Ronald A. Coutu, Jr., Ph.D., P.E.
Professor of Electrical Engineering
V. Clayton Lafferty Endowed Chair
(414) 288-72316
Marquette University
Opus College of Engineering
Dept. of Electrical and Computer Engineering
Engineering Hall 248
1637 W. Wisconsin Avenue
Milwaukee, WI 53233
Low-Cost, MEMS Membrane Pressure Sensors
/0 Comments/in Research Projects /by Wes GilmoreProject 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.
Nematic Liquid Crystal Composite Materials for DC and RF Switching
/0 Comments/in Research Projects /by Wes GilmoreProject by Mohiuddin Munna
Liquid Crystals (LC) are widely used in displays, electro-optic modulators, and optical switches. In these types of devices, an electric field is applied which modulates the optical properties of the LC material. It is attractive for its low power consumptions. Opto-electronic devices and switches made from LC materials consume comparatively less power than opto-mechanical counterparts and other electronic display technologies. There are only a few works done on all electrical switches and sensors. In this research, our goal is to design, simulate and fabricate LC switching devices and test the capacitive and resistive responses under DC and low-frequency AC and RF loads, using various electrode configurations. We will study electrode configurations that result in high sensitivity, low response time, and high on/off ratio. We have already done simulation and design using a simple analytic model, and a lithography mask. Our simulations and RF analysis suggest that RF switching with acceptable performance may be possible. LC materials in DC and RF switching application may open a new avenue for a low-cost solution.
MEMS based Gas Sensing
/0 Comments/in Research Projects /by Wes GilmoreProject by Turja Nandy
In this project, we will introduce MEMS membrane-based photo-acoustic (PA) detection system for a hazardous gas sensing application with high accuracy and low cost. We will use thin and deformable micro-machined SOI membrane to detect the acoustic vibration created via light-gas interaction inside the PA chamber. In this work, firstly, we will analyze the theory behind photo-acoustic phenomena and pressure change inside gas chambers for proper modeling of a MEMS membrane. Then, we will fabricate the MEMS membrane and prepare the whole optical experimental set-up with a LED-based infrared (IR) light source and detector according to the absorption spectra of target gases. Finally, we will detect the membrane deflection caused by acoustic vibrations and pressure change through a white light interferometer. These deflection values will give the sensitivity towards the particular gas.