Free-standing macroporous silicon membranes over a large cavity for filtering and lab-on-chip applications

This work presents a new electrochemical process for the formation of free-standing macroporous silicon membranes over a large cavity. The developed technique is based on a two-step electrochemical process of silicon dissolution, starting from thick macroPS membrane formation under the appropriate conditions and continuing with different anodization conditions that lead to formation of a nanoporous silicon layer underneath the macroporous membrane. The obtained structure is a double-layer of a macroporous over a nanoporous layer. By selective dissolution of the nanoporous layer, a free-standing macroporous silicon membrane over a large cavity in silicon is obtained. Interesting applications of this micromechanical structure include particle filtering and lab-on-chip devices. (c) 2006 Elsevier B.V. All rights reserved.