Principles of Meniscus-Based MEMS Gas or Liquid Pressure Sensors

Pressure sensing using a trapped-gas volume-liquid meniscus interface offers several advantages over other microelectromechanical systems technologies for certain applications, including the potential for smaller footprints, harsh environment survivability, simple CMOS integration, and ease of fabrication. The small effective hydraulic diameter of microchannels can be exploited to produce gas/liquid interfaces that create menisci used to trap gas in sealed chambers. The pressure is monitored by optically or electronically measuring the displacement of the meniscus which behaves according to gas laws. This paper reports on the theory and realization of several fundamental concepts for this type of sensor, including the autocalibration of meniscus forces regardless of the sensor material or liquid; electrode integration for electronic interrogation in addition to optical measurements; simple repeatable manufacturing; and long-term drift. Hundreds of sensor devices were fabricated from silicon and glass and demonstrated positive pressure sensitivities of 42.5 μm/kPa near atmospheric pressure.