Perhaps the most abundant form of waste energy in our surrounding is the parasitic magnetic noise arising from electrical power transmission system. In this work, a flexible and rollable magneto-mechano-electric nanogenerator (MMENG) based wireless IoT sensor has been demonstrated in order to capture and utilize the magnetic noise. Free standing magnetoelectric composites are fabricated by combining magnetostrictive nickel ferrite (NiFe 2 O 4 ) nanoparticles and piezoelectric polyvinylidene-co-trifluoroethylene (P(VDF-TrFE)) polymer. The magnetoelctric 0-3 type nanocomposites possess maximum magnetoelectric voltage co-efficient (α) of 11.43 mV/cm-Oe. Even, without magnetic bias field 99 % of the maximum value is observed due to self-bias effect. As a result, the MMENG generates peak-to-peak open circuit voltage of 1.4 V, output power density of 0.05 µW/cm 3 and successfully operates commercial capacitor under the weak (⁓ 1.7× 10 -3 T) and low frequency (⁓ 50 Hz) stray magnetic field arising from the power cable of home appliances such as, electric kettle. Finally, the harvested electrical signal has been wirelessly transmitted to a smart phone in order to demonstrate the possibility of position monitoring system construction. This cost effective and easy to integrate approach with tailored size and shape of device configuration is expected to be explored in nextgeneration self-powered IoT sensors including implantable biomedical devices and human health monitoring sensory systems.

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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.