Maghemite/Polyvinylidene Fluoride Nanocomposite for Transparent, Flexible Triboelectric Nanogenerator and Noncontact Magneto-Triboelectric Nanogenerator

Propelled by the development of the Internet of things and other low-power devices such as in health care or sensing applications, there is growing emphasis on development of energy harvesting devices based on piezoelectric and triboelectric harvesting. We demonstrate a highly flexible and transparent triboelectric nanogenerator (TENG) prepared by incorporating maghemite (γ-Fe₂O₃) fillers in polyvinylidene fluoride (PVDF) with polyethylene terephthalate (PET) as a triboelectric counterpart for potential application in powering wearable electronic devices. Addition of γ-Fe₂O₃ fillers in the PVDF matrix results in a power output with an average open circuit voltage of 250 V and short circuit current of 5 μA, which is substantially higher than that from only-PVDF-based TENG. With manually applied force, the lightweight TENG device (area ∼14.5 cm² and weight ∼1 g) can induce a maximum power output of 0.17 mW with a power density of 0.117 W m^–2. In addition, this device is extremely robust with excellent long-term stability for approximately 3000 s. We harvested biomechanical motion in the form of slow and fast foot movement by attaching this device to the sole of footwear. Moreover, the TENG device could continuously supply enough power to light up 108 light-emitting diodes (LEDs) connected in series, without the use of a capacitor and has potential applications in self-powered wearable and portable electronics obviating the use of batteries. Moreover, this device is shown to harvest energy from the rotary pump to charge a 1 μF capacitor to a value of ∼30 V in just 90 s. In addition, a thick magnetic γ-Fe₂O₃/PVDF nanocomposite film was also successfully tested as a magneto-triboelectric nanogenerator (M-TENG) in noncontact mode showing potential for harvesting of the stray magnetic field.