Projects

Vacuum Web processing
Prof. H.E. Assender, Dr. V. Tobin, X. Tao, H. Potter, Z. Wu
Development of coating techniques and materials using our unique roll-to-roll vacuum web processing capability. The coater can run a 35cm polymer web at speeds of up to 5m/s to allow the deposition of multiple layers from the following sources: i) evaporation, ii) dual magnetron sputter, iii) plasma iv) flash evaporation of organic materials with e-beam cure. Films can be produced for applications such as controlled optical properties and surface finish, high and low energy surfaces, barrier layers, biocompatibilisation or electronic devices.

Roll-to-roll processing for wearable and flexible technologies
V. Tobin, Prof. H.E. Assender
Electronics components that can be manufactured using roll-to-roll processing offer the possibility of lower cost devices as well as those that might be mechanically flexible in use. Roll-to-roll (R2R) processing, using a flexible substrate (typically a polymer film) allows for cheap production of many components very rapidly, with low energy requirements. Key areas of exploitation of this technology include flexible sensors as well as displays and energy generation and storage components.
This project seeks to exploit the existing industrialised technology of vacuum R2R processing, widely used for example in the packaging industry, to develop the manufacture of devices and circuits suitable for wearable technoligies. This manufacturing route, like solvent based systems, is cheap and provides flexible product. Additional advantages of the solvent-free vacuum processes include: a) likely enhanced web-speed, b) integration with vacuum-based metal deposition for conducting channels, and metal or ceramic deposition for barrier layers and possible interfacial modification, and c) the ability to deposit multiple thin layers to build up device structures without solvent interactions with underlying layers. One particular thread of this project is the in-line patterning of layers of various functional materials to bridge the gap between shadow masking and lithographic techniques in a manner that is suitable for high-throughput roll-to-roll processing.

Roll-to-roll manufacture of organic field effect transistor-based sensors
H. Potter, K. Zhang, Prof. H.E. Assender
Design, manufacture and testing of sensors based on vacuum-evaporated organic charge modulated field effect transistors. A basic pH sensor and strain sensor has already been demonstrated, and this project extend this to other analytes and understanding of the parameters to maximize sensitivity and selectivity, as well as development of flexible circuit elements for amplification and signal control.

Deposition of acrylate layers on polymer substrates by roll-to-roll coating in vacuum
Z. Wu, Prof. H.E. Assender
An investigation into the deposition of polymer layers by flash evaporation of monomer followed by curing in a high-speed roll-to-roll process. This project will consider the control of the degree and area of cure, and the role of acrylate chemistry and monomer mixtures.

High resolution pattern deposition of metal contacts for flexible electronics
H. Potter, Prof. H.E. Assender
Patterned metallization by evaporation can be achieved by printing an oil with a negative pattern on the substrate and metallizing over this oil as it evaporates. This project is investigating a novel approach to increase the resolution of this patterning method as well as further understanding the oil patterning parameters.

Roll-to-roll deposition of thermoelectric materials
X. Tao, Prof. H.E. Assender
The large-area manufacture of thermoelectric devices based on sputter-deposited semiconductor layers is investigated considering the manufacture of devices by roll-to-roll deposition onto polymer substrates.

Characterization of the defect populations in ultra-high barrier materials
G. Matsui, Prof. H.E. Assender
Transparent, flexible, ultra-high barriers are required for encapsulation of flexible electronics. Traditional approaches have relied on reducing the density of micron-scale defects in the ceramic barrier layers to reduce water vapour permeation, but our recent studies have highlighted the importance of nano-scale defects to the overall water vapour permeation. We are applying recently developed techniques, based on the Ca test, to further characterize the role of nanodefect populations in a range of barrier films.

Ordering in thin film polymers
H. Luo, Prof P.D. Nellist, Prof. H.E. Assender
Thin film polymers have been shown to show particular crystalline morphologies and crystallization temperatures due to diffusion and molecular mobility constraints associated both with the thickness of the film, but also interfacial interactions. We are investigating such near-free surface and near-interfacial ordering using atomic force and electron microscopies, in particular using high resolution electron microscopy with ptychography to directly image the local crystal structure, boundaries between crystals, and orientation of the polymers.

High resolution TEM of peptide hydrogels
B. Hao, Prof P.D. Nellist, Prof. H.E. Assender
Hydrogel materials made from short-chain peptides form fibrillar structures that are interlocked to form the gel. We are using high resolution electron microscopy to directly image the secondary structure and investigate the link between the amino acid sequence and the secondary structure, and to consider the fibre morphology in gelating materials.

Thin film polymer-dispersed liquid crystals
J. Mason, Prof. H.E. Assender
We are casting monomer/liquid crystal mixtures as thin films and solidifying the mix using radiation or thermal curing to cast a thin film PDLC. The properties of these layers will be investigated particularly with a view to optical, mechanical or topographical changes as the liquid crystal is reorientated in an electric field.