Comparison of piezoelectric responses of flexible tactile sensors based on hydrothermally-grown ZnO nanorods on ZnO seed layers with different thicknesses

One peculiar property of ZnO nanorods (NRs) is their piezoelectricity, which opens up a wealth of possibilities in the fields of piezoelectric electronics and piezoelectric optoelectronics, such as pressure sensors, actuators, energy-capture and energy-storage devices. For further clarifying the relation between the piezoelectric properties and structural morphology of ZnO NRs, the effect of their aspect ratio on piezoelectric response was analyzed by simulation method. A piezoelectric tactile sensor with ZnO NRs as a sensitive layer hydrothermally grown on a sputtered ZnO seed layer (SL) was fabricated on a polydimethylsiloxane (PDMS) substrate. The effects of the SL thickness on the structural properties and morphology of ZnO NRs were investigated, and a comparative study on the piezoelectric sensing of the tactile sensors with different SL thicknesses was done. The results show that the ZnO SL thickness has a clear influence on the structural morphology of the ZnO NRs and the sensitivity of the ZnO-NRs-based sensor, and the sensor with a SL thickness of 80 nm has a maximum sensitivity of 524.5 mV/N due to the high aspect ratio. Moreover, the sensors have a good linear response to external pressure within the range of less than 1 N, and so exhibit excellent application prospects in tactile perception and detection of weak dynamic force.