Fabrication of a Gas-Flow Device consisting ofMicro Jet Pump and Flow Sensor

摘要

A gas-flow device consisting of a valveless micro jet pump and flow sensor has been designed and fabricated using aSi micromachining process. The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT)diaphragm actuator and flow channels. The design of the valvless pump focuses on a crosss junction formed by the neckof the pump chamber and one outlet and two opposite inlet channnels. The structure allows differences in the fluidicresistance and fluidic momentum inside the channels during each pump vibration cycle, which leads to the gas flowbeing rectified without valves. Before the Si micro-pump was developed, a prototype of it was fabricated usingpolymethyl methacrylate (PMMA) and a conventional machining techinique, and experiments on it confirmed theworking principles underlying the pump. The Si micro-pump was designed and fabricated based on these workingprinciples. The Si pump was composed of a Si flow channel plate and top and botom covers of PMMA. The flowchannels were easily fabricated by using a silicon etching process. To investigate the effects of the step nozzle structureon the gas flow rate, two types of pumps with different channel depths (2D- and 3D-nozzle structures) were designed,and flow simulations were done using ANSYS-Fluent software. The simulations and excperimental data revealed that the3D-nozzle structure is more advantageous than the 2D-nozzle structure. A flow rate of 4.3 ml/min was obtained for thepump with 3D-nozzle structure when the pump was driven at a resonant frequency of 7.9 kHz by a sinusoidal voltage of40Vpp. A hot wire was fabricated as a gas-flow sensor near the outlet port on the Si wafer.