Dr Carol Crean


Reader in Physical and Materials Chemistry
+44 (0)1483 686640
30 AZ 03
08:15 - 17:00 (Mon-Thurs) 08:15 - 14.15 (Fri)

Academic and research departments

Department of Chemistry.

Biography

Areas of specialism

Materials Chemistry; Flexible electrode materials; Textile electrodes for healthcare applications; Materials for Energy storage

University roles and responsibilities

  • Director of Employability

    My qualifications

    BSc (Hons) in Chemistry with German
    Dublin City University, Ireland
    PhD in Chemistry
    Dublin City University, Ireland
    Graduate Certificate in Learning and Teaching
    University of Surrey, UK

    Research

    Research interests

    Research collaborations

    Supervision

    Postgraduate research supervision

    Completed postgraduate research projects I have supervised

    My teaching

    My publications

    Publications

    WILLIAM LOCKLEY, Carol Crean, John R Varcoe Modern Raman spectromicroscopy: Some early investigations with deuterated compounds, In: JOURNAL OF LABELLED COMPOUNDS & RADIOPHARMACEUTICALS5pp. 465-466 Wiley

    Raman spectroscopy is used less commonly than other spectroscopic techniques by isotopic chemists. The University of Surrey has recently become a regional centre for the technique following our acquisition of a powerful high-resolution multi-laser Raman spectromicroscope (Renishaw inVia, model RE04, via EPSRC grant EP/M022749/1). This poster reports some early experience with the technique as applied to the analysis of deuterated compounds. The spectrometer is based around Raman scattering from any of five lasers ranging from the ultraviolet to blue, green, red and near infrared (244–785 nm). The sampling beam has an area of just 2-10µm and hence the spectrometer has the ability to automatically scan tiny sample areas, offering the possibility of obtaining Raman imaging for 2-D and (via confocality) even 3-D samples. Investigations into isotopic applications of these multidimensional abilities are in progress.  The high resolution of the system also enables excellent spectra to be recorded from very tiny samples, e.g. from a small part of this 200µm crystal of [2H8]naphthalene.  The poster provides examples of the following advantages when deuterated compounds are analysed by Raman:Improved sensitivity is available via powerful lasers and digital spectral accumulationRapid generation of high quality one-dimensional Raman spectra from various sample typesLow matrix effects for glass enables direct analysis within ordinary sealed glass lab vialsHigh spectral and spacial resolution provides the ability to work with tiny samples/areasHighly specific results, as vibrational modes can be very sensitive to isotopic substitutionDirect quantitative analysis of isotopic mixtures is possible by selecting the appropriate peaksLow background from silicagel means TLC & HPTLC applications are possibleSurface enhanced Raman spectra (SERS) can be simply obtained via stable silver colloids

    SUAD SAEED ALGHAMDI, S BENNETT, CAROL CREAN, Joydip Ghosh , Harry Gibbard, Robert Moss , Justin Reiss, Douglas Wolfe, PAUL JONATHAN SELLIN (2022)Polycrystalline Formamidinium Lead Bromide X-ray Detectors, In: Applied sciences12(4)2013 MDPI
    James B Robinson, Kai Xi, Vasant Kumar, Andrea C Ferrari, Heather Au, Maria-Magdalena Titirici, Andres Parra-Puerto, Anthony R Kucernak, Samuel D S Fitch, Nuria Garcia-Araez, Zachary L Brown, Mauro Pasta, Liam Furness, Alexander J Kibler, Darren A Walsh, Lee R Johnson, Conrad Holc, Graham N Newton, Neil R Champness, Foivos Markoulidis, Carol Crean, Robert C T Slade, Eleftherios I Andritsos, Qiong Cai, Shumaila Babar, Teng Zhang, Constantina Lekakou, Nivedita Kulkarni, Alexander J E Rettie, Rhodri Jervis, Michael Cornish, Monica Marinescu, Gregory Offer, Zhuangnan Li, Liam Bird, Clare P Grey, Manish Chhowalla, Daniele Di Lecce, Rhodri E Owen, Thomas S Miller, Dan J L Brett, Sebastien Liatard, David Ainsworth, Paul R Shearing (2022)2021 roadmap on lithium sulfur batteries, In: JPhys Energy3(3)031501 IOP Publishing

    Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space.

    Ahmad I. Ayesh, SUAD SAEED ALGHAMDI, Belal Salah, S.H. Bennett, CAROL CREAN, PAUL JONATHAN SELLIN (2022)High sensitivity H2S gas sensors using lead halide perovskite nanoparticles, In: Results in physics35105333 Elsevier
    C Crean, C Mcgeough, R O'Kennedy (2012)Wearable biosensors for medical applications, In: Biosensors for Medical Applicationspp. 301-330 Woodhead Publishing

    Over the past decade, the design and development of wearable sensors for biomedical applications has garnered considerable attention in the scientifi c community and in industry. This chapter aims to review research conducted into wearable sensors for healthcare monitoring. Acceptance of this approach in observation of physiological data depends strongly on the cost, wearability, usability and performance of such devices. An outline of body sensor network systems (and applications of wearable computing devices) is provided with a summary of electronic textiles. A synopsis of the clinical applications of this type of technology is given at the end of the chapter © 2012 Woodhead Publishing Limited All rights reserved.

    Rachel E. Smith, Stella Totti, Eirini Velliou, Paola Campagnolo, Suzanne M. Hingley-Wilson, Neil I. Ward, John R. Varcoe, Carol Crean (2019)Development of a novel highly conductive and flexible cotton yarn for wearable pH sensor technology, In: Sensors and Actuators B: Chemical287pp. 338-345 Elsevier

    The simple and effective approach of “dipping and drying” cotton yarn in a dispersion of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNT) resulted in the development of a highly conductive and flexible cotton fibres. Subsequent polyaniline (PANi) deposition yielded electrodes with significant biocompatible and antibacterial properties that could be fabricated (alongside quasi-reference electrodes) into solid-state wearable pH sensors, which achieve rapid, selective, and Nernstian responses (-61 ± 2 mV pH-1) over a wide pH range (2.0 – 12.0), even in a pH-adjusted artificial sweat matrix. This development represents an important progression towards the realisation of real-time, on-body, wearable sensors.

    Jose Garcia-Torres, Carol Crean (2017)Multilayered Flexible Fibers with High Performance for Wearable Supercapacitor Applications, In: Advanced Sustainable Systems2(2)1700143 Wiley

    Multilayered flexible fibers, consisting of carbon black-carbon nanotube fibers, manganese oxides and conducting polymers, were fabricated for use as electrodes in supercapacitors. Carbon-based fibers were initially prepared by wet-spinning using carbon-based nanomaterials (carbon black and carbon nanotubes) and chitosan as a matrix. Subsequent coatings with manganese oxides and conducting polymers form a multilayered structure. Different MnO2 crystalline structures (ε-MnO2, γ-MnO2) were grown onto the fibre by electrodeposition and different conducting polymers (polyethylenedioxythiophene and polypyrrole) used as a conductive wrapping. Each layer improved the performance of the fibre by adding different functionalities. While MnO2 improved the capacitance of the fibre, the presence of conducting polymers creates a conductive network increasing the capacitance further and conferring cycling stability. Capacitance values up 600 F g-1 and capacitance retention of 90% can be achieved with these multilayered hybrid fibers. A symmetric supercapacitor device, prepared from two hybrid fibres showed no significant change in properties when the device was bent, demonstrating their potential in flexible electronic devices and wearable energy systems.

    Sutthima Sriprasertsuk, Simone C. Mathias, John R. Varcoe, Carol Crean (2021)Polypyrrole-coated carbon fibre electrodes for paracetamol and clozapine drug sensing, In: Journal of Electroanalytical Chemistry897115608 Elsevier

    Polypyrrole (PPy) fibre electrodes were studied to determine their ability to sense paracetamol (as a model drug) in the presence of the interferents dopamine and ascorbic acid. PPy was electropolymerised onto carbon fibres using cyclic voltammetry in the presence of two different counter anions: sodium dodecyl sulfate (SDS) and potassium nitrate (KNO3). The surface of the PPy.SDS and PPy.KNO3 fibre electrodes was characterised using Raman spectroscopy and scanning electron microscopy. The PPy.SDS-coated carbon fibre had a 14-fold larger electrochemical surface area compared to a bare carbon fibre (calculated using the Randles-Sevcik equation). The use of a large counter anion as dopant (dodecyl sulfate) produced fibres with a greater drug sensing response (cf. the use of smaller nitrate anion). The use of the PPy.SDS fibre electrode in differential pulse voltammetry (DPV) allowed sensing of paracetamol with a detection limit (3σ S/N) of 34 µM. For the anodic peak current (0.5 V vs. Ag/AgCl), a linear response range was observed for 50–500 µM. At a paracetamol concentration of 100 µM, the DPV anodic peak current (at 0.5 V vs. Ag/AgCl) was unaffected by the addition of interferents: 100 µM dopamine and 100 µM ascorbic acid. A real-world application of drug sensing was trialled with the anti-psychotic medication clozapine; where the PPy.SDS carbon fibre could sense clozapine with a detection limit of (3σ S/N) of 6 µM and a sensitivity of 15 μA cm−2 μmol−1 L.

    Daniel O. Reid, Rachel Smith, Jose Garcia-Torres, John J. Watts, Carol Crean (2019)Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing, In: Sensors19(19)4213pp. 1-10 MDPI

    There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 μm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm−1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.

    RACHIDA BANCE-SOUALHI, MOHAMMADMEHDI CHOOLAEI, SIAN ALICE FRANKLIN, TERRENCE WILLSON, Judy Lee, DANIEL KEITH WHELLIGAN, CAROL CREAN, JOHN VARCOE (2021)Radiation-grafted anion-exchange membranes for reverse electrodialysis: a comparison of N,N,N′,N′-tetramethylhexane-1,6-diamine crosslinking (amination stage) and divinylbenzene crosslinking (grafting stage), In: Dataset The Royal Society of Chemistry

    Radiation-grafted anion-exchange membranes (RG-AEM) are being developed to evaluate a range of chemistries that have relevance to a variety of electrochemical applications including reverse electrodialysis (RED) salinity gradient power. RG-AEMs are typically fabricated using an electron-beam activated (peroxidated) polymer substrate film. These activated films are first grafted with a monomer, such as vinylbenzyl chloride (VBC) and then reacted with a variety of tertiary amines to yield the desired RG-AEMs. The amination process forms covalently bound quaternary ammonium (QA) head-groups that allow the RG-AEMs to conduct anions such as Cl−. RG-AEMs are of interest as they exhibit high conductivities (100 mS cm−1 at elevated temperatures when containing Cl− anions). However, the current generation of RG-AEMs have two main Achilles' heels: (1) they exhibit low permselectivities; and (2) they exhibit a high degree of swelling in water. Introducing covalent crosslinking into ion-exchange membranes is a well-known strategy to overcome these issues but it often comes with a price – a significantly lowered conductivity (raised in situ resistance). Therefore, the level of crosslinking must be carefully optimised. RG-AEMs can be primarily crosslinked using two methods: (1) introduction of a divinyl monomer into the monomer mixture used during grafting; or (2) introduction of a diamine agent into the amination process. This study looks into both methods where either divinylbenzene (DVB) is added into the grafting mixture or N,N,N′,N′-tetramethylhexane-1,6-diamine (TMHDA) is added into the amination mixture. We show that on the balance of two application-relevant properties (resistances in aqueous NaCl (0.5 mol dm−3) solution and permselectivity), the diamine crosslinking method is the most effective for RG-AEMs being used in RED cells.

    Emily A. M. Smith, Yuqing Liu, Chris Stirling, David J. Watson, Robert C. T. Slade, Jun Chen, Carol Crean (2019)Plasma functionalisation of few-layer graphenes and carbon nanotubes for graphene microsupercapacitors, In: Electrochimica Acta Elsevier

    Plasma processing, as a commercial and large-scale technology, was used to functionalize few-layer graphene (FLG) and multi-walled carbon nanotubes (MWCNT) in this work. The successful functionalities of FLG and MWCNT have been confirmed by elemental microanalysis, X-ray photoelectron spectroscopy, acid-base titration and zeta potential measurements. With the assistance of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT/PSS), a water-dispersible and conductive polymer, a composite of functionalized FLG and MWCNT was fabricated into large-size flexible films and also interdigitated microelectrodes for microsupercapacitor application via simple and scalable techniques (i.e. doctor blading and laser-etching). When normalised by volume and area, the device made from FLG(NH3)-MWCNT(Acid) (19.9 F cm-3 at 5 mV s-1 and 12.2 F cm-3 at 200 mV s-1) and FLG-MWCNT(Acid) (19.5 mF cm-2 at 5 mV s-1 and 12.8 mF cm-2 at 200 mV s-1) show the best performing composites, respectively, indicating how effective functionalization of FLG and MWCNT is for the enhancement of electrochemical capacitance. In-situ Raman microscopy confirmed the reversible pseudo-capacitive behaviour of electrode materials and the stable electrochemical performance of the devices. The facile techniques used in this work and the good device performance show their great potential for wearable applications.

    Mona N. Sweilam, Sarah F. Cordery, Stella Totti, Eirini G. Velliou, Paola Campagnolo, John R. Varcoe, M. Begoña Delgado-Charro, Carol Crean (2020)Textile-based non-invasive lithium drug monitoring: a proof-of-concept study for wearable sensing, In: Biosensors and Bioelectronics150111897 Elsevier

    Flexible wearable chemical sensors are emerging tools which target diagnosis and monitoring of medical conditions. One of the potential applications of wearable chemical sensors is therapeutic drug monitoring for drugs that have a narrow therapeutic range such as lithium. We have investigated the possibility of developing a fibre-based device for non-invasive lithium drug monitoring in interstitial fluid. A flexible cotton-based lithium sensor was coupled with a carbon fibre-based reference electrode to obtain a potentiometric device. In vitro reverse iontophoresis experiments were performed to extract Li+ from under porcine skin by applying a current density of 0.4 mA cm-2 via two electrodes. Carbon fibre-based reverse iontophoresis electrodes were fabricated and used instead of a conventional silver wire-based version and comparable results were obtained. The fibre-based Li+ sensor and reference electrodes were capable of determining the Li+ concentration in samples collected via reverse iontophoresis and the results compared well to those obtained by ion chromatography. Additionally, biocompatibility of the used materials have been tested. Promising results were obtained which confirm the possibility of monitoring lithium in interstitial fluid using a wearable sensor.

    M Schulz, C Crean, R Brinkhuis, R.P Sear, J.L Keddie (2021)Determination of parameters for self-stratification in bimodal colloidal coatings using Raman depth profiling, In: Progress in Organic Coatings157106272 Elsevier B.V

    In waterborne mixtures of colloidal particles with differing sizes, the spontaneous stratification of one species of particle in a coating – driven by diffusiophoresis - offers the possibility to tailor the surface properties. However, despite strong research interest in stratification in recent years, the acceptable range of experimental parameters has not been fully explored, and the extent of stratification that is achievable has not yet been quantified. Here, we study the stratification of bimodal mixtures of waterborne polyurethane particles mixed with larger acrylic particles. We use ultra-low angle microtoming to prepare cross-sections of coating samples and analyse compositions quantitatively with Raman mapping. We use this method to obtain high-resolution depth profiles of the polyurethane phase in the coating with spacing between measurements corresponding to a few tens of nm. We experimentally test a model of diffusiophoresis and observe stratification when the processing parameters (evaporation rates, film thickness, and volume fraction of small particles) fall within the required range. Samples that exhibit stratification have top layer thicknesses on the order of tens of μm, which is a significant depth for exploitation in coatings aiming to modify surface properties. To guide the design of coatings in applications, we draw on the model to define the range of parameters in which self-stratification is expected. Our results provide a fundamental understanding that will enable the fabrication of tailored coatings in which the properties of the surface differ from the bulk material.

    Khaled Yahya Alqurashi, Carol Crean, James R. Kelly, Tim W. C. Brown, Mohsen Khalily (2019)Liquid Metal Application for Continuously Tunable Frequency Reconfigurable Antenna, In: Proceedings of the 13th European Conference on Antennas and Propagation (EuCAP 2019) Institute of Electrical and Electronics Engineers (IEEE)

    This paper presents two different designs for frequency reconfigurable antennas capable of continuous tuning. The radiator, for both antenna designs, is a microstrip patch, formed from liquid metal, contained within a microfluidic channel structure. Both patch designs are aperture fed. The microfluidic channel structures are made from polydimethylsiloxane (PDMS). The microfluidic channel structure for the first design has a meander layout and incorporates rows of posts. The simulated antenna provides a frequency tuning range of approximately 118% (i.e. 4.36 GHz) over the frequency range from 1.51 GHz to 5.87 GHz. An experimental result for the fully filled case shows a resonance at 1.49 GHz (1.3% error compared with the simulation). Experienced rheological behavior of the liquid metal necessitates microfluidic channel modifications. For that reason, we modified the channel structure used to realise the radiating patch for the second design. Straight channels are implemented in the second microfluidic device. According to simulation the design yields a frequency tuning range of about 77% (i.e. 3.28 GHz) from 2.62 GHz to 5.90 GHz.

    Jose Garcia-Torres, Alexander J. Roberts, Robert C.T. Slade, Carol Crean (2019)One-step wet-spinning process of CB/CNT/MnO2 nanotubes hybrid flexible fibres as electrodes for wearable supercapacitors, In: Electrochimica Acta296pp. 481-490 Elsevier

    Fibres made from different nanostructured carbons (carbon black (CB)), carbon nanotubes (CNT) and CB/CNT were successfully developed by wet-spinning. The variation of dispersion conditions (carbon nanomaterial concentration, dispersant/Carbon nanomaterial concentration ratio, CB/CNT concentration ratio, pH) resulted in different electrochemical performance for each type of fibres. Fibres with the best capacitance values (10 F g-1) and good cycling stability (89%) were obtained from fibres containing 10% carbon black and 90% carbon nanotubes. A solid-state supercapacitor was fabricated by assembling the CB/CNT fibres resulting in 9.2 F g-1 electrode capacitance. Incorporation of 0.2 wt.% birnessite-type potassium manganese oxide nanotubes dramatically increased the capacitance of the fibres up to 246 F g-1 due to the high specific capacitance of birnessite phase and the tubular nature of the nanomaterial.

    C.S. Nagi, S.L. Ogin, I. Mohagheghian, C. Crean, A.D. Foreman (2018)Interlaminar Toughening of Carbon Fibre Reinforced Polymers using Graphene / Thermoplastic Inserts, In: Proceedings of ECCM 18 - 18th European Conference on Composite Materials European Society for Composite Materials

    This paper outlines preliminary work developing graphene modified thermoplastic inserts to be used for the toughening of CFRP. The paper outlines laminate manufacture, mechanical testing and fracture analysis of graphene modified CFRP.

    Jose Garcia-Torres, Carol Crean, Elisa Vallés (2017)Co-Ni-carbon flexible composite fibres for directional magnetic actuation, In: Materials & Design141pp. 9-16 Elsevier

    Flexible microcomponents are being widely employed in the microelectronic industry; however; they suffer from a lack of complex movement. To address this problem, we have developed flexible, electrically conductive, magnetic composite fibres showing complex motion in three dimensions with the capacity to be selectively actuated. Flexible carbon-based fibres were prepared by wet-spinning and were subsequently modified by electrodepositing Co-Ni. The high aspect ratio of the fibre (40 μm diameter, 3.5 cm length) causes a directional dependence in the magnetostatic energy, which will allow for anisotropic actuation of the composite. Thus, the application of magnetic fields allows for a precise control of the movement with high reproducibility and accuracy.

    W Lee, Carol Crean, John Varcoe, Rachida Bance-Soualhi (2017)A Raman spectro-microscopic investigation of ETFE-based radiation-grafted anion-exchange membranes, In: RSC Advances7pp. 47726-47737 Royal Society of Chemistry

    This study used Raman spectro-microscopy to investigate the synthesis and degradation of radiation-grafted anion-exchange membranes (RG-AEM) made using 50 μm thick poly(ethylene-co-tetrafluoroethylene) (ETFE) films, vinylbenzyl chloride (VBC) monomer, and 1-methylpyrrolidine (MPY) amination agent. The data obtained confirmed the operation of the grafting-front mechanism. VBC grafting times of 1 and 4 h led to low degrees of grafting homogeneity, while 72 h led to extreme levels of grafting that resulted in mechanically weak RG-AEMs due to the excessive H2O contents. A grafting time of 16 h was optimal yielding a RG-AEM with an ion-exchange capacity (IEC) of 2.06 ± 0.02 mmol g-1 (n = 3). An excess of grafting was detected at the surface of this RG-AEM (at least within the first few μm of the surface). This RG-AEM was then degraded in O2-purged aqueous KOH (1.0 mol dm-3) for 14 d at 80 °C. Degradation was detected throughout the RG-AEM cross-section, where the Raman data was quantitatively consistent with the loss of IEC. A slight excess of degradation was detected at the surface of the RG-AEM. Degradation involved the loss of whole benzyl-1-methypyrrolidinium grafted units as well as the direct attack on the pendent (cationic) pyrrolidinium groups by the hydroxide anions.

    N Gilmartin, C Crean (2014)Nanoparticle technologies in detection science, In: RSC Detection Science2014-J(3)pp. 116-141
    Mona N. Sweilam, John R. Varcoe, Carol Crean (2018)Fabrication and Optimization of Fiber-Based Lithium Sensor: A Step towards Wearable Sensors for Lithium Drug Monitoring in Interstitial Fluid, In: ACS Sensors3(9)pp. 1802-1810 American Chemical Society

    A miniaturized, flexible fiber-based lithium sensor was fabricated from low-cost cotton using a simple, repeatable dip-coating technique. This lithium sensor is highly suited for ready-to-use wearable applications and can be used directly without the preconditioning steps normally required with traditional ion-selective electrodes. The sensor has a stable, rapid and accurate response over a wide Li+ concentration range that spans over the clinically effective and the toxic concentration limits for lithium in human serum. The sensor is selective to Li+ in human plasma even in the presence of a high concentration of Na+ ions. This novel sensor concept represents a significant advance in wearable sensor technology which will target lithium drug monitoring from under the skin.

    Khaled Alqurashi, James R. Kelly, Zhengpeng Wang, Carol Crean, Raj Mittra, Mohsen Khalily, Yue Gao (2020)Liquid Metal Bandwidth-Reconfigurable Antenna, In: IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS19(1)pp. 218-222 Institute of Electrical and Electronics Engineers

    This letter shows how slugs of liquid metal can be used to connect/disconnect large areas of metalization and achieve a radiation performance not possible by using conventional switches. The proposed antenna can switch its operating bandwidth between ultrawideband and narrowband by connecting/disconnecting the ground plane for the feedline from that of the radiator. This could be achieved by using conventional semiconductor switches. However, such switches provide point-like contacts. Consequently, there are gaps in electrical contact between the switches. Surface currents, flowing around these gaps, lead to significant back radiation. In this letter, the slugs of a liquid metal are used to completely fill the gaps. This significantly reduces the back radiation, increases the bore-sight gain, and produces a pattern identical to that of a conventional microstrip patch antenna. Specifically, the realized gain and total efficiency are increased by 2 dBi and 24%, respectively. The antenna has potential applications in wireless systems employing cognitive radio (CR) and spectrum aggregation.

    José García-Torres, Carol Crean (2018)Ternary composite solid-state flexible supercapacitor based on nanocarbons/manganese dioxide/PEDOT:PSS fibres, In: Materials & Design155pp. 194-202 Elsevier

    Flexible fibre supercapacitors were fabricated by wet-spinning from carbon nanotube/carbon black dispersions, followed by straightforward surface treatments to sequentially deposit MnO2 and PEDOT:PSS to make ternary composite fibres. Dip coating the fibres after the initial wet-spinning coagulation creates a simple solution-based continuous process to produce fibre-based energy storage. Well-controlled depositions were achieved and have been optimised at each stage to yield the highest specific capacitance. A single ternary composite fibre exhibited a specific capacitance of 351 F g−1. Two ternary composite fibre electrodes were assembled together in a parallel solid-state device, with polyvinyl alcohol/H3PO4 gel used as both an electrolyte and a separator. The assembled flexible device exhibited a high specific capacitance of 51.3 F g−1 with excellent both charge-discharge cycling (84.2% capacitance retention after 1000 cycles) and deformation cycling stability (82.1% capacitance retention after 1000 bending cycles).