2. Current Techniques for Fabricating Microfluidic and Optofluidic Devices

A wide variety of techniques have been developed for fabricating microfluidic and optofluidic components and devices using polymer, glass, and silicon substrates. This chapter gives a brief overview of these techniques, which can be categorized into two classes: parallel processing techniques based on photolithography and serial processing techniques based on direct writing. Some representative examples of these two categories are discussed, including photolithography on glass, soft lithography on poly(dimethylsiloxane) (PDMS), and femtosecond-laser-induced two-photon polymerization. The main advantages and disadvantages of parallel and serial processing are compared. Polymers are currently the most commonly used material for microfluidic and optofluidic applications because fabrication in polymers is easy, rapid, and cost effective. In contrast, glass offers better chemical durability and optical performance. Femtosecond laser direct writing enables microfluidic and integrated optofluidic structures with complex three-dimensional geometries to be directly embedded in glass, eliminating the need to use multistep procedures such as stacking and bonding.