A PVDF/Au/PEN Multifunctional Flexible Human-Machine Interface for Multidimensional Sensing and Energy Harvesting for the Internet of Things

In the picture of the Internet of Things (IoT), smart human-machine interfaces (HMIs) play a significant role. Desired attributes for smart HMIs include multidimensional sensing, flexibility with stable responsiveness, and a long operational lifetime. To this end, in this article, we present a polyvinylidene fluoride (PVDF)/Au/polyethylene naphthalate (PEN) sandwiched architecture. Piezoelectric property of the PVDF is utilized for dynamic force sensing and touch-induced energy harvesting. A mutual capacitive based technique is employed for two-dimensional (2D) position recognition, hover distance measurement and curvature self-detection, as well as helping in compensating the static force detection shortage of the piezoelectric sensing layer. The presented HMI system achieved an overall force sensitivity at 0.07 N and capacitive resolution at 0.004 pF; and a force responsivity at 2.36 V/N in the pressure range of 1 N-30 N. In each touch event, the maximum capacitance change and the electric energy harvested in a stored capacitor are averaged at 0.016 pF and 0.038 nJ, respectively. Furthermore, interdigitated electrodes are implemented for self-detecting the device curvature. With pre-correlating of the force-voltage response under different bending degrees, a stable force detection response is realized when the shape of the device changes. The work presented in this article advances the field of human-machine interactivities.