Waste to Electronics: Fly Ash Derived Self‐Powered Tactile and Multimodal Flexible Sensors

Fly ash is a very well‐known waste material from thermal power plants in developing countries and is known to cause huge pollution if not properly treated. Considering its composition and huge abundance in developing countries, it has been aimed to utilize fly ash directly in wearable self‐powered electronics, viz., flexible tactile motion sensor, temperature and pressure sensors. The fly ash‐derived filler nanoparticles were processed using ball milling followed by annealing and the product is termed ball‐milled and annealed fly ash (BAFA). This BAFA was used to tailor the electroactive β‐phase of polyvinylidene fluoride (PVDF) polymer. Electrical characteristics of the composite films were studied rigorously, aiming to establish the trade‐off point between the filler loading percentage and electrical attributes. Results showed that 1.5 wt.% PVDF/BAFA nanocomposite film is most promising for piezoelectric nanogenerator (PENG), static pressure and temperature sensing applications. Prototype PENG device yielded rectified open‐circuit voltage of about 64 V through simple human finger tapping. The PENG showcased a maximum power density of 21.77 kW/m 3 (i.e., 152.39 μW/cm 2 ), which is a highly promising value to be exploited from a waste material. Considering the impressive piezo‐sensitivity of the composite film, tactile motion sensors with this have also been fabricated that displayed significant results. Furthermore, the device performed well in terms of static pressure and temperature sensing with sensitivity values of 0.1542 kPa −1 and 0.00393°C −1 , respectively. The results clearly suggest that this device can effectively be integrated into wearable electronics for health monitoring and several other internet‐of‐things (IoT) systems.