I have had a longstanding interest in the use of inkjet printing as a fabrication tool. Past projects include: the use of inkjet printing to fabricate ceramic objects, determining the physical limitations of drop ejection on high viscosity fluids, 3D printing and splashing thresholds. Current active projects include:
Interactions of Droplets on Surfaces
We are studying how inkjet printed drops behave on a range of solid and porous surfaces (including paper and textiles). Drop shape is strongly influenced by the properties of the interfaces present and also by the proximity of neighbouring drops. The evolution of the drop shape depends on dynamic forces, surface forces and drying or solidification kinetics, each with its own associated time constants. We are combining experimental and modelling approaches to study the phenomena and using high speed imaging to characterise the time evolution of drops. This project is part of an Industry/University collaboration on Next Generation Inkjet Technology.
Inkjet Printing Biosensors
We are studying the use of inkjet printers to fabricate protein based biosensors. There are concerns that the high shear rates during droplet ejection and impact may influence protein shape and hence enzymatic performance post-printing; a range of proteins are under study. We are also investigating printable electrodes and protein/electrode interactions. In collaboration with Xaar, AET, Ellis Developments, Oxford Biomaterials.
Direct Write Processes
We are working with colleagues in industry to develop inkjet printing and other direct write methods to produce functional devices on existing structures. We are studying metallisation through novel printable silver precursors and studying ink/surface interactions. In collaboration with BAE Systems, Airbus, GEM, CERAM Research, NW Aerospace Alliance, GSI LUmonics, APT, Materials Solutions
Inkjet Printing Cells and Biomaterials
We are developing the use of inkjet printers to co-deposit living cells with biomaterials to generate hybrid cell-containing structures with potential applications in tissue engineering and cell-based sensors. We have studied the response of a range of cell types to the stresses of printing and are now studying the patterning of structured surfaces with controllable cell-adhesion. We are also exploring novel methods for the delivery of hydrogel materials. In collaboration with Prof. Nicola Tirelli (School of Pharmacy), Mr. Tim Woolford (Manchester Royal Infirmary), Xaar, AET, Ellis Developments, Oxford Biomaterials.
Mechanical Characterisation of Biological Structures and Biomaterials
Changes in the mechanical properties of cells and extracellular matrix are characteristic pathologies of a number of diseases, medical conditions and the ageing process. Although there are many techniques through which tissue mechanics can be characterised and mechanical properties determined, it is difficult to correlate changes in tissue properties with histology or changes on the molecular level. Our target is to develop methods of mechanical property measurement that can be used with conventional histological sections and produce spatially resolved measurements that are on a scale compatible with optical microscopy.
Nanoindentation of Histological Sections
We are using nanoindentation to characterise the changes in stiffness of blood vessels that occur in diabetic patients. We are also investigating changes in arterial stiffness with ageing. In order to use nanoindentation with histological sections we are developing methods used to measure the mechanical properties of thin coatings. In collaboration with Kennedy Cruickshank (Manchester Royal Infirmary), Mike Sherratt (School of Medicine), Rachel Watson (School of Medicine).
Acoustic Microscopy of Histological Sections
We are developing novel ultra-high frequency acoustic methods to image histological sections and extract quantified mechanical data through analysing the images. The spatial resolution of the microscope is comparable to conventional optical microscopy. Once developed the technique will be used to analyse a number of biological and medical problems identified by a number of collaborators. In collaboration with Mike Sherratt (School of Medicine), Rachel Watson (School of Medicine).
Acoustic Imaging and Analysis of Cells
Cell stiffness is related to the properties of the cell cytoskeleton. We are working with colleagues in the Faculty of Life Sciences who have developed methods to control signalling pathways that influence cell adhesion and the mechanical properties of the cytoskeleton. We are developing methods based on acoustic microscopy to enable us to characterise the mechanical properties f individual cells and sections of cells. We are also working with Cancer Research UK to determine the mechanical properties of invasive and metastasison cell lines. In collaboration with Christoph Ballestrem (Faculty of Life Sciences), Erik Sahie (Cancer Research UK, London).
Nanoindentation of Contact Lens Materials
Soft contact lenses are made from very high compliance hydrogel materials. The mechanical properties of contact lenses must be compatible with the human cornea. We are developing nanoindentation methods for use with contact lens materials. In collaboration with Carole Maldonado-Codina (Faculty of Life Sciences)
Mechanics of Nanoporous Foams and Metal Micropillars
We are studying the dislocation mechanisms that operate in metal nanostructures and developing micromechanical models of deformation.