fibrillar tubular and flat scaffolds with controlled fiber orientation, Annals of Biomedical Engineering39(10)pp. 2510-2520
    Lekakou C, Johari MAKB, Bader MG (1996) Compressibility and flow permeability of two-dimensional woven reinforcements in the processing of composites, POLYMER COMPOSITES17(5)pp. 666-672 SOC PLASTICS ENG INC
    Mohammed U, Lekakou C, Bader MG (1999) Experimental studies and computer simulations of the draping of woven fabrics, PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON FLOW PROCESSES IN COMPOSITE MATERIALSpp. 53-60 ADVANCED COMPOSITES MANUFACTURING CENTRE
    Rebord G, Hansrisuk N, Lindsay B, Lekakou C, Reed GT, Watts JF (2008) Electrofunctional Polymer Nanocomposites, ESTC 2008: 2ND ELECTRONICS SYSTEM-INTEGRATION TECHNOLOGY CONFERENCE, VOLS 1 AND 2, PROCEEDINGSpp. 1401-1405 IEEE
    Murugesh AK, Uthayanan A, Lekakou C (2010) Electrophoresis and orientation of multiple wall carbon nanotubes in polymer solution, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING100(1)pp. 135-144 SPRINGER
    Gosman AD, Lekakou C, Politis S, Issa RI, Looney MK (1992) Multidimensional modeling of turbulent two-phase flows in stirred vessels, AICHE JOURNAL38(12)pp. 1946-1956
    This article outlines a computational procedure for the prediction of dispersed two-phase, solid-liquid and gas-liquid, turbulent flows in baffled, impeller-stirred vessles common in the chemical industries. A two-flow Eulerian model is employed, based on the main assumption of interpenetrating coexisting continua. Mean momentum and mass conservation equations are solved for each phase and turbulent closure is effected by extending the single phase k- epsilon turbulence model to two-phase flows. The resulting set of highly coupled equations is solved by a two-phase implicit algorithm, PISO-2P, which allows calculation for a wide range of phase fraction, particle size and phase density ratios. Predictions are presented for solid-liquid and gas-liquid (bubbly) flows. Comparisons are made with experimental data for the mean phase velocities and volume fraction, mean slip velocity and turbulence quantities. (from Authors)
    Amico S, Lekakou C (2004) Flow through a two-scale porosity, oriented fibre porous medium, TRANSPORT IN POROUS MEDIA54(1)pp. 35-53 KLUWER ACADEMIC PUBL
    De Pinto S, Lu Q, Camocardi P, Chatzikomis C, Sorniotti A, Lekakou C (2016) Electric vehicle driving range extension using photovoltaic panels,VPPC Conference Proceedings
    This paper investigates the potential benefits of photovoltaic (PV) panels on electric vehicles. In addition to the PV panels on the roof of the car, in this study a PV panel is installed below the windshield to increase energy capture when the car is parked. An electro-mechanical actuator makes the PV panel disappear under the roof when the passengers are in the vehicle. The paper presents the simulation model of the overall PV architecture, including the DC/DC converter and the energy storage system. Based on recorded temperature and solar irradiance profiles, the model calculates the energy input and the corresponding range extension. The resulting values are discussed for a prototype four-wheel-drive urban electric vehicle operating in five European locations.
    Elsayed Y, Lekakou C, Ranzani T, Cianchetti M, Morino M, Arezzo A, Menciassi A, Geng T, Saaj CM, Chirurgia M (2015) Crimped braided sleeves for soft, actuating arm in robotic abdominal surgery,Minimally Invasive Therapy & Allied Technologies24(4)pp. 204-210 Taylor & Francis
    Background: This paper investigates different types of crimped, braided sleeve used for a soft arm for robotic abdominal surgery, with the sleeve required to contain balloon expansion in the pneumatically actuating arm while it follows the required bending, elongation and diameter reduction of the arm. Material and methods: Three types of crimped, braided sleeves from PET (BraidPET) or nylon (BraidGreyNylon and BraidNylon, with different monofilament diameters) were fabricated and tested including geometrical and microstructural characterisation of the crimp and braid, mechanical tests and medical scratching tests for organ damage of domestic pigs. Results: BraidPET caused some organ damage, sliding under normal force of 2-5 N; this was attributed to the high roughness of the braid pattern, the higher friction coefficient of polyethylene terephthalate (PET) compared to nylon, and the high frequency of the crimp peaks for this sleeve. No organ damage was observed for the BraidNylon, attributed to both the lower roughness of the braid pattern and the low friction coefficient of nylon. BraidNylon also required the lowest tensile force during its elongation to similar maximum strain as that of BraidPET, translating to low power requirements.
    Elsayed Y, Lekakou C, Labeed F, Tomlins P (2016) Smooth muscle tissue engineering in crosslinked electrospun gelatin scaffolds,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A104(1)pp. 313-321 WILEY-BLACKWELL
    Reece R, Lekakou C, Smith PA (2014) Sulphur cross-linked graphene nano platelets as structural composite supercapacitor electrodes,16th European Conference on Composite Materials, ECCM 2014
    Graphene nano platelets cross-linked with elemental sulphur have been used as supercapacitor electrode material to provide successful energy storage in a structural device. Chemical crosslinking of the composite produces a mechanically stable material, with both high conductivity and surface area. Characterisation was conducted using scanning electron microscopy and energy dispersive X-ray spectroscopy. Different concentrations of graphene-sulphur are investigated, along with addition of conductive carbon black and multiwall carbon nanotubes. The effects of these variables on the performance of the sulphur cross-linked graphene as a supercapacitor electrode are presented through impedance spectrometry, cyclic voltammetry and galvanostatic charge-discharge. Analysis of the structural performance of the material is conducted by flexural three-point-bend testing.
    Sadykov D, Nouicer L, Lekakou C (2017) Hybrid Woven Glass Fibre Fabric-Multi-walled Carbon Nanotube-Epoxy Composites Under Low Rate Impact,Journal of Composites Science1(1) MDPI AG (Basel, Switzerland)
    This research work addresses the issue of developing light composite materials with increased ability for impact energy absorption. Novel, hybrid plain woven glass fibre fabric-epoxy laminates with multi-walled carbon nanotube (MWNT) interlayers were fabricated in this study so that (a) only a few MWNT interlayers were placed close to the face of the laminate to be subjected to impact and (b) the interlayers were fabricated via innovative wide-line electrospinning of MWNT/epoxy/solvent solutions, depositing a mixture of aligned fibres and spray on the woven glass fibre fabrics; the laminate was then fabricated via resin transfer moulding (RTM). Hybrid nano-micro-composite laminates with 0.15 wt% MWNT were prepared with this method and were subjected to single low rate impact tests. It was found that the optimised hybrid laminates had 22% greater total penetration energy translated to 15% weight reduction in the laminate armour for an equivalent amount of energy penetration.
    Salifu A, Lekakou C, Labeed F (2017) Electrospun oriented gelatin-hydroxyapatite fibre scaffolds for bone tissue engineering,Journal of Biomedical Materials Research Part A105(7)pp. 1911-1926 Wiley
    Tissue engineering of human foetal osteoblast (hFOB) cells was investigated on gelatin-hydroxyapatite (HA), crosslinked, electrospun oriented fibre scaffolds at the different hydroxyapatite concentrations of 0, 10, 20 and 25 wt% in the dry fibres and different fibre diameter, pore size and porosity of scaffolds. Rheological tests and proton NMR spectroscopy were conducted for all solutions used for electrospinning. It was found that 25 wt% HA-gelatin scaffolds electrospun at 20 kV led to the greatest cell attachment, cell proliferation and extracellular matrix (ECM) production while fibre orientation improved the mechanical properties, where crosslinked electrospun 25 wt% HA-gelatin fibre scaffolds yielded a Young?s modulus in the range of 0.5 to 0.9 GPa and a tensile strength in the range of 4 to 10 MPa in the fibre direction for an applied voltage of 20 to 30 kV, respectively, in the electrospinning of scaffolds. Biological characterisation of cell seeded scaffolds yielded the rate of cell growth and ECM (collagen and calcium) production by the cells as a function of time; it included cell seeding efficiency tests, alamar blue cell proliferation assay, alkaline phosphate (ALP) assay, collagen assay, calcium colorimetric assay, fluorescence microscopy for live and dead cells, and scanning electron microscopy (SEM) for cell culture from 1 to 18 days. After 18 days, cells seeded and grown on the 25 wt% HA-gelatin scaffold, electrospun at 20 kV, reached production of collagen at 370 mg/L and calcium production at 0.8 mM.
    Salifu A, Lekakou C, Labeed F (2016) Multilayer cellular stacks of gelatin-hydroxyapatite fiber scaffolds for bone tissue engineering,Journal of Biomedical Materials Research: Part A105(3)pp. 779-789 Wiley
    Multilayer cellular stacks of crosslinked, electrospun 25 wt% hydroxyapatite (HA)-gelatin and pure gelatin fiber scaffolds, seeded with human foetal osteoblasts (hFOBs), were studied for up to 18 days in static and dynamic cell culture. Two types of stack models were investigated: a four-layer stack with cells seeded at the bottom surface of the first/top layer and the top surface of the fourth/bottom layer, so that the two middle layers were not seeded with cells with the aim to act as continuing conduits of culture medium and nutrients supply to the adjacent cell-populated zones; a three-layer stack with cells seeded at the bottom surface of each layer. hFOBs exhibited lower migration rate through the stack thickness for the 25 wt% HA-gelatin scaffolds compared to the pure gelatin scaffolds, due to the small pores of the former. Hence, the regularly seeded three-layer stack maintained cell-free porous zones in all layers through which the culture medium could continuously perfuse, while good fusion was achieved at the interface of all layers via the cross-migrating cells with a preference to downwards vertical migration attributed to gravity. Dynamic cell culture conditions enhanced overall cell growth by about 6% for the regularly seeded three-layer stack.
    Elsayed Y, Vincensi A, Lekakou C, Geng T, Saaj CM, Ranazani T, Cianchetti M, Menciassi A (2014) Finite element analysis (FEA) and design optimisation of a pneumatically actuating silicone module for robotic surgery applications,Soft Robotics1(4)pp. 255-262 Mary Ann Liebert
    The design of a pneumatically actuated silicone module, resembling soft tissue, with three pneumatic chambers is considered and optimized in this study with the aim of using it in a soft robot arm for robotic surgery applications. Three types of silicone materials, Ecoflex 0030 and 0050 and Dragonskin 0030, have been investigated, and a constitutive model has been derived for each of them. Design optimization of the silicone module was based on finite element analysis (FEA) that was validated against experimental data of one-degree bending under one-channel actuation. This was followed by FEA parametric studies for module design optimization to minimize the ballooning effect in one-degree bending as well as reduce the actuation pressure. Modules made from Ecoflex 0030 and Ecoflex 0050 exhibited the same bending shape in FEA, but about three times higher actuation pressure was required for the harder Ecoflex 0050. Design parameters under investigation in the parametric FEA studies included the shape of the pneumatic channel cross section, the ratio of channel length to module length, the distance of channel from the module wall, and the ratio of channel to module cross-sectional area. After FEA design optimization yielded least ballooning for pneumatic chambers of semicircular cross section, an internal dragonskin structure was added internally below the module surface to enable and guide the bending under one-channel pneumatic actuation and further contain the ballooning effect: the benefits of this design were successfully verified under both FEA and experimental analysis.
    Mustaza S, Mahdi D, Saaj CM, Comin F, Lekakou C (2017) Development of Tunable Stiffness Control for Soft Continuum Surgical Manipulators,International Journal of Humanoid Robotics World Scientific Publishing
    Lekakou C, Mustaza S, Crisp T, Elsayed Y, Saaj CM (2017) A Material-based Model for the Simulation and Control of Soft Robot Actuator,
    This study includes a novel approach of applying an equivalent electric circuit model of two resistors and three constant phase elements (CPEs) to the galvanostatic charge-discharge of supercapacitors which provides virtual monitoring of the electrochemical processes taking place in parallel at different timescales and offers remarkable insights into the coexistence composition and cascade of such processes during the charge-discharge of cells at different current densities. This modelling method has been applied to analyse the performance of high energy density supercapacitors based on a microporous, phenolic-derived, activated carbon fabric (ACF) with different interlayers with the current collector (CC). Associated experimental studies deal with the challenge of overcoming the high contact resistance between the ACF and the current collector (CC) by employing innovative interlayers containing conductive features or structures to fill or bridge the interface gaps between the ACF fibers and the CC foil and the pores of the activated carbon (AC) fiber surface. Such interlayers involve tree-like microstructures of carbon black nanoparticles or deflocculated graphite platelets or multiwall carbon nanotubes (MWCNTs) deposited electrophoretically on the aluminium foil and the ACF. The use of PEDOT:PSS binder in such interlayer raises performance to maximum 44 Wh/kg and 9 kW/kg for electrolyte 1.5 M TEABF4/AN. These are further raised by 17% and 13%, respectively, using electrolyte 1.5 M SBPBF4/AN, and by 19% (both) using a thin polyolefinic separator against the thicker, cellulose-based separator.
    Shumbayawonda Elizabeth, Salifu Ali A., Lekakou Constantina, Cosmas John P. (2018) Numerical and Experimental Simulations of the Wireless Energy Transmission and Harvesting by a Camera Pill,Journal of Medical Devices12(2) American Society of Mechanical Engineers (ASME)
    This paper investigates the energy transmitted to and harvested by a camera pill travelling along the gastrointestinal tract. It focuses on the transmitted electromagnetic (EM) energy in the frequency range of 0.18 to 2450 MHz and compares it to the mechanical energy due to the motion of the pill and the force exerted from the intestine in its peristalsis onto the pill, and the electrochemical energy due to the change of pH along the path of the pill. A comprehensive multilayer EM power transmission model is constructed and implemented in a numerical code, including power attenuation through each layer and multi-reflections at material interfaces. Computer simulations of EM power transmission through a multilayer abdomen to a pill travelling in the intestine are presented for the human abdominal cavity as well as phantom organs and phantom environments, coupled with corresponding experimental studies using these phantom components and environments. Two types of phantom abdomen are investigated: a ballistic gel and a multilayer duck breast. Phantom small intestine involves gelatin gel layers with embedded phantom chyme. Due to limitations related to the energy safety limit of skin exposure and energy losses in the transmission through the abdomen and intestines, inductive range frequencies are recommended which may yield energy harvesting of 10-50 mWh during 8 hours of pill journey, complemented by about 10 mWh of mechanical energy and 10 mWh of electrochemical energy harvesting, in addition to about 330 mWh typically stored in the coin batteries of a camera pill.
    Energy storage is a fundamental requirement for utilising clean but intermittent renewable resources, maintaining a resilient power grid and powering a multitude of portable electric devices and systems. The work presented in this thesis investigates methods of filling the performance gap between electrochemical capacitors (EC) (commonly known as supercapacitors) and batteries; the former often have high power capability but low energy density while the latter often have high energy density but low power capability. Three approaches towards this are taken during this work: first, capacitance balancing of a traditional electrical double-layer capacitor (EDLC) type EC device is attempted by electrode material asymmetry; this approach advances upon previous techniques in which cells have electrode material symmetry but electrode mass asymmetry. The benefits of capacitance balancing were found to be improved device energy density and reduced capacitance loss during long term operation. Second, a novel type of lithium ion capacitor (LIC) which uses a silicon based negative electrode is developed. Such a device was found to offer high power capability (23 kW kg-1) while demonstrating an energy density of over 97 W h kg-1, both values are per total electrode mass. Third, layer-targeted spray deposition was used to deposit multi-walled carbon nanotubes (MWCNTs) at specific locations within an electrode structure. It was found that spray depositing MWCNTs at the outer electrode surface may increase its power capability. A consequence of this targeted deposition may be a reduction in the current collector material alongside improvements in energy storage and power capabilities.
    Mustaza Seri M., Saaj Chakravarthini M., Comin Francisco J., Albukhanajer Wissam A., Mahdi Duale, Lekakou Constantina (2018) Stiffness Control for Soft Surgical Manipulators,International Journal of Humanoid Robotics15(5)1850021 World Scientific Publishing
    Tunable stiffness control is critical for undertaking surgical procedures using soft manipulators. However, active stiffness control in soft continuum manipulators is very challenging and has been rarely realized for real-time surgical applications. Low stiffness at the tip is much preferred for safe navigation of the robot in restricted spaces inside the human body. On the other hand, high stiffness at the tip is demanded for efficiently operating surgical instruments. In this paper, the manipulability and characteristics of a class of soft hyper-redundant manipulator, fabricated using Ecoflex-0050TM silicone, is discussed and a new methodology is introduced to actively tune the stiffness matrix, in real-time, for disturbance rejection and stiffness control. Experimental results are used to derive a more accurate description of the characteristics of the soft manipulator, capture the varying stiffness effects of the actuated arm and consequently offer a more accurate response using closed loop feedback control in real-time. The novel results presented in this paper advances the state-of-the-art of tunable stiffness control in soft continuum manipulators for real-time applications.
    Current laparoscopic techniques for achieving a safe hysterectomy rely heavily on manipulating and stabilizing the uterus using a transvaginal uterine elevator. Commercially available uterine manipulators are rigid in design and lack attributes like flexibility for pose control, force sensing or ease of adaptability. The current technique in using uterine elevator is to have an assistant manually reposition the uterus in response to the surgeon's command. Inefficient response to these commands, lack of experience, poor commands by the surgeon or fatigue are some of the issues arising from the use of the current manipulation technique. Furthermore, the manipulation of a rigid and stiff uterine elevator could potentially damage the uterine wall. A flexible uterine manipulator which can be controlled remotely whilst the surgeon is sitting at the operating console would be a big step forward in advancing robotic gynaecological surgery. These issues motivate this research on the development of an innovative flexible uterine elevator. This research was aimed at developing pneumatically controlled, octopus inspired robotic exible uterine manipulator, GENTLER (Gynaecological ENdoscopic uTerine eLEvatoR), based on soft continuum mechanism with integrated force and pose sensors. The use of soft robotics technology for practical applications requires modelling of the shape, movement and dynamics of the robot. Based on the literature, efforts in modelling the behaviour of this manipulator have focused mainly on kinematic modelling, while dynamics of the system is poorly studied which restricts the full potential of the technology. Another aspect that remains open is robust or stiffness control design of this pneumatically driven soft tube. Variable stiffness control is of prime importance to achieve the accuracy required to satisfy the desired position and force commands. Therefore, this research focused on the development of material-based dynamic modelling, a novel approach to embody the inherent nonlinearity exhibited by soft continuum manipulator as well as the design of real-time tunable stiffness control. Semi-empirical approach was used, which combined both theoretical modelling and experimental analysis of data obtained in laboratory to develop the model and the control architecture. Finally, the proposed modelling approach and control architecture were implemented into the prototype of GENTLER. The working prototype was validated in real-time using ex-vivo testing.
    Rutt Mathew, Lekakou Constantina, Smith Paul, Sordon Alessandro, Santoni Claudio (2018) Methods for Process-related Resin Selection and Optimisation in High-Pressure Resin Transfer Moulding,Materials Science and Technology35(3)pp. 327-335 Taylor & Francis
    A framework for process-related resin selection and optimisation is proposed in the context of research and development for industrial applications of high-pressure resin transfer moulding (HP-RTM). The first stage involves the validation of the reaction kinetics model by differential scanning calorimetry (DSC) and determination of the reaction constants, and the characterisation of viscosity, storage- and viscous-shear moduli by dynamic mechanical analysis (DMA) in a rheometer as a function of time. It also includes capillary pressure measurements for a curing resin impregnating a vertical fibre yarn. Process-related resin selection criteria are based on the optimisation of cycle time, including filling time against gel time, micro-infiltration time and demould time. The proposed framework and the associated test and analysis methodologies have been applied to three epoxy resin systems in connection with carbon fibre reinforcement.
    Mustaza Seri Mastura, Elsayed Y., Lekakou Constantina, Chakravarthini S., Fras J. (2019) Dynamic Modeling of Fiber-Reinforced Soft Manipulator: A Visco-hyperelastic Material-based Continuum Mechanics Approach,Soft Robotics6(3) Mary Ann Liebert
    Robot assisted surgery is gaining popularity worldwide and there is increasing scientific interest to explore the potential of soft continuum robots for minimally invasive surgery. However, the remote control of soft robots is much more challenging compared to their rigid counterparts. Accurate modeling of manipulator dynamics is vital to remotely control the diverse movement configurations and is particularly important for safe interaction with the operating environment. However, current dynamic models applied to soft manipulator systems are simplistic and empirical which restricts the full potential of the new soft robots technology. Therefore, this paper provides a new insight into the development of a nonlinear dynamic model for a soft continuum manipulator based on a material model. The continuum manipulator used in this study is treated as a composite material and a modified non-linear Kelvin-Voigt material model is utilized to embody the visco-hyperelastic dynamics of soft silicone. The Lagrangian approach is applied to derive the equation of motion of the manipulator. Simulation and experimental results prove that this material modeling approach sufficiently captures the nonlinear time- and rate-dependent behavior of a soft manipulator. Material model-based closed-loop trajectory control was implemented to further validate the feasibility of the derived model and increase the performance of the overall system.
    Reece Richard, Lekakou Constantina, Smith Paul (2018) A structural supercapacitor based on activated carbon fabric and a solid electrolyte,Materials Science and Technology35(3)pp. pp 368-375 Taylor & Francis
    This paper presents investigations to create a structural supercapacitor with activated carbon fabric electrodes and a solid composite electrolyte, consisting of organic liquid electrolyte 1 M TEABF4 in propylene carbonate and an epoxy matrix where different compositions were considered of 1:2, 1:1 and 2:1 w/w epoxy: liquid electrolyte. Vacuum-assisted resin transfer moulding was used for the impregnation of the electrolyte mixture into the electrochemical double layer capacitor (EDLC) assembly. The best electrochemical performance was exhibited by the 1:2 w/w epoxy: liquid electrolyte ratio, with a cell equivalent-in-series resistance of 160 W cm2 and a maximum electrode specific capacitance of 101.6 mF g-1 while the flexural modulus and strength were 0.3 GPa and 29.1 MPa, respectively, indicating a solid EDLC device.
    Elsayed Y., Lekakou C., Tomlins P. (2019) Modeling, simulations and optimization of smooth muscle cell tissue engineering for the production of vascular grafts,Biotechnology and Bioengineering116(6)pp. pp 1509-1522 Wiley
    The paper presents a transient, continuum, two?phase model of the tissue engineering in fibrous scaffolds, including transport equations for the flowing culture medium, nutrient and cell concentration with transverse and in?plane diffusion and cell migration, a novel feature of local in?plane transport across a phenomenological pore and innovative layer?by?layer cell filling approach. The model is successfully validated for the smooth muscle cell tissue engineering of a vascular graft using crosslinked, electrospun gelatin fiber scaffolds for both static and dynamic cell culture, the latter in a dynamic bioreactor with a rotating shaft on which the tubular scaffold is attached. Parametric studies evaluate the impact of the scaffold microstructure, cell dynamics, oxygen transport, and static or dynamic conditions on the rate and extent of cell proliferation and depth of oxygen accessibility. An optimized scaffold of 75% dry porosity is proposed that can be tissue engineered into a viable and still fully oxygenated graft of the tunica media of the coronary artery within 2 days in the dynamic bioreactor. Such scaffold also matches the mechanical properties of the tunica media of the human coronary artery and the suture retention strength of a saphenous vein, often used as a coronary artery graft.
    Reece Richard, Lekakou Constantina, Smith Paul A., Grilli Rossana, Trapalis Christos (2019) Sulphur-linked graphitic and graphene oxide platelet-based electrodes for electrochemical double layer capacitors,Journal of Alloys and Compounds792pp. 582-593 Elsevier
    This study presents novel investigations of sulphur-graphitic nanoplatelet (S-GNP) and sulphur-microwave expanded graphene oxide (S-MWGO) composite electrodes for structural electrochemical double layer capacitors (EDLCs) with liquid organic electrolyte 1/M TEABF4 (tetraethylammonium tetrafluoroborate) in propylene carbonate (PC). Elucidating the chemical structure of these electrodes, XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy indicated the presence of CSSC links while mixed EDX (energy dispersive X-ray spectroscopy) elemental maps displayed elemental S outlining the edges of nanoplatelets, concluding the presence of S-links between nanoplatelets. While S-linking improved the mechanical properties and ensured structural integrity of the produced monoliths without the need of any binder, it also decreased the specific surface area of the resulting materials. Furthermore, additional sulphur might have been trapped in other forms, amounting to up to 26/wt% sulphur in the composite graphitic and graphene oxide-based electrodes. Three-point bend testing yielded that an S-GNP-MWCNT monolith with 20/wt% S and 0.24/wt% MWCNT exhibited similar mechanical properties to those of a rigid polyurethane foam. The same S-GNP-MWCNT monolith exhibited an average electrode capacitance of 12.2/F/g?1 during discharge at 2.2/mA/cm2. An S-MWGO-MWCNT monolith electrode with 9.6/wt% S, 16.4/wt% carbon black and 0.24/wt% MWCNT exhibited an average electrode capacitance of 64.9/F/g?1 during discharge at 2.2/mA/cm2 but higher resistance than the S-GNP electrodes.
    Pope Jonathan, Lekakou Constantina (Tina) (2019) Thermoelectric polymer composite yarns and an energy harvesting wearable textile,Smart Materials and Structures28(9)095006pp. 1-14 IOP Publishing
    A thermoelectric wearable is proposed based on an innovative 3d wearable design, with p- type polymer impregnated cotton yarns and n-type polymer impregnated cotton yarns, where the ratio of the p-/n-type yarn cross-sections is optimised to maximise the thermoelectric conversion efficiency. The thermoelectric yarns are embroidered through a double-layer cotton fabric, using plain-stitch, and connected via painted silver electrodag patches. The first stage of this study involved the characterisation of P3HT-, PEDOT:PSS- and PCBM-cotton fabric composite samples, in terms of their fibre volume fraction, specific heat capacity, thermal conductivity, electrical conductivity, Seebeck coefficient, Z and power factors. In this initial assessment, P3HT was selected as the p-type polymer compared to PEDOT:PSS, and PCBM was selected as the n-type polymer. A small, 3d wearable prototype was fabricated and tested: it exhibited a Seebeck coefficient of 380 mV K-1 but a relatively high resistance. It was estimated that scaling up this thermoelectric wearable to body coverage would produce about 1.5-2 mW for a temperature difference of 40 oC applied on the thermoelectric device.
    This project investigated methods for manufacture of electrochemical capacitor, or supercapacitor, -based structural energy storage devices. Investigations were made into introducing structural components to supercapacitor designs, attempting to produce a cell with inherent load-bearing capability and mechanical strength. Design- led developments were also conducted into the combination of supercapacitors with composite materials, in particular embedding energy storage within sandwich panel composites and fibre reinforced polymer composites. Electrochemical and mechanical testing and analysis were performed experimentally on all designs. Electrochemical impedance spectroscopy was carried out at the frequency range 10 mHz to 1 MHz for all manufactured cells. Cyclic voltammetry was undertaken using scan rates in the range 0.5 mV/s to 10 V/s depending on supercapacitor size. Galvanostatic charge-discharge was performed for current densities ranging from 0.5 mA/cm2 to 30 mA/cm2. Together these testing regimes allow for presentation of electrode specific gravimetric capacitance, energy and power, total device specific gravimetric energy and power, and total device volumetric energy and power density. Mechanical testing was undertaken to the three- point bend test standard ASTM.D790, providing results for flexural modulus and strength. Initial investigations were carried out to explore the viability of solid or part-solid electrolytes using epoxy-electrolyte mixes, and mechanically stable electrodes using sulfur-graphene structural coatings doped with carbon nanomaterials. Later developments in the project introduced the incorporation of existing supercapacitor technology with organic liquid electrolytes into composite material panels. Novel contributions were made in the successful design of composite sandwich panels with embedded supercapacitors as structural energy storage devices. These designs used supercapacitor current collectors as multifunctional materials that provide strength to the sandwich panel core. Low and high-density designs were investigated, with additional preliminary work on supercapacitor embedded composite flat panels presented with a view to further development within the subject.
    Markoulidis Foivos, Todorova Nadia, Grilli Rossana, Lekakou Constantina, Trapalis Christos (2019) Composite Electrodes of Activated Carbon and Multiwall Carbon Nanotubes Decorated with Silver Nanoparticles for High Power Energy Storage,Journal of Composites Science3(4)97 MDPI
    Composite materials in electrodes for energy storage devices can combine different materials of high energy density, in terms of high specific surface area and pseudocapacitance, with materials of high power density, in terms of high electrical conductivity and features lowering the contact resistance between electrode and current collector. The present study investigates composite coatings as electrodes for supercapacitors with organic electrolyte 1.5 M TEABF4 in acetonitrile. The composite coatings contain high surface area activated carbon (AC) with only 0.15 wt% multiwall carbon nanotubes (MWCNTs) which, dispersed to their percolation limit, offer high conductivity. The focus of the investigations is on the decoration of MWCNTs with silver nanoparticles, where smaller Ag crystallites of 16.7 nm grew on carboxylic group-functionalized MWCNTs, MWCNT?COOH, against 27?32 nm Ag crystallites grown on unfunctionalized MWCNTs. All Ag-decorated MWCNTs eliminate the contact resistance between the composite electrode and the current collector that exists when undecorated MWCNTs are used in the composite electrodes. Ag-decorated MWCNT?COOH tripled the power density and Ag-decorated MWCNT additive doubled the power density and increased the maximum energy density by 6%, due to pseudocapacitance of Ag, compared to composite electrodes with undecorated MWCNTs.
    Within this project, investigations have been made into the materials and processes involved in resin transfer moulding (RTM), the process used to produce McLaren Automotive?s mono-cell, used as the monocoque in its various models. Following an assessment of the literature surrounding RTM and an analysis of the state-of-the-art technology on the market, fundamental material property data was obtained for multiple components used in the production of the mono-cell. These materials include matrix resin, carbon fibre, preform binder, assembly adhesive, structural foams, primer and aluminium. A framework for process-related resin selection and optimisation was produced to increase prospective matrix system assessment and reduce the cost of doing so through an efficient regime of investigations into cycle time, including filling time against gel time, micro-infiltration time and demould time. Reaction kinetics modelling using differential scanning calorimetry (DSC) and characterisation of viscosity, storage- and viscous-shear moduli by dynamic mechanical analysis (DMA) in a rheometer were used in the initial down selection while further investigations were performed using capillary pressure measurements of curing resin impregnating a fibre yarn. Investigations were carried out into the optimised usage of binder and adhesive additives in conjunction with fibre reinforcements in the RTM process. Their effect on the processability and final product quality was assessed through the use of mechanical testing and microscopy. Structural foams and metallic inserts were investigated as comoulded assemblies for their processability and in-service performance through the use of mechanical and contact angle testing, microscopy and DSC measurements. The data obtained from the investigations into each material and their interactions with each other and the high-pressure RTM (HP-RTM) process as well as the methodologies of investigation have been adopted to optimise McLaren Automotive?s mono-cell production process through the timely and cost-effective production of data transferrable to large scale composite component manufacture.
    Markoulidis Foivos, Bates Josh, Lekakou Constantina, Slade Bob, Laudone Guliano M. (2020) Supercapacitors with lithium-ion electrolyte: an experimental study and design of the activated carbon electrodes via modelling and simulations,Carbon Elsevier
    Electrochemical double layer capacitors (EDLCs) are investigated with activated carbon electrodes and a lithium-ion electrolyte, in anticipation of potential future applications in hybridised battery-supercapacitor devices and lithium ion capacitors. An experimental study of a symmetric electrochemical double layer capacitor (EDLC) with activated carbon (AC) electrodes on aluminium foil current collectors and electrolyte 1 M LiPF6 in EC:EMC 50:50 v/v concludes a stability window to a maximum potential of 3 V, an equivalent in series resistance of 48 ohm for 1 cm2 cell area (including the contact resistance between electrode and current collector) and an average specific electrode capacitance of 50.5 F g-1. Three AC electrode materials are assessed via computer simulations based on a continuum ion and charge transport model with volume-averaged equations, considering the pore size distribution for each electrode material and, depending on pore size, transport of tetrahedral solvated or flat solvated Li+ ions and solvated or desolvated PF6- ions. The computer simulations demonstrate that the best electrode material is an AC coating electrode with a hierarchical pore size distribution measured in the range of 0.5-180 nm and bimodal shape, and specific surface area BET = 808 m2 g-1.
    Reece Richard, Lekakou Constantina, Smith Paul A. (2020) A High-Performance Structural Supercapacitor,ACS Applied Materials and Interfaces American Chemical Society
    Considering the low specific capacitance of structural solid supercapacitors, which is due to the low ion diffusivity in solid electrolytes and the small specific surface area of some structural electrodes such as carbon fiber fabrics, novel structural supercapacitor designs are proposed and evaluated in this study based on supercapacitor-functional sandwich composite materials. Typical electrochemical double layer capacitors (EDLCs) are proposed with liquid organic electrolyte 1 M TEABF4 in PC (propylene carbonate). In the innovative sandwich structured composites, supercapacitors are embedded in the skins and integrated in the honeycomb core where the aluminium faces of the core constitute the current collectors of the supercapacitor-functional core. The sandwich composite material exhibited a flexural modulus of 5.07 GPa and a flexural strength of 413.9 MPa. The EDLCs embedded in the skins increased the skin flexural modulus and strength by 47% and 56%, respectively, for embedded lateral EDLCs, and by 91% and 106%, respectively, for embedded lateral and longitudinal EDLCs. Compared to typical EDLCs with the same electrolyte, the structural supercapacitors in this study demonstrated superior specific electrode capacitance, Csp,el = 153 F g-1 for the honeycomb supercapacitor and Csp,el = 95.7 F g-1 for the skin supercapacitor, translating to overall structural composite material performance of 0.68 Wh/m2honeycomb and 30.5 W/m2honeycomb for the supercapacitor-functional honeycomb, and 0.02 Wh/m2skin and 5.4 W/m2skin for the supercapacitor-functional skin.
    Lei Chunhong, Fields Richard, Wilson Peter, Lekakou Constantina, Amini Negar, Tennison Stephen, Perry John, Gosso Michele, Martorana Brunetto (2020) Development and evaluation of a composite supercapacitor-based 12 V transient start-stop (TSS) power system for vehicles: modelling, design and fabrication scaling up,Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy SAGE Publications
    The study involves a bottom-up approach, from bottom cells to large supercapacitor pouch cells, encompassing the design, modelling and fabrication stages of the cells leading to a 12 V transient start-stop (TSS) power system for automotive applications. More specifically, the design of a large composite supercapacitor is presented, consisting of a high power density component and a high energy density component, hybridised at material level. The composition of the composite supercapacitor is optimised to be application-specific so that it satisfies a specified energy-to-maximum power ratio for the 12 V TSS system. The testing of the large composite supercapacitor pouch cells and the 12 V TSS system proves the validity of the bottom-up approach, validates the design and the proposed electric circuit model and its parameters, fitted according to experimental data of small laboratory cells and applied successfully to the large cells, and proves the high quality of the scaled up fabrication processes. The 12 V TSS power system of seven large composite supercapacitor cells satisfies the set criteria of energy and maximum power for the specified duration, 15 Wh and 4.2 kW respectively, at a total mass of 3.94 kg, below the original set limit of 5 kg.

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