All-Organic High-Performance Piezoelectric Nanogenerator with Multilayer Assembled Electrospun Nanofiber Mats for Self-Powered Multifunctional Sensors

Rapid development of wearable electronics, piezoelectric nanogenerator (PNG), has been paid a special attention because of its sustainable and accessible energy generation. In this context, we present a simple yet highly efficient design strategy to enhance the output performance of an all-organic PNG (OPNG) based on multilayer assembled electrospun poly­(vinylidene fluoride) (PVDF) nanofiber (NF) mats where vapor-phase polymerized poly­(3,4-ethylenedioxythiophene)-coated PVDF NFs are assembled as electrodes and neat PVDF NFs are utilized as an active component. In addition to the multilayer assembly, electrode compatibility and durability remain a challenging task to mitigate the primary requirements of wearable electronics. A multilayer networked three-dimensional structure integrated with a compatible electrode thereby provides enhanced output voltage and current (e.g., open-circuit voltage, <i>V</i>_oc ≈ 48 V, and short-circuit current, <i>I</i>_sc ≈ 6 μA, upon 8.3 kPa of the applied stress amplitude) with superior piezoelectric energy conversion efficiency of 66% compared to the single-mat device. Besides, OPNG also shows ultrasensitivity toward human movements such as foot strikes and walking. The weight measurement mapping is critically explored by principal component analysis that may have enormous applications in medical diagnosis to smart packaging industries. More importantly, fatigue test under continuous mechanical impact (over 6 months) shows great promise as a robust wearable mechanical energy harvester

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/cm³ 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

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Biomechanical and Acoustic Energy Harvesting from TiO₂ Nanoparticle Modulated PVDF Nanofiber Made High Performance Nanogenerator

An integrated platform made with a piezoelectric nanogenerator (NG) is designed to convert daily human activities and acoustic vibration into useable electrical energy. The titanium dioxide (TiO₂) nanoparticles (NPs) are playing a significant role as external fillers in poly­(vinylidene fluoride) (PVDF) electrospun nanofiber that improves the overall performance of the NG. It effectively enhanced the piezoelectric β-phase content (16% higher F (β)) and mechanical (148% increment of tensile strength) properties of composite PVDF nanofiber. The superior integration of NG has been demonstrated to generate electricity from a human gait. The acoustic sensitivity and energy conversion efficiency are found to be 26 V Pa^–1 and 61%, respectively, which are superior in comparison to the reported results. By scavenging the mechanical energy, NG is capable of charging up a 1 μF capacitor; for example, ∼20 V is within 50 s that ensures its ability to power up commercial LED tape and a LCD screen. Thus, in this work, a high performance piezoelectric NG is presented that has potential application in the health care sector and robotics area, in particular for use as a self-powered system

Controlled Molecular Orientation through Intercalation in PVDF Thin Films: Exhibiting Ultralong Retention and Improved Leakage Current

Ferroelectric switching and retention performance of poly(vinylidene fluoride) (PVDF) thin films improve by the incorporation of unmodified smectite montmorillonite (MMT) clay nanodielectric. In the present study, an intercalated PVDF (clay/PVDF) thin film with edge-on β-crystallite is fabricated via a heat-controlled spin coating (HCSC) technique. This provides an efficient and simple way to fabricate the edge-on oriented crystallite lamellae with an electroactive β-phase, facilitating nanoscale ferroelectric switching at a lower voltage compared to the face-on orientation. Here, we demonstrate the polarization retention for periods longer than 20 days (∼480 h, i.e., 1.8 × 106 s), with no degradation in switched nanoscale domains. In addition, by maintaining the relatively high dielectric constant, the incorporation of nanoclay effectively lowers the leakage current by 102 factors. The obtained memory window in the edge-on orientation is 7 V, approximately twice the memory window obtained in the face-on orientation. In short, our findings provide a simple and promising route to fabricate edge-on oriented PVDF thin films, with ultralong retention, high dielectric constant, and improved leakage current

Design of In Situ Poled Ce³⁺-Doped Electrospun PVDF/Graphene Composite Nanofibers for Fabrication of Nanopressure Sensor and Ultrasensitive Acoustic Nanogenerator

We report an efficient, low-cost in situ poled fabrication strategy to construct a large area, highly sensitive, flexible pressure sensor by electrospun Ce³⁺ doped PVDF/graphene composite nanofibers. The entire device fabrication process is scalable and enabling to large-area integration. It can able to detect imparting pressure as low as 2 Pa with high level of sensitivity. Furthermore, Ce³⁺-doped PVDF/graphene nanofiber based ultrasensitive pressure sensors can also be used as an effective nanogenerator as it generating an output voltage of 11 V with a current density ∼6 nA/cm² upon repetitive application of mechanical stress that could lit up 10 blue light emitting diodes (LEDs) instantaneously. Furthermore, to use it in environmental random vibrations (such as wind flow, water fall, transportation of vehicles, etc.), nanogenerator is integrated with musical vibration that exhibits to power up three blue LEDs instantly that promises as an ultrasensitive acoustic nanogenerator (ANG). The superior sensing properties in conjunction with mechanical flexibility, integrability, and robustness of nanofibers enabled real-time monitoring of sound waves as well as detection of different type of musical vibrations. Thus, ANG promises to use as an ultrasensitive pressure sensor, mechanical energy harvester, and effective power source for portable electronic and wearable devices

Target Characterization and Scattering Power Decomposition for Full and Compact Polarimetric SAR Data

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Hydrogen Bonding-Assisted Complete Ferroelectric β‑Phase Conversion in Poly(vinylidene fluoride) Thin Films: Exhibiting an Excellent Memory Window and Long Retention

Organic nonvolatile memory with low power consumption is a critical research demand for next-generation memory applications. Ferroelectric switching characteristics of poly(vinylidene fluoride) (PVDF) thin films modified with a trace amount of hydrated Cu salt (CuCl2·2H2O) are explored in the present study. Herein, a Cu salt-mediated PVDF (Cu/PVDF) thin film with preferential edge-on β-crystallites is fabricated through the orientation-controlled spin coating (OCSC) technique. This work proposes a convenient and effective approach to produce edge-on-oriented electroactive PVDF thin films with a high degree of polar β-phase, so as to realize the favorable switching under low operating voltages. Herein, chemically modified PVDF is anticipated to form a complex intermediate, which attains its stability by undergoing favorable hydrogen bonding that reorients the C–C structure of PVDF to obtain the β-conformation. Such information is verified by X-ray photoelectron spectroscopy (XPS). Grazing incidence Fourier transform infrared (GI-FTIR) spectroscopy revealed that the Cu salt incorporated into the PVDF matrix favored the formation of the electroactive β-phase with edge-on crystallite lamellae. Consequently, the Cu/PVDF thin film demonstrates a good contrast between electric field-assisted written and erased data bits in the piezoresponse force microscopy (PFM) phase image. Furthermore, to obtain the ferroelectric memory window, a metal–ferroelectric–insulator–semiconductor (MFIS) diode with Cu/PVDF as a ferroelectric layer has been fabricated. The capacitance–voltage (C–V) characteristic of the MFIS diode exhibits a memory window of 12 V with a long-term retention behavior (∼longer than 7 days). In a nutshell, we tried to represent a clear understanding of the interfacial interactions of the Cu salt with PVDF, which favor the edge-on formation that results in the promising low-voltage ferroelectric switching and excellent retention response, where any additional electrical poling and/or external stretching is completely possible to be ruled out, thus offering a new prospect for the evolution of devices with long-lasting nonvolatile memories

Organo-Lead Halide Perovskite Induced Electroactive β‑Phase in Porous PVDF Films: An Excellent Material for Photoactive Piezoelectric Energy Harvester and Photodetector

Methylammonium lead iodide (CH₃NH₃PbI₃) (MAPI)-embedded β-phase comprising porous poly­(vinylidene fluoride) (PVDF) composite (MPC) films turns to an excellent material for energy harvester and photodetector (PD). MAPI enables to nucleate up to ∼91% of electroactive phase in PVDF to make it suitable for piezoelectric-based mechanical energy harvesters (PEHs), sensors, and actuators. The piezoelectric energy generation from PEH made with MPC film has been demonstrated under a simple human finger touch motion. In addition, the feasibility of photosensitive properties of MPC films are manifested under the illumination of nonmonochromatic light, which also promises the application as organic photodetectors. Furthermore, fast rising time and instant increase in the current under light illumination have been observed in an MPC-based photodetector (PD), which indicates of its potential utility in efficient photoactive device. Owing to the photoresponsive and electroactive nature of MPC films, a new class of stand-alone self-powered flexible photoactive piezoelectric energy harvester (PPEH) has been fabricated. The simultaneous mechanical energy-harvesting and visible light detection capability of the PPEH is promising in piezo-phototronics technology

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/cm³) 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