A MEMS Flow Sensor and Its Application in Adaptive Liquid Dispensing

A high speed MEMS flow sensor was proposed to enhance the reliability and accuracy of liquid dispensing system. Benefiting from the feedback of sensor information, the system can self-adjust the open time of the solenoid valve to accurately dispensing desired reagent volume without pre-calibration. This paper focuses on the design, fabrication and application of this flow sensor. Firstly, the design, fabrication and characteristics of the MEMS flow sensor based on the measurement of the pressure difference across a flow channel are presented. Secondly, the liquid dispensing system in which the flow sensor is integrated will be introduced. A novel closed-loop control strategy is proposed to calculate valve open-time for each dispensing cycle. Finally, experiments results are presented with different dispensing volumes, coefficient of variance (CV) has been shown to be below 3% at 1 mul and approach 4% at 100 nl. It indicates that integration of the MEMS flow sensor and using of a compound intelligent control strategy make the system immune to liquid viscosity, pressure fluctuation and some other disturbances.