A Flow Visualization Experiment for a First Course in Micro-fluidics

Abstract

Abstract Physical intuition developed for fluid flows at the macro-scale can be very misleading when applied to flows in microchannels. The Reynolds number of these flows is typically low, and thus they remain totally laminar. Under microflow conditions, familiar phenomena such as fluid mixing behave counter to the intuition developed by students in a standard engineering curriculum. We present a laboratory project designed to stress this point to students taking a first-year graduate introduction to microsystems. The pilot group found the results surprising and counter-intuitive. It appears that the project was instrumental in clarifying key concepts in microfluidics. Introduction After several decades in which microsystems research mainly addressed electromechanical systems [1], the focus has begun to shift to fluidic systems. This shift is driven primarily by potential application of microsystems to chemistry, biology and medicine [2]. An introductory course in microsystems at Texas Tech University (TTU), offered to graduate students and advanced undergraduates, includes several modular projects in photolithography, surface micromachining and bulk micromachining [3]. The course also includes a microfluidics project using “soft lithography” [4]. The microfluidics component has undergone several iterations. This paper describes the most recent version, which requires the design, fabrication and test of a micromixer. It should be stressed that this course is the first of a three-semester sequence with 3 credit hours, and that subsequent projects require integration of valves, pumps and mixers with other components [3]. The main purpose of the module described here is to teach the basic