Piezoelectric Earcanal Bending Sensor

The earcanal shape is unique for each human being and temporarily changes when the jaw moves due to eating, chewing, or speaking. The earcanal deformation can be studied by the geometrical analysis of a distorted earpiece custom-fitted inside the earcanal, but the distortion of the earpiece is complex in nature and complicated to analyze. An earcanal bending sensor consisting of a thin piezoelectric strip attached to a custom-fitted earpiece is presented in this paper. An analytical approach based on computing the geometrical parameters of distorted and undistorted earpieces is developed to: 1) estimate the average bending moment and the resulting stress applied to the custom-fitted earpiece while opening the jaw and 2) calculate the sensitivity of the piezoelectric earcanal bending sensor. The theoretical model is experimentally validated. The proposed approach can be applied to measure the bending of any curved body in general, and custom-fitted earpieces in particular. It, therefore, enables the designing of versatile in-ear sensors capable of tracking jaw activity and evaluating the energy capacity of earcanal deformation for in-ear energy harvesting purposes.