Calibration-free force sensors using liquid crystal arrays

A capacitive force sensor is developed from a liquid crystal (LC) array. Experimental result shows that the force-dependent capacitance curve shifts to larger capacitance with increasing applied voltage. Accordingly, the force range of the sensor can be divided into many sub-ranges at one of the capacitance values. The number of the input voltage is equal to that of the output capacitance in each of the sub-ranges, and the voltage-to-capacitance number is small (large) in the high (low)-force sub-range. This sensor measures force by the voltage-to-capacitance number and avoids a need to create a function for transferring the capacitance into the force.