Experimental Investigation of Geometric Effect on Micro Fluidic Diodicity

The Micro pump is an essential component in a Micro Total Analysis System (μTAS). A feasible and reliable design of the micro pump is a key for the development of the μTAS. The Valve-less Rectification Micro Pump (VRMP) has many advantages, such as: non-moving parts, independent of fluids and channels properties, reliable, and easy to fabricate. Fluid diodicity is an essential parameter of the VRMP design. In this study, we investigate the fluid diodicity (the ratio of forward to reverse flow’s pressure drop) of micro rectifying geometries for more effective design of VRMPs. An experimental apparatus is designed and constructed. In our preliminary experiments, we measured diodicities of four different rectifying geometries, including bifurcation, heart shape, semi-circle and triangle. Experimental results demonstrate that rectifying geometries can take different designs that differ from the conventional diffuser-nozzle and Tesla’s designs; therefore, there is an opportunity to enhance the performances of VRMP by choosing the applicationspecific rectifying geometries INTRODUCTION With technological advancements in microelectromechanical (MEMS) systems and semiconductor micro-fabrication methods, along with the influx of genomic and proteomic data, μTAS will continue to provide superior benefits in many fields including pharmaceuticals, biotechnology, life science, defense, public health, and food/agriculture. An effective micro pump is a key component in any micro system that contains liquids flow. There are a large number of publications focusing on the design, fabrication, testing, optimization, analysis, and modeling of micro pumps that have different pumping mechanisms [1]. One of those is VRMP, which has several advantages over other types of micro pumps. First, it has no moving parts and has a much simpler design than typical mechanical micro pumps, which require components such as check valves [2]. Second, VRMP can pump a wide range of fluids regardless of their conductivity. In contrast, other types of non-mechanical micro pumps are restricted to fluids with a narrower range of conductivity; for example, magnetohydrodynamic micro pumps use high conductivity liquids [3] and electrohydrodynamic micro pumps typically use low conductivity liquids. Third, VRMP can pump liquids in micro channels made of different kinds of materials; other types of non-mechanical micro pumps require specific channel materials. For example, electro-osmotic micro pumps depend on the wall properties of the micro channels [4]. The design of VRMP is similar to the design of checkvalve pumps. The only difference is using rectifying geometries instead of check valves for flow rectification. Rectification efficiency is a function of fluidic diodicity, which characterize the performance of the rectifying structures: