University of Connecticut

Events Calendar

PhD Defense

Wednesday, August 16, 2017
10:00am – 12:00pm

Storrs Campus
Physics Building, P121

Adimali Piyadasa, Department of Physics, University of Connecticut

Design and Fabrication of Micro-pillar Based Piezoresistive Flow Sensors

This dissertation is focused on designing, fabricating, and validating a new type of micro-scale gas flow sensors using finite element modeling by COMSOL Multiphysics module, and microfabrication and electrical probing techniques. The designed miniaturized flow sensor fully utilizes the anisotropic piezoresistive property of Silicon micro-pillar arrays that are sensitive and dependent on the geometry selection, density distribution, and chemical doping profile, as predicted by finite element modeling. Change in resistivity tensor due to gas flow induced stress in the piezoresistive layer results in generating of an output voltage proportional to the gas flow rate in the channel, which can be spatially resolved through pillar physical and chemical characteristic design at microscale or even nanoscale. As such, our results show that the Silicon micro-pillar flow sensor can be readily used to not just detect the mass (gas) flow rate, but also differentiate flow components in different directions within a microscale three-dimensional (3D) space. Furthermore, the complementary modeling and experimental study successfully predicts and validates its applicability in measuring 3D local flow fields in high resolution due to its micro-scale dimensions that could be extended to nanoscale regime. With fundamental understanding obtained by the micro-pillar device design, parameter analysis, and the experimental process developed, this study provides a useful and timely guidance in designing and fabricating miniaturized flow sensors with ability to differentiate local flow directional components at high spatial resolution. The micro- or nano-pillar array based flow sensors could find applications in harsh environments such as high pressure, high temperature, and high mass flow conditions in combustion engines, and in integrated micro-electromechanical systems such as lab-on-chip devices.


Dr. Pu-Xian Gao

Physics Department (primary)

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