Light and Pressure Sensors Based on PVDF with Sprayed and Transparent Electrodes for Self-Powered Wireless Sensor Nodes

In this paper, we report on the fabrication of light and pressure sensors based on the piezo- and pyro-material polyvinylidene fluoride (PVDF). In addition, to the operation as sensors, the presented devices are characterized as energy harvesters. To form an electrical connection to the $39\:\mu \text{m}$ thick PVDF foil, solution-based and transparent electrode (TE) materials, such as silver nanowires (AgNWs) and poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) are utilized and compared with commercial aluminum electrodes on polymer substrate. We show that the performance with regard to sensitivity and generated output power of the TE-PVDF devices outperforms the one for the aluminum foil devices. For the piezo- and pyroelectric effect, a pressure and light sensitivity of 3.6 mV/Pa and 42 Vcm²/W, respectively, are measured. The maximum RMS power for the piezo- and pyro effect yield to 1 and $0.42~\mu \text{W}$ , respectively, for an active PVDF area of 8 cm². At the end of this contribution, we show that this power suffices to drive an energy autarkic wireless sensor node that is capable of measuring and transmitting an analog sensor signal using ultra-low power components. This application contributes substantially to the notion of the Internet of Things since paramount aspects, such as wireless technology, embedded electronics, and environmental sensor data together with an ultra-low power management are addressed.