A capacitive ice detection microsensor

An ice detection system using a microfabricated diaphragm as the sensing element and portable capacitance detection circuitry is presented. During operation, actuation forces are applied electrostatically to cause diaphragm deformation. Accumulation of ice on the diaphragm leads to an increase in its effective stiffness. Therefore, for a given actuation voltage, the ice-covered diaphragm exhibits a smaller deflection than the corresponding ice-free diaphragm. This deflection is measured using a customized, portable, high-sensitivity, differential capacitance measurement circuit. Finite-element analysis (FEA) is used to optimize the sensor geometry for enhanced sensitivity to ice accretion. The sensor is fabricated by bulk micromachining and wafer bonding of silicon and glass substrates. The sensor is operated with the diaphragm in the stiffness-sensitive mode, enabling the discrimination between ice and water (or deicing fluids) films. Calibration experiments reveal that the miniature ice detection sensor system can successfully detect ice and water film thicknesses between approximately 0.5-1.5 mm. Finally, dynamic testing indicates that the adhesion of ice to silicon is poor when the sensor is driven continuously.