3-Axis, Ultrahigh-Sensitivity, Miniature Acceleration Sensor

This paper introduces a miniature, 3-axis, acceleration sensor with extremely high sensitivity. The sensor is of the variable capacitance type. However, instead of using a conventional variable capacitor configuration, the sensor is based on a variable ultracapacitor (or supercapacitor). A very small droplet of electrolyte is positioned in between six electrodes that are arranged in the form of a cube. The inner surfaces of the electrodes are coated with carbon nanotubes (CNTs), and hence a variable ultracapacitor exists between any two of the six electrodes. Acceleration forces the electrolyte droplet to move in different directions and take different shapes, thereby altering the capacitance between any two given electrodes in the device. The prototype described in this paper has shown an inter-electrode capacitance variation of 7.5 μF under an acceleration increase from 0 to 100 g. The sensitivity is therefore 75 nF/g.