Development of highly sensitive capacitive proximity sensor based on stacked monocharged electrets

Recently, the demand for miniaturization and high sensitivity of the capacitive proximity sensors has increased noticeably for development of sensor networks. However, the volume and weight of conventional sensor devices are emerging as limitations in the practical application. In this paper, the stacked electrets-based highly sensitive noncontact capacitive sensor system (SENS) is proposed. The SENS is fabricated in compact-sized and light weight because electrets, which are dielectric materials that have quasi-permanent injected electric charges so can form external electric field, substitute the transmitter electrode and the external power source. Also, sensitivity of the SENS is effectively improved by stacking electrets. For experimental analysis, the electrostatic properties of the stacked electrets, which are due to the injected charges, and resultant influences on the sensitivity of the SENS are studied. In addition, based on experimental results, a proximity notification system with the SENS is developed using a LabVIEW program to demonstrate the practicality of the SENS.