Battery-less shock-recording device consisting of a piezoelectric sensor and a ferroelectric-gate field-effect transistor

Abstract

By converting the kinetic energy of a shock into voltages by a piezoelectric sensor and changing the channel resistance of a ferroelectric-gate field-effect transistor (FeFET) by generated voltages, we propose a battery-less shock-recording device. Although the electrical energy generated by a shock is very small, it is enough to change the channel resistance of the FeFET, which itself has very low power consumption. Because of the unconventional characteristics of battery-less and multi-level recording, a large number of products can be monitored in this way. To rectify the output from the piezoelectric sensor, we placed a Zener diode parallel to it. However, because the negative gate voltage needed to reset the FeFET is the forward direction of the Zener diode, this design does not permit resetting of the FeFET. By applying the dynamics of channel resistance change, however, we succeeded in resetting the FeFET. The stored resistance in the FeFET was changed by the output voltage from the piezoelectric sensor, to which different intensities of shock were applied by means of a drop test. The stored resistance showed multi-level values in response to shock intensity. This device can detect the presence of the stronger shock than previously designated intensity. Moreover, if the shock intensity is smaller than the threshold intensity, the intensity can be calculated. We have also designed a non-contact shock-recording device that has proven convenient for practical use. This device was designed such that the resistance of the FeFET could be announced as the color of a lit LED when electric power was transmitted by a radio feeding system. The drop test resulted in the correct LED color. As the recording operation can be performed without a battery, these devices have the potential to be key devices for the secure transportation.