Silicon and glass micromachining for μTAS

This chapter explores the micromachining of fluidic structures in silicon, and presents several examples of demonstrated functionality of devices in silicon. An often-used method for micromachining of silicon is anisotropic wet chemical etching. This is the most frequently used for the fabrication of membranes for pressure sensors. Such membranes may also serve as check valves or membranes in micropumps. The main advantage of anisotropic etching is the limited design freedom in the fabrication of channels with sharp bends but this method also allows the largest degree of freedom of structural design. Glass shows excellent chemical and optical properties and allows a variety of design possibilities. To obtain the desired microstructures in glass, batch fabrication techniques similar to those used for silicon micromachining, based on photolithography, can be used. Those processes help in achieving features with a size down to several tens of nanometers. So this method is useful for shallow structures. To fabricate micron and nano-scale structures with high yield and quality, high demands are put on the purity, uniformity of materials and surfaces and on the cleanness of the fabrication processes and fabrication environment, such that cleanroom environments and materials like silicon and glass become desirable, not only for prototype systems but also for commercial applications.