ABSTRACT
This chapter discusses the photolithography process to fabricate SU-8 structures with dimensions ranging from millimeters to hundreds of nanometers. It explains the reader will get acquainted with the origin and properties of SU-8 as a material and why it is so useful in microfluidics. The material has become a major workhorse in miniaturization science because of its low UV absorption, high chemical and thermal resistance, and good mechanical properties that make it suitable as a structural material. Polyetheretherketone (PEEK) and poly(methyl methacrylate) (PMMA) closely resemble SU-8, with PEEK exhibiting a higher operating temperature and improved solvent resistance than PMMA. Substrate cleaning is the first and a very important step in any lithographic process, as the adhesion of the resist to the substrate could be severely compromised by the presence of impurities and residual coatings. Poor adhesion can result in leaks at the substrate/ SU-8 interface and compromise the performance of the microfluidic device.
