Low-Cost, Water Pressure Sensing and Leakage Detection Using Micromachined Membranes

This work presents the only known SOI membrane approach, using Microelectromechanical systems (MEMS) fabrication techniques, to address viable water leakage sensing requirements at low cost. 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. MEMS membrane arrays will be used to determine operational 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 demonstrate that robustness of these membranes depends on their thickness and surface area. Their mechanical strength and robustness against applied pressure are determined using 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. The second application of this device is water leak detection. In devices such as pressure sensors, microvalves and micropumps, membranes can be subjected to immense pressure that causes them to fail or burst. However, this event can be used to indicate the precise pressure level that malfunction occurred. These membrane arrays can be used to determine pressure values by bursting. We discuss the background information related to the proposed device: MEMS fabrication processes (especially related to proposed device), common MEMS materials, general micromachining process steps, packaging and wire bonding techniques, and common micromachined pressure sensors. Besides, FEA on SOLIDWORKS simulation module is utilized to understand membrane sensitivity and robustness. In addition, we focus on theories supporting the simulated results. We also discuss the device fabrication process, which consists of the tested device’s fabrication process, Deep Reactive Ion Etching (DRIE) for membrane formation, two different realizable fabrication technique (depending on sensing material) of sensing element, metal contact pads, and connectors deposition. In addition, a brief description and operation procedures of the device fabrication tools are provided as well. We also include detailed electrical and mechanical testing procedures and the collected data

Modeling, simulation and design of a laser-type pressure sensor

In the field of photoelectric sensing and measurement, laser triangulation is a superior and widely used technology due to its advantages of high accuracy, rapidity, and non-contact. This paper first applied it to the measurement of pressure, and proposed and designed a laser-type pressure sensor. The sensor measured the center deflection of the circular pressure-sensitive diaphragm using the laser triangulation, then determined the pressure on the diaphragm according to the small-deflection theory. In the aspect of optical system, the sensor used the principle of lens imaging of magnification and constant focus combining with high-resolution photodetector, which further improved the system accuracy effectively. First the paper created the mathematical model of the laser triangulation in view of the high accuracy, small size requirements. Afterward determined the parameters of the diaphragm in light of the linear range and measurement accuracy of the pressure, and did the finite element analysis of the diaphragm using ANSYS. The analysis demonstrates that within the pressure range, meeting the small-deflection theory, the relationship between the pressure and the deflection is nearly linear. The minimum pressure of the sensors designed is 50Pa, the pressure range is 1.4614MPa, and the maximum relative nonlinearity error of the diaphragm is 1.273%. This simulation design provides a forceful and important basis for the realization of the sensor. ? 2011 ACADEMY PUBLISHER