An Improved Capacitance-Based Intentionally Imperfect Sensor for Measuring Mechanical Parameters

In this paper, details of an improved imperfect sensor for measuring mechanical parameters is presented. A PDMS (Polydimethylsiloxane) membrane filled with randomly distributed conductive balls is the sensing element. The random distribution of the balls make the sensor imperfect and unique, like sensors in nature. Mechanical forces such as pressure, tilt and acceleration deform the membrane. Capacitive electrodes transform the movement of the membrane filled with conductive balls into change in capacitance. As all the conductive balls are randomly distributed, an Interdigitated Electrode (IDE) structure offers less sensitivity. An improved electrode structure is also proposed. The performance of the improved electrode is compared with IDE for pressure, tilt and acceleration. Simulation and test results showed that the improved electrode offers higher sensitivity compared to the IDE. Further more, the improved electrode also improves the directional sensitivity. A ground plane is provided to to reduce the fixed offset capacitance and minimize the effect of noise. The sensor is simple, robust and easy to fabricate.