2. Fabrication of Microfluidic Devices

Microfluidics could not be thought about without advances in micro- and nanofabrication. Following an approach that has been adapted from microelectronics fabrication is carried out in a cleanroom environment using monocrystalline silicon as base material. It typically involves mask-based photolithography, dry and wet etching and thin film deposition. Glass can be used as an alternative or in combination with silicon and allows optical access to the fluid in the microdevices. A different approach using the so-called soft lithography and PDMS (polydimethylsiloxane) material has found widespread applications because it is relatively cheap and easy to use. In most cases the manipulation of fluids at microscales takes place in closed volumes or channels. Several bonding techniques have been developed allowing closure by a lid which in many cases can be transparent. Recently, maskless techniques like inkjet- or 3D-printing, laser micromachining, and microelectrical discharge machining get more and more attention.