Pressure sensors that can both directly visualize and record applied pressure/stress are essential for e-skin and medical/health monitoring. Here, using a WO3 -film electrochromic device (ECD) array (10 × 10 pixels) and a ZnO-nanowire-matrix pressure sensor (ZPS), a pressure visualization and recording (PVR) system with a spatial resolution of 500 µm is developed. The distribution of external pressures can be recorded through the piezotronic effect from the ZPS and directly expressed by color changes in the ECD. Applying a local pressure can generate piezoelectric polarization charges at the two ends of the ZnO nanowires, which leads to the tuning of the current to be transported through the system and thus the color of the WO3 film. The coloration and bleaching process in the ECD component show good cyclic stability, and over 85% of the color contrast is maintained after 300 cycles. In this PVR system, the applied pressure can be recorded without the assistance of a computer because of the color memory effect of the WO3 material. Such systems are promising for applications in human-electronic interfaces, military applications, and smart robots.
Keywords: ZnO nanowire arrays; electrochromic devices; piezotronic effect; pressure visualization, pressure recording.
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