Highly flexible, biocompatible, large-scale production of BaTiO3 nanocube (BTO NC)/poly­(dimethylsiloxane) (PDMS) composite films (CFs) prepared via a simple, cost-effective solution casting technique are reported for the first time for high-performance piezoelectric nanogenerators (PNGs). The crystalline BTO NCs were synthesized via a simple low-temperature molten salt method. The piezoelectric output performance of the CF was investigated as a function of the weight ratio of the BTO NCs in the polymer matrix, electrical poling, constant mechanical loading, and low-frequency biomechanical energy harvesting. The composite PNG (CPNG) with 15 wt % of BTO NCs displayed an excellent peak-to-peak voltage (V pp) of 126.3 V and current density (J) of 77.6 μA/cm2 and generated a maximum instantaneous areal power density of 7 mW/cm2 at 100 MΩ at the low input mechanical pressure of 988.2 Pa. The generated output was sufficient to drive commercial light-emitting diodes and low-powered consumer electronic devices. Next, the CPNG was tested to harness waste biomechanical energy in our daily life; it generated a V pp of 29 V (human hand palm force) and 55.9 V (human foot stress). The proposed device was lightweight, flexible, eco-friendly, cost-effective, and a potential candidate to generate high electrical output at low mechanical pressure.

In contrast with the conventional ceramic/oxide humidity sensors (HSs), a self-powered piezoelectric biopolymer HS with reasonable sensitivity, reliability, and a nontoxic and eco-friendly nature is highly desirable. A piezoelectric nanogenerator (PNG)-driven biopolymer-based HS provides a pathway toward a sustainable and greener environment in the field of smart sensors. For that, a piezoelectric collagen nanofibril biopolymer coated on to a cotton fabric has dual functionality (energy harvesting and sensor). Collagen PNG generates a maximum of 45 V/250 nA upon 5 N and can also work as a sensor to measure various percentages of relative humidity (% RH). The HS shows a linear response with a good sensitivity (0.1287 μA/% RH) in the range of 50-90% RH. These results open a field of eco-friendly multifunctional nanomaterials toward the development of noninvasive, implantable smart bio-medical systems.

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Scavenging of ambient dissipated mechanical energy addresses the limitations of conventional batteries by providing an auxiliary voltaic power source, and thus has significant potential for self-powered and wearable electronics.

A lightweight, flexible, cost-effective, and robust, single-electrode-based Smart Seat-Triboelectric Nanogenerator (SS-TENG) is introduced as a promising eco-friendly approach for harvesting energy from the living environment, for use in integrated self-powered systems. An effective method for harvesting biomechanical energy from human motion such as walking, running, and sitting, utilizing widely adaptable everyday contact materials (newspaper, denim, polyethylene covers, and bus cards) is demonstrated. The working mechanism of the SS-TENG is based on the generation and transfer of triboelectric charge carriers between the active layer and user-friendly contact materials. The performance of SS-TENG (52 V and 5.2 μA for a multiunit SS-TENG) is systematically studied and demonstrated in a range of applications including a self-powered passenger seat number indicator and a STOP-indicator using LEDs, using a simple logical circuit. Harvested energy is used as a direct power source to drive 60 blue and green commercially available LEDs and a monochrome LCD. This feasibility study confirms that triboelectric nanogenerators are a suitable technology for energy harvesting from human motion during transportation, which could be used to operate a variety of wireless devices, GPS systems, electronic devices, and other sensors during travel.