Low-Cost, Environmentally Friendly, and High-Performance Triboelectric Nanogenerator Based on a Common Waste Material

Scott-Russel Linkage-Based Triboelectric Self-Powered Sensor for Contact Material-Independent Force Sensing and Tactile Recognition

The rapid growth of Internet of Things (IoT) in recent years has increased demand for various sensors to collect a wide range of data. Among various sensors, the demand for force sensors that can recognize physical phenomena in 3D space has notably increased. Recent research has focused on developing energy harvesting methods for sensors to address their maintenance problems. Triboelectric nanogenerator (TENG) based force sensors are a promising solution for converting external motion into electrical signals. However, conventional TENG-based force sensors that use the signal peak can negatively affect data accuracy. In this study, a Scott-Russell linkage-inspired TENG (SRI-TENG) is developed. The SRI-TENG has completely separate signal generation and measurement sections, and the number of peaks in the electrical output is measured to prevent disturbing output signals. In addition, the lubricant liquid enhances durability, enabling stable force signal measurements for 270 000 cycles. The SRI system demonstrates consistent peak counts and high accuracy across different contacting surfaces, indicating that it can function as a contact material-independent self-powered force sensor. Furthermore, using a deep learning method, it is demonstrated that it can function as a multimodal sensor by realizing the tactile properties of various materials.

Unveiling the Impact of Tailoring Ionic Conductor Characteristics on the Performance of Wearable Triboelectric Nanogenerators

This work reveals the correlation between the performance of triboelectric nanogenerators (TENGs) and the characteristics of deformable solid-state ionic conductors (referred to as ionogels). For this purpose, we modify ionogel characteristics by incorporating additional plasticizers (propylene carbonate) and solid salts (lithium bis(trifluoromethylsulfonyl)imide) into the ionogels. We conclude that the high capacitance of the ionogel is crucial for achieving a high-performance TENG platform. The optimized ionogel-based TENG (i-TENG) exhibits a power density of ∼372.4 mW·m-2 (based on 95 V and 36 mA·m-2 outputs) with outstanding long-term stability over 2 weeks. Additionally, successful demonstrations of wearable nanogenerators are performed by leveraging the high stretchability (up to ∼1000%) and optical transparency (∼90%) of the ionogels. Overall, the results provide insight into the design of deformable ionic conductors for high-performance, reliable, and wearable TENGs.

Advances of Strategies to Increase the Surface Charge Density of Triboelectric Nanogenerators: A Review

Triboelectric nanogenerators (TENGs) have manifested a remarkable potential for harvesting environmental energy and have the prospects to be utilized for various uses, for instance, self-powered sensing devices, flexible wearables, and marine corrosion protection. However, the potential for further development of TENGs is restricted on account of their low output power that in turn is determined by their surface charge density. The current review majorly focuses on the selection and optimization of triboelectric materials. Subsequently, various methods capable of enhancing the surface charge density of TENGs, including environmental regulation, charge excitation, charge pumping, electrostatic breakdown, charge trapping, and liquid-solid structure are comprehensively reviewed. Lastly, the review is concluded by highlighting the existing challenges in enhancing the surface charge density of TENGs and exploring potential opportunities for future research endeavors in this area.

Crystalline Porous Material-Based Nanogenerators: Recent Progress, Applications, Challenges, and Opportunities

Nanogenerator (NG) is a potential technology that allows to build self-powered systems, sensors, flexible and portable electronics in the current Internet of Things (IoT) generation. Nanogenerators include piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), convert different forms of mechanical motion into useful electrical signals. They have evolved and expanded their applications in various fields since their discovery in 2006 and 2012. Material selection is crucial for designing efficient NGs, with high conversion efficiencies. In the recent past, crystalline porous mat erials (metal-organic frameworks (MOFs) and covalent organic frameworks (COFs)) have been widely reported as potential candidates for nanogenerators, owing to their special properties of large surface area, porosity tailoring, ease of surface, post-synthesis modification, and chemical stability. The present organized review provides a complete overview of all the crystalline porous materials (CPMs)-based nanogenerator devices reported in the literature, including synthesis, characterization, device fabrication, and potential applications. Additionally, this review article discusses current challenges, future directions, and perspectives in the field of CPMs-NGs.

A Bistable Triboelectric Nanogenerator for Low-Grade Thermal Energy Harvesting and Solar Thermal Energy Conversion

Converting ubiquitous ambient low-grade thermal energy into electricity is of great significance for tackling the fossil energy shortage and environmental crisis but poses a considerable challenge. Here, a novel thermal-driven triboelectric nanogenerator (TD-TENG) is developed, which utilizes a bimetallic beam with a bi-stable dynamic feature to induce continuous mechanical oscillations, and the mechanical motion is then converted into electric power using a contact-separation TENG. The thermal process inside the device is systematically investigated and effective thermal management is conducted accordingly. After optimization, the TD-TENG can produce a power density of 323.9 mW m-2 at 59.5 °C, obtaining the highest record of TENG-based thermal energy harvesters. Besides, the first prototype of TENG-based solar thermal harvester is successfully demonstrated, with a power density of 364.4 mW m-2 . Moreover, the TD-TENG can harvest and dissipate the heat at the same time, exhibiting great potential in over-heated electronics protection as well as architectural energy conservation. Most importantly, the operation temperature range of the TD-TENG is tunable by adjusting the bimetal parameters, allowing the device a wide and flexible working thermal gradient. These unique properties validate the TD-TENG is a simple, feasible, cost-effective, and high-efficient low-grade thermal energy harvester.

Rational design on high-performance triboelectric nanogenerator consisting of silicon carbide@silicon dioxide nanowhiskers/polydimethylsiloxane (SiC@SiO2/PDMS) nanocomposite films

The relatively low output performance of triboelectric nanogenerator (TENG), which faces a challenge in performance improvement, limits its practical applications. Here, a high-performance TENG consisting of a silicon carbide@silicon dioxide nanowhiskers/polydimethylsiloxane (SiC@SiO2/PDMS) nanocomposite film and a superhydrophobic aluminum (Al) plate as triboelectric layers is demonstrated. The 7 wt% SiC@SiO2/PDMS TENG presents a peak voltage of 200 V and a peak current of 30 μA, which are ~ 300 and ~ 500% over that of the PDMS TENG, owing to an increase in dielectric constant and a decrease in dielectric loss of the PDMS film because of electric insulated SiC@SiO2 nanowhiskers. Furthermore, a 10 μF capacitor can be charged up to 3 V within ~ 87 s, which can be continuously operated on the electronic watch for 14 s. The work provides an effective strategy for improving output performance of TENG by adding core-shell nanowhiskers to modulate the dielectric properties of organic materials.

Roadmap to sustainable plastic waste management: a focused study on recycling PET for triboelectric nanogenerator production in Singapore and India

This study explores the implications of plastic waste and recycling management on recyclates for manufacturing clean-energy harvesting devices. The focus is on a comparative analysis of using recycled polyethylene terephthalate (PET) for triboelectric nanogenerator (TENG) production, in two densely populated Asian countries of large economies, namely Singapore and India. Of the total 930,000 tonnes of plastic waste generated in Singapore in 2019, only 4% were recycled and the rest were incinerated. In comparison, India yielded 8.6 million tonnes of plastic waste and 70% were recycled. Both countries have strict recycling goals and have instituted different waste and recycling management regulations. The findings show that the waste policies and legislations, responsibilities and heterogeneity in collection systems and infrastructure of the respective country are the pivotal attributes to successful recycling. Challenges to recycle plastic include segregation, adulterants and macromolecular structure degradation which could influence the recyclate properties and pose challenges for manufacturing products. A model was developed to evaluate the economic value and mechanical potential of PET recyclate. The model predicted a 30% loss of material performance and a 65% loss of economic value after the first recycling cycle. The economic value depreciates to zero with decreasing mechanical performance of plastic after multiple recycling cycles. For understanding how TENG technology could be incorporated into the circular economy, a model has estimated about 20 million and 7300 billion pieces of aerogel mats can be manufactured from the PET bottles disposed in Singapore and India, respectively which were sufficient to produce small-scale TENG devices for all peoples in both countries.

Spherical Micro/Nano Hierarchical Structures for Energy and Water Harvesting Devices

Three-dimensional (3D) hierarchical structures have been explored for various applications owing to the synergistic effects of micro- and nanostructures. However, the development of spherical micro/nano hierarchical structures (S-HSs), which can be used as energy/water harvesting systems and sensing devices, remains challenging owing to the trade-off between structural complexity and fabrication difficulty. This paper presents a new strategy for facile, scalable S-HS fabrication using a thermal expansion of microspheres and nanopatterned structures. When a specific temperature is applied to a composite film of microspheres and elastomers with nanopatterned surfaces, microspheres are expanded and 3D spherical microstructures are generated. Various nanopatterns and densities of spherical microstructures can thereby be quantitatively controlled. The fabricated S-HSs have been used in renewable electrical energy harvesting and sustainable water management applications. Compared to a triboelectric nanogenerator (TENG) with bare film, the S-HS-based TENG exhibited 4.48 times higher triboelectric performance with high mechanical durability. Furthermore, an S-HS is used as a water harvesting device to capture water in a fog environment. The water collection rate is dramatically enhanced by the increased surface area and locally concentrated vapor diffusion flux due to the spherical microstructures.

Improving Wastewater Treatment by Triboelectric-Photo/Electric Coupling Effect

The ability to meet higher effluent quality requirements and the reduction of energy consumption are the biggest challenges in wastewater treatment worldwide. A large proportion of the energy generated during wastewater treatment processes is neglected and lost in traditional wastewater treatment plants. As a type of energy harvesting system, triboelectric nanogenerators (TENGs) can extensively harvest the microscale energies generated from wastewater treatment procedures and auxiliary devices. This harvested energy can be utilized to improve the removal efficiency of pollutants through photo/electric catalysis, which has considerable potential application value in wastewater treatment plants. This paper gives an overall review of the generated potential energies (e.g., water wave energy, wind energy, and acoustic energy) that can be harvested at various stages of the wastewater treatment process and introduces the application of TENG devices for the collection of these neglected energies during wastewater treatment. Furthermore, the mechanisms and catalytic performances of TENGs coupled with photo/electric catalysis (e.g., electrocatalysis, photoelectric catalysis) are discussed to realize higher pollutant removal efficiencies and lower energy consumption. Then, a thorough, detailed investigation of TENG devices, electrode materials, and their coupled applications is summarized. Finally, the intimate coupling of self-powered photoelectric catalysis and biodegradation is proposed to further improve removal efficiencies in wastewater treatment. This concept is conducive to improving knowledge about the underlying mechanisms and extending applications of TENGs in wastewater treatment to better solve the problems of energy demand in the future.

Wearable Triboelectric Sensors Enabled Gait Analysis and Waist Motion Capture for IoT-Based Smart Healthcare Applications

Gait and waist motions always contain massive personnel information and it is feasible to extract these data via wearable electronics for identification and healthcare based on the Internet of Things (IoT). There also remains a demand to develop a cost-effective human-machine interface to enhance the immersion during the long-term rehabilitation. Meanwhile, triboelectric nanogenerator (TENG) revealing its merits in both wearable electronics and IoT tends to be a possible solution. Herein, the authors present wearable TENG-based devices for gait analysis and waist motion capture to enhance the intelligence and performance of the lower-limb and waist rehabilitation. Four triboelectric sensors are equidistantly sewed onto a fabric belt to recognize the waist motion, enabling the real-time robotic manipulation and virtual game for immersion-enhanced waist training. The insole equipped with two TENG sensors is designed for walking status detection and a 98.4% identification accuracy for five different humans aiming at rehabilitation plan selection is achieved by leveraging machine learning technology to further analyze the signals. Through a lower-limb rehabilitation robot, the authors demonstrate that the sensory system performs well in user recognition, motion monitoring, as well as robot and gaming-aided training, showing its potential in IoT-based smart healthcare applications.

Triboelectric Nanogenerator from Used Surgical Face Mask and Waste Mylar Materials Aiding the Circular Economy

Apart from claiming the lives of more than 3.2 million people, the COVID-19 pandemic is worsening the global plastic pollution every day, mainly with the overflux of single-use polypropylene (PP) face masks. In this scenario, as an innovative solution to mitigate plastic pollution as well as to meet the rising electrical energy demand, we are introducing an all-flexible and facile waste material-based triboelectric nanogenerator (WM-TENG), aiding toward the circular economy. The WM-TENG operating in contact separation mode is fabricated using the PP from a used face mask in combination with recovered Mylar sheets from solid wastes as triboelectric contact layers and a flexible supporting structure. After detailed investigation and trials to study the effect of various disinfection mechanisms of PP materials on the energy output of WM-TENG, UV-C radiation is selected for disinfecting the used masks owing to the retention of electrical energy output. Under a tapping force of 3 N, the WM-TENG having an active area of 6 cm² delivers an open-circuit voltage of 200 V and a short-circuit current density of 0.29 mA/m², respectively. The WM-TENG also delivered a maximum power density of 71.16 mW/m² under 10⁸ Ω load. Additionally, the WM-TENG is demonstrated for powering electronic gadgets such as a calculator, digital thermometer, and LCD clock. This flexible and low-cost nanogenerator without any complex fabrication steps is a sustainable solution for the alarming plastic pollution as well as the rising energy demands.