Triboelectric nanogenerators (TENGs) combine contact electrification and electrostatic induction effects to convert waste mechanical energy into electrical energy. As conventional devices contribute to electronic waste, TENGs based on ecofriendly and biocompatible materials have been developed for various energy applications. Owing to the abundance, accessibility, low cost, and biodegradability of biowaste (BW), recycling these materials has gained considerable attention as a green approach for fabricating TENGs. This review provides a detailed overview of BW materials, processing techniques for BW-based TENGs (BW-TENGs), and potential applications of BW-TENGs in emerging bioelectronics. In particular, recent progress in material design, fabrication methods, and biomechanical and environmental energy-harvesting performance is discussed. This review is aimed at promoting the continued development of BW-TENGs and their adoption for sustainable energy-harvesting applications in the field of bioelectronics.

The impact of electrical stimulation has been widely investigated on the wound healing process; however, its practicality is still challenging. This study explores the effect of electrical stimulation on fibroblasts in a culture medium containing different electrically-charged polysaccharide derivatives including alginate, hyaluronate, and chitosan derivatives. For this aim, an electrical stimulation, provided by a zigzag triboelectric nanogenerator (TENG), was exerted on fibroblasts in the presence of polysaccharides\' solutions. The analyses showed a significant increase in cell proliferation and an improvement in wound closure (160 % and 90 %, respectively) for the hyaluronate-containing medium by a potential of 3 V after 48 h. In the next step, a photo-crosslinkable hydrogel was prepared based on hyaluronic acid methacrylate (HAMA). Then, the cells were cultured on HAMA hydrogel and treated by an electrical stimulation. Surprisingly, the results showed a remarkable increase in cell growth (280 %) and migration (82 %) after 24 h. Attributed to the electroosmosis phenomenon and an amplified transfer of soluble growth factors, a dramatic promotion was underscored in cell activities. These findings highlight the role of electroosmosis in wound healing, where TENG-based electrical stimulation is combined with bioactive polysaccharide-based hydrogels to promote wound healing.

As an emerging high-efficiency energy conversion device, improving the output of triboelectric nanogenerators (TENGs) is still a key method to promote practical application of TENGs. This paper systematically investigated the influence of component composition, thickness, and surface morphology of the metal conducting layer on the performance of triboelectric nanogenerators. It has been established that these three factors have a significant influence on the output performance of TENGs. Among the four common metals Au, Pt, Ag, and Cu, the triboelectric nanogenerator achieves its maximum output when utilizing Ag as the conducting layer, with optimal performance observed at a thickness of 278 nm. TENGs with nanostructured conducting layers have better output as the nanostructure amplifies the induction charging area, thereby effectively augmenting the performance of TENGs. In particular, when contrasted with a triboelectric nanogenerator utilizing copper foil as the conducting layer alongside poly(vinylidene difluoride) and Nylon-11 as friction layers in the common work, the short-circuit current of the triboelectric nanogenerator increased by 2.3 times, and the maximum short-circuit current reached 149 μA when the conducting layer was replaced with Ag, and the enhanced triboelectric nanogenerator successfully illuminated 1536 commercial LEDs. In addition, the TENG-based smart insoles combined with pedometers can realize signal sensing and the real-time recording of steps during exercise. This research provides a new simple and reliable method to further improve the output of the TENG.

An advanced energy autonomous system that simultaneously harnesses and stores energy on the same platform offers exciting opportunities for the near-future self-powered miniature electronics. However, achieving optimal synchronization between the power output of an energy harvester and the storage unit or integrating it seamlessly with real-time microelectronics to build a highly efficient energy autonomous system remains challenging. Herein, a unique bimetallic layered double hydroxide (LDH) based tribo-positive layer is introduced for a high-voltage sliding triboelectric nanogenerator (S-TENG) with an output voltage of ≈1485 V and power output of 250 µW, respectively. To demonstrate the potential of a self-charging power system, S-TENG is integrated with on-chip micro-supercapacitors (MSCs) as a storage unit. The MSC array effectively self-charged up to 4.8 V (within 220s), providing ample power to support micro-sensory systems. In addition, by utilizing the high-voltage output of the S-TENG, the efficient operation of electrostatic actuators and digital microfluidic (DMF) systems driven directly by simple mechanical motion is further demonstrated. Overall, this work can provide a solid foundation for the advancement of next-generation energy-autonomous systems.

The transmission lines galloping severely threatens the safety operation of the power grid. A reliable operation and maintenance alternative is to monitor the transmission lines by wireless sensing and warning devices. In this work, a triboelectric nanogenerator with the double-mass pendulum integrated spacer (DMPS-TENG) is proposed for harvesting the galloping energy of transmission lines and powering the wireless monitoring devices. Specifically, by introducing a double-mass pendulum system, the response frequency of the DMPS-TENG is reduced, allowing it to harvest energy at lower frequencies in the range of transmission lines galloping (0-3 Hz). Hereby, enhancing the energy harvesting bandwidth and the efficiency. The experiments show that with the introduction of the double-mass pendulum, the optimum frequency of the harvester is reduced from 2.4 to 1.9 Hz, enhances the harvesting bandwidth by 18%, and enables an average power output of up to 0.32 mW. Additionally, to demonstrate the practical value, a prototype is designed and fabricated to perform three different application experiments in the multi-split transmission lines simulation system. This work presents an innovative approach for galloping energy harvesting of transmission lines, which can be used to inform further development of sensor networks and visualization of the power grid.

Sleep plays a role in maintaining our physical well-being. However, sleep-related issues impact millions of people globally. Accurate monitoring of sleep is vital for identifying and addressing these problems. While traditional methods like polysomnography (PSG) are commonly used in settings, they may not fully capture natural sleep patterns at home. Moreover, PSG equipment can disrupt sleep quality. In recent years, there has been growing interest in the use of sensors for sleep monitoring. These lightweight sensors can be easily integrated into textiles or wearable devices using technology. The flexible sensors can be designed for skin contact to offer continuous monitoring without being obtrusive in a home environment. This review presents an overview of the advancements made in flexible sensors for tracking body movements during sleep, which focus on their principles, mechanisms, and strategies for improved flexibility, practical applications, and future trends.

Recent advancements in flexible triboelectric nanogenerators (TENGs) have widely focused on converting mechanical energy into electrical energy to power small wearable electronic gadgets and sensors. To effectively achieve this, an efficient energy-converted power management circuit is required. Herein, we report on Aurivillius-type strontium bismuth titanate (SrBi4Ti4O15) nanoparticles (SBT NPs)-loaded polyglucosamine (PGA) composite film-based flexible TENG to be used for energy harvesting/storage and biomechanical applications. Initially, SBT NPs were synthesized and then, different weight concentrations were loaded into PGA. The TENG devices were fabricated using different wt % composite films (SBT/PGA) and polydimethylsiloxane as positive and negative triboelectric layers, respectively, and aluminum was used as a conductive electrode attached to two tribo films. To evaluate the electrical output from the device, contact-separation operation mode was used. An optimized TENG consisting of 2 wt % SBT/PGA composite film produced the maximum electrical output voltage and current of approximately ∼239 V and ∼7.5 μA, respectively. Efficient TENG energy harvesting and storage circuits have been proposed for storing charges in capacitors and for operating electronic gadgets. The optimized TENG was employed to generate electrical energy from various biomechanical movements. Thereafter, the biodegradability of the composite film was also tested. The fabricated films were completely biodegraded within a few hours. Furthermore, the TENG was utilized as a tap-indication transducer for multipurpose switching applications.

To enhance the adaptability and synergy of the triboelectric nanogenerator (TENG) in a wave environment, this paper introduces a directional adaptive triboelectric nanogenerator (DA-TENG) with wind-water synergistic action for wave energy collection. An innovative design combining a wind vane on the top and fan-shaped blade electrodes internally allows the DA-TENG to adjust its swinging direction adaptively to align with the direction of wave motion. The internal multiple power generation units work in coordination, effectively addressing the issues of low efficiency associated with spherical TENGs in capturing multidirectional wave energy. The DA-TENG demonstrates superior performance under various wind speed conditions, showcasing its practical application potential. Experimental results show that the DA-TENG, equipped with a single tail wind vane and a 700 g mass block, can achieve an output voltage, current, and charge of 374.97 V, 84.77 μA, and 622.69 nC under a mild wind environment. Its peak power density reaches 7.51 W m-3, enabling successful data transmission for a wireless temperature and humidity sensor and powering 248 light-emitting diodes (LEDs). This research expands the possibilities of omnidirectional wave energy collection and the collaborative operation of multiple power generation units, offering an effective method for powering low-power maritime devices.

The floor constitutes one of the largest areas within a building with which users interact most frequently in daily activities. Employing floor sensors is vital for smart-building digital twins, wherein triboelectric nanogenerators demonstrate wide application potential due to their good performance and self-powering characteristics. However, their sensing stability, reliability, and multimodality require further enhancement to meet the rapidly evolving demands. Thus, this work introduces a multimodal intelligent flooring system, implementing a 4 × 4 floor array for multimodal information detection (including position, pressure, material, user identity, and activity) and human-machine interactions. The floor unit incorporates a hybrid structure of triboelectric pressure sensors and a top-surface material sensor, facilitating linear and enhanced sensitivity across a wide pressure range (0-800 N), alongside the material recognition capability. The floor array is implemented by an advanced output-ratio method with minimalist output channels, which is insensitive to environmental factors such as humidity and temperature. In addition to multimodal sensing, energy harvesting is co-designed with the pressure sensors for scavenging waste energy to power smart-building sensor nodes. This developed flooring system enables multimodal sensing, energy harvesting, and smart-sport interactions in smart buildings, greatly expanding the floor sensing scenarios and applications.

Real-time monitoring of UAV motor speed is crucial for enhancing control performance and ensuring flight safety. However, this task faces challenges such as difficult sensor installation and high costs. This study introduces a wireless rotational speed sensing system based on a UAV-rotary triboelectric nanogenerator (UR-TENG). By employing a carefully designed structure with soft contact and a freestanding-triboelectric-layer mode, UR-TENG exhibits characteristics like low friction, affordability, ease of production, and self-powering capability. This eliminates the need for an external power source and addresses the complexity of installation in the limited space of UAVs. Experimental findings demonstrate that UR-TENG possesses high sensitivity and stability, maintaining the structural integrity of the UAV. The goodness of fit is notably high at 0.99959, with a maximum error rate of only 0.014 within a range of 6270 rpm. Moreover, UR-TENG integrates with a microcontroller unit (MCU) and external circuitry to form a monitoring system. This system transmits electrical signals to a PC via a Wi-Fi module, facilitating real-time rotational speed sensing and anomaly detection. Finally, a practical application demonstration on a UAV validates the adaptability of UR-TENG to complex operational environments. This study presents a promising approach for online rotation monitoring of UAV motors, with potential for commercialization, and introduces new avenues for TENG application in UAV technology.