Electret charging utilizing the electret ionization chamber

Isothermal charge deposition on polymers to form stable electrets by using the two-electret ionization chamber with parallel-plate geometry is reported. One of the electrets exhibits a high starting voltage compared with the second electret to be charged and hence an electric field exists in the chamber volume. Charge carriers produced by irradiation of the sensitive chamber air volume drift in the electric field and cause a charge enhancement of the second electret due to compensation of surface charges of the first electret. This process is finished when both electrets reach the same value and polarity of the surface potential. The method requires no external power supply and allows two electrets of the same surface potential to be produced.     

On the Electron‐Transfer Mechanism in the Contact‐Electrification Effect

A long debate on the charge identity and the associated mechanisms occurring in contact‐electrification (CE) (or triboelectrification) has persisted for many decades, while a conclusive model has not yet been reached for explaining this phenomenon known for more than 2600 years! Here, a new method is reported to quantitatively investigate real‐time charge transfer in CE via triboelectric nanogenerator as a function of temperature, which reveals that electron transfer is the dominant process for CE between two inorganic solids. A study on the surface charge density evolution with time at various high temperatures is consistent with the electron thermionic emission theory for triboelectric pairs composed of Ti–SiO₂ and Ti–Al₂O₃. Moreover, it is found that a potential barrier exists at the surface that prevents the charges generated by CE from flowing back to the solid where they are escaping from the surface after the contacting. This pinpoints the main reason why the charges generated in CE are readily retained by the material as electrostatic charges for hours at room temperature. Furthermore, an electron‐cloud–potential‐well model is proposed based on the electron‐emission‐dominatedcharge‐transfer mechanism, which can be generally applied to explain all types of CE in conventional materials.     

乙烯/四氟乙烯共聚物薄膜驻极体的电荷储存稳定性

研究了经栅控恒压电晕充电的乙烯／四氟乙烯共聚物（ETFE）驻极体的电荷稳定性,并将其与几种重要的驻极体材料的储电性能进行了比较。结果显示,ETFE薄膜驻极体具有优良的电荷储存稳定性,负极性ETFE的电荷稳定性明显优于正极性样品。热处理工艺能明显改善ETFE驻极体的电荷储存寿命。本文还估算出两种极性ETFE驻极体的陷阱能级的活化能,阐明脱阱电荷的输运特性。     

Charge storage coating based triboelectric nanogenerator and its applications in self-powered anticorrosion and antifouling

As a novel energy-harvesting device, a triboelectric nanogenerator (TENG) can harvest almost all mechanical energy and transform it into electrical energy, but its output is low. Although the micro-nano structures of triboelectrode surfaces can improve their output efficiency, they lead to high costs and are not suitable for large-scale applications. To address this problem, we developed a novel TENG coating with charge-storage properties. In this study, we modified an acrylic resin, a friction material, with nano-BaTiO₃ particles and gas phase fluorination. The charge-trapping ability of nanoparticles was used to improve the output of TENG. The short-circuit current and the output voltage of coating-based TENGs featuring charge storage and electrification reached 15 μA and 800 V, respectively, without decay for longtime working. On this basis, self-powered anticorrosion and antifouling systems are designed to reduce the open circuit potential of A3 steel by 510 mV and reduce the adhesion rate of algae on the surface of metal materials. This study presents a high-output, stable, coating-based TENG with potential in practical applications for anticorrosion and antifouling.     

Tribo-electrification of pharmaceutical powder blends

Abstract

It is well known in industrial applications involving powders and granular materials that the presence of electrostatic charges influences drastically the material flowing properties. The triboelectric charges are produced during flow at the contacts between the grains and at the contacts between the grains and the container. Unfortunately, the triboelectric effect is still poorly understood, even at the fundamental level. Therefore, the approach to solve practical problems is mostly empirical. Moreover, reproducible electrostatic measurements are difficult to perform. In the present study, the ability of a set of excipients and active pharmaceutical ingredients (APIs) to produce electrostatic charges during flow in contact with different materials is analyzed with a recently developed instrument called GranuCharge. While different excipients have almost the same triboelectric behavior and a low chargability, APIs show complex triboelectric properties. Some APIs charge a lot while other APIs charge less. Afterward, the electrostatic behavior of API/excipient blends is considered. We show that the net charge of the blend is a complex function of the relative quantity of API in the mixture. Moreover, both the quantity and the sign of the charge are found to depend on the material in contact with the powder during the flow.     

Fully enclosed hybrid electromagnetic–triboelectric nanogenerator to scavenge vibrational energy

We propose a fully enclosed hybrid nanogenerator consisting of five electromagnetic generators (EMGs) and four triboelectric nanogenerators (TENGs).Under a vibration frequency of 15.5 Hz,one TENG can deliver a high output voltage of approximately 24 V and a low output current of approximately 24 μA,whereas one EMG can deliver a low output voltage of approximately 0.8 V and a high output current of approximately 0.5 mA.By integrating five rectified EMGs in series and four rectified TENGs in parallel,the hybrid nanogenerator can be used to charge a home-made Li-ion battery from 1 to 1.9 V in 6.3 h.By using the hybrid nanogenerator to scavenge the vibrational energy produced by human hands,a temperature-humidity sensor can be sustainably powered by the nanogenerator,which is capable of charging the 200 μF system power capacitor from 0 to 2 V in 15 s,and sustainably power the sensor in 29 s.     

Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application

The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl(5) solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.     

基片掺杂与热氧化SiO2薄膜驻极体的电荷贮存特性

运用干－湿－干温热氧化工艺,在４种不同掺杂类型的单晶硅基片上,制备成功非晶态ＳｉＯ２薄膜驻极体。恒栅压电晕充电,等温表面电位衰减及热刺激放电实验表明,不同类型基片的ＳｉＯ２薄膜其电荷动态特性差异较大,基片的掺杂成份和掺杂浓度直接影响基上二氧化硅驻极体枳地存稳定性随着掺杂浓度的增大而有所下降,ＴＳＤ放电电流峰的形状与位置也会随着掺杂成份和浓度的变化而改变。分析表明,造成这一现象的原因在于：掺杂成份在     

新型聚四氟乙烯体材料双面驻极结构振动能量收集器

提出一种新型静电式振动能量收集器，该器件采用基于聚四氟乙烯体材料驻极体的双面电晕驻极结构，提高了薄膜驻极体静电式振动能量收集器的输出功率．在电晕驻极栅网电压为-700V的条件下，体材料驻极体的上下表面分别获得了-564．0V±83．1V、-636．4V±69．7V的表面电位均值．采用组装方式制成器件，并在正弦激振条件下测试器件的输出性能．实验结果表明，在振动频率10Hz、峰值加速度1．2g的条件下，器件输出峰值功率达到30μw，平均功率达到5．5μw，优于目前多数薄膜驻极体器件的性能，接近低功耗传感器的实际功率要求．     

Influence of the polymer matrix on the efficiency of hybrid solar cells based on silicon nanowires

Poly (N-vinylcarbazole) (PVK):SiNWs and poly (2-methoxy, 5-(2-ethyl-hexyloxy)-p-phenyl vinylene) (MEH-PPV):SiNWs bulk-heterojunctions (BHJ) have been elaborated from blends of SiNWs and the polymer in solution from a common solvent. Optical properties of these nanocomposites have been investigated by UV-vis absorption and photoluminescence (PL) spectral measurements. We have studied the charge transfer between SiNWs and the two polymers using the photoluminescence quenching of PVK and MEH-PPV which is a convenient signature of the reduced radiative recombination of the generated charge pairs upon exciton dissociation. We found that PVK and SiNWs constitutes the better donor-acceptor system. In order to understand the difference between PVK:SiNWs or MEH-PPV:SiNWs behaviours, photoluminescence responses were correlated with the topography (SEM) of the thin films. The photovoltaic effect of ITO/PEDOT:PSS/SiNWs:PVK/Al and ITO/PEDOT:PSS/SiNWs:MEH-PPV/Al structures was studied by current-voltage (I-V) measurements in dark and under illumination and interpreted on the basis of the charge transfer differences resulting from the morphologies.     

非接触式摩擦纳米发电机的最新研究进展

目的 随着科学技术的快速发展，人们对可持续能源的需求不断增加。摩擦纳米发电机(TENG)利用各类微弱机械能实现自供电，有利于缓解这一需求。非接触式摩擦纳米发电机(NC?TENG)可以提高稳定性和使用寿命。总结NC?TENG的最新研究进展，为NC?TENG的结构设计、性能优化提供有益参考。方法 根据NC?TENG的器件结构与输出性能优化方法，介绍不同NC?TENG及其性能，重点综述其在智能包装领域的应用，并对未来的性能优化和应用工作进行展望。结果 基于不同的组装结构，通过介电常数调制、添加电荷捕获中间层等性能优化方案可以有效地避免静电放电问题，提高NC?TENG的电荷保留率。结论 NC?TENG相较于TENG，有着更高的稳定性和更长的使用寿命，在应对能源危机和推动新兴电子产品方面显示出巨大的潜力，预计在智能包装领域有着广泛的应用前景。     

Electrically Controlled Localized Charge Trapping at Amorphous Fluoropolymer–Electrolyte Interfaces

Charge trapping is a long‐standing problem in electrowetting on dielectric, causing reliability reduction and restricting its practical applications. Although this phenomenon is investigated macroscopically, the microscopic investigations are still lacking. In this work, the trapped charges are proven to be localized at the three‐phase contact line (TPCL) region by using three detecting methods—local contact angle measurements, electrowetting (EW) probe, and Kelvin probe force microscopy. Moreover, it is demonstrated that this EW‐assisted charge injection (EWCI) process can be utilized as a simple and low‐cost method to deposit charges on fluoropolymer surfaces. Charge densities near the TPCL up to 0.46 mC m^?2 and line widths of the deposited charge ranging from 20 to 300 µm are achieved by the proposed EWCI method. Particularly, negative charge densities do not degrade even after a “harsh” testing with a water droplet on top of the sample surfaces for 12 h, as well as after being treated by water vapor for 3 h. These findings provide an approach for applications which desire stable and controllable surface charges.     

空间电荷聚合物驻极体材料的压电效应

自20世纪70年代空间电荷驻极体压电性概念被提出以来,开发新的聚合物压电材料一直是驻极体界研究的热点.这类材料的压电效应产生机制与传统的极性聚合物压电材料不同,是由于空间电荷在机械应力的作用下非对称性地向电极移动所致.本文从理论和实验两方面,对具有闭合型或开放型空洞结构和"软"、"硬"复合有机聚合物驻极体压电膜的研究现状进行了综述,并对进一步开展这类材料的研究提出了看法.     

Lipid/polydiacetylene films for colorimetric protein surface-charge analysis

The distribution and organization of charges on a protein surface are fundamental properties which affect protein functions and interactions. We demonstrate a new approach for protein surface-charge analysis through modulating protein interactions with chromatic lipid/polydiacetylene (PDA) films. We show that visible and easily quantifiable blue-red transitions, induced on the film surface through electrostatic interactions between the negatively charged PDA and positive soluble species, constitute an effective means for characterizing protein surface charge. Specifically, protein-film interactions can be significantly modulated by complexation between the tested macromolecules and lipid-embedded multivalent calixarene ligands displaying charged residues, making possible protein discrimination based upon the abundance and organization of surface charge. The lipid/PDA film system, in conjunction with the calixarene-derived ligands, facilitates characterization of protein surface charges and identification of anomalous protein electrostatic properties.     

Point‐Defect‐Passivated MoS2 Nanosheet‐Based High Performance Piezoelectric Nanogenerator

In this work, a sulfur (S) vacancy passivated monolayer MoS₂ piezoelectric nanogenerator (PNG) is demonstrated, and its properties before and after S treatment are compared to investigate the effect of passivating S vacancy. The S vacancies are effectively passivated by using the S treatment process on the pristine MoS₂ surface. The S vacancy site has a tendency to covalently bond with S functional groups; therefore, by capturing free electrons, a S atom will form a chemisorbed bond with the S vacancy site of MoS₂. S treatment reduces the charge‐carrier density of the monolayer MoS₂ surface, thus the screening effect of piezoelectric polarization charges by free carrier is significantly prevented. As a result, the output peak current and voltage of the S‐treated monolayer MoS₂ nanosheet PNG are increased by more than 3 times (100 pA) and 2 times (22 mV), respectively. Further, the S treatment increases the maximum power by almost 10 times. The results suggest that S treatment can reduce free‐charge carrier by sulfur S passivation and efficiently prevent the screening effect. Thus, the piezoelectric output peaks of current, voltage, and maximum power are dramatically increased, as compared with the pristine MoS₂.     

Advances in triboelectric nanogenerator powered electrowetting-on-dielectric devices: Mechanism,structures, and applications

Electrowetting-on-dielectric (EWOD) phenomenon is widely employed for liquid actuation at the micro scale. Due to its simple structure, low cost, low power consumption and fast response speed, diverse applications are developed and commercialized based on EWOD, such as digital microfluidics, tunable lenses, electronic displays, small-scale propellers etc. However, the liquid actuation with EWOD requires a high-voltage but low-current power source. The accessory equipment (e.g., waveform generator and amplifier) not only attenuates the benefits originated from microscale liquid actuation, but also limits its portability, wearability, and environmental friendliness of the EWOD inspired applications. Triboelectric nanogenerator (TENG) is a promising technology to convert arbitrary mechanical energy to electricity based on triboelectrification and electrostatic induction. The output electric signal shows a high-voltage but low-current property which well matches the demands in EWOD devices. This paper reviews the technical advances in the TENG powered EWOD devices developed in recent years. The mechanisms, structures, and performance of each application are reviewed. The challenges and future perspectives are put forward. The review and discussion in this study open up opportunities for the development of TENG and EWOD based self-powered liquid actuators.     

Single‐Step Fluorocarbon Plasma Treatment‐Induced Wrinkle Structure for High‐Performance Triboelectric Nanogenerator

A triboelectric nanogenerator (TENG) has been thought to be a promising method to harvest energy from environment. To date, the utilization of surface structure and material modification has been considered the most effective way to increase its performance. In this work, a wrinkle structure based high‐performance TENG is presented. Using the fluorocarbon plasma treatment method, material modification and surface structure are introduced in one step. The output ability of TENG is dramatically enhanced. After the optimization of plasma treatment, the maximum current and surface charge density are 182 μA about 165 μC m^?2. Compared with untreated TENG, the wrinkle structure makes the current and surface charge density increase by 810% and 528%, separately. X‐ray photoelectron spectroscopy is employed to analyze the chemical modification mechanism of this fluorocarbon plasma treatment. Facilitated by its high output performance, this device could directly light 76 blue light emitting diodes under finger typing. The output electric energy could be stored then utilized to power a commercial calculator. As a result of the simple fabrication process and high output ability, devices fabricated using this method could bring forward practical applications using TENGs as power sources.     

Intelligent Sensing System Based on Hybrid Nanogenerator by Harvesting Multiple Clean Energy

The inexhaustible mechanical kinetic energy can be extracted from wind and flowing water. Besides, flowing water also possesses electrostatic energy owing to the triboelectric charges caused by contacting with surrounding media, such as air. Here, a rotating hybridized triboelectric nanogenerator (TENG) has been established, by comprising of a water‐TENG (W‐TENG), a disk‐TENG (D‐TENG), and an electromagnetic generator (EMG), which has been explored for simultaneously harvesting energies from flowing water and wind. The W‐TENG is fabricated by wheel blades, polyvinylidene fluoride (PVDF), superhydrophobic polytetrafluoroethylene (PTFE), and aluminum to harvest the electrostatic energy. Moreover, the flowing water and wind impact on the wheel blades also causes the rotation motion of D‐TENG and EMG, resulting in being converted into electricity. At the rotation speed of 200 rpm, the short circuit current of D‐TENG and EMG can reach 0.4 μA and 7 mA, respectively. The open circuit voltage of W‐TENG can be up to 10 V at a flowing water rate of 60 ml s^?1. Besides, the hybridized NG is demonstrated to harvest water and wind energy and to act as a power source to charge a lithium battery or capacitor, which can drive LEDs, PH monitoring system, and wireless temperature and humidity sensing system. All these results show the potentials of the hybridized NG for harvesting multiple types of energies from the environment and constructing different self‐powered systems.

     

An Analysis of the Induction Method of Determining the Characteristics of Electrets

Different types of electrets are analyzed from the point of view of the property of the electric fields they produce. It is shown that the effective surface charge density, usually employed to determine the parameters of electrets, is not a fundamental parameter. A set of basic parameters for any types of electrets is considered. It is suggested that the existing State Standard GOST 25209-82, which regulates the procedure for determining the parameters of electrets by an induction method, should be changed for the reasons mentioned in order to obtain the fundamental parameters.     

Electron Transfer in Nanoscale Contact Electrification: Photon Excitation Effect

Contact electrification (CE) (or triboelectrification) is a well‐known phenomenon, and the identity of the charge carriers and their transfer mechanism have been discussed for decades. Recently, the species of transferred charges in the CE between a metal and a ceramic was revealed as electron transfer and its subsequent release is dominated by the thermionic emission process. Here, the release of CE‐induced electrostatic charges on a dielectric surface under photon excitation is studied by varying the light intensity and wavelength, but under no significant raise in temperature. The results suggest that there exists a threshold photon energy for releasing the triboelectric charges from the surface, which is 4.1 eV (light wavelength at 300 nm) for SiO₂ and 3.4 eV (light wavelength at 360 nm) for PVC; photons with energy smaller than this cannot effectively excite the surface electrostatic charges. This process is attributed to the photoelectron emission of the charges trapped in the surface states of the dielectric material. Further, a photoelectron emission model is proposed to describe light‐induced charge decay on a dielectric surface. The findings provide an additional strong evidence about the electron transfer process in the CE between metals and dielectrics as well as polymers.