Biomedical subjects

C D W Wilkinson

Publications and source records attributed to C D W Wilkinson.

5 recordsLinked to original sources

PubMed2004

Making structures for cell engineering.

This is a mainly historical account of the events, methods and artifacts arising from my collaboration with Adam Curtis over the past twenty years to make exercise grounds for biological cells. Initially the structures were made in fused silica by photo-lithography and dry etching. The need to make micron-sized features in biodegradable polymers, led to the development of embossing techniques. Some cells response to grooves only a few tens of nanometers deep--this led to a desire to find the response of cells to features of nanometric size overall. Regular arrays of such features were made using electron beam lithography for definition of the pattern. Improvements were made in the lithographic techniques to allow arrays to be defined over areas bigger than 1 cm2. Structures with microelectrodes arranged inside guiding grooves to allow the formation of sparse predetermined networks of neurons were made. It is concluded that the creation of pattern, as in vivo, in assemblies of regrown cells in scaffolds may well be necessary in advanced cell engineering applications.

Absorbable Implants↗

PubMed2004

Dry etching and sputtering.

Dry etching is an important process for micro- and nanofabrication. Sputtering effects can arise in two contexts within a dry-etch process. Incoming ions cause removal of volatile products that arise from the interaction between the dry-etch plasma and the surface to be etched. Also, the momentum transfer of an incoming ion can cause direct removal of the material to be etched, which is undesirable as it can cause electrical or optical damage to the underlying material. This is largely avoided in dry-etch processes by use of reactive chemistries, although in some processes this component of the etching can be significant. Etch processes, both machine type and possible etch chemistries, are reviewed. Methods of characterizing the electrical and optical damage related to ion impact at the substrate are described. The use of highly reactive chemistries and molecular constituents within the plasma is best for reducing the effects of damage.

Journal Article↗

PubMed2004

A new design of specimen stage for in situ magnetising experiments in the transmission electron microscope.

A new stage for carrying out in situ magnetising experiments in the transmission electron microscope has been designed, constructed and tested. The principal advantages of the stage are that it delivers horizontal fields with negligible perturbation to the illumination and is suitable for operation in pulsed or continuous field mode. Details of its performance, including field calibration, are given. The paper concludes with a description of where the stage is likely to be of most use.

Journal Article↗

PubMed2004

Cells react to nanoscale order and symmetry in their surroundings.

Mammalian cells react to microstructured surfaces, but there is little information on the reactions to nanostructured surfaces, and such as have been tested are poorly ordered or random in their structure. We now report that ordered surface arrays (orthogonal or hexagonal) of nanopits in polycaprolactone or polymethylmethacrylate have marked effects in reducing cell adhesion compared with less regular arrays or planar surfaces. The pits had diameters of 35, 75, and 120 nm, respectively, with pitch between the pits of 100, 200, and 300 nm, respectively. The cells appear to be able to distinguish between different symmetries of array. We suggest that interfacial forces may be organized by the nanostructures to affect the cells in the same way as they affect liquid crystal orientations.

Animals↗

PubMed2002

Effective extra-cellular recording from vertebrate neurons in culture using a new type of micro-electrode array.

We describe the fabrication and use of a new type of extracellular micro-electrode array mounted on a flexible transparent polyimide substrate that can be rapidly moved from one part of a culture of vertebrate neurons (rat nodose) to another, which permits co-culture of glia under the neurons and is easily and rapidly replaceable in the event of damage. The array can be mounted on a micromanipulator and moved into place whenever and wherever recordings with or without stimulation are needed. The basic electrode system consists of 20-30 microm diameter gold electrodes, with or without platinisation, exposed to the cells through openings in the polyimide and joined to the recording or stimulating circuitry through gold tracks embedded in the polyimide. If rigid control over neuron placement has been achieved the patterns of electrodes can be matched to the neuron positions.

Animals↗