Monolithic MEMS vacuum valves for miniature chemical preconcentrators

A monolithic pneumatic valve is reported for use in a miniature chemical pre-concentrator. The valve comprises a perforated diaphragm above a substrate with offset perforations. The diaphragm is closed electrostatically, can be coated with adsorbent material for collecting the analyte of interest, and heated ohmically to desorb the analyte into the analytical system. The valve supports a high flow rate when open, along with the ability to maintain closure against over one bar of pressure, allowing its use with vacuum based instruments such as mass spectrometers. The fabrication process is described, and pneumatic and thermal performance are reported.