Development of porous-silicon-based active microfilters

With a goal of preparing silicon-based interactive filters in the micropore range, we have developed the first single-step etch-liftoff procedure (one-step separation) based on the formation and removal of macroporous silicon layers. With silicon wafers whose resistivities are in the range from 14 to 22 Omega cm, we are able to create, in a surprisingly controlled manner, films whose pore diameters range from 1-2 m and whose thickness ranges from 3 to 70 mu m. These silicon-based films (filters), which carry a polarizing negative charge, represent an alternative to porous alumina (films) filters (pore diameter not yet in the 1-2 mu m range) both in terms of their size range and potential interaction-reaction at elevated temperature. Preliminary experiments demonstrate that platinum and copper can be introduced to these filters using electroless solutions with a goal to creating an effective reductive surface. Using these and alternate material combinations, interactive-reactive filters in the 1 mu m size range that operate at temperatures well in excess of porous polymer films can be realized. (c) 2007 The Electrochemical Society.