Biocompatible silicon wafer bonding for biomedical microdevices

In this paper, several candidate bonding materials are reviewed for use in biomedical microdevices. These include poly propylmethacrylate (PPMA), poly methylmethacrylate (PMMA), a copolymer of poly (ethyl, butyl) methacrylate (PBEMA) and two types of silicone gels. They were evaluated based on their cytotoxicity and bond strength, as well as several other qualitative assessments. The cytotoxicity was determined through a cell growth assay protocol in which cells were grown the various substrata and their growth was compared to cells grown on control substrata. The adhesive strength was assessed by using a pressurized plate test in which the adhesive interface was pressurized to failure. All of the substrata were found (once cured) to be non-cytotoxic in an inert manner except for the industrial silicone adhesive gel (Dow Corning 736). The adhesive strengths of the various materials are compared to each other and to previously published adhesive strengths. All of the materials were found to have a sufficient bonding strength for biomedical applications, but several other factors were determined that limit the use of each material (including defect density, patternability, and ease of application).