Electrical Poling Treatment Research Articles

Silk nanoribbon films with enriched silk II structure and enhanced piezoelectricity for self-powered implantable and wearable devices

Piezoelectric biomaterials are intrinsically suitable to convert mechanical energy to electrical output and achieve electricity generation, in vivo/in vitro real-time monitoring, and sensing in biological systems. However, the inability to fabricate piezoelectric bio-materials with excellent piezoelectricity, full biodegradability, and good biocompatibility remains a challenge toward practical applications. As a solution, we present a bio-piezoelectric thin film with macroscopic piezoelectric output, high stability, fast response ability, flexibility, biocompatibility, and biodegradability based on nascent silk nanoribbons (SNRs) with high silk II-type structure. The solvent systems influence the meso/nanostructure and the piezoelectric performance of silk materials. Compared with other silk materials, the SNR fabricated by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation system (T-SNR) maintains higher silk II-type structure and more stable crystalline structure. The T-SNR film possesses electrostriction effect without electrical poling treatment. It presents an apparent piezoelectric constant (d33) of 7.7 pm/V and a piezoelectric voltage coefficient (g33) of 0.58 Vm/N, such values are superior to most reported bio-films. The piezoelectric T-SNR film can realize in vivo/in vitro real-time monitoring, sensing, and self-power ability. With its natural compatibility and degradability, the T-SNR film exhibits the potential for various implantable and wearable applications and may enable the development of fully biodegradable transient electromechanical devices.

Enhanced output performance of piezoelectric energy harvester based on hierarchical Bi3.15Nd0.85Ti3O12 microspheres/PVDF-HFP composite

The inclusion of inorganic piezoelectric fillers in the polymeric matrix of flexible ferroelectric polymer synergies the piezoelectricity for wearable electronics. Herein, hierarchical Bi3.15Nd0.85Ti3O12 microspheres (H-BNdT MPs) embedded in the polymeric matrix of polyvinylidene fluoride–hexafluoropropylene (PVDF-HFP) based piezoelectric thin films are fabricated by using a facile and cost-effective film-forming method, drop-casting. The composites possess improved dielectric and ferroelectric properties comparing with that of the pure PVDF-HFP film without any electrical poling treatment. More importantly, the highest outputs of an open-circuit voltage of 20 V and a short-circuit current of 1.9 μA under the repeated mechanical force of 10 N at the frequency of 2 Hz were successfully achieved. The maximum power of the optimal PEH can reach as high as 4.6 mW, corresponding to a power density of 938 μW/cm2, and the output electricity can light up 10 LEDs with a full-wave rectifier circuit. The enhanced output performance is attributed to the high local stress around the H-BNdT MPs arising from the hollow hierarchical architecture of the inorganic fillers. The lead-free flexible PEH is also proved to have the ability to harvest the biomechanical energy of human movements, such as finger pinching, finger tapping, and fist punching. In particular, a PEH shoe is made to harvest energy from walking and running. This PEH is confirmed to be a potential energy harvester and effective self-powered generator to drive wearable devices.

Electric-field modulated photovoltaic effect of ferroelectric double-perovskite Bi2FeMnO6 films

Ferroelectric perovskite oxide materials for photovoltaics (PV) have received considerable attention for their switchable PV responses and above-bandgap photovoltages as a type of new-generation PV device. Relatively large bandgap and low photocurrent remain major problems for their PV applications. Herein, we report the PV response of ferroelectric double-perovskite Bi2FeMnO6 (BFMO) thin films. It was found that the photocurrent density (Jsc) of a Sn:In2O3 (ITO)/BFMO/SrRuO3 (SRO) thin film device is two orders of magnitude higher than that of BiFeO3, and its power conversion efficiency is about 430 times larger than that of BiFeO3 under AM 1.5G illumination. The built-in electric field near the BFMO/SRO interface, which represents the Schottky contact, leads to the separation of photon-generated carriers. More importantly, the electric poling treatment on the BFMO device can manipulate significantly the magnitude of Jsc, which is independent of the polarization direction. This electric-field modulated PV effect in the poled BFMO device originates from the modulation of the Schottky barrier height at the BFMO/SRO interface. The redistribution of oxygen vacancies after electric poling treatment is mainly responsible for the modulation of the Schottky barrier height.

Preparation and characterization of flexible PVDF-HFP film for piezoelectric applications

We report on the preparation of electroactive β-phase in polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) without any electrical poling treatment. The PVDF-HFP film with various mass fractions (wt%) of magnesium chloride hexahydrate salt (MgCh∼6H2O) was fabricated by a solution casting technique. The morphological, mechanical, structural and dielectric properties were investigated. Results founded that the PVDF-HFP composite films show a large number of micro-pores on the top surface as a sponge-like structure. The Young’s modulus and crystallinity values tend to be linearly decreased with the MgCh2⋗6H2O concentration leading to enhance flexibility. The largest β-phase fraction of 87.2% is found in the composite with 1 wt% MgCh2⋗6H2O filler. The obtained value is 4 times higher than the value of unfilled PVDF-HFP. Moreover, the maximum value of dielectric constant is about 19.2 at 10 Hz for 4 wt% MgCh2⋗6H2O filler. Therefore, the modified composites with the excellent flexibility, dielectric constant and β-phase may be a promising material for applications in the field of piezoelectric energy conversion.

A strategy to develop an efficient piezoelectric nanogenerator through ZTO assisted γ-phase nucleation of PVDF in ZTO/PVDF nanocomposite for harvesting bio-mechanical energy and energy storage application

Extracting energy from various types of mechanical forces through piezoelectric nanogenerator (PNG) exhibits a great potential for powering up low-power portable devices and self-powered electronic systems. Here, the ferroelectric and lead-free perovskite zinc titanate (ZTO) nanoparticles mitigate to align the molecular –CH2/CF2 dipoles of PVDF, promoting the nucleation of electroactive γ-phase in the PVDF matrix (γ-PVDF), which is responsible for the generation of piezoelectricity of the PNG without any electrical poling treatment. The fabricated PNG with 2 wt% ZTO loading shows a maximum output voltage up to ∼25.7 V and current ∼1.2 μA with a power density of ∼8.22 μW. cm−2 under cyclic finger imparting with a constant pressure (∼16.5 KPa). In addition, the PNG is capable of harvesting energy from a wide variety of easily manageable mechanical stress source such as human body movement, walking, and machine vibration and exhibits high durability for about four weeks without any deterioration in the output performance. Furthermore, the ZTO/PVDF films demonstrate a higher electrical energy density of ≈0.267 J cm−3 at an electric field of 600 kV cm−1, which makes it fit for electrical energy storage device. This high performance ZTO/PVDF hybrid film paves a new and effective way to fabricate eco-friendly devices, active sensors, and flexible nanogenerators for powering small portable electronic appliances and flexible high energy density capacitors as well.

Sustainable Energy Generation from Piezoelectric Biomaterial for Noninvasive Physiological Signal Monitoring

Sustainable development of self-powered wearable electronics relies on bioinspired piezoelectric materials which could transduce minute deformation of human skin. In this work, fish-skin-based sustainable energy production is discussed in light of structure–property correlation. The developed energy harvester acts as a sensor that interacts with human body parts to monitor real-time physiological signals. Self-assembled collagen nanofibrils comprising fish skin show stable crystalline structure and possess nonlinear electrostriction effect without any electrical poling treatment. A fish-skin-based nanogenerator (FSKNG)/pressure sensor is ultrasensitive (sensitivity ∼27 mV N–1) and highly durable (over 75 000 cycles) and possesses very fast response time (∼4.9 ms). Importantly, in response to the external pressure (∼1.8 MPa), FSKNG generates open-circuit voltage, Voc ∼ 2 V, and short-circuit current, Isc ∼ 20 nA, due to inherent piezoelectric effect. The magnitude of the generated power (∼0.75 mW m–2) turn...

An effective flexible wireless energy harvester/sensor based on porous electret piezoelectric polymer

A flexible sponge-like nanogenerator (FSNG) based on ZnO nanoparticles (NPs) etched porous electret poly (vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) film is spotlighted without any electrical poling treatment. It possesses improved dielectric and ferroelectric properties than neat P(VDF-HFP) film. The FSNG harvests an open-circuit voltage (Voc) of 9 V and short circuit current (Isc) of 1.3 μAcm−2 under repeated mechanical impact of 0.36 MPa stress amplitude on the top surface. With the power density (P) of 1.21 mW/cm2 and energy conversion efficiency of 0.3% it directly operates several consumer electronics. The highly sensitive (∼1 μVPa−1) FSNG is demonstrated as a self-powered wireless sensor with 3.0% efficiency for detecting some tiny human activities including finger movements.

Porous polymer composite membrane based nanogenerator: A realization of self-powered wireless green energy source for smart electronics applications

An efficient, flexible and unvaryingly porous polymer composite membrane based nanogenerator (PPCNG) without any electrical poling treatment has been realised as wireless green energy source to power up smart electronic gadgets. Owing to self-polarized piezo- and ferro-electretic phenomenon of in situ platinum nanoparticles (Pt-NPs) doped porous poly(vinylidenefluoride-co-hexafluoropropylene)–membrane, a simple, inexpensive and scalable PPCNG fabrication is highlighted. The molecular orientations of the -CH2/-CF2 dipoles that cause self-polarization phenomenon has been realized by angular dependent near edge X-ray absorption fine structure spectroscopy. The square-like hysteresis loop with giant remnant polarization, Pr ∼ 68 μC/cm2 and exceptionally high piezoelectric charge coefficient, d33 ∼ − 836 pC/N promises a best suited ferro- and piezo-electretic membrane. The PPCNG exhibits a high electrical throughput such as, ranging from 2.7 V to 23 V of open-circuit voltage (Voc) and 2.9 μA to 24.7 μA of short-circuit current (Isc) under 0.5 MPa to 4.3 MPa of imparted stress amplitude by periodic human finger motion. The harvested mechanical and subsequent electrical energy by PPCNG is shown to transfer wirelessly via visible and infrared transmitter-receiver systems, where 17% and 49% of wireless power transfer efficiency, respectively, has been realized to power up several consumer electronics.

The preparation of γ-crystalline non-electrically poled photoluminescant ZnO–PVDF nanocomposite film for wearable nanogenerators

Polyvinylidene fluoride (PVDF) films are filled with various mass fractions (wt%) of zinc oxide nanoparticles (ZnO-NPs) to fabricate the high performance of a wearable polymer composite nanogenerator (PCNG). The ZnO-NPs can induced a fully γ-crystalline phase in PVDF, where traditional electrical poling is not necessary for the generation of piezoelectric properties. The PCNG delivers up to 28 V of open circuit voltage and 450 nA of short circuit current by simple repeated human finger imparting (under a pressure amplitude of 8.43 kPa) that generates sufficient power to turn on at least 48 commercial blue light emitting diodes (LEDs) instantly. Furthermore, it also successfully charged the capacitors, signifying practical applicability as a piezoelectric based nanogenerator for self-powering devices. The applicability of PCNG by wearable means is clarified when it gives rise to a sensible response, say up to 400 mV of output voltage synchronized with the PCNG embedded human finger in a bending and releasing gesture. UV-visible absorption spectral analysis revealed the possibility of estimating a change in the optical band gap value (Eg), refractive index (n) and optical activation energy (Ea) in different concentrations of ZnO-NP incorporated PVDF nanocomposite films, and it possesses a useful methodology where ZnO-NPs can be used as an optical probe. Near blue light emission is observed from photoluminescence spectra, which are clearly shown from a Commission Internationale de L’Eclairage (CIE) diagram. The piezoelectric charge coefficient of the nanocomposite film is estimated to be −6.4 pC/N, where even electrical poling treatment is not employed. In addition, dielectric properties have been studied to understand the role of molecular kinetic and interfacial polarization occurring in nanocomposite films at different applied frequencies.

Self Powered Flexible Electronics Based on Self Poled “Ferroelectretic” Nanogenerator

ABSTRACTA ferroelectric nanogenerator without any electric poling treatment has been realized by incorporation of ytterbium (Yb) salt incorporated porous PVDF composite film. The composite film compose of electroactive β- and γ-phases, demonstrates higher dielectric and ferroelectric polarization responses than pure PVDF film. The 3 V of open circuit voltage with 0.47 µW/cm2 power density was generated by the nanogenerator upon single finger touch. It can also operate capacitor and light emitting diode without any subsidiary batteries.

Lead-free ZnSnO3/MWCNTs-based self-poled flexible hybrid nanogenerator for piezoelectric power generation

A high-performance flexible piezoelectric hybrid nanogenerator (HNG) based on lead-free perovskite zinc stannate (ZnSnO3) nanocubes and polydimethylsiloxane (PDMS) composite with multiwall carbon nanotubes (MWCNTs) as supplement filling material is demonstrated. Even without any electrical poling treatment, the HNG possesses an open-circuit voltage of 40 V and a short-circuit current of 0.4 μA, respectively, under repeated human finger impact. It has been demonstrated that the output volume power density of 10.8 μW cm−3 from a HNG can drive several colour light emitting diodes (LEDs) and a charge capacitor that powers up a calculator, indicating an effective means of energy harvesting power source with high energy conversion efficiency (∼1.17%) for portable electronic devices.

Unidirectional High‐Power Generation via Stress‐Induced Dipole Alignment from ZnSnO3 Nanocubes/Polymer Hybrid Piezoelectric Nanogenerator

The extremely stable high‐power generation from hybrid piezoelectric nanogenerator (HP‐NG) based on a composite of single‐crystalline piezoelectric perovskite zinc stannate (ZnSnO3) nanocubes and polydimethylsiloxane without any electrical poling treatment is reported. The HP‐NG generates large power output under only vertical compression, while there is negligible power generation with other configurations of applied strain, such as bending and folding. This unique high unidirectionality of power generation behavior of the HP‐NG provides desirable features for large‐area piezoelectric power generation based on vertical mechanical compression such as moving vehicles, railway transport, and human walking. The HP‐NGs of ZnSnO3 nanocubes exhibit high mechanical durability, excellent robustness, and high power‐generation performance. A large recordable output voltage of about 20 V and an output current density value of about 1 μA cm−2 are successfully achived, using a single cell of HP‐NG obtained under rolling of a vehicle tire.

Fabrication of BaTiO 3 films on titanium by microarc oxidation method and improvement of bioactivity by electric poling treatment

A microarc oxidation (MAO) method was used to deposit a ferroelectric BaTiO 3 (BTO) film on titanium implant metal. The bioactivity of the sample was enhanced by negatively polarizing the film surface. BTO-1 and BTO-2 sample groups were fabricated by applying a constant AC current of 1.2 A/cm 2 (900 s) and 2.0 A/cm 2 (600 s), respectively. The BTO film surface was negatively polarized using a high temperature poling treatment. The bioactivity of the non-polarized BTO and polarized BTO films was compared using an immersion test in Eagle's Minimum Essential Medium (MEM). For both groups, 0.5–2 μm diameter pores were evenly distributed over the BTO film surface fabricated using the MAO method. The crystallinity and film-to-substrate bond strength of the BTO-2 film were higher than those of the BTO-1 film. The in vitro MEM immersion test demonstrated more calcium phosphate deposition on the negatively polarized BTO film than on the non-polarized BTO film.

X-ray photoelectron spectroscopy characterization of the interface between Ag electrode and PVDF film treated by electric poling

Interface changes induced by electric poling treatment between an Ag electrode deposited by vacuum thermal evaporation and a polymer thin film have been investigated. The polymer film poly (vinylidene fluoride) (PVDF), a fluoropolymer of repeat unit (–CH2–CF2–) was treated under electric poling at high temperature of 90°C. The characterization was accomplished using X-ray photoelectron spectroscopy (XPS) as a primary tool. The results indicate that the piezoelectricity of PVDF thin films and adhesion force between polymer thin film and metallic electrode are improved by electric poling and chemical bond joint.

Enhanced Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering

The engineered domain configuration was induced into potassium niobate (KNbO3) crystals, and the piezoelectric properties were investigated as a function of domain size. First, single-domain treatment was investigated, and a combination of chemical etching and 2-step electric poling treatment was effective. Using the single-domain crystals, all piezoelectric related constants were determined. On the basis of these piezoelectric constants, the d31 and d32 surfaces were calculated. The piezoelectric properties of [001]c oriented KNbO3 single-domain crystals were measured and were completely consistent with the calculated properties. Finally, the engineered domain configurations were induced into KNbO3 crystals by the control of the temperature and the electric-field along the [001]c direction. The piezoelectric properties of these KNbO3 crystals with the engineered domain configurations showed much higher values than those of the single-domain crystal. Moreover, the piezoelectric properties increased with decreasing the domain sizes of the engineered domain configuration.