Professor Mike Hughes

Professor of Biomedical Engineering and Director of the Centre for Biomedical Engineering

Qualifications: MEng(Wales), PhD(Wales), CPhys, MInstP, MIEEE, MIoN

Email:
Phone: Work: 01483 68 6775
Room no: 19 AA 02

Further information

Biography

Hailing from Holy Island off the Welsh coast, Professor Michael Pycraft Hughes was appointed Professor of Biomedical Engineering in 2008 after joining the University of Surrey as a lecturer in 1999.  His 20-year research career has focussed on the development of dielectrophoresis (DEP) – a force causing particles to move in non-uniform electric fields.  His work relates primarily to the development of DEP-based assays. DEP can be used to analyse, and selectively move or separate micro- and nano-particles, and has been applied to cancer cells, bacteria, stem cells, yeast, DNA, viruses, carbon nanotubes and nanowires, and which has led to the founding of a spin-out company to commercialise DEP technology (see “research interests” below). He also has broader interests in electric fields and cells at the microscale, and has published work with DSTL on sensor enhancement using microfluidics (which resulted in three patent applications), microelectrode devices for neural sensing, and simulations of laser removal of tattoos. He has written or co-written over 50 journal publications (making him one of the most published authors in the field of DEP) and two books, and has presented invited talks in the UK, US, France, Spain, China and India. He has been the Editor in Chief of IEEE Transactions on Nanobioscience since 2008 (Senior Editor 2005-2007), and serves as committee member for the Institute of Physics Dielectrics Society, the IEEE Nanotechnology Council, the International Council for Science Working Group on Nanomaterials, and the Engineering in Medicine and Biology Society.  

Since 2008, Mike has been Director of the Centre for Biomedical Engineering at the University of Surrey, one of the oldest since centres in the world (the first appointment having been made in 1965).  From 2008-2012, he also acted as Course Director of the MSc programme in Biomedical Engineering at Surrey (running since 1966) and from 2001-12 acted as course lead for the B/MEng Medical Engineering programmes.  

Research Interests

One of the main themes of the group has been the development of technology to enable DEP to be more widely used.  DEP has been applied to biology for over half a century but uptake has been low because research elsewhere has led to more costly and cumbersome devices.  The Surrey group has pioneered the development of technology that is low-cost, user-friendly and which complies with the needs of the user rather than the designer; to this end Mike has co-founded a company – DEPtech (www.deptech.com) – to bring the technology developed and patented by the Surrey group (the “DEP-well” and “DEP-dot” platforms) to market, with the first product - the 3DEP reader, based on the DEP-wells - now available.

DEP work within the group divides approximately into cellular and nano-scale DEP.  Cell work has largely focussed on the development of the 3DEP reader and associated technology, the DEP-DOT system for cell clustering, and cell separation and focussing using AC electro-osmosis.  Projects with collaborators have developed the applications of the equipment, using DEP to determine the electrical properties of cancer cells, both as a diagnostic tool and to assess aspects of cancer biology and drug discovery, and have also looked at stem cells and bacteria.  On the nanoscale, work has focussed on the electrical properties of nanoparticles in suspension, and has looked at DNA, nanowires and carbon nanotubes as well as exploring the underlying theories of particle behaviour.  

Research Collaborations

Collaborators in the University include Fatima Labeed (Biomedical Engineering), Maxim Shkunov (Electronics), Chris Fry, Rita Jabr and Helen Coley (Health and Medical Sciences).  Collaborators in other institutions include Stefano Fedele and Stephen Porter (Eastman Dental Institute), Lisa Flanagan (University of California Irvine) and Mark Lewis (Loughborough University).

Publications

Highlights

  • Hoettges KF, Hubner Y, Broche LM, Ogin SL, Kass GEN, Hughes MP. (2008) 'Dielectrophoresis-activated multiwell plate for label-free high-throughput drug assessment'. ANALYTICAL CHEMISTRY, 80 (6), pp. 2063-2068.
  • Fatoyinbo HO, Hoettges KF, Hughes MP, Broche L. (2008) 'Rapid-on-chip determination of dielectric properties of biological cells using imaging techniques in a dielectrophoresis dot microsystem'. ELECTROPHORESIS, 29 (1), pp. 3-10.

Journal articles

  • Faraghat S, Hoettges K , Steinbach M, Van Der Veen DR, Brackenbury W, Henslee E , Labeed F , Hughes MP. (2017) 'High-Throughput, Low-Loss, Low-Cost and Label-Free Cell Separation using Electrophysiology Activated Cell Enrichment (EPACE)'. Proceedings of the National Academy of Sciences, 114 (8), pp. pp. 4591-4596.

    Abstract

    Currently, cell separation occurs almost exclusively by density gradient methods and by fluorescence- and magnetic-activated cell sorting (FACS/MACS). These variously suffer from lack of specificity, high cell loss, use of labels, and high capital/operating cost. We present a dielectrophoresis (DEP)-based cell separation method, using 3D electrodes on a low-cost disposable chip; one cell type is allowed to pass through the chip whilst the other is retained and subsequently recovered. The method advances usability and throughput of DEP separation by orders of magnitude in throughput, efficiency, purity, recovery (cells arriving in the correct output fraction), cell losses (those which are unaccounted for at the end of the separation) and cost. The system was evaluated using three example separations; live and dead yeast; human cancer cells/red blood cells; and rodent fibroblasts/red blood cells. A single-pass protocol can enrich cells with cell recovery of up to 91.3% at over 300,000 cells/second with >3% cell loss. A two-pass protocol can process 300,000,000 cells in under 30 minutes, with cell recovery of up to 96.4% and cell losses below 5%, an effective processing rate >160,000 cells/second. A three-step protocol is shown to be effective for removal of 99.1% of RBCs spiked with 1% cancer cells, whilst maintaining a processing rate of ~170,000 cells/second. Furthermore, the self-contained and low-cost nature of the separator device means that it has potential application in low-contamination applications such as cell therapies, where GMP compatibility is of paramount importance. Significance statement. Cell separation is a fundamental process in biomedicine, but is presently complicated, cumbersome and expensive. We present a technique that can sort cells at a rate equivalent to or faster than gold-standard techniques such as FACS and MACs, but can do label-free and with very low cell loss. The system uses dielectrophoresis (DEP) to sort cells electrostatically, using a novel electrode chip that eschews microfabrication in favour of a laminate drilled with 397 electrode-bearing wells. This high level of parallelisation makes the system immune to the bubbles that limit labs-on-chip, whilst also increasing capacity and throughput to unprecedented levels, whilst the chip is cheap enough to be disposable, preventing inter-separation contamination.

  • Constantinou M, Hoettges K , Krylyuk S, Katz M, Davydov A, Rigas GP, Stolojan V , Hughes MP, Shkunov M . (2017) 'Rapid determination of nanowires electrical properties using a dielectrophoresis-well based system'. Applied Physics Letters, 110 (13)

    Abstract

    The use of high quality semiconducting nanomaterials for advanced device applications has been hampered by the unavoidable growth variability of electrical properties of one-dimensional nanomaterials, such as nanowires and nanotubes, thus highlighting the need for the characterization of efficient semiconducting nanomaterials. In this study, we demonstrate a low-cost, industrially scalable dielectrophoretic (DEP) nanowire assembly method for the rapid analysis of the electrical properties of inorganic single crystalline nanowires, by identifying key features in the DEP frequency response spectrum from 1 kHz to 20 MHz in just 60 s. Nanowires dispersed in anisole were characterized using a three-dimensional DEP chip (3DEP), and the resultant spectrum demonstrated a sharp change in nanowire response to DEP signal in 1–20 MHz frequency range. The 3DEP analysis, directly confirmed by field-effect transistor data, indicates that nanowires of higher quality are collected at high DEP signal frequency range above 10 MHz, whereas lower quality nanowires, with two orders of magnitude lower current per nanowire, are collected at lower DEP signal frequencies. These results show that the 3DEP platform can be used as a very efficient characterization tool of the electrical properties of rod-shaped nanoparticles to enable dielectrophoretic selective deposition of nanomaterials with superior conductivity properties.

  • Shumbayawonda E, Fernández A, Hughes MP, Abasolo D . (2017) 'Permutation Entropy for the Characterisation of Brain Activity Recorded with Magnetoencephalograms in Healthy Ageing'. Entropy: An International and Interdisciplinary Journal of Entropy and Information Studies, 19 (141)

    Abstract

    The characterisation of healthy ageing of the brain could help create a fingerprint of normal ageing that might assist in the early diagnosis of neurodegenerative conditions. This study examined changes in resting state MEG permutation entropy due to age and gender in a sample of 220 healthy participants (98 males and 122 females, ages ranging between 7 and 84). Entropy was quantified using normalised permutation entropy and modified permutation entropy, with an embedding dimension of 5 and a lag of 1 as the input parameters for both algorithms. Effects of age were observed over the 5 regions of the brain i.e. anterior, central, posterior, and left and right lateral, with the anterior and central regions containing the highest permutation entropy. Statistically significant differences due to age were observed in the different brain regions for both genders, with the evolutions described using the fitting of polynomial regressions. Nevertheless, no significant differences between the genders were observed across all ages. These results suggest that the evolution of entropy in the background brain activity, quantified with permutation entropy algorithms, might be considered an alternative illustration of a ‘nominal’ physiological rhythm.

  • Mohamad A, Hamzah R, Hoettges K , Hughes MP. (2017) 'A dielectrophoresis-impedance method for protein detection and analysis'. AIP Advances, 7 (1) Article number 015202

    Abstract

    Dielectrophoresis (DEP) has increasingly been used for the assessment of the electrical properties of molecular scale objects including proteins, DNA, nanotubes and nanowires. However, whilst techniques have been developed for the electrical characterisation of frequency-dependent DEP response, biomolecular study is usually limited to observation using fluorescent markers, limiting its applicability as a characterisation tool. In this paper we present a label-free, impedance-based method of characterisation applied to the determination of the electrical properties of colloidal protein molecules, specifically Bovine Serum Albumin (BSA). By monitoring the impedance between electrodes as proteins collect, it is shown to be possible to observe multi-dispersion behaviour. A DEP dispersion exhibited at 400 kHz is attributable to the orientational dispersion of the molecule, whilst a second, higher-frequency dispersion is attributed to a Maxwell-Wagner type dispersion; changes in behaviour with medium conductivity suggest that this is strongly influenced by the electrical double layer surrounding the molecule.

  • Henslee EA, Torcal Serrano RM, Labeed FH, Jabr RI, Fry CH, Hughes MP, Hoettges KF. (2016) 'Accurate quantification of apoptosis progression and toxicity using a dielectrophoretic approach'. Analyst, 141, pp. 6408-6415.

    Abstract

    A loss of ability of cells to undergo apoptosis (programmed cell death, whereby the cell ceases to function and destroys itself) is commonly associated with cancer, and many anti-cancer interventions aim to restart the process. Consequently, the accurate quantification of apoptosis is essential in understanding the function and performance of new anti-cancer drugs. Dielectrophoresis has previously been demonstrated to detect apoptosis more rapidly than other methods, and is low-cost, label-free and rapid, but has previously been unable to accurately quantify cells through the apoptotic process because cells in late apoptosis disintegrate, making cell tracking impossible. In this paper we use a novel method based on light absorbance and multi-population tracking to quantify the progress of apoptosis, benchmarking against conventional assays including MTT, Trypan Blue and Annexin-V. Analyses are performed on suspension and adherent cells, and using two apoptosis-inducing agents. IC50 measurements compared favourably to MTT and were superior to Trypan Blue, whilst also detecting apoptotic progression faster than Annexin-V.

  • Hughes MP. (2016) 'Fifty Years of Dielectrophoretic Cell Separation Technology'. Biomicrofluidics, 10 (3) Article number 032801

    Abstract

    In 1966, Herbert Pohl and Ira Hawk published the first demonstration of dielectrophoresis of living and dead yeast cells; their paper described how the different ways in which the cells responded to an applied nonuniform electric field could form the basis of a cell separation method. Fifty years later, the field of dielectrophoretic (DEP) cell separation has expanded, with myriad demonstrations of its ability to sort cells on the basis of differences in electrical properties without the need for chemical labelling. As DEP separation enters its second half-century, new approaches are being found to move the technique from laboratory prototypes to functional commercial devices; to gain widespread acceptance beyond the DEP community, it will be necessary to develop ways of separating cells with throughputs, purities and cell recovery comparable to gold-standard techniques in life sciences, such as fluorescence- and magnetically-activated cell sorting (FACS and MACS, respectively). In this paper the history of DEP separation is charted, from a description of the work leading up to the first paper, to the current dual approaches of electrode-based and electrodeless DEP separation, and the path to future acceptance outside the DEP mainstream is considered.

  • Constantinou M, Rigas GP, Castro FA, Stolojan V, Hoettges KF, Hughes MP, Adkins E, Korgel BA, Shkunov M. (2016) 'Simultaneous Tunable Selection and Self-Assembly of Si Nanowires from Heterogeneous Feedstock'. ACS NANO, 10 (4), pp. 4384-4394.
  • Mulhall HJ, Cardnell A, Hoettges KF, Labeed FH, Hughes MP. (2015) 'Apoptosis progression studied using parallel dielectrophoresis electrophysiological analysis and flow cytometry.'. Integrative biology : quantitative biosciences from nano to macro,

    Abstract

    Apoptosis is characterised by many cellular events, but the standard Annexin-V assay identifies two; the transfer of the phospholipid phosphatidylserine (PS) from inner to outer leaflets of the plasma membrane, acting as an "eat me" signal to macrophages, and the permeabilisation of the plasma membrane. In this paper we compare the results from the Annexin-V assay with electrophysiology data obtained in parallel using dielectrophoresis, which highlights two changes in cell electrophysiology; a change in cytoplasmic conductivity which correlates with PS expression, and a membrane conductance spike that correlates with permeabilisation. Combining results from both methods shows a strong inverse relationship between conductivity and PS externalisation. One mechanism which may explain this correlation is related to intracellular Ca(2+), which is known to increase early in apoptosis. PS expression occurs when enzymes called scramblases swap external and internal phospholipids, and which are usually activated by Ca(2+), whilst the change in cytoplasmic conductivity may be due to K(+) efflux from intermediate conductance (IK) ion channels that are also activated by Ca(2+).

  • Graham KA, Mulhall HJ, Labeed FH, Lewis MP, Hoettges KF, Kalavrezos N, McCaul J, Liew C, Porter S, Fedele S, Hughes MP. (2015) 'A dielectrophoretic method of discrimination between normal oral epithelium, and oral and oropharyngeal cancer in a clinical setting.'. Analyst, England: 140 (15), pp. 5198-5204.

    Abstract

    Despite the accessibility of the oral cavity to clinical examination, delays in diagnosis of oral and oropharyngeal carcinoma (OOPC) are observed in a large majority of patients, with negative impact on prognosis. Diagnostic aids might help detection and improve early diagnosis, but there remains little robust evidence supporting the use of any particular diagnostic technology at the moment. The aim of the present feasibility first-in-human study was to evaluate the preliminary diagnostic validity of a novel technology platform based on dielectrophoresis (DEP). DEP does not require labeling with antibodies or stains and it is an ideal tool for rapid analysis of cell properties. Cells from OOPC/dysplasia tissue and healthy oral mucosa were collected from 57 study participants via minimally-invasive brush biopsies and tested with a prototype DEP platform using median membrane midpoint frequency as main analysis parameter. Results indicate that the current DEP platform can discriminate between brush biopsy samples from cancerous and healthy oral tissue with a diagnostic sensitivity of 81.6% and a specificity of 81.0%. The present ex vivo results support the potential application of DEP testing for identification of OOPC. This result indicates that DEP has the potential to be developed into a low-cost, rapid platform as an assistive tool for the early identification of oral cancer in primary care; given the rapid, minimally-invasive and non-expensive nature of the test, dielectric characterization represents a promising platform for cost-effective early cancer detection.

  • Mahabadi S, Labeed FH, Hughes MP. (2015) 'Effects of cell detachment methods on the dielectric properties of adherent and suspension cells.'. Electrophoresis, Germany: 36 (13), pp. 1493-1498.

    Abstract

    Cell analyses such as flow cytometry, dielectrophoresis, and some patch-clamp techniques require that cells be in monodisperse suspension in order for analysis to occur. Where cells have a normally adherent phenotype in vivo, this requires that cells be removed from the surface of the culture flask or vessel. This can be achieved in many ways, but most commonly either by the use of a dissociation medium of some form, or by scraping the cells from the surface. Both methods have potential drawbacks; chemical methods may alter the properties of the cells to such a degree that the measurement might be regarded as meaningless, whilst scraping could cause physical damage to the structure of the cells. In this paper, we use dielectrophoresis to analyse the electrical properties of two adherent cell lines detached by multiple methods, and compare these against a control cell line of suspension cells, examined in both the native state and when subject to the same chemical treatments. The results indicate that most chemical agents do not alter the electrophysiology of cells directly, though they may trigger some potential cell deterioration processes such as apoptosis in the cells. This can be observed in the production of apoptotic body-like particles and the alteration of cytoplasmic conductivity (which has been associated with apoptotic water efflux). However, cells detached by scraping exhibited statistically significant differences in their electrophysiological properties when compared to those detached by the chemical methods, indicating that this method is unsuitable for detachment of adherent cells prior to analysis of isolates suspension cells.

  • Ismail A, Hughes M, Mulhall H, Oreffo R, Labeed F. (2015) 'Characterization of human skeletal stem and bone cell populations using dielectrophoresis'. Journal of Tissue Engineering and Regenerative Medicine, 9 (2), pp. 162-168.

    Abstract

    © 2012 John Wiley & Sons, Ltd. Dielectrophoresis (DEP) is a non-invasive cell analysis method that uses differences in electrical properties between particles and surrounding medium to determine a unique set of cellular properties that can be used as a basis for cell separation. Cell-based therapies using skeletal stem cells are currently one of the most promising areas for treating a variety of skeletal and muscular disorders. However, identifying and sorting these cells remains a challenge in the absence of unique skeletal stem cell markers. DEP provides an ideal method for identifying subsets of cells without the need for markers by using their dielectric properties. This study used a 3D dielectrophoretic well chip device to determine the dielectric characteristics of two osteosarcoma cell lines (MG-63 and SAOS-2) and an immunoselected enriched skeletal stem cell fraction (STRO-1 positive cell) of human bone marrow. Skeletal cells were exposed to a series of different frequencies to induce dielectrophoretic cell movement, and a model was developed to generate the membrane and cytoplasmic properties of the cell populations. Differences were observed in the dielectric properties of MG-63, SAOS-2 and STRO-1 enriched skeletal populations, which could potentially be used to sort cells in mixed populations. This study provide evidence of the ability to characterize different human skeletal stem and mature cell populations, and acts as a proof-of-concept that dielectrophoresis can be exploited to detect, isolate and separate skeletal cell populations from heterogeneous bone marrow cell populations.

  • Fatoyinbo HO, McDonnell MC, Hughes MP. (2014) 'Dielectrophoretic sample preparation for environmental monitoring of microorganisms: Soil particle removal.'. Biomicrofluidics, United States: 8 (4)

    Abstract

    Detection of pathogens from environmental samples is often hampered by sensors interacting with environmental particles such as soot, pollen, or environmental dust such as soil or clay. These particles may be of similar size to the target bacterium, preventing removal by filtration, but may non-specifically bind to sensor surfaces, fouling them and causing artefactual results. In this paper, we report the selective manipulation of soil particles using an AC electrokinetic microfluidic system. Four heterogeneous soil samples (smectic clay, kaolinitic clay, peaty loam, and sandy loam) were characterised using dielectrophoresis to identify the electrical difference to a target organism. A flow-cell device was then constructed to evaluate dielectrophoretic separation of bacteria and clay in a continous flow through mode. The average separation efficiency of the system across all soil types was found to be 68.7% with a maximal separation efficiency for kaolinitic clay at 87.6%. This represents the first attempt to separate soil particles from bacteria using dielectrophoresis and indicate that the technique shows significant promise; with appropriate system optimisation, we believe that this preliminary study represents an opportunity to develop a simple yet highly effective sample processing system.

  • Hoettges KF, Hughes MP, Mcdonnell MB. (2014) 'Continuous flow nanoparticle concentration using alternating current-electroosmotic flow'. Electrophoresis, 35 (4), pp. 467-473.

    Abstract

    Achieving real-time detection of environmental pathogens such as viruses and bacterial spores requires detectors with both rapid action and a suitable detection threshold. However, most biosensors have detection limits of an order of magnitude or more above the potential infection threshold, limiting their usefulness. This can be improved through the use of automated sample preparation techniques such as preconcentration. In this paper, we describe the use of AC electroosmosis to concentrate nanoparticles from a continuous flow. Electrodes at an optimized angle across a flow cell, and energized by a 1 kHz signal, were used to push nanoparticles to one side of a flow cell, and to extract the resulting stream with a high particle concentration from that side of the flow cell. A simple model of the behavior of particles in the flow cell has been developed, which shows good agreement with experimental results. The method indicates potential for higher concentration factors through cascading devices. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Mohamad AS, Jeynes JC, Hughes MP. (2014) 'Dielectrophoretic response of DNA shows different conduction mechanisms for poly(dG)-poly(dC) and poly(dA)-Poly(dT) in solution.'. IEEE Trans Nanobioscience, United States: 13 (1), pp. 51-54.

    Abstract

    Although the subject of some scrutiny over the years, the mechanism of conduction in DNA has not yet been resolved, with competing theories suggesting either electronic and ionic conduction mechanisms. In this paper we use dielectrophoresis to determine the electrical properties of poly(dG)-poly(dC) (GC) and poly(dA)-poly(dT) (AT) DNA in solution. The molecules show different conduction mechanisms; GC DNA exhibits conduction primarily through the molecule, whereas in AT DNA conduction through the counterion cloud surrounding the molecule in solution is more significant.

  • Abdul Razak MA, Hoettges KF, Fatoyinbo HO, Labeed FH, Hughes MP. (2013) 'Efficient dielectrophoretic cell enrichment using a dielectrophoresis-well based system.'. Biomicrofluidics, United States: 7 (6)

    Abstract

    Whilst laboratory-on-chip cell separation systems using dielectrophoresis are increasingly reported in the literature, many systems are afflicted by factors which impede "real world" performance, chief among these being cell loss (in dead spaces, attached to glass and tubing surfaces, or sedimentation from flow), and designs with large channel height-to-width ratios (large channel widths, small channel heights) that make the systems difficult to interface with other microfluidic systems. In this paper, we present a scalable structure based on 3D wells with approximately unity height-to-width ratios (based on tubes with electrodes on the sides), which is capable of enriching yeast cell populations whilst ensuring that up to 94.3% of cells processed through the device can be collected in tubes beyond the output.

  • Mulhall HJ, Hughes MP, Kazmi B, Lewis MP, Labeed FH. (2013) 'Epithelial cancer cells exhibit different electrical properties when cultured in 2D and 3D environments.'. Biochim Biophys Acta, Netherlands: 1830 (11), pp. 5136-5141.

    Abstract

    BACKGROUND: Many drug development and toxicology studies are performed using cells grown in monolayers in well-plates and flasks, despite the fact that these are widely held to be different to cells found in the native environment. 3D, tissue engineered, organotypical tissue culture systems have been developed to be more representative of the native tissue environment than standard monolayer cultures. Whilst the biochemical differences between cells grown in 2D and 3D culture have been explored, the changes on the electrophysiological properties of the cells have not. METHODS: We compared the electrophysiological properties of primary normal oral keratinocytes (nOK) and cancerous abnormal oral keratinocytes (aOK), cultured in standard monolayer and reconstituted 3D organotypical tissue cultures. The electrophysiological properties of populations of the cells were analysed using dielectrophoresis. The intracellular conductivity of aOK was significantly increased when grown in organotypical cultures compared to counterpart cells grown in monolayer cultures. RESULTS: 3D cultured aOK showed almost identical intracellular conductivity to nOK also grown in organotypical cultures, but significantly different to aOK grown in monolayers. The effective membrane capacitance of aOK grown in 3D was found to be significantly higher than nOK, but there was no significant difference between the electrophysiological properties of nOK grown in 2D and 3D cultures. GENERAL SIGNIFICANCE: This work suggests that factors such as cell shape and cytoplasmic trafficking between cells play an important role in their electrophysiology, and highlights the need to use in vitro models more representative of native tissue when studying cell electrophysiological properties.

  • Mohtar MN, Hoettges KF, Hughes MP. (2013) 'Factors affecting particle collection by electro-osmosis in microfluidic systems.'. Electrophoresis, Germany: 35 (2-3), pp. 345-351.

    Abstract

    Alternating-current electro-osmosis, a phenomenon of fluid transport due to the interaction between an electrical double layer and a tangential electric field, has been used both for inducing fluid movement and for the concentration of particles suspended in the fluid. This offers many advantages over other phenomena used to trap particles, such as placing particles at an electrode centre rather than an edge; benefits of scale, where electrodes hundreds of micrometers across can trap particles from the molecules to cells at the same rate; and a trapping volume limited by the vortex height, a phenomenon thus far unstudied. In this paper, the collection of particles due to alternating-current electro-osmosis driven collection is examined for a range of particle concentrations, inter-electrode gap widths, chamber heights and media viscosity and density. A model of collection behaviour is described where particle collection over time is governed by two processes, one driven by the vortices and the other by sedimentation, allowing the determination of the maximum height of vortex-driven collection, but also indicates how trapping is limited by high particle concentrations and fluid velocities. The results also indicate that viscosity, rather than density, is a significant governing factor in determining the trapping behaviour of particles.

  • Humphries A, Lister TS, Wright PA, Hughes MP. (2013) 'Determination of the thermal and physical properties of black tattoo ink using compound analysis'. Lasers in Medical Science, 28 (4), pp. 1107-1112.

    Abstract

    Despite the widespread use of laser therapy in the removal of tattoos, comparatively little is known about its mechanism of action. There is a need for an improved understanding of the composition and thermal properties of the tattoo ink in order that simulations of laser therapy may be better informed and treatment parameters optimised. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry identified that the relative proportions of the constituent compounds of the ink likely to exist in vivo are the following: carbon black pigment (89 %), carvacrol (5 %), eugenol (2 %), hexenol (3 %) and propylene glycol (1 %). Chemical compound property tables identify that changes in phase of these compounds lead to a considerable reduction in the density and thermal conductivity of the ink and an increase in its specific heat as temperature increases. These temperature-dependent values of density, thermal conductivity and specific heat are substantially different to the constant values, derived from water or graphite at a fixed temperature, which have been applied in the simulations of laser therapy as previously described in the literature. Accordingly, the thermal properties of black tattoo ink described in this study provide valuable information that may be used to improve simulations of tattoo laser therapy. © 2012 Springer-Verlag London Ltd.

  • Abdallat RG, Ahmad Tajuddin AS, Gould DH, Hughes MP, Fatoyinbo HO, Labeed FH. (2013) 'Process development for cell aggregate arrays encapsulated in a synthetic hydrogel using negative dielectrophoresis'. Electrophoresis, 34 (7), pp. 1059-1067.

    Abstract

    Spatial patterning of cells is of great importance in tissue engineering and biotechnology, enabling, for example the creation of bottom-up histoarchitectures of heterogeneous cells, or cell aggregates for in vitro high-throughput toxicological and therapeutic studies within 3D microenvironments. In this paper, a single-step process for creating peelable and resilient hydrogels, encapsulating arrays of biological cell aggregates formed by negative DEP has been devised. The dielectrophoretic trapping within low-energy regions of the DEP-dot array reduces cell exposure to high field stresses while creating distinguishable, evenly spaced arrays of aggregates. In addition to using an optimal combination of PEG diacrylate pre-polymer solution concentration and a novel UV exposure mechanism, total processing time was reduced. With a continuous phase medium of PEG diacrylate at 15% v/v concentration, effective dielectrophoretic cell patterned arrays and photo-polymerisation of the mixture was achieved within a 4 min period. This unique single-step process was achieved using a 30 s UV exposure time frame within a dedicated, wide exposure area DEP light box system. To demonstrate the developed process, aggregates of yeast, human leukemic (K562) and HeLa cells were immobilised in an array format within the hydrogel. Relative cell viability for both cells within the hydrogels, after maintaining them in appropriate iso-osmotic media, over a week period was greater than 90%. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Opoku C, Hoettges KF, Hughes MP, Stolojan V, Silva SRP, Shkunov M. (2013) 'Solution processable multi-channel ZnO nanowire field-effect transistors with organic gate dielectric'. Nanotechnology, 24 (40), pp. 405203-4(7pp).

    Abstract

    The present work focuses on nanowire (NW) applications as semiconducting elements in solution processable field-effect transistors (FETs) targeting large-area low-cost electronics. We address one of the main challenges related to NW deposition and alignment by using dielectrophoresis (DEP) to select multiple ZnO nanowires with the correct length, and to attract, orientate and position them in predefined substrate locations. High-performance top-gate ZnO NW FETs are demonstrated on glass substrates with organic gate dielectric layers and surround source-drain contacts. Such devices are hybrids, in which inorganic multiple single-crystal ZnO NWs and organic gate dielectric are synergic in a single system. Current-voltage (I-V) measurements of a representative hybrid device demonstrate excellent device performance with high on/off ratio of 10^7, steep subthreshold swing (s-s) of 400 mV/dec and high electron mobility of 35 cm2 V-1 s-1 in N2 ambient. Stable device operation is demonstrated after 3 months of air exposure, where similar device parameters are extracted including on/off ratio of 4x10^6, s-s 500 mV/dec and field-effect mobility of 28 cm2 V-1 s-1. These results demonstrate that DEP can be used to assemble multiples of NWs from solvent formulations to enable low-temperature hybrid transistor fabrication for large-area inexpensive electronics.

  • Humphries A, Lister TS, Wright PA, Hughes MP. (2012) 'Finite element analysis of thermal and acoustic processes during laser tattoo removal'. Lasers in Surgery and Medicine, 45 (2), pp. 108-115.

    Abstract

    Background and Objective Q-switched laser therapy is commonly used for the removal of tattoos. However, despite ever increasing demand for this intervention, a better understanding of the mechanisms that result in pigment reduction is required in order to optimise outcomes and reduce the number of treatment episodes. Study Design A finite element analysis computer simulation was developed to model the fragmentation response of ink granules during irradiation of a professional black tattoo using a Q-switched Nd:YAG laser. Thermal and acoustic mechanisms were considered, allowing the optimal laser settings to be predicted throughout the course of treatment. Changes in the thermal properties of the ink during heating were taken into account to improve the reliability of the results obtained. Results The simulated results are in close agreement with clinical observations. Thermal fragmentation was shown to be the dominant mechanism in pigment reduction when using a 6 nanoseconds pulse at 1,064 nm. In order to provide maximum clearance whilst maintaining acceptable levels of tissue thermal damage, later treatments were shown to benefit from higher fluence levels than initial treatments. Larger spot diameters were also preferable throughout the course of treatment. Conclusions The results from the simulation build upon previous work carried out in the field, applying ink thermal coefficients which vary with temperature for the first time. These results compliment clinical knowledge, suggesting that a proactive increase in fluence during a course of treatments is likely to improve the response to laser therapy. © 2012 Wiley Periodicals, Inc.

  • Fry CH, Salvage SC, Manazza A, Dupont E, Labeed FH, Hughes MP, Jabr RI. (2012) 'Cytoplasm resistivity of mammalian atrial myocardium determined by dielectrophoresis and impedance methods'. Biophysical Journal, 103 (11), pp. 2287-2294.

    Abstract

    Many cardiac arrhythmias are caused by slowed conduction of action potentials, which in turn can be due to an abnormal increase of intracellular myocardial resistance. Intracellular resistivity is a linear sum of that offered by gap junctions between contiguous cells and the cytoplasm of the myocytes themselves. However, the relative contribution of the two components is unclear, especially in atrial myocardium, as there are no precise measurements of cytoplasmic resistivity, Rc. In this study, Rc was measured in atrial tissue using several methods: a dielectrophoresis technique with isolated cells and impedance measurements with both isolated cells and multicellular preparations. All methods yielded similar values for R c, with a mean of 138 ± 5 Ω·cm at 23°C, and a Q10 value of 1.20. This value is about half that of total intracellular resistivity and thus will be a significant determinant of the actual value of action potential conduction velocity. The dielectrophoresis experiments demonstrated the importance of including divalent cations (Ca 2+ and Mg2+) in the suspension medium, as their omission reduced cell integrity by lowering membrane resistivity and increasing cytoplasm resistivity. Accurate measurement of Rc is essential to develop quantitative computational models that determine the key factors contributing to the development of cardiac arrhythmias. © 2012 Biophysical Society.

  • Mulhall HJ, Labeed FH, Kazmi B, Costea DE, Hughes MP, Lewis MP. (2011) 'Cancer, pre-cancer and normal oral cells distinguished by dielectrophoresis.'. Analytical and bioanalytical chemistry, 401 (8), pp. 2455-2463.

    Abstract

    Most oral cancers are oral squamous cell carcinomas (OSCC) that arise from the epithelial lining of the oral mucosa. Given that the oral cavity is easily accessible, the disease lends itself to early detection; however, most oral cancers are diagnosed at a late stage, and approximately half of oral cancer sufferers do not survive beyond five years, post-diagnosis. The low survival rate has been attributed to late detection, but there is no accepted, reliable and convenient method for the detection of oral cancer and oral pre-cancer. Dielectrophoresis (DEP) is a label-free technique which can be used to obtain multi-parametric measurements of cell electrical properties. Parameters such as cytoplasmic conductivity and effective membrane capacitance (C(Eff)) can be non-invasively determined by the technique. In this study, a novel lab-on-a-chip device was used to determine the cytoplasmic conductivity and C(Eff) of primary normal oral keratinocytes, and pre-cancerous and cancerous oral keratinocyte cell lines. Our results show that the electrical properties of normal, pre-cancerous and cancerous oral keratinocytes are distinct. Furthermore, increasing C (Eff) and decreasing cytoplasmic conductivity correlate with disease progression which could prove significant for diagnostic and prognostic applications. DEP has the potential to be used as a non-invasive technique to detect oral cancer and oral pre-cancer. Clinical investigation is needed to establish the reliability and temporal relationship of the correlation between oncologic disease progression and the electrical parameters identified in this study. To use this technique as an OSCC detection tool in a clinical setting, further characterisation and refinement is warranted.

  • Labeed FH, Lu J, Mulhall HJ, Marchenko SA, Hoettges KF, Estrada LC, Lee AP, Hughes MP, Flanagan LA. (2011) 'Biophysical characteristics reveal neural stem cell differentiation potential.'. PLoS One, United States: 6 (9)

    Abstract

    Distinguishing human neural stem/progenitor cell (huNSPC) populations that will predominantly generate neurons from those that produce glia is currently hampered by a lack of sufficient cell type-specific surface markers predictive of fate potential. This limits investigation of lineage-biased progenitors and their potential use as therapeutic agents. A live-cell biophysical and label-free measure of fate potential would solve this problem by obviating the need for specific cell surface markers.

  • Broche LM, Hoettges KF, Ogin SL, Kass GEN, Hughes MP. (2011) 'Rapid, automated measurement of dielectrophoretic forces using DEP-activated microwells'. ELECTROPHORESIS, 32 (17), pp. 2393-2399.
  • Jaber FT, Labeed FH, Hughes MP. (2009) 'Action potential recording from dielectrophoretically positioned neurons inside micro-wells of a planar microelectrode array'. JOURNAL OF NEUROSCIENCE METHODS, 182 (2), pp. 225-235.
  • Hoettges KF, Hubner Y, Broche LM, Ogin SL, Kass GEN, Hughes MP. (2008) 'Dielectrophoresis-activated multiwell plate for label-free high-throughput drug assessment'. ANALYTICAL CHEMISTRY, 80 (6), pp. 2063-2068.
  • Duncan L, Shelmerdine H, Hughes MP, Coley HM, Huebner Y, Labeed FH. (2008) 'Dielectrophoretic analysis of changes in cytoplasmic ion levels due to ion channel blocker action reveals underlying differences between drug-sensitive and multidrug-resistant leukaemic cells'. PHYSICS IN MEDICINE AND BIOLOGY, 53 (2), pp. N1-N7.
  • Selvakumaran J, Keddie JL, Ewins DJ, Hughes MP. (2008) 'Protein adsorption on materials for recording sites on implantable microelectrodes'. JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 19 (1), pp. 143-151.
  • Fatoyinbo HO, Hoettges KF, Hughes MP, Broche L. (2008) 'Rapid-on-chip determination of dielectric properties of biological cells using imaging techniques in a dielectrophoresis dot microsystem'. ELECTROPHORESIS, 29 (1), pp. 3-10.
  • Hoettges KF, Dale JW, Hughes MP. (2007) 'Rapid determination of antibiotic resistance in E. coli using dielectrophoresis'. Physics in Medicine and Biology, 52 (19), pp. 6001-6009.

    Abstract

    In recent years, infections due to antibiotic-resistant strains of bacteria such as methillicin-resistant Staphylococcus aureus and ciprofloxacin-resistant Escherichia coli are on the rise, and with them the demand for rapid antibiotic testing is also rising. Conventional tests, such as disc diffusion testing, require a primary sample to be tested in the presence of a number of antibiotics to verify which antibiotics suppress growth, which take approximately 24 h to complete and potentially place the patient at severe risk. In this paper we describe the use of dielectrophoresis as a rapid marker of cell death, by detecting changes in the electrophysiology of the cell caused by the administration of an antibiotic. In contrast to other markers, the electrophysiology of the cell changes rapidly during cell death allowing live cells to be distinguished from dead (or dying) cells without the need for culturing. Using polymyxin B as an example antibiotic, our studies indicate that significant changes in cell characteristics can be observed as soon as 1 h passes after isolating a culture from nutrient broth. © 2007 IOP Publishing Ltd.

  • Fatoyinbo HO, Hoettges KF, Reddy SM, Hughes MP. (2007) 'An integrated dielectrophoretic quartz crystal microbalance (DEP-QCM) device for rapid biosensing applications'. BIOSENSORS & BIOELECTRONICS, 23 (2), pp. 225-232.
  • Coley HM, Labeed FH, Thomas H, Hughes MP. (2007) 'Biophysical characterization of MDR breast cancer cell lines reveals the cytoplasm is critical in determining drug sensitivity'. Biochimica et Biophysica Acta - General Subjects, 1770 (4), pp. 601-608.

    Abstract

    Dielectrophoresis (DEP) was used to examine a panel of MCF-7 cell lines comprising parental MCF-7 cells and MDR derivatives: MCF-7TaxR (paclitaxel-resistant, P-glycoprotein (P-gp) positive), MCF-7DoxR (doxorubicin-resistant MRP2 positive) plus MCF-7MDR1 (MDR1 transfected, P-gp positive). MCF-7DoxR and MCF-7MDR1 were broadly cross-resistant to natural product anticancer agents, whereas MCF-7TaxR cells were not, contrary to P-gp expression. Whilst DEP revealed modest membrane changes in MDR sub-lines, we saw significant changes in their cytoplasmic conductivity: MCF-7TaxR < MCF-7 < MCF-7MDR1 < MCF-7DoxR (range 0.14-0.40 S/m). Cytoplasmic conductivity is affected by the movement of molecules e.g. as in intracellular trafficking MCF-7TaxR showed a reduced membrane potential, whereas MCF-7DoxR and MCF-7MDR1 showed an increase. Thus, altered membrane potential is associated with an MDR phenotype, but in a complex manner. DEP data suggest a model whereby relative increases in cytoplasmic conductivity are correlated with MDR, whilst relative decreases equate with a sensitised phenotype e.g. MCF-7TaxR. Moreover, extent of anthracycline accumulation was inversely related to cytoplasmic conductivity. These data are representative of a model where drug sensitivity is associated with low ionic conductance (reduced cellular trafficking and ion transport) and substantial anthracycline accumulation. For classical MDR i.e. MCF-7MDR1, we saw the reverse picture. Thus, the drug resistance phenotypes of this panel of MCF-7 lines can be delineated by assessment of cytoplasmic biophysical properties using DEP. © 2006 Elsevier B.V. All rights reserved.

  • Broche LM, Bhadal N, Lewis MP, Porter S, Hughes MP, Labeed FH. (2007) 'Early detection of oral cancer - Is dielectrophoresis the answer?'. ORAL ONCOLOGY, 43 (2), pp. 199-203.
  • Hübner Y, Hoettges KF, McDonnell MB, Carter MJ, Hughes MP. (2007) 'Applications of dielectrophoretic/electrohydrodynamic "zipper" electrodes for detection of biological nanoparticles'. International Journal of Nanomedicine, 2 (3), pp. 427-431.

    Abstract

    A major problem for surface-based detection techniques such as surface plasmon resonance and quartz crystal microbalances is that at low concentrations, diffusion is an insufficient driving force to bring colloidal submicron-scale particles to the detection surface. In order to overcome this, it has previously been demonstrated that a combination of dielectrophoresis and AC-electro-hydrodynamic flow can be used to focus cell-sized particles from suspension onto a large metal surface, in order to improve the detection capabilities of such systems. In this paper we describe how the combination of these two phenomena, using the so-called "zipper" electrode array, can be used to concentrate a wide range of nanoparticles of biological interest, such as influenza virus, dissolved albumin, and DNA molecules as well as latex beads of various sizes. We also demonstrate that the speed at which particles are transported towards the centre of the electrode pads by dielectrophoresis and electro-hydrodynamic flow is not related to the particle size for colloidal particles. © 2007 Dove Medical Press Limited. All rights reserved.

  • Fatoyinbo HO, Hughes MP, Martin SP, Pashby P, Labeed FH. (2007) 'Dielectrophoretic separation of Bacillus subtilis spores from environmental diesel particles'. JOURNAL OF ENVIRONMENTAL MONITORING, 9 (1), pp. 87-90.
  • Mureau N, Mendoza E, Silva SRP, Hoettges KF, Hughes MP. (2006) 'In situ and real time determination of metallic and semiconducting single-walled carbon nanotubes in suspension via dielectrophoresis'. APPLIED PHYSICS LETTERS, 88 (24) Article number ARTN 243109
  • Labeed FH, Coley HM, Hughes MP. (2006) 'Differences in the biophysical properties of membrane and cytoplasm of apoptotic cells revealed using dielectrophoresis'. BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS, 1760 (6), pp. 922-929.
  • Chin S, Hughes MP, Coley HM, Labeed FH. (2006) 'Rapid assessment of early biophysical changes in K562 cells during apoptosis determined using dielectrophoresis.'. International journal of nanomedicine, 1 (3), pp. 333-337.

    Abstract

    Apoptosis, or programmed cell death, is a vital cellular process responsible for causing cells to self-terminate at the end of their useful life. Abrogation of this process is commonly linked to cancer, and rapid detection of apoptosis in vitro is vital to the discovery of new anti-cancer drugs. In this paper, we describe the application of the electrical phenomenon dielectrophoresis for detecting apoptosis at very early stages after drug induction, on the basis of changes in electrophysiological properties. Our studies have revealed that K562 (human myelogenous leukemia) cells show a persistent elevation in the cytoplasmic conductivity occurring as early as 30 minutes following exposure to staurosporine. This method therefore allows a far more rapid detection method than existing biochemical marker methods.

  • Hübner Y, Hübner Y, Hoettges KF, Kass GEN, Ogin SL, Hughes MP. (2005) 'Parallel measurements of drug actions on Erythrocytes by dielectrophoresis, using a three-dimensional electrode design'. IEE Proceedings Nanobiotechnology, 152 (4), pp. 150-154.

    Abstract

    A type of well-based assay that uses a laminated three-dimensional electrode design to characterise the effects of different drugs on red blood cells using dielectrophoresis is presented. The capability of the system to determine the effects of chemical agents on the electrophysiology of red blood cells is demonstrated using saponin and valinomycin as two examples of drugs that can penetrate the cell membrane and therefore change the dielectric properties of the cell. Light intensity changes are measured in the well over a period of time at various frequencies and the dielectric properties of the cells determined using an ellipsoidal multi-shell model. It is shown that the laminated electrode permits a high degree of automation and thus a high number of parallel experiments, which reduces both the time and effort needed to examine differences between populations of red blood cells. The technique is directly compatible with the industry-standard 1536 well-plate analysis technique. © IEE, 2005.

  • Fatoyinbo HO, Kamchis D, Whattingham R, Ogin SL, Hughes MP. (2005) 'A high-throughput 3-D composite dielectrophoretic separator'. IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, 52 (7), pp. 1347-1349.
  • Hughes MP, Banks DJ, Ewins DJ. (2005) 'Action potential velocity detection using a penetrating microprobe'. MEASUREMENT SCIENCE AND TECHNOLOGY, 16 (3), pp. N7-N10.
  • Broche LM, Labeed FH, Hughes MP. (2005) 'Extraction of dielectric properties of multiple populations from dielectrophoretic collection spectrum data'. Physics in Medicine and Biology, 50 (10), pp. 2267-2274.

    Abstract

    In this paper we show how simplifying assumptions can be used to extract useful data from the dielectrophoretic collection spectrum, in particular for the cytoplasm, and hence determine the properties of multiple populations of cells within a sample. Specifically, the observation of the frequencies of onset of dielectric dispersion allows the identification and enumeration of populations of cells according to cytoplasmic conductivity, with particular relevance to the determination of the action of drugs for high-throughput screening applications. © 2005 IOP Publishing Ltd.

  • Hughes MP. (2004) 'Numerical simulation of dielectrophoretic ratchet structures'. JOURNAL OF PHYSICS D-APPLIED PHYSICS, 37 (8) Article number PII S0022-3727(04)69865-2 , pp. 1275-1280.
  • Hübner Y, Hoettges KF, Hughes MP. (2003) 'Water quality test based on dielectrophoretic measurements of fresh water algae Selenastrum capricornutum.'. J Environ Monit, England: 5 (6), pp. 861-864.

    Abstract

    A method is described whereby dielectrophoresis of algal cells is used to perform rapid water quality analysis, specifically detecting the presence of CuSO4. The dielectric collection spectrum of the fresh water alga Selenastrum capricornutum was determined for a range of concentrations of CuSO4 from 25 mg L(-1) to 0.25 mg L(-1) for exposure times of 15 min and 18 h. In all cases increasing the concentration of CuSO4 reduced cell collection, but a step reduction was observed in collection between 2 mg L(-1) and 5 mg L(-1). This method has potential for forming a rapid, low-cost test for water quality with broad specificity and significantly reduced analysis time compared to current methods.

  • Hoettges KF, Hughes MP, Cotton A, Hopkins NAE, McDonnell MB. (2003) 'Optimizing particle collection for enhanced surface-based biosensors'. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE, 22 (6), pp. 68-74.
  • Labeed FH, Coley HM, Thomas H, Hughes MP. (2003) 'Assessment of multidrug resistance reversal using dielectrophoresis and flow cytometry'. BIOPHYSICAL JOURNAL, 85 (3), pp. 2028-2034.
  • Johari J, Hübner Y, Hull JC, Dale JW, Hughes MP. (2003) 'Dielectrophoretic assay of bacterial resistance to antibiotics'. Physics in Medicine and Biology, 48 (14)

    Abstract

    The dielectrophoretic collection spectra of antibiotic-sensitive and antibiotic-resistant strains of Staphylococcus epidermidis have been determined. These indicate that in the absence of antibiotic treatment there is a strong similarity between the dielectric properties of sensitive and resistant strains, and that there is a significant difference between the sensitive strains before and after treatment with the antibiotic streptomycin after 24 h exposure. This method offers possibilities for the assessment of bacterial resistance to antibiotics.

  • Hoettges KF, McDonnell MB, Hughes MP. (2003) 'Use of combined dielectrophoretic/electrohydrodynamic forces for biosensor enhancement'. Journal of Physics D: Applied Physics, 36 (20)

    Abstract

    Dielectrophoretic and electrohydrodynamic forces have been demonstrated in the literature to cause movement of particles across the surface of planar electrodes when exposed to low-frequency (≈1 kHz) electric fields. In this paper we describe the development of this phenomenon for collection of particles, covering a range of sizes, out of a liquid and focusing them at the centre of a novel electrode consisting of large interlocking circles. The volume of analyte across which this effect is observed is significantly larger than has been reported for conventional dielectrophoretic arrays. By altering the experimental conditions, particles can either be collected or cycled across the surface and then removed. This technique offers great scope for enhancement of surface-based detection methods.

  • Hughes MP. (2002) 'Strategies for dielectrophoretic separation in laboratory-on-a-chip systems.'. Electrophoresis, Germany: 23 (16), pp. 2569-2582.

    Abstract

    Dielectrophoresis--the induced motion of polarizable particles in nonuniform fields--has proven to be an effective method for the separation of bioparticles such as cells, viruses and proteins. In this paper, the application of dielectrophoresis in miniaturized laboratories-on-a-chip is discussed, and strategies are described for using dielectrophoresis both for the binary separation of bioparticles and for the fractionation of many populations in such devices.

  • Hughes MP. (2002) 'Dielectrophoretic behavior of latex nanospheres: low-frequency dispersion.'. J Colloid Interface Sci, United States: 250 (2), pp. 291-294.

    Abstract

    The electrostatic manipulation of nanoparticles using nonuniform electric fields (dielectrophoresis) has proved a useful method of investigating the movement of charge around colloidal particles. While previous work has explained many of the ways in which particle behavior deviates from that predicted by classical Maxwell-Wagner interfacial polarization theory, there exists an additional, anomalous polarization mechanism observed in media of high conductivity, causing an unexpected observation of positive dielectrophoresis. Here this is suggested that this may be explained in terms of the polarization of the Stern layer.

  • Hughes MP, Green NG. (2002) 'The influence of stern layer conductance on the dielectrophoretic behavior of latex nanospheres.'. J Colloid Interface Sci, United States: 250 (1), pp. 266-268.

    Abstract

    The influence of the Stern layer conductance on the dielectrophoretic behavior of sub-micrometer-sized latex spheres is examined. The dielectrophoretic response of the particles is measured and analyzed in terms of a model of surface conductance divided into discrete components related to the structure of the double layer. The effect of both co- and counterions in the bulk solution on the Stern layer conductance is demonstrated.

  • Hughes MP, Morgan H, Rixon FJ. (2002) 'Measuring the dielectric properties of herpes simplex virus type 1 virions with dielectrophoresis.'. Biochim Biophys Acta, Netherlands: 1571 (1), pp. 1-8.

    Abstract

    An investigation has been performed into the biophysical properties of the enveloped mammalian virus, herpes simplex virus type 1 (HSV-1). The dielectrophoretic behaviour of the virus particles was measured as a function of applied frequency (over the range 100 kHz-20 MHz) and conductivity of the suspending medium (over the range 1-100 mS m(-1)). The dielectric properties of the virus were determined from the dielectrophoretic data using the smeared-out shell model. The data suggest that the intact particle has a surface conductance of 0.3 nS, an internal and membrane permittivity of 75varepsilon(o) and 7.5varepsilon(o), respectively, an internal conductivity of approximately 0.1 S m(-1) and a zeta potential of 70 mV. The dielectric properties were measured for intact, fresh virus particles and also for particles following exposure to various modifying agents, such as treatment with enzymes, ionophores and ageing. It is shown that the observed changes in the dielectrophoretic spectrum, and the variations in the dielectric properties of the virus concur with the expected physiological effects of these agents.

  • Hughes MP. (2002) 'Theoretical evaluation of asynchronous ac dielectric nanomotors'. Nanotechnology, 13 (2), pp. 157-162.

    Abstract

    A design for an electric nanomotor driven by ac electric fields is presented and evaluated. The motor induces torque by means of a rotating electric field, which induces a dipole in the rotor; the interactions between field and dipole are responsible for both the generation of torque and the repulsion of the rotor, which stabilizes its position without contact and removes the need for bearings. The applied electric field is generated by square-wave pulses, allowing the direct computer control of the device without any digital-to-analogue requirement; the amount of torque generated can be controlled precisely by varying the number of clock cycles between digital state changes. The technology is scaleable, and a motor consisting of a rotor 1μm long and 100 nm diameter is shown to be capable of generating approximately 10-15 N m-1, equivalent to a bacterial flagellar motor.

  • Hughes MP, Morgan H, Rixon FJ. (2001) 'Dielectrophoretic manipulation and characterization of herpes simplex virus-1 capsids.'. Eur Biophys J, Germany: 30 (4), pp. 268-272.

    Abstract

    The dielectrophoretic behaviour of the capsids of herpes simplex virus type-1 has been measured over a range of conductivities of KCl solutions, with and without the addition of mannitol. The dielectrophoretic response of the capsids was recorded by measuring the frequency corresponding to zero dielectrophoretic force. The data were analysed using a multi-shelled model, and the permittivity and conductivity of the particles estimated. The capsid was modelled as a porous protein shell through which suspending medium passes, an inner chamber containing suspending medium in equilibrium with the outside, and a central core of protein (the scaffold). Capsids suspended in KCl without mannitol exhibited a different behaviour to those suspended in KCl with mannitol.

  • Hughes MP. (2000) 'AC Electrokinetics: Applications for Nanotechnology'. Nanotechnology, 11, pp. 124-132.
  • Hughes MP, Morgan H, Flynn MF. (1999) 'The dielectrophoretic behavior of submicron latex spheres: Influence of surface conductance'. JOURNAL OF COLLOID AND INTERFACE SCIENCE, 220 (2), pp. 454-457.
  • Hughes MP, Morgan H. (1999) 'Dielectrophoretic characterization and separation of antibody-coated submicrometer latex spheres'. Analytical Chemistry, 71 (16), pp. 3441-3445.

    Abstract

    The dielectrophoretic behavior of carboxylated 216-nm-diameter latex spheres has been characterized as a function of both medium conductivity and applied field frequency. Dielectrophoretic crossover measurements and analysis were used to characterize the dielectric properties of the particles. The particles were functionalized with antibodies using 1-ethyl- 3-(3-dimethylaminopropyl)carbodiimide (EDAC)-based coupling. Measurements indicated that the surface conductance of the native particles was 1.2 nS and that this reduced to a value of 0.7 nS after EDAC treatment and 0.25 nS after antibody coupling. Changes in the dielectrophoretic spectrum of the particles were exploited to demonstrate the principle of separation of unlabeled and protein-labeled particles. This demonstrates the potential for the development of new affinity separation systems based on ac electrokinetic methods.

  • Hughes MP, Morgan H. (1999) 'An evanescent-field technique for dielectrophoresis studies of colloidal particles'. Measurement Science and Technology, 10 (8), pp. 759-762.

    Abstract

    Dielectrophoretic collection rates have been used to measure the dielectric properties of particles. For accurate collection-rate measurements it is important to be able to discriminate between particles collecting on an electrode and particles that are in the bulk solution. In this paper we demonstrate how evanescent-imaging methods can be used to observe only those particles that are in the plane of the electrode array, so that significant improvements in the signal-to-noise ratio compared with conventional imaging methods are achieved.

  • Morgan H, Hughes MP, Green NG. (1999) 'Separation of submicron bioparticles by dielectrophoresis.'. Biophys J, UNITED STATES: 77 (1), pp. 516-525.

    Abstract

    Submicron particles such as latex spheres and viruses can be manipulated and characterized using dielectrophoresis. By the use of appropriate microelectrode arrays, particles can be trapped or moved between regions of high or low electric fields. The magnitude and direction of the dielectrophoretic force on the particle depends on its dielectric properties, so that a heterogeneous mixture of particles can be separated to produce a more homogeneous population. In this paper the controlled separation of submicron bioparticles is demonstrated. With electrode arrays fabricated using direct write electron beam lithography, it is shown that different types of submicron latex spheres can be spatially separated. The separation occurs as a result of differences in magnitude and/or direction of the dielectrophoretic force on different populations of particles. These differences arise mainly because the surface properties of submicron particles dominate their dielectrophoretic behavior. It is also demonstrated that tobacco mosaic virus and herpes simplex virus can be manipulated and spatially separated in a microelectrode array.

  • Hughes MP, Morgan H. (1999) 'Measurement of bacterial flagellar thrust by negative dielectrophoresis.'. Biotechnol Prog, UNITED STATES: 15 (2), pp. 245-249.

    Abstract

    The force produced by the flagella of the bacterium Salmonella typhimurium has been measured using negative dielectrophoretic methods. The bacteria are held in a force funnel, produced using a nonuniform electric field. When the motor force is balanced against an opposing negative dielectrophoretic force the bacteria become motionless. Numerical simulations have been used to estimate the electric field gradient in the electrodes. Together with experimental observations of bacterial motion the data gives a value of the force produced by the bacterial motor to be 0.37 pN.

  • Hughes MP, Archer S, Morgan H. (1999) 'Mapping the electrorotational torque in planar microelectrodes'. Journal of Physics D: Applied Physics, 32 (13), pp. 1548-1552.

    Abstract

    The dielectric properties of a polarizable particle can be characterized by measuring the frequency dependence of the torque in a rotating electric field. Measurements performed using planar electrodes indicate a spatial variation in the torque across the dimensions of the array. In this paper the variation in rotation rate of elliptical latex beads was measured in 203 discrete positions within a 400 μm × 400 μm polynomial electrorotation electrode array. It is shown that torque variations across the electrode array can exceed 50% of the mean value at the centre. Data averaging and smoothing were performed to reveal trends that match theoretical predictions made using numerical models. The results indicate that the torque depends on variations in both the magnitude and phase of the electric field.

  • Hughes MP. (1998) 'Computer-aided analysis of conditions for optimizing practical electrorotation'. Physics in Medicine and Biology, 43 (12), pp. 3639-3648.

    Abstract

    Previous studies have indicated that the variations in torque induced in particles in electrorotation electrode arrays are sufficiently large to cause errors in electrorotation measurements. In order to avoid this, experimenters usually study particles bounded by an arbitrary region near the centre of the electrodes. By simulating the time-dependent electric field for polynomial electrodes, we have assessed the variation in torque across the centre of the array. By considering both the variation in applied torque and the dielectrophoretic force in the electrode chamber, the optimal conditions for electrorotation experiments have been determined. Further to this, by comparing the torque variation across the electrode chamber for a number of common electrode designs, a comparison of the suitability of each electrode design for multi-particle electrorotation analysis has been made.

  • Hughes MP, Morgan H, Rixon FJ, Burt JP, Pethig R. (1998) 'Manipulation of herpes simplex virus type 1 by dielectrophoresis.'. Biochim Biophys Acta, NETHERLANDS: 1425 (1), pp. 119-126.

    Abstract

    The frequency-dependent dielectrophoretic behaviour of an enveloped mammalian virus, herpes simplex virus type 1 is described. It is demonstrated that over the range 10 kHz-20 MHz, these viral particles, when suspended in an aqueous medium of conductivity 5 mS m(-1), can be manipulated by both positive and negative dielectrophoresis using microfabricated electrode arrays. The observed transition from positive to negative dielectrophoresis at frequencies around 4.5 MHz is in qualitative agreement with a simple model of the virus as a conducting particle surrounded by an insulating membrane.

  • Hughes MP, Morgan H. (1998) 'Dielectrophoretic trapping of single sub-micrometre scale bioparticles'. JOURNAL OF PHYSICS D-APPLIED PHYSICS, 31 (17), pp. 2205-2210.
  • Morgan H, Green NG, Hughes MP, Monaghan W, Tan TC. (1997) 'Large-area travelling-wave dielectrophoresis particle separator'. JOURNAL OF MICROMECHANICS AND MICROENGINEERING, 7 (2), pp. 65-70.
  • Green NG, Hughes MP, Monaghan W, Morgan H. (1997) 'Large Area Multilayered Arrays for Dielectrophoretic Fractionation'. Microelectronic Engineering, 35, pp. 421-424.
  • Hughes MP, Pethig R, Wang XB. (1996) 'Dielectrophoretic forces on particles in travelling electric fields'. JOURNAL OF PHYSICS D-APPLIED PHYSICS, 29 (2), pp. 474-482.
  • WANG XB, HUGHES MP, HUANG Y, BECKER FF, GASCOYNE PRC. (1995) 'NONUNIFORM SPATIAL DISTRIBUTIONS OF BOTH THE MAGNITUDE AND PHASE OF AC ELECTRIC-FIELDS DETERMINE DIELECTROPHORETIC FORCES'. BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS, 1243 (2), pp. 185-194.
  • HUGHES MP, WANG XB, BECKER FF, GASCOYNE PRC, PETHIG R. (1994) 'COMPUTER-AIDED ANALYSES OF ELECTRIC-FIELDS USED IN ELECTROROTATION STUDIES'. JOURNAL OF PHYSICS D-APPLIED PHYSICS, 27 (7), pp. 1564-1570.

Conference papers

  • Shumbayawonda E, Fernández A, Escudero J, Hughes MP, Abasolo D . (2017) 'Characterisation Of Resting Brain Network Topologies Across The Human Lifespan With Magnetoencephalogram Recordings: A Phase Slope Index And Granger Causality Comparison Study'. Proceedings of Biosignals 2017, Porto, Portugal: Biosignals 2017
    [ Status: Accepted ]

    Abstract

    This study focuses on the resting state network analysis of the brain, as well as how these networks change both in topology and location throughout life. The magnetoencephalogram (MEG) background activity from 220 healthy volunteers (age 7-84 years), was analysed combining complex network analysis principles of graph theory with both linear and non-linear methods to evaluate the changes in the brain. Granger Causality (GC) (linear method) and Phase Slope Index (PSI) (non-linear method) were used to observe the connectivity in the brain during rest, and as a function of age by analysing the degree, clustering coefficient, efficiency, betweenness, modularity and maximised modularity of the observed complex brain networks. Our results showed that GC showed little linear causal activity in the brain at rest, with small world topology, while PSI showed little information flow in the brain, with random network topology. However, both analyses produced complementary results pertaining to the resting state of the brain.

  • Mohamad AS, Hughes MP. (2016) 'Characterization of Impedance Spectroscopy for Single-Walled Carbon Nanotubes with Ionic Liquid of Dielectrophoretic Assembly Method'. SPRINGER INTERNATIONAL CONFERENCE FOR INNOVATION IN BIOMEDICAL ENGINEERING AND LIFE SCIENCES, ICIBEL2015, Putrajaya, MALAYSIA: International Conference for Innovation in Biomedical Engineering and Life Sciences (ICIBEL) 56, pp. 279-282.
  • Mohamad AS, Hoettges KF, Hughes MP. (2015) 'Impedance spectroscopy of Zinc Oxide nanoparticles in dielectrophoresis biotechnology'. 2014 IEEE Asia-Pacific Conference on Applied Electromagnetics, APACE 2014 - Proceeding, , pp. 127-130.

    Abstract

    © 2014 IEEE.This study investigates nanowires using Dielectrophoresis (DEP) in non-aqueous suspension of Zinc Oxide (ZnO) nanoparticles dispersed in N,N-DIMENTHYLFORMAMIDE (DMF). The self assembly of nanowires in DEP impedance spectroscopy can be determined. In this work, dielectrophoretic measurements of inorganic have been used to estimate the permittivity and conductivity characteristic of the nanowires. As in aqueous such as salt solution has been dominating the transport of ZnO, which are the wire growth threshold, depend on applied voltage. While DEP assembly of nanowires depend on applied frequency, the applications of dielectrophoretic collection are measured using impedance spectroscopy.

  • Simons S, Abasolo D, Hughes M. (2015) 'Investigation of Alzheimer's Disease EEG Frequency Components with Lempel-Ziv Complexity'. SPRINGER-VERLAG BERLIN 6TH EUROPEAN CONFERENCE OF THE INTERNATIONAL FEDERATION FOR MEDICAL AND BIOLOGICAL ENGINEERING, Dubrovnik, CROATIA: 6th European Conference of the International-Federation-for-Medical-and-Biological-Engineering (MBEC) 45, pp. 46-49.
  • Mahabadi S, Hughes MP, Labeed FH. (2014) 'Measurement of Gifinitib (ZD1839) effect on electrophysiological properties of head and neck cancer cells using Dielectrophoresis (DEP)'. AMER ASSOC CANCER RESEARCH CANCER RESEARCH, San Diego, CA: 105th Annual Meeting of the American-Association-for-Cancer-Research (AACR) 74 (19)
  • Simons S, Abásolo D, Hughes M. (2013) 'Distance Measure Based on Lempel-Ziv Complexity for Analysis of Electroencephalograms in Alzheimer's Disease'. Guildford, UK : University of Surrey Proceedings of the 7th United Kingdom & Republic of Ireland Postgraduate Conference in Biomedical Engineering and Medical Physics (PGBiomed 2013), Guildford, UK: 7th United Kingdom & Republic of Ireland Postgraduate Conference in Biomedical Engineering and Medical Physics (PGBiomed 2013)
  • Jaber FT, Labeed FH, Hughes MP. (2013) 'A dielectrophoresis and image processing based system for loading single-neurons per micro-well in planar microelectrode arrays'. 2013 8th International Workshop on Systems, Signal Processing and Their Applications, WoSSPA 2013, , pp. 180-184.

    Abstract

    In this article, which is related to the biomedical signal processing applications area of the workshop, we present a system for positioning a single-neuron inside each micro-well of a 4-by-4 planar microelectrode array (MEA). Neurons are moved toward the electrode sites of the MEA (located at the bottom of the wells) using dielectrophoresis. The system utilizes the image acquisition and processing capabilities of MATLAB to detect the presence of a neuron inside each micro-well and stop the dielectrophoretic force, thus preventing more cells from being loaded. This method provides a fast, simple and relatively inexpensive way for loading cells on MEAs embedded with micro-wells for the purpose of acquiring and processing action potentials from geometrically defined biological neural networks at the single-cell level. Recordings from neurons that were positioned using this system have been obtained and are presented. © 2013 IEEE.

  • Mohamad AS, Jeynes JC, Hughes MP. (2012) 'Dielectrophoresis of poly at and poly GC DNA Nanomanipulation'. Proceedings of the IEEE Conference on Nanotechnology,

    Abstract

    Dielectrophoresis (DEP) is the induced motion of polarizable particles in non-uniform electric fields. Used for many years for the manipulation of particles from cell-scale to macromolecules, we present here the application of the technique for manipulation of DNA containing only adenine-thymine (poly AT) bases, and that of DNA containing only cytosine-guanine (poly GC), using microfabricated electrode structures. Poly AT was stained with DAPI and JOJO-1 for poly GC DNA. It was found that there were differences between the frequency-dependent DEP behavior of the two molecules; when looking at the difference between the two types on crossover frequency (the point where DEP changes from attractive to repulsive), it was found that they varied by up to a factor of 2. This points to possible insigns in the charge conduction mechanism in different DNA forms, as well as potential new mechanisms for gene separations and sequencing. © 2012 IEEE.

  • Kadri NA, Fatoyinbo HO, Hughes MP, Labeed FH. (2011) 'Semi-automated dielectrophoretic cell characterisation module for lab-on-chip applications'. Springer IFMBE Proceedings, Kuala Lumpur, Malaysia: BIOMED 2011: 5th Kuala Lumpur International Conference on Biomedical Engineering 35 (14), pp. 582-586.

    Abstract

    Dielectrophoresis is an electrical phenomenon that occurs when a polarisable particle is placed in non-uniform electrical fields. The magnitude of the generated force is dependent upon the electrophysiological make-up of the particle, therefore the specific DEP profile may be attained for any polarisable particles based on the intrinsic electrical properties alone. Any changes to these parameters may be detected by observing the corresponding DEP spectra. Despite having the advantages of being non-invasive, DEP applications are still not widely used due to the time-consuming processes involved. This study presents the preliminary outcomes in the development of a semi-automated DEP-based cell characterisation tool that allowed concurrent DEP experiments to be conducted serially, thus significantly reducing the time taken to complete the required sets of experiments. The results showed that the system is capable of producing a DEP spectrum for K562 leukaemic cells between the 10 kHz to 1 MHz range in less than 10 minutes, when recorded at eight points per decade.

  • Mulhall HJ, Abdallat R, Liang X, Fedele S, Lewis MP, Porter S, Tsinkalovsky O, Johannessen AC, Hughes MP, Costea DE, Labeed FH. (2010) 'Rapid detection of oral cancer: Electrophysiological characterization by dielectrophoresis technology'. Technical Proceedings of the 2010 NSTI Nanotechnology Conference and Expo, Anaheim, USA: Nanotech Conference & Expo 2010 3, pp. 35-38.
  • Kadri NA, Hoettges KF, Hughes MP. (2009) 'Development of a generic multiple frequency signal generator for BioMEMS'. Springer IFMBE Proceedings, Munich, Germany: World Congress on Medical Physics and Biomedical Engineering 25 (8), pp. 120-123.

    Abstract

    AC electrokinetics have played an important role in the advancement of BioMEMS research. Although the various AC electrokinetics methods offers a myriad of advantages in conducting bioparticle electrophysiology, the uptake of the technology has been limited only to research centres. One reason is due to the time-consuming procedures involved. This report documents the development of a programmable, multiple frequency signal generator that may be used in any AC electrokinetics experimental setup in conducting parallel electrophysiology assays. The development employs commercially available tools and components, which hopefully encourages the uptake of the various AC electrokinetics methods in conducting BioMEMS research.

  • Kadri NA, Hoettges KF, Hughes MP. (2008) 'Microelectrode Fabrication Using Indium Tin Oxide (ITO) For Microfluidic Devices Employing Dielectrophoresis'. SPRINGER IFMBE Proceedings, Kuala Lumpur, Malaysia: BIOMED 2008: 4th Kuala Lumpur International Conference on Biomedical Engineering 21 (1-2), pp. 719-722.

    Abstract

    Dielectrophoresis (DEP) has been widely employed as one of the techniques in developing various micro-electromechanical systems (MEMS). The manipulation of particles using DEP forces is dependent upon the particles’ dipole moment that is produced in the presence of an electric field gradient. The paper documents the fabrication processes employed at the University of Surrey in developing the microelectrodes to be used in generating the said field gradient.

  • Huebner Y, Mulhall H, Hoettges KF, Kass GEN, Ogin SL, Hughes MP. (2007) 'Dielectrophoresis: A new in vitro approach to measure drug-induced cytotoxicity'. ELSEVIER IRELAND LTD TOXICOLOGY, Univ Surrey, Guildford, ENGLAND: Annual Congress of the British-Toxicological-Society 240 (3), pp. 183-184.
  • Mureau N, Mendoza E, Hoettges KF, Silva SRP, Hughes MP. (2006) 'Determination of relative concentrations of metallic and semi-conducting SWNTs in suspension via dielectrophoresis'. 2006 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2006 Technical Proceedings, 1, pp. 110-112.

    Abstract

    Dielectrophoresis (DEP) is a phemomenon of induced particle motion in non-uniform electric fields. The effect is frequency dependent; by monitoring the motion of particles in AC fields and ananlysing the change in motion with frequency, it is possible to determine the electrical properties of nanoparticles in lab-on-a-chip systems. In this paper, we demonstrate how DEP can be used to determine the ratio of semiconducting and metallic carbon nanotubes in solution, by monitoring the frequency-dependent impedance change between two electrodes as a function of energising frequency.

  • Hughes MP, Dean Astumian R. (2006) 'Dielectrophoretic ratchets for linear and rotary nanomotors'. 2006 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2006 Technical Proceedings, 3, pp. 377-380.

    Abstract

    Dielectrophoresis (DEP) is a phemomenon of induced particle motion in non-uniform electric fields. In this paper, we will describe how the phenomenon can be used to design electrokinetic ratchet devices to provide both linear and rotary motion. Such devices exploit Brownian motion through the imposition of an asymmetrical potential energy field, to provide motion. Since Brownian motion is a prerequisite, such devices are most applicable to the transport of nanoparticles. In this paper, we present the results of modelling of such devices capable of linear translation, and of particular novelty, rotary motion and show the torque of the rotary motor is of the order of that generated by a bacterial motor.

  • Fatoyino HO, Huebner Y, Hoettges KF, Hughes MP, Labeed FH. (2006) 'Applications of Dielectrophoretic / electrohydrodynamic electrodes for concentration of biological nanoparticles'. 2006 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2006 Technical Proceedings, 2, pp. 275-277.

    Abstract

    Dielectrophoresis (DEP) is a phenomenon of induced particle motion in non-uniform electric fields. The effect is frequency dependent; by monitoring the motion of particles in AC fields and analyzing the change in motion with frequency, it is possible to determine the electrical properties of single cells in lab-on-a-chip systems. By combining two common electrokinetic phenomena dielectrophoresis and electrohydrodynamic fluid flow - we demonstrate that it is possible to manipulate, concentrate and trap particles from cell to molecular scale, and show how the trapping phenomenon is not related to particle size. We also discuss application of the phenomenon, from particle preconcentration in sensor systems to the deposition of particles on sensor surfaces.

  • Labeed FH, Chin S, Broche LM, Coley HM, Thomas H, Hughes M. (2005) 'Rapid assessment of biophysical changes in K562 cells during apoptosis, determined using dielectrophoresis'. BIOPHYSICAL SOCIETY BIOPHYSICAL JOURNAL, Long Beach, CA: 49th Annual Meeting of the Biopysical-Society 88 (1), pp. 565A-565A.
  • Hughes MP, Hoettges KF. (2005) 'Dielectrophoresis for drug discovery and cell analysis: novel electrodes for high-throughput screening'. BIOPHYSICAL JOURNAL, 88 (1), pp. 172A-172A.
  • Fatoyinbo HO, Hughes MP. (2004) 'Finite element modelling of a 3 dimensional dielectrophoretic flow separator device for optimal bioprocessing conditions.'. Conf Proc IEEE Eng Med Biol Soc, United States: 4, pp. 2587-2590.

    Abstract

    Planar 2-dimensional dielectrophoresis electrode geometries are limited in only being capable of handling fluid volumes ranging from picolitres to hundreds of microliters per hour. A 3-dimensional electrode system has been developed capable of handling significantly larger volumes of fluid. Using finite element modeling the electric field distribution within various bore sizes was realized. From these simulations it is possible to optimize bioprocessing factors influencing the performance of a dielectrophoretic separator. Process calculations have shown that flow-rates of 25ml hr/sup -1/ or more can be attained for the separation of heterogeneous populations of bio-particles based on their dielectric properties.

  • Labeed FH, Hughes MP, Charlton P, Coley HM. (2002) 'Assessment of modulator action on drug-resistant and sensitive cancer cells using dielectrophoretic methods'. NATURE PUBLISHING GROUP BRITISH JOURNAL OF CANCER, 86, pp. S22-S23.
  • Selvakumaran J, Hughes MP, Keddie JL, Ewins DJ. (2002) 'Assessing biocompatibility of materials for implantable microelectrodes using cytotoxicity and protein adsorption studies'. 2ND ANNUAL INTERNATIONAL IEEE-EMBS SPECIAL TOPIC CONFERENCE ON MICROTECHNOLOGIES IN MEDICINE & BIOLOGY, PROCEEDINGS, , pp. 261-264.
  • Hughes MP. (2000) 'AC electrokinetics: applications for nanotechnology'. IOP PUBLISHING LTD NANOTECHNOLOGY, SANTA CLARA, CALIFORNIA: 7th Annual Foresight Conference on Molecular Nanotechnology 11 (2), pp. 124-132.
  • Selvakumaran J, Hughes MP, Ewins DJ, Richards PR. (2000) 'Biocompatibility studies of materials used for chronically implantable microelectrodes'. IEEE 1ST ANNUAL INTERNATIONAL IEEE-EMBS SPECIAL TOPIC CONFERENCE ON MICROTECHNOLOGIES IN MEDICINE & BIOLOGY, PROCEEDINGS, LYON, FRANCE: 1st Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine & Biology, pp. 521-525.
  • Hughes MP, Bustamante K, Banks DJ, Ewins DJ. (2000) 'Effects of electrode size on the performance of neural recording microelectrodes'. IEEE 1ST ANNUAL INTERNATIONAL IEEE-EMBS SPECIAL TOPIC CONFERENCE ON MICROTECHNOLOGIES IN MEDICINE & BIOLOGY, PROCEEDINGS, LYON, FRANCE: 1st Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine & Biology, pp. 220-223.
  • Hughes MP, Flynn MF, Morgan H. (1999) 'Dielectrophoretic measurements of sub-micrometre latex particles following surface modification'. IOP PUBLISHING LTD ELECTROSTATICS 1999, CAMBRIDGE, ENGLAND: 10th Internatioal Conference on Electrostatics 163, pp. 81-84.
  • Bakewell DJG, Hughes MP, Milner JJ, Morgan H. (1998) 'Dielectrophoretic manipulation of avidin and DNA'. IEEE PROCEEDINGS OF THE 20TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 20, PTS 1-6, HONG KONG, PEOPLES R CHINA: 10th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society 20, pp. 1079-1082.
  • Hughes MP, Morgan H, Rixon FJ. (1998) 'Characterisation of herpes simplex virus particles by dielectrophoreic crossover methods'. IEEE PROCEEDINGS OF THE 20TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 20, PTS 1-6, HONG KONG, PEOPLES R CHINA: 10th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society 20, pp. 2816-2819.
  • Chan KL, Green NG, Hughes MP, Morgan H. (1998) 'Cellular characterisation and separation: Dielectrophoretically Activated Cell Sorting (DACS)'. IEEE PROCEEDINGS OF THE 20TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 20, PTS 1-6, HONG KONG, PEOPLES R CHINA: 10th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society 20, pp. 2953-2956.
  • Green NG, Hughes MP, Monaghan W, Morgan H. (1997) 'Large area multilayered electrode arrays for dielectrophoretic fractionation'. ELSEVIER SCIENCE BV MICROELECTRONIC ENGINEERING, UNIV GLASGOW, GLASGOW, SCOTLAND: Micro and Nano Engineering Conference 1996 (MNE 96) 35 (1-4), pp. 421-424.
  • Hughes MP, Morgan H, Rixon FJ. (1997) 'Dielectrophoretic characterisation and separation of herpes simplex virus particles'. BIOPHYSICAL SOCIETY BIOPHYSICAL JOURNAL, 72 (2), pp. MP447-MP447.
  • WANG XB, HUANG Y, HUGHES MP, PETHIG R, GASCOYNE PRC, BECKER FF. (1994) 'SEPARATION OF BIOLOGICAL CELLS USING TRAVELING ELECTRIC-FIELDS'. BIOPHYSICAL SOCIETY BIOPHYSICAL JOURNAL, 66 (2), pp. A281-A281.
  • HUGHES MP, WANG XB, BURT JPH, PETHIG R, WATKINS LR. (1994) 'SIMULATION OF TRAVELING ELECTRIC-FIELD MANIPULATION OF BIOPARTICLES'. INST ELECTRICAL ENGINEERS SECOND INTERNATIONAL CONFERENCE ON COMPUTATION IN ELECTROMAGNETICS, UNIV NOTTINGHAM, NOTTINGHAM, ENGLAND: 2nd International Conference on Computation in Electromagnetics (384), pp. 48-51.

Books

  • Hughes MP. (2010) Nanoelectromechanics in Engineering and Biology. CRC Press

    Abstract

    The field of nanotechnology is inherently multidisciplinary-in its principles, in its techniques, and in its applications-and meeting its current and future challenges will require the kind of approach reflected in this book.

  • Hughes MP, Hoettges KF. (2010) Microengineering in biotechnology. Humana Press

Book chapters

  • Hughes MP, Fatoyinbo HO. (2012) 'Biosensors'. in Bhushan B (ed.) Encyclopedia of Nanotechnology Springer

    Abstract

    At least one-third of the authors are expected to be from Europe and Japan. Since this encyclopedia is the first book in this emerging and potentially large field, the market is expected to be large and steady.

  • Hughes MP. (2012) 'Nanoparticle manipulation by electrostatic forces'. in William A Goddard III, Brenner DW, Lyshevski SE, Iafrate GJ (eds.) Handbook of Nanoscience, Engineering, and Technology CRC PressI Llc
  • Hughes MP, Hoettges KF. (2008) 'Bacterial manipulation by dielectrophoresis'. in Zourob M, Elwary S, Turner APF (eds.) Principles of Bacterial Detection Springer
  • Labeed F, Hughes MP, Hoettges K, Fatoyinbo HO. (2004) 'AC Electrokinetics of Particles'. in Dorf RC (ed.) Handbook of Engineering Boca Raton : CRC Press

Patents

  • Hughes MP, Hoettges MP. Apparatus for Collecting Particles.
  • Hughes MP, Hoettges KF. Apparatus for Detecting Particles.
  • Fatoyinbo HO, Hoettges KF, Hughes MP. Microelectrode device for dielectrophoretic characterisation of particles.
  • Hughes MP, Hoettges KF. Particle concentration in a liquid flow.
  • Hughes MP, Ogin SL, Hoettges KF, Wattingham R. (2005) Device for Dielectrophoretic Manipulation of Particles.

Other publications

  • Hughes MP. (2003) Micro- and nanoelectrokinetics in medicine. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE, 22 (6), pp. 32-32.

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