Rapid prototyping of PDMS devices using SU-8 lithography.

This protocol describes the fabrication of single and multi-layer SU-8 microstructures for generating microfluidic devices via PDMS (polymethyldisiloxane) casting. SU-8 is a negative, thick-film, epoxy based photoresist that has become widespread in the MEMS industry for producing durable, high aspect ratio microstructures for a variety of applications. It has become especially popular with microfluidics researchers to produce molds for PDMS casting since such molds allow for the rapid replication of prototype microfluidic structures made from PDMS. Although SU-8 processing does allow for rapid and straightforward development of devices it is prone to numerous pitfalls which have gained it a reputation of being somewhat of a "black art." This protocol attempts to give as full an account as possible of all the tricks and tips the author has learned over the years for processing SU-8. It also describes the casting of PDMS and plasma bonding for the generation of complete microfluidic devices ready for use in the lab.