Experimental study on a micro flow sensor

Abstract

This thesis is to introduce a micro flow sensor for many applications in biological reactions and processes, fuel cells, high performance heat exchangers and cooling devices, chemical processes, to name a few. The micro flow sensor is integrated on the quartz wafer and is manufactured by simple and convenient microfabrication processes which are the sputtering processes. In the microfabrication processes, stainless steel masks with different patterns are used to deposit alumel and chromel for the temperature sensors in the micro flow sensor and nichrome for the heater in the micro flow sensor on the quartz wafer. These stainless steel masks are more practical than PR(PhotoResist) masks because of low cost and reduced manufacturing time. The microchannel is made of PDMS (Polydimethysloxane) easily. The micro flow sensor is bonded to the PDMS microchannel by using air plasma. First of all, simple scale analysis is performed to investigate parameters influencing on the performance of the micro flow sensor. Using the micro flow sensor, temperatures distributions on the surface of the micro flow sensor are obtained as mass flow rate and input power variance by experiments. It is shown that the relation between mass flow rate and temperature difference is linear at low mass flow rate. The relation between temperature differences and temperature sensor positions are also presented. From experimental results, as temperature sensor positions are far from the heater, temperature difference between upstream and downstream decreases.