Low-Cost, MEMS Membrane Pressure Sensors

Project by Anwar Farhana

Microelectromechanical Systems (MEMS) membranes are widely used in various applications ranging from stiffness tuning to gas pressure sensing. Superior properties such as higher sensitivity of MEMS membranes can be utilized in water-related applications [1,2]. However, lack of reliable processing, testing procedure, and packaging methods leads to electrical and mechanical failures and thereby restrict their progress in water applications. In this research, membrane thickness and diameter are used in concert to target specific stiffness values that will result in targeted operational pressure ranges of approximately 0-120 psi. A MEMS membrane device constructed using silicon-on-insulator (SOI) wafers, has been tested and packaged for the water environment. Microelectromechanical systems (MEMS) membrane arrays will be used to determine the operating pressure range by bursting.

Two applications of these SOI membranes in aqueous environment are investigated in this research. The first one is water pressure sensing. We demonstrated that robustness of these membranes depends on their thickness and surface area. Their mechanical strength and robustness against applied pressure were observed with Finite Element Analysis (FEA). The mechanical response of a membrane pressure sensor is determined by physical factors such as surface area, thickness and material properties (e.g. Elastic modulus and Poisson’s ratio). This is the only known SOI membrane approach, using MEMS fabrication techniques, to meet a low-cost water pressure sensing requirement.

Another application of this device is water leak detection. Devices such as pressure sensors, microvalves, and micropumps, membranes can be subjected to immense pressure that causes them to fail or burst [3]. Once the membrane bursts, the device will stop functioning. However, this event can be used to indicate the precise pressure level that malfunction occurred. These microelectromechanical systems (MEMS) membrane arrays can be used to determine pressure values by bursting. The failure event can be used to detect leakages in household appliances, ranging from automatic sinks to dishwashers.

Figure 1: Dimensions of MEMS membrane.