ENHANCED ENZYME-ACTIVITY IN SILICON INTEGRATED ENZYME REACTORS UTILIZING POROUS SILICON AS THE COUPLING MATRIX

The performance of porous silicon as a coupling matrix for silicon int egrated enzyme reactors has been investigated. A porous silicon layer in a wafer is expected to yield an increased catalytic activity when c oupling an enzyme to the wafer due to the surface enlargement of the p orous structure. The porous silicon layer is obtained by anodizing a 1 cm x 1 cm silicon die in a hydrofluoric acid/ethanol mixture at a con stant current density of 10, 50 or 100 mA cm(-2) for 50 min. Glucose o xidase is immobilized on the porous matrix of three dice and the enzym e activity of the silicon samples is monitored using a colorimetric as say. As a reference sample a polished die is also submitted to the enz yme immobilization. The three porous dice display higher glucose turn- over rates than the unetched reference die. Samples etched at lower cu rrent densities show increased turn-over rates. The maximum rise in tu rn-over rate is more than 30 times for the 10 mA cm(-2) sample compare d with the reference die. Porous silicon has the potential of being in corporated in a micro total analysis system (mu TAS) to give highly ef ficient enzyme reactors.