Designing & Fabrications of Silicon MEMS Piezoresistive Pressure Sensor for Biomedical Applications Abdulmunaem ShanebMMEWashington State University : Fall2010 Designing & Fabrications of Silicon MEMS Piezoresistive Pressure Sensor for Biomedical Applications Abdulmunaem ShanebMMEWashington State University How Piezoresistive Pressure Sensors Work? : 1.Diaphragm : converts the pressure to mechanical stress. 2.Piezoresistor: converts the mechanical stress into resistance change. 3.Wheatstone bridge :converts the resistance change into output voltage . How Piezoresistive Pressure Sensors Work? The sensitivity of Piezoresistive Pressure Sensors: : The sensitivity of Piezoresistive Pressure Sensors: Applications & Specifications desired: : Applications & Specifications desired: Ventilators. Spirometers. Respirators Blood Pressure measurement. Applications: Specifications Thickness of diaphragm: 10µm-15µm Diameter of circular diaphragm & the side length of square diaphragm: 500µm-700µ Measure a pressure :0-1 bar Resolution :1 mbar Sensitivity : 30 mv/vbar Slide 5: Design assumptions and conditions:
1. The diaphragm is flat and of uniform thickness (t).
2. Pressure is applied normally to the plane of diaphragm.
3. The effect of temperature on sensitivity is not considered in this project
4. The resistors are located at the rim of the diaphragm where the stress is very high .
5. The maximum deflection must not exceed 30% of the diaphragm thickness.
6. The thickness of diaphragm is not too thick (maximum 20% of diaphragm diameter
or the side length for the square diaphragm).
7. The elastic limit of the material is not exceeded (tensile strain less than 0.7GPa). Designing calculation : Designing calculation Slide 7: 1. An IC Piezoresistive Pressure Sensor for Biomedical Instrumentation. Samaun, Kensall D.Wise , and
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