Investigating superior performance by configuring bimetallic electrodes on fabric triboelectric nanogenerators (F-TENGs) for IoT enabled touch sensor applications

Fabric Triboelectric Nanogenerators (F-TENGs) are increasingly becoming more significant in wearable monitoring and beyond. These devices offer autonomous energy generation and sensing capabilities, by replacing conventional batteries in flexible wearables. Despite the substantial effort, however, achieving high output with optimal stability, durability, comfort, and washability poses substantial challenges, so we have yet to see any practical commercial uses of these materials. This study focuses on output and investigates the impacts of mono and bimetallic composite fabric electrode configurations on the output performance of F-TENGs. Our findings showcase the superiority of bimetallic configurations, particularly those incorporating Copper (Cu) with Nickel (Ni), over monometallic (Cu only) electrodes. These configurations demonstrate remarkable results, exhibiting a maximum instantaneous voltage, current, and power density of ∼ 199 V (a twofold increase compared to monometallic configurations), ∼22 μA (a threefold increase compared to monometallic configurations), and 2992 mW/m², respectively. Notably, these bimetallic configurations also exhibit exceptional flexibility, shape adaptability, structural integrity, washability, and mechanical stability. Furthermore, the integration of passive component-based power management circuits significantly enhances the performance capabilities of the F-TENGs, highlighting the essential role of power management circuits and electrode selection in optimizing F-TENGs. In addition, we have developed a complete IoT-enabled touch sensor system using CuNi-BEF EcoFlex layered F-TENGs for precise detection of soft and hard touches. This advanced system enhances robotic functionality, enabling nuanced touch understanding essential for precision tasks and fostering more intuitive human-machine interactions

Wearable nanocomposite textile-based piezoelectric and triboelectric nanogenerators: progress and perspectives

In recent years, the widespread adoption of next-generation wearable electronics has been facilitated by the integration of advanced nanogenerator technology with conventional textiles. This integration has led to the development of textile-based nanogenerators (t-NGs), which hold tremendous potential for harvesting mechanical energy from the surrounding environment and serving as power sources for self-powered electronics. Textile structures are inherently flexible, making them well-suited for wearable applications. However, their electrical performance as nanogenerators is significantly limited when used without any modifications. To address this limitation and enhance the electrical performance of textile-based nanogenerators, nanocomposite textiles have been extensively utilized for fabricating advanced nanogenerators. This critical review focuses on the recent progress in wearable nanocomposite textiles-based piezoelectric and triboelectric nanogenerators. The review covers the fundamentals of piezoelectricity and triboelectricity, the working principles of nanogenerators, and the selection of materials. Furthermore, it provides a detailed discussion of nanocomposite textiles in various forms, such as fibers or yarns, fabrics, and electrospun nanofibrous webs, which are employed in piezoelectric and triboelectric nanogenerators. The review also highlights the challenges associated with their implementation and outlines the prospects of textile-based nanogenerators. It can be concluded that nanocomposite textile based piezoelectric and triboelectric nanogenerators exhibit better electrical output and mechanical strength compared to conventional textile based nanogenerators. Nanocomposite electrospun web based piezoelectric nanogenerators exhibit higher piezoelectric output compared with nanocomposite fibre/yarn or fabric based piezoelectric nanogenerators. This is because an in-situ poling takes place in electrospinning unlike with fibre or fabric based piezoelectric nanogenerators. Nanocomposite electrospun web based triboelectric nanogenerators also show better triboelectric output compared to the fibre or fabric-based equivalents. This is due to the higher contact area developed with electrospun nanocomposite webs compared to the fibre or fabric cases. Overall, it can be concluded that while nanocomposite construction can boost output and durability of textile based nanogenerators, more research is required to bring output, stability and durability up to the levels achievable with non-textile based devices

A critical review on polyvinylidene fluoride (PVDF)/zinc oxide (ZnO) based piezoelectric and triboelectric nanogenerators

In the recent era of energy crisis, piezoelectric and triboelectric effects are surfacing out of several research topics. Polyvinylidene fluoride (PVDF) and its copolymers are well known piezoelectric polymers due to their high piezoelectricity and widely used in flexible devices. PVDF is greatly utilized in preparation of triboelectric layer also due to its higher electronegative nature amongst common polymers. On the other hand, zinc oxide (ZnO) has been studied widely to investigate its multifunctional properties including piezoelectricity, pyroelectricity and antibacterial activity. This versatile material can be prepared, using low cost and environmental friendly routes, in various morphologies. Various research is already performed to capture the synergistic effect of reinforcing ZnO within PVDF polymeric matrix. This work firstly describes the basic principles of piezoelectric and triboelectric effects. Thereafter, piezoelectric and triboelectric performances of PVDF and ZnO based materials are briefly depicted based on their structures. Finally, challenges and future scopes, associated with the mechanical energy harvesting from such materials, are highlighted

An Overview of Advances and Challenges in Developing Nanofiber Yarns for Wearable Technology

The rapid progress in science and technology has resulted in substantial growth in the nanotextiles market and holds promising potential for the future. There is important research on nanotextiles, focusing on advancing wearable technology and widening its end uses. Nanofiber-based yarns are the foundation of this endeavor due to their exceptional electrical, mechanical, thermal, and optical properties, size, and interface/surface effects. These characteristics make nanofiber yarns well-suited for diverse applications, such as energy devices, sensors, protective clothing, aerospace, automotive, and biomedical engineering. However, nanotextiles face limitations for practical applications in terms of stability, durability, mechanical strength, and particularly scalability. Successfully addressing these challenges is important for the effective use of nanotextiles. Electrospinning emerges as a versatile nanofiber fabrication process, where substantial effort has been made in the direction of nanofiber yarn fabrication by optimizing process conditions and modifying fiber collecting mechanisms. Although these innovations are aiming towards achieving stable nanofiber yarns, many challenges still remain. This review offers a comprehensive analysis of the modified electrospinning processes employed in laboratory setups for nanoyarn production and discusses critically the reasons behind its limitations. It presents an in-depth overview of the fundamental properties of nanoyarns/textiles and critically examines the formations of nanoyarns and their properties. Additionally, the review explores how material selection, nanofiber morphology, strength, and mechanical properties affect the efficiency, stability, and durability of nanofiber yarns. Furthermore, the review highlights the importance of post-processing and it recommends how optimizing material, process, and post-process conditions can facilitate the rapid development of wearable smart textile applications

A Garment-Integrated Textile Stitch-Based Strain Sensor Device, IoT-Enabled for Enhanced Wearable Sportswear Applications

The field of wearable technology is undergoing a transformative shift with the integration of IoT-enabled, AI-assisted sensors into sportswear, bringing sophisticated performance analysis within reach for a broader audience. Despite advancements in stitch strain sensors, there is a significant research gap in developing high-performance, stable, and IoT-connected complete stitch strain wearable sensor systems. These advanced sensors are essential for enhancing wearable technology and meeting the growing demands for improved user experience and functionality. In this study by utilizing conductive sewing threads and innovative stitching techniques, we fabricated textile strain sensors that offer high sensitivity, flexibility, and durability. Extensive calibration tests revealed strong linear relationships between resistance and tensile strain, with highest sensor sensitivity (2.08 Ω/mm during loading and 2.72 Ω/mm during unloading). These sensors demonstrate reliable performance with minimal hysteresis, particularly in shorter lengths. The wearable sportswear device, tested in gym environments, demonstrated the sensor’s capability to provide real-time feedback on knee flexing/bending and body movement during exercise. This functionality supports injury prevention and enhances workout efficiency. The sensor system is IoT-enabled, powered by an ESP8266 microcontroller, facilitating data transmission to the Thing Speak platform for advanced analysis and remote monitoring. This comprehensive approach not only advances wearable technology but also opens new avenues for remote health monitoring and smart e-textiles, contributing significantly to the fields of sports science and fitness technology

Disposable pH sensor on paper using screen-printed graphene-carbon ink modified zinc oxide nanoparticles

Estimation of pH is vital to assess the biochemical and biological processes in a wide variety of applications ranging from water to soil, health, and environment monitoring. This work reports a screen-printed flexible and disposable pH sensor using the impedimetric method. The pH sensor was fabricated by screen printing Graphene-Carbon modified Zinc Oxide based active layer on a paper substrate and shows nearly three orders of change in impedance magnitude in the pH range of 2 – 9. The sensor was carefully designed using COMSOL® Multiphysics software to understand the influence of electrode geometry and the electrical potential developed across the structure. The developed sensor was used for pH monitoring of soil and exhibited high sensitivity of 5.27 kΩ /pH (2-8) with a correlation coefficient (R 2 ) of 0.99. Finally, an IoT-enabled smart pH detection system was implemented for continuous pH monitoring for potential application in digital agriculture. The outcome demonstrates that the presented flexible and disposable pH sensor could open new opportunities for monitoring of water, product process, human health, and chemical (or bio) reactions even using small volumes of samples

Semiconductive Filler-Based Hybrid Piezoelectric Materials

This chapter presents an extensive examination of semiconductive filler-based hybrid piezoelectric materials, with a specific focus on lead-based and lead-free compositions. Lead-based materials, including lead titanate (PbTiO3) and lead zirconate (PbZrO3), undergo modification or are employed in solid solutions to amplify their piezoelectric properties. Techniques such as doping and modification, such as the addition of yttria-stabilized zirconia (YSZ) or Sb2O3, are discussed to enhance the mechanical and electrical characteristics of lead-based ceramics. Moreover, alternative lead-free options, such as potassium sodium niobate (KNN) are explored, with an emphasis on customizing their properties through chemical modifications. Furthermore, the incorporation of semiconductive fillers such as PZT and graphene into piezoelectric matrices is emphasized as a viable strategy for creating nanocomposites with improved piezoelectric properties. These hybrid materials exhibit significant potential for diverse applications in energy-harvesting, structural health monitoring, and related fields.</p