A Thermally Actuated Microelectromechanical (MEMS) Device For Measuring Viscosity

A thermally actuated non-cantilever-beam microelectromechanical viscosity sensor is presented. The proposed device is based on thermally induced vibrations of a simple silicon diaphragm and its damping due to the surrounding fluid. This vibration viscometer device utilizes thermal actuation through an in situ resistive heater and piezoresistive sensing, both of which utilize CMOS compatible materials leading to an inexpensive and reliable system. Thermal analysis was performed utilizing temperature diodes in the silicon diaphragm to determine the minimum heater voltage pulse amplitude and time in order to prevent heat loss to the oil under test that would lead to local viscosity changes. Viscosity measurements were performed and compared to motor oil measured on a commercial cone-and-plate viscometer.