Glass micromachining application

Substrates The substrates in microelectronics are mainly Si wafers. For mobile applications, silicon-on-insulator (SOI) wafers increasingly replace bulk Si wafers and for very specific high-frequency applications, III-V compound semiconductors (e.g., GaAs) are used. The majority of substrates in microfabrication are Si wafers, but metal, glass, and ceramic substrates are also common. Particularly when using glass, quartz, and ceramic wafers in CMP processes, it has to be taken into account that they are brittle and easy to break. The situation is worse when the material is also under stress induced by deposited layers. For applications where the backside of the wafer has to be structured (e.g., in bulk micromachining), double-side polished substrates are employed. 

Giridhar MS, Seong K, Schulzgen A, Khulbe P, Peyghambarian N, Mansuripur M. Femtosecond pulsed laser micromachining of glass substrates with application to microfluidic devices. Appl Opt 2004 43 4584-9. 

Lee KB, Lin LW (2004) Surface micromachined glass and polysilicon microchannels using MUMPs for BioMEMS applications. Sens Actuator A lll(l) 44-50... 

Research in laser micromachining wiU continue to new methods for the fabrication of microfluidic devices, particularly from polymers and glass. The development of 3D channel networks is important for numerous fluidic applications which wiU fuel the future demand for more research in this area. As these methods are refined, the processes wiU be tailored to processing of many different types of polymers. Future work will continue to seek methods to decrease the roughness of microchannels. 

Amperometry can be used in conjunction with capillary electrophoresis (CE). On chip the CE system uses an electric held for separation of analyte molecules in a narrow channel or capillary on the basis of electrophoretic mobilities of molecules. The CE system usually consists of a sample injection channel, a separation channel, and electrodes for application of electric held, as well as measurement of current signals. There are quite a few instances of such development [56-58]. For example, Wang et al. integrated micromachined capillary electrophoresis with amperometric detection for dopamine detection [59]. The glass chips consist of a separation channel, a sample injection channel, and a thin layer of sputtered An (acting as working electrode) at the outlet of the separahon channel (Fig. 5.11). Dopamine was delected with LOD of 1 pM and linear response from 20 to 200 pM. 

---