Dr Chris Mills
Dr. Chris Mills is a member of the research staff within the Nanoelectronics Research Centre at the Advanced Technology Institute.
He has held previous post-doctoral research positions in the UK and abroad. He has completed research at the Centre for Nuclear and Radiation Physics, University of Surrey, and at the Department of Electronics and Electrical Engineering, University of Glasgow, and was awarded a Spanish Ministry of Science and Technology “Ramon-y-Cajal” postdoctoral fellowship to study at the Nanobioengineering laboratory of the Catalan Institute for Bioengineering, Barcelona Science Park, Spain. Throughout his post-doctoral work, Chris has concentrated on the characterisation and application of polymers in different aspects of engineering.
Chris completed his PhD under the supervision of Prof. Martin Taylor, at the School of Electronic Engineering, Bangor University, looking into the characterisation of a low band-gap semiconducting polymer and its development as a semiconducting polymer memory element.
My research interests are related to the characterisation and application of structural and electronically conducting polymers in different engineering aspects.
I am currently involved in the production and development of large area organic light emitting diodes (OLEDs) at the Advanced Technology Institute. This involves the production of thin film semiconducting polymer diodes, incorporating carbon nanoparticle-based charge transport layers, over large areas, for the efficient generation of light of different colours. The OLEDs require characterisation of their physical and electrical properties, using a variety of methods, as well as the characterisation of the emitted light with respect to colour and intensity.
For this, I regularly draw on my previous experience in polymer characterisation and device production, including my previous work on semiconducting polymer X-radiation detectors, the production of polymeric nanotechnology systems for biomedical applications, and the development of polymer-based sensor systems for a variety of applications, including gas sensors for the analysis of exhaled breath and lab-on-a-chip based sensor systems for deep vein thrombosis (DVT) markers.
I have previously collaborated with diverse companies involved in the Microfabrication (Netscientific, UK, AMO GmBH, Germany), Nuclear (Centronix, BNFL, Lab Impex, NPL, all UK), Biotechnology (Oryzon, Spain), Health care (Haptogen [now Wyeth], UK) and Medical device (Helena Biosciences, UK) industries. I have also worked with non-profit making organisations, including the Centre for Nanotechnology, Microtechnology and Photonics (Cenamps [now CPI]), a north east of England based development office, and Anticoagulation Europe (ACE), a thrombosis patient support group.
I have been involved in the preparation of proposals for, and in the execution of, a number of national and European projects. These include:
- “SMARTONICS: Development of smart machines, tools and processes for the precision synthesis of nanomaterials with tailored properties for Organic Electronics” EC FP7 (STREP) 310229
- “Organic Radiation Detectors” STFC (MiniPIPPS) ST/F006667/1
- “TheraEDGE: An integrated platform enabling Theranostic applications at the Point of Primary Care” EC FP7 (IP) 216027; “DVT-IMP: Deep Vein Thrombosis - Impedimetric Microanalysis System” EC FP6 (STREP) 034256
- “MapTech: Training for Micro-Analytical Platform Technology” EC FP6 (Marie Curie) 020316-2
- "Nano-2-life, A network for bringing NANOtechnologies TO LIFE”, EC FP6 (NoE) NMP4-CT-2003-500057
- “CellPROM: Cell Programming by nanoscaled devices” EC FP6 (IP) NMP4-CT-2004-500039
- “Nanobiosensors based on individual molecules” The Spanish Ministry of Science and Technology, Ramon y Cajal Fellowship.
) nanoparticles (Z=83 for Bi) are added to a poly(triarylamine) (PTAA) semiconducting polymer in the active layer of an x-ray detector. Scanning electron microscopy (SEM) reveals that the Bi
nanoparticles are reasonably distributed in the PTAA active layer. The reverse bias dc currentvoltage characteristics for PTAABi
diodes (with indium tin oxide (ITO) and Al contacts) have similar leakage currents to ITO/PTAA/Al diodes. Upon irradiation with 17.5keV x-ray beams, a PTAA device containing 60wt% Bi
nanoparticles demonstrates a sensitivity increase of approximately 2.5 times compared to the plain PTAA sensor. These results indicate that the addition of high-Z nanoparticles improves the performance of the dosimeters by increasing the x-ray stopping power of the active volume of the diode. Because the Bi
has a high density, it can be used very efficiently, achieving a high weight fraction with a low volume fraction of nanoparticles. The mechanical flexibility of the polymer is not sacrificed when the inorganic nanoparticles are incorporated. © 2012 IOP Publishing Ltd.
poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene). Diode structures produced on aluminium-metallised poly(imide)
substrates, and with gold top contacts, have been examined with respect to their electrical properties. The results suggest
that a Schottky conduction mechanism occurs in the reverse biased diode, with a barrier to charge injection at the
aluminium electrode. Optical absorption/emission spectra reveal a band gap of 2.48 eV for the polymer. The diodes have
been used for direct charge detection of 17 keV X-rays, generated by a molybdenum source. Using operating voltages of
-10 and -50 V respectively, sensitivities of 54 and 158 nC/mGy/cm3 have been achieved. Increasing the operating
voltage shows that the diodes are stable up to approximately -200 V without significant increase in the dark current of
the device (
and flow of charges through the device, driving demand for cheap and effective electron transport/hole
blocking layers. Some materials, such as conjugated polyelectrolytes, have been identified as potential
candidates but the production of these materials requires complex, and hence costly, synthesis routes.
We have utilized a soluble small molecule naphthalene diimide derivative (DC18) as a novel electron
transport/hole blocking layer in common PLED architectures, and compared its electronic properties to
those of the electron transport/hole blocking small molecule bathocuproine (BCP). PLEDs incorporating
DC18 as the electron transport layer reduce turn on voltage by 25%; increase brightness over three and
a half times; and provide a full five-fold enhancement in efficiencies compared to reference devices.
While DC18 has similar properties to the effective conjugated polyelectrolytes used as electron transport
layers, it is simpler to synthesise, reducing cost while retaining favourable electron transport properties,
and producing a greater degree of efficiency enhancement. The impact on device lifetime is
hypothesized to be significant as well, due to the air-stability seen in many naphthalene diimide derivatives.
Pre-patterns of adhesive molecules, i.e. fibronectin and poly-L-lysine, have been produced on anti-adhesive poly
(ethylene) oxide films deposited by plasma-enhanced chemical vapour deposition, which prevents cell adsorption. The
structures consisted of adhesive squares and lines with 10¼m lateral dimensions, which correspond approximately to the
size of one cell nucleus, separated by 10¼m anti-adhesive gap. The stem cells cultured on these platforms redistribute their
cytoplasm on the permitted areas. Spherical cells were deposited on the square patterns in a single cell mode, while on the
lines they spread longitudinally; the extent of elongation being dependent on the specific (fibronectin) or non-specific
(poly-L-lysine) attachment biomolecule. The cell patterns were retained up to 12 days, which will be useful for recording
statistical data of individual chronic responses to chemical, physical or physiologically relevant stimuli.
Sensing Platforms, In: Demarchi D, Tagliaferro A (eds.), Carbon for Sensing Devices 5 pp. 105-132 Springer International Publishing Switzerland
platforms. The ability to chemically functionalize the surfaces of the
nano-carbon, using hybrid or nano-composite structures, can further
enhance the material properties. Complementary to the addition of
any requisite chemical or biochemical functionality, such
enhancements can take the form of improved electrical, optical or
morphological properties which improve the transduction capabilities
of the carbon nano-material, or facilitate detection of the transduced
signal, for example by improving charge transfer to detection
electronics. Here we review the methods of producing hybrid and
nano-composite carbon structures for sensing systems, highlighting
the advantages of the functionalization in each case and benchmark
their performance against existing carbon-only devices. Finally, we
detail some of the recent applications of hybrid and nano-composite
carbon technologies in a wide variety of sensor technologies.
nanostructures for biomedical applications using pattern
replication techniques, Contributions to Science 3 (1) pp. 47-56
is placed on imprint production of polymeric replicas, with master fabrication using focussed ion-beam technology, as a relatively simple method for reproducibly obtaining large numbers
of nanostructures. The use of these structures in polymercasting techniques is also described, together with some specific fabrication considerations. The maturity reached by
polymer-based nanotechnologies, together with the first polymer-based applications for single-cell analysis and for counting single DNA molecules, demonstrates that polymers constitute
a viable alternative to silicon-based nanotechnologies for biomedical applications.
security, with many potential uses limited by system cost and/or detector dimensions.
Current X-ray detector sensitivities are limited by the bulk X-ray attenuation of the
materials and consequently necessitate thick crystals (~ 1 mm ? 1 cm), resulting in rigid
structure, high operational voltages and high cost. Here we present a disruptive,
flexible, low cost, broad-band, and high sensitivity direct X-ray transduction technology
produced by embedding high atomic number bismuth oxide nanoparticles in an organic
bulk heterojunction. These hybrid detectors demonstrate sensitivities of 1712 µC mGy-1
cm-3 for ?soft? X-rays and ~30 and 58 µC mGy-1 cm-3 under 6 and 15 MV ?hard? X-rays
generated from a medical linear accelerator; strongly competing with the current solid state detectors, all achieved at low bias voltages (-10 V) and low power, enabling
detector operation powered by coin cell batteries.
The electric field behaviour of different TENG architectures is studied using Maxwell?s equations, leading to the derivation of the distance-dependent electric field (DDEF) model. This new model is capable of fully explaining the electric field behaviour and working principle of TENGs, overcoming the drawbacks of previous models. The DDEF model is developed initially for the vertical contact-separation mode TENG and expanded to represent all working modes which utilise contact-separation movement, via the development of unified DDEF model. The models are then used to simulate the output trends of different experimental TENG devices. An experimental setup is developed and TENG devices fabricated to assess the DDEF model predictions, which verifies the higher accuracy of the new model over previous capacitor-based circuit models.
Using the unified DDEF model as a framework, the effect of different structural and motion parameters of TENGs on their power output is studied. A number of new analysis techniques are introduced, including the TENG power transfer equation and TENG impedance plots, to identify the output trends and optimisation routes to design TENG devices, resulting an increase of power and reduction of TENG internal impedance by more than an order of magnitude. Finally, application of theoretical knowledge gained from the DDEF model is demonstrated by constructing a direct current output TENG device. This new design produces a constant power output subjected to continuous input motion, showing the potential to be used in self-powered electronic applications.