Mid Sweden University

Inks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. Herein, high-output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper-based triboelectric nanogenerators (WP–TENGs)) are reported. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W m−2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper. The maximum open circuit voltage (V OC) and short circuit current (I SC) are 774 V and 3.92 mA (784 mA m−2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society. 

The triboelectric properties of the tribolayers are essential factors affecting the current density of triboelectric nanogenerators (TENGs). To enhance the current density, composites have been developed to tune their triboelectric properties. Previous studies have reported enhanced TENG performance with composite materials, primarily based on their composition, while chemical interactions between the components have been less analyzed. In this study, we report a novel approach to improve the current density of a TENG by introducing dipole-dipole interactions between a nylon filter membrane and graphene oxide (GO) through hydrogen bonds. The Raman spectroscopy confirmed the occurrence of the interactions resulting from hydrogen bonding. The enhancing mechanisms of hydrogen bonds were further analyzed by Kelvin probe force microscope (KPFM) measurement, which demonstrated that hydrogen bonding could influence the surface potential of the coated GO, leading to increased output of the nylon/GO@NFM TENG (NGN-TENG). Our results show that an ultrahigh current density of 1757 mA·m−2 was obtained with a 2 × 2 cm2 NGN-TENG. Additionally, we demonstrated the feasibility of using the NGN-TENG as a motion sensor to sense finger motions. These findings suggest that the introduction of hydrogen bonds in TENG composites can provide a promising route for improving their performance. 

nks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. In this study, we report high- output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper-based triboelectric nanogenerators (WP–TENGs)) [1]. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W·m-2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper [2]. The maximum open circuit voltage (VOC) and short circuit current (ISC) are 774 V and 3.92 mA (784 mA m-2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society.

[1] Zhang, R., Hummelgård, M., Örtegren, J., Andersson, H., Olsen, M., Chen, W., Wang, P., Eivazi, A., Dahlström, C. & Norgren, M. Adv. Engin. Mater., in press, 2023; https://doi.org/10.1002/adem.202300107

[2] Zhang, Z., Jie, Y., Zhu, J., Zhu, Z., Chen, H, Lu, Q., Zeng, Y., Cao, X., Wang, N. & Wang, Z. Nano Res. 15, 1109, 2022; https://doi.org/10.1007/s12274-021-3612-8

Material development is essential when studying triboelectric nanogenerators (TENGs). This importance is because the performance of TENGs is highly dependent on the properties of the utilized triboelectric materials. To obtain more specific properties, composites have been developed that combine the features of their components. According to Google Scholar, 55% of published papers related to triboelectric nanogenerators have utilized or mentioned composites. This number is 34.5% if one searches with the keyword nanocomposites instead of composites. The importance of composites is because they can exhibit new dielectric properties, better mechanical strength, enhanced charge affinities, etc. Therefore, the development of new composites has great importance in TENG studies. In this paper, we review the production of nanocomposites, the types of nanocomposites, and their application in TENG studies. This review gives an overview of how nanocomposites boost the performance of TENGs and provides guidance for future studies. 

Engineering polymers with quantified charge affinities are commonly used materials in triboelectric nanogenerators (TENGs). A polymer can have only one specific charge affinity due to its uniform chemical composition, leading to the need for two different materials to make an effective TENG. However, unlike engineering polymers, half-cell plant skins can have different charge affinities on their outer and inner surfaces. Here, we report a study on the hetero-triboelectric effects (HTEs) of half-cell allium plant skins such as leek, scallion and onion. Single-material TENGs (SM-TENGs) have been fabricated based on the two surfaces of these plant skins, taking advantage of their HTEs. The highest output power density of up to 35 W m−2 has been achieved with an output stability of over 5400 cycles. Multiple applications of SM-TENGs have been discovered, including energy harvesting, gas sensing, and humidity sensing, which are unique from other TENGs. Additionally, these SM-TENGs have an advantage due to the natural biological and chemical structures of the skins. 

Human-computer interaction (HCI) strategies communicate the human mind and machine intelligence based on different devices and technologies. The majority of HCI strategies assume normal physical conditions that limit accessibility for users with disabilities. Certain products, such as Braille keyboards, work fine for people with specific disabilities. However, a more general HCI strategy that can neglect users’ physical conditions would enhance the accessibility of these tools for disabled persons. Here, we report an HCI strategy that utilises triboelectricity of the human body (TEHB) for HCI. The TEHB can be generated by many parts of the human body, eliminating the obstacles imposed by physical function disabilities. Such an HCI approach has been used for text inputs, graphical inputs, and mimicked mouse functions. With the assistance of deep learning, an accuracy of approximately 98.4 % is achieved for text inputs obtained directly from handwriting. Our findings provide a new approach for HCI and demonstrate the feasibility of multiple interaction modes. 

Triboelectrification can occur between any two materials with different charge affinities. This phenomenon represents the fundamental physics of triboelectric nanogenerators (TENGs). Organic materials such as polymers have been widely used in TENGs because of their dielectric properties. Inorganic materials are, however, not widely studied despite the increasing attention paid to perovskite materials. In this paper, a new type of TENG has been fabricated based only on inorganic materials such as Mo6S3I6 and indium tin oxide (ITO). The output power density of the TENG operating in contact-separation mode reaches 18 W m−2. Mechanisms of the high output involve the unique semiconducting property of Mo6S3I6 and the unique chemical composition of ITO. The findings in this study indicate that inorganic materials can be used for fabricating high-output TENGs for energy harvesting. 

Triboelectrification (contact electrification) as a physical phenomenon appeared for the first time in a dialogue by Plato around 400 B.C. The phenomenon described in the dialogue is about amber that people wear attracting dry hair. The description also indicated that triboelectrification was first discovered on the human body. However, the studies that have been carried out on triboelectrification were mostly based on other materials, such as polymers, rather than on the human body. The invention of triboelectric nanogenerators (TENGs) has recently opened a door for both fundamental and applied research and brought triboelectrification into real applications. The human body's triboelectricity, as a vital part of studies, has also attracted much interest in the past ten years. Research and review articles were published during this period. However, few articles included the biological fundamentals of the triboelectrification of the human body. Moreover, most of the review articles missed two important parts: the electrostatic discharge (ESD) of the human body, which has been widely studied in electronics, and the cosmetics that reduce the triboelectrification of hair. A systematic review including the fundamentals and the applications could help readers understand the human body's triboelectricity. Given this, we proposed this review article on the human body's triboelectricity. The paper will cover a brief history and a brief mechanism summary of triboelectrification; the epidermis structure of the human hair and skin, including how the chemicals on the epidermal layer contribute to the skin's triboelectricity; fundamental studies of the human body's triboelectricity; and applications that utilize the human body's triboelectricity. Perspectives for future studies and conclusions will be given at the end of the review. 

Triboelectric nanogenerators (TENGs) have attracted increasing attention because of their excellent energy conversion efficiency, the diverse choice of materials, and their broad applications in energy harvesting devices and self-powered sensors. New materials have been explored, including green materials, but their performances have not yet reached the level of that for fluoropolymers. Here, a high-performance, fully green TENG (FG-TENG) using cellulose-based tribolayers is reported. It is shown that the FG-TENG has an output power density of above 300 W m−2, which is a new record for green-material-based TENGs. The high performance of the FG-TENG is due to the high positive charge density of the regenerated cellulose. The FG-TENG is stable after more than 30 000 cycles of operations in humidity of 30%–84%. This work demonstrates that high-performance TENGs can be made using natural green materials for a broad range of applications. 

Industrially scalable methods for the production of graphene and other nanographites are needed to achieve cost-efficient commercial products. At present, there are several available routes for the production of these materials but few allow large-scale manufacturing and environmentally friendly low-cost solvents are rarely used. We have previously demonstrated a scalable and low-cost industrial route to produce nanographites by tube-shearing in water suspensions. However, for a deeper understanding of the exfoliation mechanism, how and where the actual exfoliation occurs must be known. This study investigates the effect of shear zone geometry, straight and helical coil tubes, on this system based on both numerical simulation and experimental data. The results show that the helical coil tube achieves a more efficient exfoliation with smaller and thinner flakes than the straight version. Furthermore, only the local wall shear stress in the turbulent flow is sufficient for exfoliation since the laminar flow contribution is well below the needed range, indicating that exfoliation occurs at the tube walls. This explains the exfoliation mechanism of water-based tube-shear exfoliation, which is needed to achieve scaling to industrial levels of few-layer graphene with known and consequent quality.