Design And Fabrication Of Wide Range Flow Velocity Sensor Based On Flexible MEMS Technology

Demand of the field of aerospace,military and bio-medical on the flow velocity sensor is exigent,and the traditional flow velocity sensors are unable to meet the requirements.With the development of microelectronics processing technology and MEMS technology,MEMS thermal flow velocity sensors based on thermal transport principles become mainstream because of its miniaturization,high precision and being able to distinguish direction of flow.Currently,most of the flow velocity sensors are only applied for lowspeed or high-speed measurement and can not get accurate measurements over a wide range.Most of the sensors are processed on a silicon substrate,making a lot of heat loss to the substrate and the the sensors can not be installed on surfaces with complex curvature,which greatly affects the scope of application.In this paper,a flow velocity sensor based on flexible MEMS technology is designed and fabricated,which can be used for both lowspeed and high-speed flow to achieve wide-range measurement.Moreover,the flow velocity sensor can be installed on the surface with complex curvature.The main work of this paper is concluded as follows:(1)Structure design and simulation of the wide range flexible flow velocity sensor.Based on flexible MEMS technology,two kinds of structures of wide-range flow velocity sensor,employing combination of principles of anemometer and calorimeter,are designed.Using finite element simulation software COMSOL multiphysics,the structural influencing laws of flow velocity sensor are studied through thermal-fluid simulations based on principle of anemometer and principle of calorimeter respectively.(2)Simulation and analysis of the feasibility to use the wide range flexible flow velocity sensor to measure the flight speed of mortar bomb for trajectory identification.The mounting position of the flexible thermal flow velocity sensor in fuze and the relationship between flow velocity in fuze and mortar bomb's flight speed are studied through flow field simulation of mortar bomb's fuze and joint simulation of the sensor and fuze using COMSOL,which provides a new method for the flow velocity sensors used for trajectory identification of the motar bomb.(3)Micro fabrication of the designed flexible flow velocity sensor.Based on flexible MEMS technology,the two kinds of structures of the flow velocity sensor are fabricated on the same wafer employing top-down processing flow.The dimensions of the fabricated flow velocity sensor chips for two kinds of structures are 9mm×7mm and 6.5mm×7mm,respectively.(4)Circuits design and preliminary tests of the flexible flow velocity sensor.Control circuits of the constant temperature difference mode are employed for the fabricated flow velocity sensor,and bridge circuits corresponding to high flow measurement and low flow measurement are designed respectively.With wires of the sensor be connected,the TCR of the thermistors of the sensor are mearsured for calibration.A simple flow rate test was carried out and the working current and voltage is determined,it proved that the heating resistor of the flow velocity sensor can meet the requirements to mesure the change of flow velocity.