Tailoring of porous silicon morphology in chip integrated bioreactors

The influence of the carrier matrix depth and homogeneity was investigated for porous silicon enzyme bioreactors. For the experiments < 110 > oriented silicon, p-type (20-70 Omega cm), was used. Porous silicon was generated o n planar surfaces and on anisotropically pre-etched high aspect ratio paral lel channel reactors. Samples were prepared with three depths, controlled b y the anodisation time, and two current densities yielding different morpho logies. In a second study, in order to make the porous layer more homogeneo us, reactors were fabricated with different channel widths and wall thickne ss. Glucose oxidase (GO(lambda)) was immobilised onto the porous matrix fol lowing standard procedures fur immobilisation of enzyme to silica. The enzy me activity of the samples was monitored following a colourimetric assay. T he results clearly display the influence of the matrix depth for both the p lanar and the reactor structures. An 170-fold increase in catalytic turn-ov er, when compared to an identical non-porous reference, was recorded for a reactor with an average porous depth of 10 mum. The importance of a homogen eous porous layer was illustrated, giving an increase in catalytic performa nce of three times between different structures with the: same geometric ar ea prior to anodisation.