Cell engineering is concerned with the combination of engineered materials with biological cells to create useful devices. Cells in the body are organised spatially and this organisation is reflected in the shapes of the cells themselves and in how they are positioned relative to their neighbours. A necessary first step in re-growing cells to form a tissue-like implant is to re-create this original pattern in the re-grown cells.
A brief account is given of the effects of topographic and chemical patterning on the behaviour of cells.
The methods by which such patterning can be transferred into materials suitable for cell and tissue engineering are given. The advantages of using mechanical transfer in one of its many forms for this purpose are stressed.
This paper describes work carried out to evaluate the performance of Shipley UV5 DUV positive tone photoresist for electron beam lithography using experimental design techniques. Factors which affect the results of resist processing have been identified by initially performing two level factorial screening test followed by detailed response surface analyses. Lines and spaces with a 120 nm period were produced using optimized conditions and there was no evidence of process delay effects over three hour periods in air. Separate batches of the resist were found to have similar optimum baking temperatures. The result obtained have been used to develop reliable techniques for the fabrication of 'T' shaped and Gamma shaped metallized gates for high frequency circuit applications. Comparisons have been made with result obtained using Shipley UV3 photoresist. We conclude that UV5 resist is a useful resist for electron beam lithography applications.
We present experimental and theoretical results on the low temperature luminescence intensity of dry etched GaAs-AlxGa1-xAs quantum dots. The luminescence intensity was found to decrease by two orders of magnitude with the decrease of dot sizes from 1 micrometers to 60 nm. Our intrinsic model of the emission yield invokes slower momentum and energy relaxation mechanisms as the lateral dimensions decrease. The extrinsic effect, which we include in our interpretation of the luminescence intensity, involves carrier diffusion with a surface nonradiative recombination velocity. The combined effect (intrinsic and extrinsic) gives a very good fit to our data. The surface recombination velocity needed for the fit was approximately 105 cm/s. Raman studies on the quantum dots showed enhanced surface phonons with the decrease of the nanostructure sizes. `GaAs'-like and `AlAs'-like surface phonons were also observed for the first time in etched nanostructures, in good agreement with the theoretical predications.