Characterization of micromachined silicon membranes for immunoisolation and bioseparation applications

The application of microfabrication technology to create precise separation and isolation membranes for biomedical applications is described. By utilizing fabrication techniques commonly employed in the microelectronics industry (MEMS), membranes can be fabricated with well-controlled and uniform pore sizes, allowing the optimization of membrane parameters for biomedical applications in cell immunoisolation and viral ®ltration. Using bulk and surface micromachining to create diffusion membranes, pore sizes down to 18 nm have been attained through deposition and subsequent etching of sacri®cial layers on silicon. Membranes were shown to be suf®ciently permeable to small biomolecules such as oxygen, glucose, and insulin, while excluding the passage of larger proteins such as immunoglobulin G (IgG). The semipermeability of microfabricated membranes, their biocompatibility, ease in sterilization, along with their thermal and chemical stability, may provide a signi®cant advantages for biomedical applications. Microfabrication technology may also be applied to other materials of interest for the development of highly controlled membranes. # 1999 Elsevier Science B.V. All rights reserved.