Mid Sweden University

Additive manufacturing is rapidly growing, where selective laser sintering technology dominates for industrial use. In the case of polymer selective laser sintering, polyamide is the standard material. However, polyamide is an electrical insulator, and for specific applications, it would be desirable to be able to manufacture polymer-based electrically conductive parts. Electromagnetic Compatibility is one of the most significant targeted applications, where the introduction of electric vehicles raises new electromagnetic compatibility demands. The goal is, therefore, to develop an electrically conductive composite material for selective laser sintering using graphene as the additive. Composites are prepared by mixing polyamide, graphene, and additives with varying graphene/polyamide ratios. The aim of this investigation is the laser-assisted processing of the resulting graphene/polyamide composites with various parameters to sinter the material, forming a solid conductive structure. The structure is characterized using SEM and resistance measurements. Results show sheet resistance values of about 700Ω/sq after laser-assisted processing with good powder flowability. 

Lithium-ion batteries are widely used today due to their high energy density, long life cycles, and low self-discharge rates. It commonly uses graphite as an anode material with a high theoretical capacity of 372mAh/g. At the same time, several research groups explore ways to further increase the energy storage capacity of lithium-ion batteries by, for example, adding silicon to the graphite anode material. Silicon is naturally abundant and inexpensive, with low environmental impact and a significantly higher theoretical specific capacity of ~4200mAh/g. A drawback is that graphite-silicon composite anode materials tend to degrade during the charge/discharge cycles, leading to decreased storage capacity over time. This degradation is associated with the size of the silicon particles, where large, micrometer-sized silicon particles are more susceptible to instability than smaller, nanometre-sized particles. To address this issue, we present an investigation using laser-assisted processing of nano-graphite-silicon composites. This process uses low-cost micrometer-sized silicon particles mixed with nano-graphite powder and a 1064 nm continuous wave laser to process the nano-graphite-silicon-coated anode material under various conditions and atmospheres (ambient and nitrogen). The performance of the lithium-ion battery is affected by different processing conditions. Specifically, the intensity of the 0.25V and 0.5V anodic peaks, which indicate the delithiation of silicon, is particularly affected, with the inclusion of an additional broader shoulder peak at around 0.3-0.35V. Our investigation suggests that laser-assisted processing of nano-graphite-silicon-composite materials is a scalable concept with the potential to improve the performance of nano-graphite-silicon anodes for lithium-ion batteries. 

Lithium-ion batteries are pivotal in modern energy storage, commonly utilizing graphite anodes for their high theoretical capacity and long cycle life. However, graphite anodes face inherent limitations, such as restricted lithium-ion storage capacity and slow diffusion rates. Enhancing the porosity of graphite and increasing d-spacing in expanded graphite anodes have been explored to improve lithium-ion diffusion and intercalation. Recent advancements suggest that nanoscale modifications, such as utilizing nano-graphite and graphene, can further enhance performance. Laser processing has emerged as a promising technique for synthesizing and modifying graphite and graphene-related materials, offering control over surface defects and microstructure. Here, we demonstrate an industrially compatible one-step laser processing method to transform a nano-graphite and graphene mixture into a nanoporous matrix, significantly improving lithium-ion battery performance. The laser-processed anodes demonstrated significantly enhanced specific capacities at all charge rates, with improved relative performance at higher charge rates. Additionally, long-term cycling at 1 C showed that laser-processed cells outperformed their non-processed counterparts, with specific capacities of 323 and 241 mAh/g, respectively.

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. 

Biometric signatures based on either the physiological or behavioural features of a person have been widely used for identification and authentication. However, few strategies have been developed that combine the two types of features in one signature. Here, we report a type of biometric signature based on the triboelectricity of the human body (TEHB) that combines these two types of features. This triboelectric biometric signature (TEBS) can be accomplished by anyone regardless of the physical condition, as it can be performed by many parts of the body. Different TEBS can be identified using a convolutional neural network (CNN) model with a test accuracy of up to 1.0. The TEBS has been further used for text encryption and decryption with a high sensitivity to changes. Moreover, a dual signed digital signature for enhanced security has been proposed. Our findings provide a new type of TEBS that can be generally used and demonstrated in applications. 

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.