Development of a Needle-shaped Compact Thermal Flow Meter

Abstract

Thermal flow sensor which has micro size electrode patterns was made for measuring water flow speed up to 2.3 mm/s. Even though previous studies and industry products show many types of liquid flow sensor, they are limited to flow measurements only in specific closed and huge systems. On the other hand, our needle-shaped compact thermal flow meter can be flexibly applied to various flow environments such as natural fluids, liquid chemicals, and plants due to small body size and external needle application. To predict sensor operation, thermal transport simulation was conducted using COMSOL software, which is based on multi-physics modeling composed of laminar flow, joule heating, and heat transfer in fluids. The model verification work is accomplished as compared to experimental data, and the effect of sensor application condition and better sensor design are also predicted from the simulation analysis. To realize the needle-based flow sensor, various fabrication processes have been used such as oxide and nitride deposition, plasma ashing, wet and dry etching, photolithography, and thin metal film deposition. In addition, deep reactive ion etching (DRIE) fabrication process was also applied to make the needle shape properly. To systemize control and measurement, microprocessor-based experimental platform equipped with a voltage regulator and an amplifier was made, and the sensor verification work is well conducted from this system. This graduation thesis includes developing procedures of a needle-shaped compact thermal flow meter such as simulation, fabrication, control and measurement system, sensor verification, and application.