Study On Fabrication And Circuits Of Polyimide-Based Flexible MEMS Flow Sensor

The flow sensor can reflect the change of the velocity in real time through the change of the physical characteristics such as temperature and pressure.Based on the working principle of the temperature difference and hot wires,a flexible MEMS velocity sensor based on flexible polyimide film is designed to create good flexibility,wide measuring range and high measuring precision performance.The main work of this paper is as follows:(1)Design and fabrication of flexible MEMS flow velocity sensor.In this paper,the structure of flow velocity sensor is designed based on the combined principles of thermal temperature difference and hot wire.Polyimide(PI)was selected as the substrate materials and platinum thin film was used as thermal sensing elements.The flexible MEMS flow sensor chip in size of 9mm×7mm×30?m was fabricated employing MEMS process based on metal sacrificial layer.(2)Design of the measurement and control circuit of the flexible MEMS flow sensor.The principle and application of velocity sensor control circuit working mode,Wheatstone bridge and temperature compensation circuits are described in detail.Two kinds of control circuits of high speed and low speed are designed.The control circuit with temperature compensation function is based on the detection principle of constant temperature difference,and the principle of Wheatstone bridge is used to process the measuring signals.(3)Simulation and fabrication of measurement and control circuit of flexible MEMS flow sensor.According to the simulation results of low speed and high speed test circuit,the parameters of each component are optimized.The circuit board is designed and drawn,and the PCB board of low speed and high speed measurement and control circuit is made.(4)Test experiment of the flexible MEMS flow sensor.The TCR coefficient of thermal resistance of the fabricated sensor is tested.The wind speed input test system with flexible flow sensor and measurement and control circuit is set up,and the output voltage of the sensor is measured at a wide range of speed.The test experiment achieved a 0-36 m/s inputted wind speed measurement,where the sensitivity was 2 mV/(m/s)at the range of 0-22 m/s wind speed.Therefore,the sensor showed excellent performance of large measuring range and high sensitivity.