3 © Woodhead Publishing Limited, 2012 1 Microfabrication of polymers for bioMEMS P. REZAI, W-I. WU and P. R. SELVAGANAPATHY, McMaster University, Canada Abstract: Use of microfabrication methods derived from the semiconductor industry have been adapted to new materials in the recent past to produce electromechanical and fluidic systems in the microscale. Polymers are one such class of new materials as they are considered more suited for biomedical applications due to low cost, abundance, and availability of a wide range of functionality in addition to properties such as low protein adsorption, chemical resistance, and low electrical and thermal conductivities. This chapter describes in detail the properties, microfabrication methods and applications associated with most of the widely used polymers such as polydimethylsiloxane, parylene, SU-8, hydrogels, biodegradable materials and thermoplastics. Key words: polymers, microfabrication, polydimethylsiloxane (PDMS), parylene, SU-8, hydrogels, porous monoliths, biodegradable polymers, paraffin, thermoplastic polymers. 1.1 Introduction BioMEMS and lab-on-chip-based automation and miniaturization of analytical assays have significantly improved their performance, through- put, and the cost associated with them in areas as diverse as medical diag- nostics, drug delivery, drug discovery, analytical chemistry, and molecular diagnosis (Dittrich and Manz, 2006). Use of microfabrication methods to produce lots of precisely replicable devices has led to repeatable and reliable performances. Automation eliminates the human interfering fac- tors and increases the confidence in the analysis (Selvaganapathy et al., 2003). Polymers have been widely used in bioMEMS devices primarily due their low cost, chemical inertness, low electrical and thermal conductivi- ties, ease of surface modification, and their biocompatibility. Since poly- mers cost less, they are ideally suited for disposable bioMEMS devices where cross contamination is an issue. The low cost of polymeric materi- als and their processing technique is one of the biggest advantages that provide impetus for development of novel processing technologies for microfabrication of polymeric MEMS/microfluidic systems. This chapter