δ-phase comprising polyvinylidene fluoride (PVDF) nanoparticles are fabricated through an electrospray technique by applying a 0.1 MV/m electric field, which is 103 times lower than the typical value, required for δ-phase transformation. X-ray diffraction and selected area electron diffraction patterns clearly indicate the δ-phase formation that limits the infrared vibrational spectroscopic technique due to identical molecular chain conformations to that of non-polar α-phase. The piezo- and ferro-electric response of δ-PVDF nanoparticles have been demonstrated through a scanning probe microscopic technique based on piezoresponse force microscopy. The localized piezoelectric response, indicated by d33 coefficient, is found to be ∼−11 pm/V. To utilize the distinct electromechanical response of δ-PVDF nanoparticles, the piezoelectric nanogenerator (PNG) has been fabricated. Due to the stress confinement effect in the spherical shape of δ-PVDF nanoparticles, the PNG exhibits synergistic effect than that of the film-based counterpart. The maximum power, i.e., 930 μW/m2 determined by the PNG under ∼4.5 N of periodic force impact, indicates the potential to use it as a self-powered sensor. As a proof of concept, a self-powered pressure sensor mapping has been demonstrated for representing its realistic technological applicability.

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In recent years, lead-free perovskite materials are exponentially emerging in photovoltaic and optoelectronic applications due to their low toxicity and superior optical properties. On the other hand, the demand for flexible, wearable, and lightweight optoelectronic devices is significantly growing in sensor and actuator technologies. In this scenario, lead-free perovskite-based flexible piezoelectric polymer composites have sparked considerable attention in this field due to their excellent piezo-, pyro-, ferroelectric, and photovoltaic properties. Thus, in this work, a long-term stable lead-free Cs 3 Bi 2 I 9 -PVDF composite is introduced. The in situ growth of the Cs 3 Bi 2 I 9 perovskite induces 92% yield of the electroactive phase in the PVDF matrix. The possible mechanism behind the electroactive β-phase transformation is presented via interfacial interactions of PVDF moieties with the Cs 3 Bi 2 I 9 (CBI) perovskite, which also give rise to long-term environmental stability. Next, a piezoelectric nanogenerator (PNG) has been fabricated with the Cs 3 Bi 2 I 9 -PVDF composite for mechanical energy harvesting, biophysiological motion monitoring, and voice recognitions that have potential utility in the health-care sector. Furthermore, a photodetector is developed to realize the piezophototronic effect. It exhibits a fast photoswitching behavior with rise and decay times of 141 and 278 ms, respectively. Thus, it is confirmed that the flexible Cs 3 Bi 2 I 9 -PVDF composite has shown tremendous potential to be used as an optical signal-modulated piezo-responsive wearable sensor.

A ferroelectret cellular structure of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] is fabricated by a 3D printing technique that exhibits a giant piezoelectric coefficient of 1200 pC/N, which is 40 times higher than its commonly known film counterpart. It attributes that the bi-polar charge separation in cellular voids upon the corona discharge behaves as macroscopic dipoles. An increase in the surface potential and dielectric constant (from 10 to 20 at 1 kHz) also attributes to charged voids. Furthermore, the deviation of ferroelectric behavior, for instance, the continuous increasing trend in dielectric constant and remanent polarization as a function of temperature attributes to ferroelectret behavior of a 3D printed P(VDF-TrFE) specimen. The mechanical energy harvester (MEH) made with this ferroelectret structure shows prompt response with [Formula: see text]4 W/m2 of the power density. Furthermore, the benefit of the giant piezoelectric coefficient of the MEH is used to demonstrate self-powered tactile mapping.

Harvesting energy from waste resources shows significant potential in low‐power electronics, self‐powered devices, and waste‐energy management. Herein, a possible mechanism is demonstrated to harvest waste electromagnetic (EM) energy produced by the induction heater where recycled aluminum foil is utilized as an energy‐harvester unit. As a consequence, ≈5.34 μW of harvested power is manifested under the operating condition of the induction heater. In this connection, a demonstration of the real‐time calculator operation, 26 blue light‐emitting diode lighting, and smartphone battery charging are presented. It indicates an excellent opportunity to harvest the abundantly available waste EM energy using the recycled and widely used food‐packaging Al foil. Thus, it is expected that the waste EM energy can be utilized to power up consumer electronic appliances.