Self-Charging Piezo-Supercapacitor: One-Step Mechanical Energy Conversion and Storage

With the contemplations of ecological and environmental issues related to energy harvesting, piezoelectric nanogenerators (PNGs) may be an accessible, sustainable, and abundant elective wellspring of energy in the future. The PNGs' power output, however, is dependent on the mechanical energy input, which will be intermittent if the mechanical energy is not continuous. This is a fatal flaw for electronics that need continuous power. Here, a self-charging flexible supercapacitor (PSCFS) is successfully realized that can harvest sporadic mechanical energy, convert it to electrical energy, and simultaneously store power. Initially, chemically processed multimetallic oxide, namely, copper cobalt nickel oxide (CuCoNiO₄) is amalgamated within the poly(vinylidene fluoride) (PVDF) framework in different wt % to realize high-performance PNGs. The combination of CuCoNiO₄ as filler creates a notable electroactive phase inside the PVDF matrix, and the composite realized by combining 1 wt % CuCoNiO₄ with PVDF, coined as PNCU 1, exhibits the highest electroactive phase (>86%). Under periodic hammering (∼100 kPa), PNGs fabricated with this optimized composite film deliver an instantaneous voltage of ∼67.9 V and a current of ∼4.15 μA. Furthermore, PNG 1 is ingeniously integrated into a supercapacitor to construct PSCFS, using PNCU 1 as a separator and CuCoNiO₄ nanowires on carbon cloth (CC) as the positive and negative electrodes. The self-charging behavior of the rectifier-free storage device was established under bending deformation. The PSCFS device exhibits ∼845 mV from its initial open-circuit potential ∼35 mV in ∼220 s under periodic bending of 180° at a frequency of 1 Hz. The PSCFS can power up various portable electronic appliances such as calculators, watches, and LEDs. This work offers a high-performance, self-powered device that can be used to replace bulky batteries in everyday electronic devices by harnessing mechanical energy, converting mechanical energy from its environment into electrical energy.

Gold nanoparticle–cellulose/PDMS nanocomposite: a flexible dielectric material for harvesting mechanical energy

Cellulose is an abundant natural piezoelectric polymer and is also a renewable resource of significant importance. Here in this work we realize an enhanced piezoelectric response with cellulose in a polydimethylsiloxane (PDMS) matrix by forming a nanocomposite with the incorporation of gold nanoparticles (Au NPs). In the Au NP–cellulose/PDMS nanocomposite an enhancement in the dielectric constant is recorded due to the presence of cellulose alone and a reduction of dielectric loss is found owing to the presence of Au NPs. This opens the possibility of realizing a nanodielectric material from the nanocomposite under current study. This also indicates the significant potential of the nanocomposite towards energy conversion applications. Subsequently, a mechanical energy harvesting device was fabricated using the Au NP–cellulose/PDMS nanocomposite, which is named as a piezoelectric nanogenerator (PNG). The PNG delivered an enhanced open circuit voltage of ∼6 V, short circuit current of ∼700 nA and a peak power density of 8.34 mW m⁻² without performing any electrical poling steps. The PNG could charge a 10 μF capacitor to 6.3 V in 677 s and could light two commercial blue light emitting diodes (LEDs) simultaneously. The PNG exhibited a good energy conversion efficiency of 1.8%. A touch sensor application of the PNG is also shown.

A gold nanoparticle–cellulose/PDMS based piezoelectric nanogenerator (PNG) is reported in this work. The PNG delivers an efficiency of 1.8%. It can light LEDs and sense finger touch.

Materials and Wearable Devices for Autonomous Monitoring of Physiological Markers

Wearable devices are gaining considerable attention owing to the ease with which they can collect crucial information in real-time, both continuously and noninvasively, regarding a wearer's health. A concise summary is given of the three main elements that enable autonomous detection and monitoring of the likelihood or the existence of a health-risk state in continuous and real-time modes, with an emphasis on emerging materials and fabrication techniques in the relevant fields. The first element is the sensing technology used in the noninvasive detection of physiological markers relevant to the state of health. The second element is self-powered devices for longer periods of use by drawing energy from bodily movement and temperature. The third element is the self-healing properties of the materials used in the wearable devices to extended usage if they become scratched or cut. Promises and challenges of the separately reviewed parts and the combined parts are presented and discussed. Ideas regarding further improvement of skin-based wearable devices are also presented and discussed.

Native Cellulose Microfiber-Based Hybrid Piezoelectric Generator for Mechanical Energy Harvesting Utility

A flexible hybrid piezoelectric generator (HPG) based on native cellulose microfiber (NCMF) and polydimethylsiloxane (PDMS) with multi wall carbon nanotubes (MWCNTs) as conducting filler is presented where the further chemical treatment of the cellulose and traditional electrical poling steps for piezoelectric voltage generation is avoided. It delivers a high electrical throughput that is an open circuit voltage of ∼30 V and power density ∼9.0 μW/cm(3) under repeated hand punching. We demonstrate to power up various portable electronic units by HPG. Because cellulose is a biocompatible material, suggesting that HPG may have greater potential in biomedical applications such as implantable power source in human body.

An Effective Electrical Throughput from PANI Supplement ZnS Nanorods and PDMS-Based Flexible Piezoelectric Nanogenerator for Power up Portable Electronic Devices: An Alternative of MWCNT Filler

We demonstrate the requirement of electrical poling can be avoided in flexible piezoelectric nanogenerators (FPNGs) made of low-temperature hydrothermally grown wurtzite zinc sulfide nanorods (ZnS-NRs) blended with polydimethylsiloxane (PDMS). It has been found that conductive fillers, such as polyaniline (PANI) and multiwall carbon nanotubes (MWCNTs), can subsequently improve the overall performance of FPNG. A large electrical throughput (open circuit voltage ∼35 V with power density ∼2.43 μW/cm(3)) from PANI supplement added nanogenerator (PZP-FPNG) indicates that it is an effective means to replace the MWCNTs filler. The time constant (τ) estimated from the transient response of the capacitor charging curves signifying that the FPNGs are very much capable to charge the capacitors in very short time span (e.g., 3 V is accomplished in 50 s) and thus expected to be perfectly suitable in portable, wearable and flexible electronics devices. We demonstrate that FPNG can instantly lit up several commercial Light Emitting Diodes (LEDs) (15 red, 25 green, and 55 blue, individually) and power up several portable electronic gadgets, for example, wrist watch, calculator, and LCD screen. Thus, a realization of potential use of PANI in low-temperature-synthesized ZnS-NRs comprising piezoelectric based nanogenerator fabrication is experimentally verified so as to acquire a potential impact in sustainable energy applications. Beside this, wireless piezoelectric signal detection possibility is also worked out where a concept of self-powered smart sensor is introduced.

p-type ZnTe:Ga nanowires: controlled doping and optoelectronic device application

p-type ZnTe:Ga nanowires with a tunable electrical conductivity can be used to fabricate a high-performance semiconductor/graphene Schottky diode photodetector.