Tham khảo tài liệu 'the mems handbook (1st ed) - m. gad el hak part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Microdroplet generators usually employ mechanical actuation to generate high pressure to overcome liquid surface tension and viscous force for droplet ejection. Depending on the droplet size the applied pressure is usually greater than several atmospheres. The operation principles structure process designs and materials often play key roles in the performance of droplet generators. The applications of microdroplet generators in addition to the well-known application of inkjet printing cover a wide spectrum of fields including direct writing fuel injection solid freeform solar cell fabrication light emitting polymer display LEPD fabrication packaging microoptical components particle sorting microdosage plasma spraying drug screening delivery dosage micropropulsion integrated circuit cooling and chemical deposition. Many of these applications may become key technologies for integrated microsystems in the near future. This chapter provides the reader with an overview of the operation principles physical properties design issues fabrication process and issues characterization methods and applications of microdroplet generators. Operation Principles of Microdroplet Generators Many attempts have been made to generate controllable microdroplets Buehner et al. 1977 Twardeck 1977 Carmichael 1977 Ashley et al. 1977 Bugdayci et al. 1983 Darling et al. 1984 Lee et al. 1984 Myers and Tamulis 1984 Nielsen 1985 Bhaskar and Aden 1985 Allen et al. 1985 Krause et al. 1995 Chen and Wise 1995 Tseng et al. 1996 Hirata et al. 1996 Zhu et al. 1996 . Most of these methods have employed the principle of creating pressure differences either by lowering the outer pressure or increasing the inner pressure of a nozzle to push or pull liquid out of the nozzle to form droplets. Typical examples are pneumatic piezoelectric thermal bubble thermal buckling focused acoustic-wave and electrostatic actuations. The basic principles of those droplet generators are introduced in the following .
