Generation of hard X-ray radiation using the triboelectric effect by peeling adhesive tape

The triboelectric effect describes electrical charging when bringing different materials into contact. We report on the generation of hard X-ray radiation by peeling various adhesive tapes under medium vacuum conditions. Beside vacuum housing and pumps as instrumentation only an electric motor, two rolls and a metal foil as target material are necessary. The spectral distribution of generated X-rays was analyzed using an energy-dispersive detector. Depending on peeling speed, pressure and choice of material combination, electrons with energies sufficient to excite emission in the hard X-ray region are produced. The results are discussed in terms of triboelectric separation of charge carriers.     

A study on the triboelectric charging of display glass during the roller transfer process–modeling and characterization

Glass substrates for displays are insulating materials capable of generating and maintaining high levels of triboelectric charges posing a risk of electrostatic discharge (ESD) damage to electronic display components. In this work, an apparatus for triboelectric charging characterization of display glass during the roller transfer process was designed and fabricated. In order to establish the reliability of the characterization, the triboelectric charge and the electrostatic potential distribution measurement system was automated. The preconditioning process of the glass and the rollers was also addressed. In order to analyze the measurements' results, a multiphysics model that considered both electrical and mechanical properties was proposed. The test parameters that were expected to affect the triboelectric charging characteristics are defined and discussed, as well as some of the characterization results such as the effects of acceleration/deceleration and maximum velocity, relative humidity and moisture on the glass and the rollers, and the conductivity of the rollers. The peak-to-peak deviation of the de-embedded triboelectric charges, due to a steady-state velocity period with different combinations of acceleration/deceleration and maximum velocities, was 14.2%. The triboelectric charges increased as the relative humidity increased from 30% to 50% with the same temperature. They also increased when the insulating rollers were replaced with dissipative rollers.     

Brush drawing multifunctional electronic textiles for human-machine interfaces

Electronic textiles are a promising candidate for futuristic multifunctional clothes. However, the fabrication of robust and reproducible printed electrodes with high mechanical durability, high biocompatibility, and stable electrical performance under various mechanical deformations continues to pose a challenge. In this study, a silk fabric with printed carbon nanotube (CNT) patterns is used to produce a smart electronic textile (E-textile) for multifunctional applications. The printed CNT electrodes are used in triboelectric devices, electrically activated heaters, real-time electrophysiological sensors, and tactile sensors. The E-textile can be used as an electrically activated thermal patch to generate heat on cloth for providing warmth to the human skin and for therapy. Owing to the micro hierarchical pores of the fabric, skin contact generates a power density of about 0.7 mW cm⁻² via effective contact electrification.     

The effects of chemical pretreatment on tribocharging of density fraction coal

Dry triboelectric separation of coal depends on tribocharge difference of the coal and gangue mineral. The coal samples of different density fraction prepared by sink-and-float method were pretreated by chemicals and their effects on the tribocharge performance with stainless steel were studied by measuring the charge-to-mass and relative dielectric constant. The results show the tribocharging performance of middle density fraction coal is the worst compared with other density fractions. The charge of lower density fraction was increased by chemical conditioning with light diesel oil, ammonia, and kerosene, while the charge of higher density fraction was decreased with ethanol and lignin.     

High output triboelectric nanogenerator based on PTFE and cotton for energy harvester and human motion sensor

Recently, a novel mechanical energy harvesting method named triboelectric nanogenerator (TENG) is reported, and it has aroused great repercussions in the academic fields. But, the complex preparation process still limits its wide application. In this paper, the cotton film was used as the triboelectric material to fabricate a novel wearable TENG (W-TENG). The polytetrafluoroethylene (PTFE) film and cotton film play the role of triboelectric pair. The W-TENG can be used to harvest low-frequency mechanical energy in our environment, especially for human body mechanical energy, and then convert them to electrical energy. In addition, the cotton coated with conductive ink plays the role of conductive material for TENG. The V_oc and I_sc of W-TENG can reach 556 V and 26 μA, respectively. As for the maximum power density of W-TENG, it can arrive at 0.66 mW/cm². Also, a combined W-TENG was proposed to improve the electrical output. Moreover, the W-TENG can play the role of human motion sensor for human walking posture monitoring. This will open up a new path for the preparation of high output TENG at low cost, and promote the TENG devices in the field of sports monitoring.     

Improving the performances of direct-current triboelectric nanogenerators with surface chemistry

Over the past decade, triboelectric nanogenerators (TENGs) – small and portable devices designed to harvest electricity from mechanical vibrations and friction – have matured from a niche theme of electrical engineering research into multidisciplinary research encompassing materials science, physics, and chemistry. Recent advances in both the fundamental understanding and performances of TENGs have been made possible by surface chemistry, electrochemistry, and theoretical chemistry research entering this active and promising field. This short review focuses on the recent developments of direct-current (DC) TENGs, where sliding friction or repetitive contact–separation cycles between the surface of polymers, metals, chemically modified semiconductors, and more recently even by the simple contact of surfaces with water solutions, can output DC suitable to power electronic devices without the need of additional rectification. We critically analyze the role of surface chemistry toward maximizing DC TENG outputs and device longevity. The major current hypotheses about their working mechanism(s) are also discussed.     

Facile and low-cost synthesis of flexible nano-generators based on polymeric and porous aerogel materials

Triboelectric nano-generators (TE-NGs) can be utilized as a power supply for wireless systems, sensors, and operators. In this paper, new flexible TE-NGs that use sodium carboxymethyl cellulose (CMC), poly dimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), poly (4,4′-oxydiphenylene-pyromellitimide) (KAPTON) films and also sugar as a piezoelectric material were developed and are reported. Also, the outputs of NGs made by linear power under a periodic pressure of ~ 0.2 MPa at a frequency of 3 Hz showed that the highest output of NGs are related to PDMS–KATTON, PDMS, PVDF–KAPTON, PVDF, CMC NGs, respectively. It has been also observed that NGs connected in series to each other have a higher output than paralleled NGs so that their voltages increase at higher frequencies. Besides, a significant point is that the NGs are made in a low-cost, affordable, and environmentally-friendly route, which is a superior characteristic with respect to the rest of the NGs.     

Relationship between triboelectric charge and contact force for two triboelectric layers

A relationship between triboelectric charge and contact force for two triboelectric layers is presented, by combining the theories of insulator contact charging and contact mechanics. Experimental verification has been successfully performed using contact-mode triboelectric nanogenerators (TENGs) in two cases: (a) under varying contact forces while keeping the surface roughness profile constant, and (b) under varying surface roughness profiles while keeping the contact force constant. The theory presented here can serve as an important guide in the design of triboelectric systems, particularly of a contact-mode TENG structure for specific applications and self-powered systems.