The fast expanding field of wearable technology requires light-weight, low-cost, scalable, flexible and efficient energy harvesters as a source of uninterrupted green power. This work reports fabrication of sub-micron graphite platelet/PVDF composite film-based flexible piezoelectric energy harvester (PGEH) for scavenging the wasted mechanical energy associated with human body motion. The addition of graphite platelet leads to the enhancement of electroactive β phase in PVDF; consequently, the piezoelectric and dielectric properties of the composite are enhanced. 0.5 wt% filler-loaded composite has 96% β phase fraction and dielectric constant 32 at 100 Hz (tanδ = 0.18).The PGEH produces open circuit voltage of 40 V and instantaneous power density of 3.35 mW cm− 3 with energy conversion efficiency of 22.5% under periodic finger tapping. It can generate fair electrical output under gentle heel (0.8 V) and toe movements (1.2 V). A PGEH is directly employed for powering 50 commercial LEDs and quick charging of a 2.2-μF capacitor upto 19.2 V. The device is also employed as self-powered dynamic pressure sensor which shows high sensitivity (0.9 VkPa− 1) with fast response time (1 ms). Therefore, this durable, flexible, efficient PGEH can have promising applications in wearable electronics as a green power source cum self-powered mechanosensor.

Cobalt coated tungsten carbide-cobalt composite powder has been prepared through wet chemical reductionmethod. The cobalt sulfate solution was converted to the cobalt chloride then the cobalt hydroxide. The tungsten carbidepowders were added in to the cobalt hydroxide, the cobalt hydroxide was reduced and coated over tungsten carbidepowder using hypo-phosphorous acid. Both the cobalt and the tungsten carbide phase peaks were evident in the tungstencarbide-cobalt composite powder by X-ray diffraction. The average particle size measured via scanning electron micro-scope, particle size analysis was around 380 nm and the thickness of coated cobalt was determined to be 30~40 nm bytransmission electron microscopy.