Nishagar Raventhiran Mechanical Engineering MS Thesis Defense
- Thursday, July 8, 2021 at 2:00pm
- Norm Asbjornson Hall, 337 and via WebEx Meeting number: 138 733 4640 Password: UcvfzPbJ359 - view map
Design and Fabrication of membrane-based pressure sensor for capillary pressure measurement in 2D micromodels
Pressure is a fundamental quantity in virtually all problems in fluid dynamics from macro-scale to micro/nano scale flows. Although technologies are well developed for its measurement at the macro-scale, pressure quantification at the microscale is still not trivial. Yet, precise pressure mapping at microscale such as in microfluidics is imperative in a variety of applications, including porous media flows and biomedical engineering. In particular, pore-scale capillary pressure is a defining variable in multiphase flow in porous media and has rarely been directly measured. To that end, this study aims to design and fabricate an on-chip sensor that enables quantification of capillary pressure in microfluidic porous media, called micromodels. The micromodel was fabricated in polydimethylsiloxane (PDMS) using soft lithography with a thin membrane incorporated that deflects with pressure variations in the fluid flow. Employing a microscope coupled with a high-speed camera and the astigmatism particle tracking principle, precise pressure measurement was achieved with an accuracy of ~ 60Pa. This sensor was then applied to characterize the viscous pressure drop in single-phase flows, and the capillary pressure in a water-air multiphase in microchannels, and good agreement was obtained between the sensor measurement, theoretical values and measurements employing a commercial pressure transducer. This thesis provides a novel method for in-situ quantification of local pressure and potentially 2D pressure field in microfluidics and thus opens the door to a renewed understanding of pore-scale physics of multiphase flow in porous media.
- Department of Mechanical & Industrial Engineering