The significance of water energy harvesting in the context of renewable energy utilization is steadily increasing.In response to the need for more efficient utilization of water resources,the nascent technology of liq...The significance of water energy harvesting in the context of renewable energy utilization is steadily increasing.In response to the need for more efficient utilization of water resources,the nascent technology of liquid-solid triboelectric nanogenerators(TENGs)has emerged as a prospective candidate for the harvesting of water energy.Liquid-solid TENGs show several distinct advantages,including their lightweight,low cost,and efficient energy harvesting capabilities.Herein,this review presents a comprehensive exposition of the latest advancements in the field of liquid-solid TENGs.It delves into the underlying principles and different operational modes while also addressing the factors influencing its output performance from a multifaceted perspective.The factors comprise the intrinsic properties of friction materials,the chemical properties of the liquid,and the ambient temperature of liquid-solid TENGs.Furthermore,this review delineates the applications of liquid-solid TENGs as self-powered sensors in physics,chemistry,and biomedical contexts,as well as their applications in various other fields such as corrosion resistance,and so on.Last but not least,it concludes by providing a forward-looking on the future developmental trends of liquid-solid TENGs.展开更多
TriboElectric NanoGenerators(TENGs),introduced in 2012 by Wang et al.,have revolutionized the way we harvest energy,converting mechanical energy into electrical power with remarkable efficiency.Since their inception,T...TriboElectric NanoGenerators(TENGs),introduced in 2012 by Wang et al.,have revolutionized the way we harvest energy,converting mechanical energy into electrical power with remarkable efficiency.Since their inception,TENGs have unlocked innumerable applications,driving a surge in innovative research and development.This study utilizes the Scopus database to conduct a bibliographic analysis,highlighting the diverse applications,influential authors,and citation patterns that define the TENG landscape.Through the use of MATLAB and VOSviewer,we provide a visually compelling analysis that not only shows the integration of artificial intelligence in scientific literature but also explores the challenges and future potential of TENG technology.The document concludes by discussing TENGs challenges and the promising paths for their future applications.展开更多
Recycling plastic waste into triboelectric nanogenerators(TENGs)presents a sustainable approach to energy harvesting,self-powered sensing,and environmental remediation.This study investigates the recycling of polyviny...Recycling plastic waste into triboelectric nanogenerators(TENGs)presents a sustainable approach to energy harvesting,self-powered sensing,and environmental remediation.This study investigates the recycling of polyvinyl chloride(PVC)pipe waste polymers into nanofibers(NFs)optimized for TENG applications.We focused on optimizing the morphology of recycled PVC polymer to NFs and enhancing their piezoelectric properties by incorporating ZnO nanoparticles(NPs).The optimized PVC/0.5 wt%ZnO NFs were tested with Nylon-6 NFs,and copper(Cu)electrodes.The Nylon-6 NFs exhibited a power density of 726.3μWcm^(-2)—1.13 times higher than Cu and maintained 90%stability after 172800 cycles,successfully powering various colored LEDs.Additionally,a 3D-designed device was developed to harvest energy from biomechanical movements such as finger tapping,hand tapping,and foot pressing,making it suitable for wearable energy harvesting,automatic switches,and invisible sensors in surveillance systems.This study demonstrates that recycling polymers for TENG devices can effectively address energy,sensor,and environmental challenges.展开更多
This paper provides an overview of the recent advancements in magnetic structured triboelectric nanogenerators(MSTENGs)and their potential for energy harvesting and sensing in coastal bridge infrastructure.This paper ...This paper provides an overview of the recent advancements in magnetic structured triboelectric nanogenerators(MSTENGs)and their potential for energy harvesting and sensing in coastal bridge infrastructure.This paper begins with a brief discussion on the fundamental physics modes of triboelectric nanogenerators(TENGs),triboelectric series,and factors affecting TENG power generation and transmission,providing a foundation for the subsequent sections.The review focuses on the different types of MSTENGs and their applications in coastal infrastructure.Specifically,it covers magnetic spherical TENG networks,magnet-assisted TENGs,MSTENGs for bridges,and magnetic multilayer structures based on TENGs.The advantages and limitations of each type of MSTENG are discussed in detail,highlighting their respective suitability for different coastal bridge infrastructure applications.In addition,the paper addresses the challenges and provides insights into the future of MSTENGs.These include the need for improved durability and sustainability of MSTENGs in harsh coastal environments,increasing their power-output levels to fulfll high energy needs,and the requirement for collaborative efforts between academia,industry,and government institutions to optimize MSTENG performance.展开更多
High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)m...High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)membranes doped with barium titanate(BTO)nanoparticles and multi-walled carbon nanotubes(MWCNTs).The piezoelectric BTO nanoparticles were incorporated to boost the electric outputs by the synergistic effect of piezoelectricity and triboelectricity and MWCNTs were incorporated to provide a microcapacitor structure for enhancing the performance of TENGs.When the mass fraction of the BTO nanoparticle was 10%and the mass fraction of the MWCNT was 0.1%,the corresponding TENG achieved optimum electric outputs(an open-circuit voltage of around 65 V,a short-circuit current of about 20.0μA and a transferred charge of about 25.0 nC),much higher than those of the TENG with a single PI membrane.The TENG is potentially used to supply energy for commercial light-emitting diodes and as self-powered sensors to monitor human physical training conditions.This research provides a guideline for developing TENGs with high performance,which is crucial for their long-term use.展开更多
The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans.As a burgeoning technological method for electrom...The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans.As a burgeoning technological method for electromechanical conversion,triboelectric nanogenerator(TENG)has significant advantages in marine energy for its low weight,cost-effectiveness,and high efficiency in low-frequency range.It can realize the efficient and economical harvesting of low-frequency blue energy by constructing the floating marine energy harvesting TENG.This paper firstly introduces the power transfer process and structural composition of TENG for marine energy harvesting in detail.In addition,the latest research works of TENG on marine energy harvesting in basic research and structural design are systematically reviewed by category.Finally,the advanced research progress in the power take-off types and engineering study of TENG with the marine energy are comprehensively generalized.Importantly,the challenges and problems faced by TENG in marine energy and in situ electrochemical application are summarized and the corresponding prospects and suggestions are proposed for the subsequent development direction and prospects to look forward to promoting the commercialization process of this field.展开更多
The embodied artificial intelligence(EAI)is driving a significant transformation in robotics,enhancing their autonomy,efficiency and evolution ability.In this rapidly evolving technological landscape,robots need numer...The embodied artificial intelligence(EAI)is driving a significant transformation in robotics,enhancing their autonomy,efficiency and evolution ability.In this rapidly evolving technological landscape,robots need numerous sensors to realize high levels of perception,precision,safety,adaptability,and intelligence.Triboelectric and piezoelectric sensors address these needs by providing high sensitivity,flexibility,and the capability of self-powered sensing,leveraging the revolutionary nature of nanogenerators to convert mechanical energy into electrical energy on basis of Maxwell’s displacement current.These sensors surpass externally powered passive sensors by offering continuous operation,reduced maintenance,and the capability to function in remote or harsh environments.The integration of EAI with advanced nanogenerators sensors could position robotics to perform autonomously,efficiently,and safely,paving the way for innovative applications in various domains such as industrial automation,environmental monitoring,healthcare,and smart homes.In this paper,the fundamental theories,design,manufacturing,and applications of nanogenerators are comprehensively reviewed as afoundation of the advanced sensors for intelligent robotics in the new era,with three major application fields:sensing(including human–robot interaction,exteroceptive sensing and proprioceptive sensing),computing and actuating.Perspectives are addressed for nanogenerators systems in future development.展开更多
Additive manufacturing(AM),with its high flexibility,cost-effectiveness,and customization,significantly accelerates the advancement of nanogenerators,contributing to sustainable energy solutions and the Internet of Th...Additive manufacturing(AM),with its high flexibility,cost-effectiveness,and customization,significantly accelerates the advancement of nanogenerators,contributing to sustainable energy solutions and the Internet of Things.In this review,an in-depth analysis of AM for piezoelectric and triboelectric nanogenerators is presented from the perspectives of fundamental mechanisms,recent advancements,and future prospects.It highlights AM-enabled advantages of versatility across materials,structural topology optimization,microstructure design,and integrated printing,which enhance critical performance indicators of nanogenerators,such as surface charge density and piezoelectric constant,thereby improving device performance compared to conventional fabrication.Common AM techniques for nanogenerators,including fused deposition modeling,direct ink writing,stereolithography,and digital light processing,are systematically examined in terms of their working principles,improved metrics(output voltage/current,power density),theoretical explanation,and application scopes.Hierarchical relationships connecting AM technologies with performance optimization and applications of nanogenerators are elucidated,providing a solid foundation for advancements in energy harvesting,self-powered sensors,wearable devices,and human-machine interaction.Furthermore,the challenges related to fabrication quality,cross-scale manufacturing,processing efficiency,and industrial deployment are critically discussed.Finally,the future prospects of AM for nanogenerators are explored,aiming to foster continuous progress and innovation in this field.展开更多
Triboelectric nanogenerators(TENGs)offer a selfsustaining power solution for marine regions abundant in resources but constrained by energy availability.Since their pioneering use in wave energy harvesting in 2014,nea...Triboelectric nanogenerators(TENGs)offer a selfsustaining power solution for marine regions abundant in resources but constrained by energy availability.Since their pioneering use in wave energy harvesting in 2014,nearly a decade of advancements has yielded nearly thousands of research articles in this domain.Researchers have developed various TENG device structures with diverse functionalities to facilitate their commercial deployment.Nonetheless,there is a gap in comprehensive summaries and performance evaluations of TENG structural designs.This paper delineates six innovative structural designs,focusing on enhancing internal device output and adapting to external environments:high space utilization,hybrid generator,mechanical gain,broadband response,multi-directional operation,and hybrid energy-harvesting systems.We summarize the prevailing trends in device structure design identified by the research community.Furthermore,we conduct a meticulous comparison of the electrical performance of these devices under motorized,simulated wave,and real marine conditions,while also assessing their sustainability in terms of device durability and mechanical robustness.In conclusion,the paper outlines future research avenues and discusses the obstacles encountered in the TENG field.This review aims to offer valuable perspectives for ongoing research and to advance the progress and application of TENG technology.展开更多
Wearable bioelectronic devices are rapidly evolving towards miniaturization and multifunctionality,with remarkable features such as flexibility and comfort.However,achieving a sustainable power supply for wearable bio...Wearable bioelectronic devices are rapidly evolving towards miniaturization and multifunctionality,with remarkable features such as flexibility and comfort.However,achieving a sustainable power supply for wearable bioelectronic devices is still a great challenge.Triboelectric nanogenerators(TENGs)provide an efficient solution by converting irregular,low-frequency bioenergy from the human body into electrical energy.Beyond sustainably powering wearable bioelectronics,the harvested electrical energy also carries rich information for human body sensing.In this conversion process,the choice of material plays a crucial role in affecting the output performance of the TENGs.Among various materials,silicone rubber(SR)stands out due to its exceptional plasticity,flexibility,comfortability and other favorable properties.Moreover,with appropriate treatment,SR can achieve extreme functionalities such as high robustness,good stability,self-healing capabilities,rapid response,and more.In this review,recent advances in wearable SR-based TENGs(SR-TENGs)are systematically reviewed with a focus on their application in different parts of the human body.Given that the manufacturing method of SR-TENGs largely determines its output performance and sensitivity,this paper introduces the design of SR-TENGs,including material selection,process modulation,and structure optimization.Additionally,this article discusses the current challenges in the SR-TENG fabrication technology and potential future directions,aiming to promote the effective development of SR-TENGs in biomechanical energy harvesting and self-powered sensing applications.展开更多
Fueled by the increasing imperative for sustainable energy solutions and the burgeoning emphasis on health awareness,self-powered techniques have undergone notable strides in advancement.Triboelectric nanogenerators(T...Fueled by the increasing imperative for sustainable energy solutions and the burgeoning emphasis on health awareness,self-powered techniques have undergone notable strides in advancement.Triboelectric nanogenerators(TENGs)stand out as a prominent device capitalizing on the principles of triboelectrification and electrostatic induction to generate electricity or electrical signals.In efforts to augment the electrical output performance of TENGs and broaden their range of applications,researchers have endeavored to refine materials,surface morphology,and structural design.Among them,physical morphological modifications play a pivotal role in enhancing the electrical properties of TENGs by increasing the contact surface area,which can be achieved by building micro-/nano-structures on the surface or inside the friction material.In this review,we summarize the common morphologies of TENGs,categorize the morphologies into surface and internal structures,and elucidate their roles in enhancing the electric output performance of devices.Moreover,we systematically classify the methodologies employed for morphological preparation into physical and chemical approaches,thereby furnishing a comprehensive survey of the diverse techniques.Subsequently,typical applications of TENGs with special morphology divided by energy harvesting and self-powered sensors are presented.Finally,an overview of the challenges and future trajectories pertinent to TENGs is conducted.Through this endeavor,the aim of this article is to catalyze the evolution of further strategies for enhancing performance of TENGs.展开更多
As intelligent sensors for marine applications rapidly advance,there is a growing emphasis on developing efficient,low-cost,and sustainable power sources to enhance their performance.With the continuous development of...As intelligent sensors for marine applications rapidly advance,there is a growing emphasis on developing efficient,low-cost,and sustainable power sources to enhance their performance.With the continuous development of triboelectric nanogenerators(TENGs),known for their simple structure and versatile operational modes,these devices exhibit promising technological potential and have garnered extensive attention from a broad spectrum of researchers.The single-electrode mode of TENGs presents an effective means to harness eco-friendly energy sourced from flowing water.In this study,the factors affecting the output performance were investigated using different structures of single-electrode solid-liquid TENGs placed in a circulating water tank.In addition,the solid‒liquid contact process was numerically simulated using the COMSOL Multiphysics software,and significant potential energy changes were obtained for the solid‒liquid contact and liquid flow processes.Finally,the energy generated is collected and converted to power several light-emitting diodes,demonstrating that solid‒liquid TENGs can generate effective electrical power in a flowing water environment.Through several experimental investigations,we finally determined that the flow rate of the liquid,the thickness of the friction electrode material,and the contact area have the most significant effect on the output efficiency of TENGs in the form of flowing water,which provides a guide for improving their performance in the future.展开更多
This study explores how the performance of triboelectric nanogenerators can be enhanced by incorporating Fe_(3)O_(4) nanoparticles into nylon films using a spray coating technique.Five triboelectric nanogenerator prot...This study explores how the performance of triboelectric nanogenerators can be enhanced by incorporating Fe_(3)O_(4) nanoparticles into nylon films using a spray coating technique.Five triboelectric nanogenerator prototypes were created:one with regular nylon and four with nylon/Fe_(3)O_(4) nanocomposites featuring varying nanoparticle densities.The electrical output,measured by open-circuit voltage and short-circuit current,showed significant improvements in the nanocomposite-based triboelectric nanogenerators compared to the nylon-only triboelectric nanogenerator.When a weak magnetic field was applied during nanocomposite preparation,the maximum voltage and current reached 56.3 V and 4.62μA,respectively.Further analysis revealed that the magnetic field during the drying process aligned the magnetic domains,boosting output efficiency.These findings demonstrate the potential of Fe_(3)O_(4) nanoparticles to enhance electrostatic and magnetic interactions in triboelectric nanogenerators,leading to improved energy-harvesting performance.This approach presents a promising strategy for developing high-performance triboelectric nanogenerators for sustainable energy and sensor applications.展开更多
Blue energy,which includes rainfall,tidal current,wave,and water-flow energy,is a promising renewable resource,although its exploitation is limited by current technologies and thus remains low.This form of energy is m...Blue energy,which includes rainfall,tidal current,wave,and water-flow energy,is a promising renewable resource,although its exploitation is limited by current technologies and thus remains low.This form of energy is mainly harvested by electromagnetic generators(EMGs),which generate electricity via Lorenz force-driven electron flows.Triboelectric nano genera tors(TENGs)and TENG networks exhibit superiority over EMGs in low-frequency and high-entropy energy harvesting as a new approach for blue energy harvesting.A TENG produces electrical outputs by adopting the mechanism of Maxwell’s displacement current.To date,a series of research efforts have been made to optimize the structure and performance of TENGs for effective blue energy harvesting and marine environmental applications.Despite the great progress that has been achieved in the use of TENGs in this context so far,continuous exploration is required in energy conversion,device durability,power management,and environmental applications.This review reports on advances in TENGs for blue energy harvesting and marine environmental monitoring.It introduces the theoretical foundations of TENGs and discusses advanced TENG prototypes for blue energy harvesting,including TENG structures that function in freestanding and contact-separation modes.Performance enhancement strategies for TENGs intended for blue energy harvesting are also summarized.Finally,marine environmental applications of TENGs based on blue energy harvesting are discussed.展开更多
The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based ...The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based on gel materials(with excellent conductivity,mechanical tunability,environmental adaptability,and biocompatibility)are considered an advanced approach for developing a new generation of flexible sensors.This review comprehensively summarizes the recent advances in gel-based TENGs for flexible sensors,covering their principles,properties,and applications.Based on the development requirements for flexible sensors,the working mechanism of gel-based TENGs and the characteristic advantages of gels are introduced.Design strategies for the performance optimization of hydrogel-,organogel-,and aerogel-based TENGs are systematically summarized.In addition,the applications of gel-based TENGs in human motion sensing,tactile sensing,health monitoring,environmental monitoring,human-machine interaction,and other related fields are summarized.Finally,the challenges of gel-based TENGs for flexible sensing are discussed,and feasible strategies are proposed to guide future research.展开更多
Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators(TENGs).Unstable dynamic processes influence the change of the charge density on th...Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators(TENGs).Unstable dynamic processes influence the change of the charge density on the surface and inside of triboelectric materials.The charge density of triboelectric materials depends on the surface and the internal charge transfer processes.The focus of this review is on recent advances in high charge density triboelectric materials and advances in the fabrication of TENGs.We summarize the existing strategies for achieving high charge density in triboelectric materials as well as their fundamental properties.We then review current optimization methods for regulating dynamic charge transfer processes to increase the output charge density:first,increasing charge injection and limiting charge dissipation to achieve a high average surface charge density,and second,regulating the internal charge transfer process and storing charge in triboelectric materials to increase the output charge density.Finally,we present the challenges and prospects in developing high-performance triboelectric materials.展开更多
Wearable bioelectronic devices have the capacity for real-time human health monitoring,the provision of tailored services,and natural interaction with smart devices.However,these wearable bioelectronic devices rely on...Wearable bioelectronic devices have the capacity for real-time human health monitoring,the provision of tailored services,and natural interaction with smart devices.However,these wearable bioelectronic devices rely on conventional rigid batteries that are frequently charged or replaced and are incompatible with the skin,leading to a discontinuity in complex therapeutic tasks related to human health monitoring and human-machine interaction.Stretchable triboelectric nanogenerator(TENG)is a high-efficiency energy harvesting technology that converts mechanical into electrical energy,effectively powering wearable bioelectronic devices.This study comprehensively overviews recent advances in stretchable TENG for use in wearable bioelectronic devices.The working mechanism of stretchable TENG is initially explained.A comprehensive discussion presents the approaches for fabricating stretchable TENG,including the design of stretchable structures and the selection of stretchable materials.Furthermore,applications of wearable bioelectronic devices based on stretchable TENG in human health monitoring(body movements,pulse,and respiration)and human-machine interaction(touch panels,machine control,and virtual reality)are introduced.Ultimately,the challenges and developmental trends regarding wearable bioelectronic devices based on stretchable TENG are elaborated.展开更多
Nanogenerator technologies have gained significant attention as sustainable methods for harvesting energy and powering various applications.We review the research progress and obstacles related to triboelectric and pi...Nanogenerator technologies have gained significant attention as sustainable methods for harvesting energy and powering various applications.We review the research progress and obstacles related to triboelectric and piezoelectric nanogenerators utilized for wind energy extraction.This is crucial given the increasing demand for clean energy sources and the importance of technologies that can efficiently harvest such energy.We highlight the role of triboelectric and piezoelectric nanogenerators as promising solutions for capturing mechanical energy from wind sources.First,the fundamental physics modes of triboelectric and piezoelectric nanogenerators are discussed.The mechanisms underlying the triboelectric effect and the piezoelectric effect are explained,emphasizing their relevance to energy harvesting applications.An overview of energy harvesting using triboelectric and piezoelectric nanogenerators is then provided,encompassing the latest developments in the field.This review encompasses the design principles,materials,and fabrication techniques employed in the construction of triboelectric and piezoelectric nanogenerators.Specifically,we delve into how nanogenerators are utilized for wind energy harvesting.Various approaches for optimizing the performance of these devices are examined,along with methods of integration into wind energy harvesting systems.The potential applications of these devices are highlighted,along with the challenges that may come with their implementation.We conclude by discussing the current state of research,future perspectives,and insights into wind energy harvesting using triboelectric and piezoelectric nanogenerators.Accordingly,we recommend that future research addresses issues such as scalability,durability,and system integration.This review provides a comprehensive analysis of the use of triboelectric and piezoelectric nanogenerators for wind energy harvesting.It serves as a reference for researchers and engineers working in wind engineering,offering insights and directions for future advancements.展开更多
In engineering practice,the output performance of contact separation TENGs(CS-TENGs)increases with the increase of tribo-pair area,which includes increasing the size of single layer CS-TENGs(SCS-TENGs)or the number of...In engineering practice,the output performance of contact separation TENGs(CS-TENGs)increases with the increase of tribo-pair area,which includes increasing the size of single layer CS-TENGs(SCS-TENGs)or the number of units(zigzag TENGs).However,such two strategies show significant differences in output power and power density.In this study,to seek a universal CS-TENG design solution,the output performance of a SCS-TENG and a zigzag TENG(Z-TENG)is systematically compared,including voltage,current,transferred charge,instantaneous power density,and charging power density.The relationship between contact area and output voltages is explored,and the output voltage equation is fitted.The experimental results reveal that SCS-TENGs yield better performance than Z-TENGs in terms of voltage,power,and power density under the same total contact area.Z-TENGs show energy loss during the transfer of mechanical energy,and such loss is aggravated by the increasing number of units.The instantaneous peak power of the SCS-TENG is up to 22 times that of the Z-TENG(45 cm^(2)).Furthermore,the power density of capacitor charging of SCS-TENGs is 131%of that of Z-TENGs,which are relatively close.Z-TENG is a feasible alternative when the working space is limited.展开更多
In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs h...In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.展开更多
基金supported by the National Natural Science Foundation Project of China(No.52201056)the funding of postdoctoral researchers in Anhui Province(No.2022B613)the College Excellent Young Foundation of Anhui Province(No.2023AH030029).
文摘The significance of water energy harvesting in the context of renewable energy utilization is steadily increasing.In response to the need for more efficient utilization of water resources,the nascent technology of liquid-solid triboelectric nanogenerators(TENGs)has emerged as a prospective candidate for the harvesting of water energy.Liquid-solid TENGs show several distinct advantages,including their lightweight,low cost,and efficient energy harvesting capabilities.Herein,this review presents a comprehensive exposition of the latest advancements in the field of liquid-solid TENGs.It delves into the underlying principles and different operational modes while also addressing the factors influencing its output performance from a multifaceted perspective.The factors comprise the intrinsic properties of friction materials,the chemical properties of the liquid,and the ambient temperature of liquid-solid TENGs.Furthermore,this review delineates the applications of liquid-solid TENGs as self-powered sensors in physics,chemistry,and biomedical contexts,as well as their applications in various other fields such as corrosion resistance,and so on.Last but not least,it concludes by providing a forward-looking on the future developmental trends of liquid-solid TENGs.
基金supported by the government of the Republic of Korea(MSIT)and the National Research Foundation(NRF)of Korea(2022R1A2C1003900,2023K2A9A 1A01098512(FY2023)).
文摘TriboElectric NanoGenerators(TENGs),introduced in 2012 by Wang et al.,have revolutionized the way we harvest energy,converting mechanical energy into electrical power with remarkable efficiency.Since their inception,TENGs have unlocked innumerable applications,driving a surge in innovative research and development.This study utilizes the Scopus database to conduct a bibliographic analysis,highlighting the diverse applications,influential authors,and citation patterns that define the TENG landscape.Through the use of MATLAB and VOSviewer,we provide a visually compelling analysis that not only shows the integration of artificial intelligence in scientific literature but also explores the challenges and future potential of TENG technology.The document concludes by discussing TENGs challenges and the promising paths for their future applications.
基金supported by the research projects AP23486880 from the Ministry of Higher EducationScience of the Republic of Kazakhstan and 111024CRP2010,20122022FD4135 from Nazarbayev University.
文摘Recycling plastic waste into triboelectric nanogenerators(TENGs)presents a sustainable approach to energy harvesting,self-powered sensing,and environmental remediation.This study investigates the recycling of polyvinyl chloride(PVC)pipe waste polymers into nanofibers(NFs)optimized for TENG applications.We focused on optimizing the morphology of recycled PVC polymer to NFs and enhancing their piezoelectric properties by incorporating ZnO nanoparticles(NPs).The optimized PVC/0.5 wt%ZnO NFs were tested with Nylon-6 NFs,and copper(Cu)electrodes.The Nylon-6 NFs exhibited a power density of 726.3μWcm^(-2)—1.13 times higher than Cu and maintained 90%stability after 172800 cycles,successfully powering various colored LEDs.Additionally,a 3D-designed device was developed to harvest energy from biomechanical movements such as finger tapping,hand tapping,and foot pressing,making it suitable for wearable energy harvesting,automatic switches,and invisible sensors in surveillance systems.This study demonstrates that recycling polymers for TENG devices can effectively address energy,sensor,and environmental challenges.
文摘This paper provides an overview of the recent advancements in magnetic structured triboelectric nanogenerators(MSTENGs)and their potential for energy harvesting and sensing in coastal bridge infrastructure.This paper begins with a brief discussion on the fundamental physics modes of triboelectric nanogenerators(TENGs),triboelectric series,and factors affecting TENG power generation and transmission,providing a foundation for the subsequent sections.The review focuses on the different types of MSTENGs and their applications in coastal infrastructure.Specifically,it covers magnetic spherical TENG networks,magnet-assisted TENGs,MSTENGs for bridges,and magnetic multilayer structures based on TENGs.The advantages and limitations of each type of MSTENG are discussed in detail,highlighting their respective suitability for different coastal bridge infrastructure applications.In addition,the paper addresses the challenges and provides insights into the future of MSTENGs.These include the need for improved durability and sustainability of MSTENGs in harsh coastal environments,increasing their power-output levels to fulfll high energy needs,and the requirement for collaborative efforts between academia,industry,and government institutions to optimize MSTENG performance.
基金National Natural Science Foundation of China(No.52103267)。
文摘High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)membranes doped with barium titanate(BTO)nanoparticles and multi-walled carbon nanotubes(MWCNTs).The piezoelectric BTO nanoparticles were incorporated to boost the electric outputs by the synergistic effect of piezoelectricity and triboelectricity and MWCNTs were incorporated to provide a microcapacitor structure for enhancing the performance of TENGs.When the mass fraction of the BTO nanoparticle was 10%and the mass fraction of the MWCNT was 0.1%,the corresponding TENG achieved optimum electric outputs(an open-circuit voltage of around 65 V,a short-circuit current of about 20.0μA and a transferred charge of about 25.0 nC),much higher than those of the TENG with a single PI membrane.The TENG is potentially used to supply energy for commercial light-emitting diodes and as self-powered sensors to monitor human physical training conditions.This research provides a guideline for developing TENGs with high performance,which is crucial for their long-term use.
基金supported by the Talent Fund of Beijing Jiaotong University(2023XKRC034)China National Postdoctoral Program for Innovative Talents(BX20230037)+3 种基金China Postdoctoral Science Foundation(2023M730205)National key research and development program(2021YFB3203202)Beijing Municipal Natural Science Foundation(4232074)Fundamental Research Funds for the Central Universities(2020JBZD011)。
文摘The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans.As a burgeoning technological method for electromechanical conversion,triboelectric nanogenerator(TENG)has significant advantages in marine energy for its low weight,cost-effectiveness,and high efficiency in low-frequency range.It can realize the efficient and economical harvesting of low-frequency blue energy by constructing the floating marine energy harvesting TENG.This paper firstly introduces the power transfer process and structural composition of TENG for marine energy harvesting in detail.In addition,the latest research works of TENG on marine energy harvesting in basic research and structural design are systematically reviewed by category.Finally,the advanced research progress in the power take-off types and engineering study of TENG with the marine energy are comprehensively generalized.Importantly,the challenges and problems faced by TENG in marine energy and in situ electrochemical application are summarized and the corresponding prospects and suggestions are proposed for the subsequent development direction and prospects to look forward to promoting the commercialization process of this field.
基金supported by the National Natural Science Foundation of China(Grants Nos.62104125and 62311530102)Shenzhen Science and Technology Program(Grant Nos.JCYJ20220530143013030 and JCYJ20240813111910014)+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2021ZT09L197)Tsinghua Shenzhen International Graduate School-Shenzhen Pengrui Young Faculty Program of Shenzhen Pengrui Foundation(Grant No.SZPR2023005)。
文摘The embodied artificial intelligence(EAI)is driving a significant transformation in robotics,enhancing their autonomy,efficiency and evolution ability.In this rapidly evolving technological landscape,robots need numerous sensors to realize high levels of perception,precision,safety,adaptability,and intelligence.Triboelectric and piezoelectric sensors address these needs by providing high sensitivity,flexibility,and the capability of self-powered sensing,leveraging the revolutionary nature of nanogenerators to convert mechanical energy into electrical energy on basis of Maxwell’s displacement current.These sensors surpass externally powered passive sensors by offering continuous operation,reduced maintenance,and the capability to function in remote or harsh environments.The integration of EAI with advanced nanogenerators sensors could position robotics to perform autonomously,efficiently,and safely,paving the way for innovative applications in various domains such as industrial automation,environmental monitoring,healthcare,and smart homes.In this paper,the fundamental theories,design,manufacturing,and applications of nanogenerators are comprehensively reviewed as afoundation of the advanced sensors for intelligent robotics in the new era,with three major application fields:sensing(including human–robot interaction,exteroceptive sensing and proprioceptive sensing),computing and actuating.Perspectives are addressed for nanogenerators systems in future development.
基金support from the Research Committee of The Hong Kong Polytechnic University(Project codes:RMJK and 4-ZZSJ)supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.PolyU15212523).
文摘Additive manufacturing(AM),with its high flexibility,cost-effectiveness,and customization,significantly accelerates the advancement of nanogenerators,contributing to sustainable energy solutions and the Internet of Things.In this review,an in-depth analysis of AM for piezoelectric and triboelectric nanogenerators is presented from the perspectives of fundamental mechanisms,recent advancements,and future prospects.It highlights AM-enabled advantages of versatility across materials,structural topology optimization,microstructure design,and integrated printing,which enhance critical performance indicators of nanogenerators,such as surface charge density and piezoelectric constant,thereby improving device performance compared to conventional fabrication.Common AM techniques for nanogenerators,including fused deposition modeling,direct ink writing,stereolithography,and digital light processing,are systematically examined in terms of their working principles,improved metrics(output voltage/current,power density),theoretical explanation,and application scopes.Hierarchical relationships connecting AM technologies with performance optimization and applications of nanogenerators are elucidated,providing a solid foundation for advancements in energy harvesting,self-powered sensors,wearable devices,and human-machine interaction.Furthermore,the challenges related to fabrication quality,cross-scale manufacturing,processing efficiency,and industrial deployment are critically discussed.Finally,the future prospects of AM for nanogenerators are explored,aiming to foster continuous progress and innovation in this field.
基金supported by the National Key R&D Project from Ministry of Science and Technology,China(2021YFA1201603)National Natural Science Foundation of China(52073032 and 52192611)the Fundamental Research Funds for the Central Universities.
文摘Triboelectric nanogenerators(TENGs)offer a selfsustaining power solution for marine regions abundant in resources but constrained by energy availability.Since their pioneering use in wave energy harvesting in 2014,nearly a decade of advancements has yielded nearly thousands of research articles in this domain.Researchers have developed various TENG device structures with diverse functionalities to facilitate their commercial deployment.Nonetheless,there is a gap in comprehensive summaries and performance evaluations of TENG structural designs.This paper delineates six innovative structural designs,focusing on enhancing internal device output and adapting to external environments:high space utilization,hybrid generator,mechanical gain,broadband response,multi-directional operation,and hybrid energy-harvesting systems.We summarize the prevailing trends in device structure design identified by the research community.Furthermore,we conduct a meticulous comparison of the electrical performance of these devices under motorized,simulated wave,and real marine conditions,while also assessing their sustainability in terms of device durability and mechanical robustness.In conclusion,the paper outlines future research avenues and discusses the obstacles encountered in the TENG field.This review aims to offer valuable perspectives for ongoing research and to advance the progress and application of TENG technology.
基金supported by the National Natural Science Foundation of China(Grant No.52442104)the Application Research Program of Liaoning Province(Grant No.2022JH2/01300219)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.3132024210)the Scientific Research Fund of the Educational Department of Liaoning Province(Nos.LJ212410151013,LJKMZ20220359)。
文摘Wearable bioelectronic devices are rapidly evolving towards miniaturization and multifunctionality,with remarkable features such as flexibility and comfort.However,achieving a sustainable power supply for wearable bioelectronic devices is still a great challenge.Triboelectric nanogenerators(TENGs)provide an efficient solution by converting irregular,low-frequency bioenergy from the human body into electrical energy.Beyond sustainably powering wearable bioelectronics,the harvested electrical energy also carries rich information for human body sensing.In this conversion process,the choice of material plays a crucial role in affecting the output performance of the TENGs.Among various materials,silicone rubber(SR)stands out due to its exceptional plasticity,flexibility,comfortability and other favorable properties.Moreover,with appropriate treatment,SR can achieve extreme functionalities such as high robustness,good stability,self-healing capabilities,rapid response,and more.In this review,recent advances in wearable SR-based TENGs(SR-TENGs)are systematically reviewed with a focus on their application in different parts of the human body.Given that the manufacturing method of SR-TENGs largely determines its output performance and sensitivity,this paper introduces the design of SR-TENGs,including material selection,process modulation,and structure optimization.Additionally,this article discusses the current challenges in the SR-TENG fabrication technology and potential future directions,aiming to promote the effective development of SR-TENGs in biomechanical energy harvesting and self-powered sensing applications.
基金financially supported by the Natural Science Foundation of Guangdong Province(No.2024A1515010639)PolyU Postdoc Matching Fund Scheme(No.1-W327),PolyU Grant(No.1-CE0H)+3 种基金Shenzhen Science and Technology Program(No.ZDSYS20220606100406016)Shenzhen Key Laboratory of Photonics and Biophotonics(No.ZDSYS20210623092006020)National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment(Shenzhen)(No.868-000003010103)National Natural Science Foundation of China(No.52208272)。
文摘Fueled by the increasing imperative for sustainable energy solutions and the burgeoning emphasis on health awareness,self-powered techniques have undergone notable strides in advancement.Triboelectric nanogenerators(TENGs)stand out as a prominent device capitalizing on the principles of triboelectrification and electrostatic induction to generate electricity or electrical signals.In efforts to augment the electrical output performance of TENGs and broaden their range of applications,researchers have endeavored to refine materials,surface morphology,and structural design.Among them,physical morphological modifications play a pivotal role in enhancing the electrical properties of TENGs by increasing the contact surface area,which can be achieved by building micro-/nano-structures on the surface or inside the friction material.In this review,we summarize the common morphologies of TENGs,categorize the morphologies into surface and internal structures,and elucidate their roles in enhancing the electric output performance of devices.Moreover,we systematically classify the methodologies employed for morphological preparation into physical and chemical approaches,thereby furnishing a comprehensive survey of the diverse techniques.Subsequently,typical applications of TENGs with special morphology divided by energy harvesting and self-powered sensors are presented.Finally,an overview of the challenges and future trajectories pertinent to TENGs is conducted.Through this endeavor,the aim of this article is to catalyze the evolution of further strategies for enhancing performance of TENGs.
基金the support from Natural Science Foundation of Heilongjiang Province(No.YQ2022A004)National Natural Science Foundation of China(No.12372268,No.12332014).
文摘As intelligent sensors for marine applications rapidly advance,there is a growing emphasis on developing efficient,low-cost,and sustainable power sources to enhance their performance.With the continuous development of triboelectric nanogenerators(TENGs),known for their simple structure and versatile operational modes,these devices exhibit promising technological potential and have garnered extensive attention from a broad spectrum of researchers.The single-electrode mode of TENGs presents an effective means to harness eco-friendly energy sourced from flowing water.In this study,the factors affecting the output performance were investigated using different structures of single-electrode solid-liquid TENGs placed in a circulating water tank.In addition,the solid‒liquid contact process was numerically simulated using the COMSOL Multiphysics software,and significant potential energy changes were obtained for the solid‒liquid contact and liquid flow processes.Finally,the energy generated is collected and converted to power several light-emitting diodes,demonstrating that solid‒liquid TENGs can generate effective electrical power in a flowing water environment.Through several experimental investigations,we finally determined that the flow rate of the liquid,the thickness of the friction electrode material,and the contact area have the most significant effect on the output efficiency of TENGs in the form of flowing water,which provides a guide for improving their performance in the future.
文摘This study explores how the performance of triboelectric nanogenerators can be enhanced by incorporating Fe_(3)O_(4) nanoparticles into nylon films using a spray coating technique.Five triboelectric nanogenerator prototypes were created:one with regular nylon and four with nylon/Fe_(3)O_(4) nanocomposites featuring varying nanoparticle densities.The electrical output,measured by open-circuit voltage and short-circuit current,showed significant improvements in the nanocomposite-based triboelectric nanogenerators compared to the nylon-only triboelectric nanogenerator.When a weak magnetic field was applied during nanocomposite preparation,the maximum voltage and current reached 56.3 V and 4.62μA,respectively.Further analysis revealed that the magnetic field during the drying process aligned the magnetic domains,boosting output efficiency.These findings demonstrate the potential of Fe_(3)O_(4) nanoparticles to enhance electrostatic and magnetic interactions in triboelectric nanogenerators,leading to improved energy-harvesting performance.This approach presents a promising strategy for developing high-performance triboelectric nanogenerators for sustainable energy and sensor applications.
基金the National Key Research and Development Project from the Minister of Science and Technology(2021YFA1201601 and 2021YFA1201604)the Innovation Project of Ocean Science and Technology(22-3-3-hygg-18-hy)+2 种基金the project supported by the Fundamental Research Funds for the Central Universities(E2E46805)the China National Postdoctoral Program for Innovative Talents(BX20220292)the China Postdoctoral Science Foundation(2022M723100)。
文摘Blue energy,which includes rainfall,tidal current,wave,and water-flow energy,is a promising renewable resource,although its exploitation is limited by current technologies and thus remains low.This form of energy is mainly harvested by electromagnetic generators(EMGs),which generate electricity via Lorenz force-driven electron flows.Triboelectric nano genera tors(TENGs)and TENG networks exhibit superiority over EMGs in low-frequency and high-entropy energy harvesting as a new approach for blue energy harvesting.A TENG produces electrical outputs by adopting the mechanism of Maxwell’s displacement current.To date,a series of research efforts have been made to optimize the structure and performance of TENGs for effective blue energy harvesting and marine environmental applications.Despite the great progress that has been achieved in the use of TENGs in this context so far,continuous exploration is required in energy conversion,device durability,power management,and environmental applications.This review reports on advances in TENGs for blue energy harvesting and marine environmental monitoring.It introduces the theoretical foundations of TENGs and discusses advanced TENG prototypes for blue energy harvesting,including TENG structures that function in freestanding and contact-separation modes.Performance enhancement strategies for TENGs intended for blue energy harvesting are also summarized.Finally,marine environmental applications of TENGs based on blue energy harvesting are discussed.
基金supported by the National Natural Science Foundation of China(22068005,22278091)the Training Program for 1000 Backbone Teachers in Guangxi(2022).
文摘The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable,portable,and self-powered flexible sensing devices.Triboelectric nanogenerators(TENGs)based on gel materials(with excellent conductivity,mechanical tunability,environmental adaptability,and biocompatibility)are considered an advanced approach for developing a new generation of flexible sensors.This review comprehensively summarizes the recent advances in gel-based TENGs for flexible sensors,covering their principles,properties,and applications.Based on the development requirements for flexible sensors,the working mechanism of gel-based TENGs and the characteristic advantages of gels are introduced.Design strategies for the performance optimization of hydrogel-,organogel-,and aerogel-based TENGs are systematically summarized.In addition,the applications of gel-based TENGs in human motion sensing,tactile sensing,health monitoring,environmental monitoring,human-machine interaction,and other related fields are summarized.Finally,the challenges of gel-based TENGs for flexible sensing are discussed,and feasible strategies are proposed to guide future research.
文摘Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators(TENGs).Unstable dynamic processes influence the change of the charge density on the surface and inside of triboelectric materials.The charge density of triboelectric materials depends on the surface and the internal charge transfer processes.The focus of this review is on recent advances in high charge density triboelectric materials and advances in the fabrication of TENGs.We summarize the existing strategies for achieving high charge density in triboelectric materials as well as their fundamental properties.We then review current optimization methods for regulating dynamic charge transfer processes to increase the output charge density:first,increasing charge injection and limiting charge dissipation to achieve a high average surface charge density,and second,regulating the internal charge transfer process and storing charge in triboelectric materials to increase the output charge density.Finally,we present the challenges and prospects in developing high-performance triboelectric materials.
基金supported by the National Natural Science Foundation of China(No.52203310)the China Postdoctoral Science Foundation(Nos.2023T160195 and 2023M730993)+1 种基金the Henan Province Science and Technology Research and Development Program Joint Fund Advantageous Discipline Cultivation Project(No.232301420033)the Henan Agricultural University Start-up Grant(No.30501054).
文摘Wearable bioelectronic devices have the capacity for real-time human health monitoring,the provision of tailored services,and natural interaction with smart devices.However,these wearable bioelectronic devices rely on conventional rigid batteries that are frequently charged or replaced and are incompatible with the skin,leading to a discontinuity in complex therapeutic tasks related to human health monitoring and human-machine interaction.Stretchable triboelectric nanogenerator(TENG)is a high-efficiency energy harvesting technology that converts mechanical into electrical energy,effectively powering wearable bioelectronic devices.This study comprehensively overviews recent advances in stretchable TENG for use in wearable bioelectronic devices.The working mechanism of stretchable TENG is initially explained.A comprehensive discussion presents the approaches for fabricating stretchable TENG,including the design of stretchable structures and the selection of stretchable materials.Furthermore,applications of wearable bioelectronic devices based on stretchable TENG in human health monitoring(body movements,pulse,and respiration)and human-machine interaction(touch panels,machine control,and virtual reality)are introduced.Ultimately,the challenges and developmental trends regarding wearable bioelectronic devices based on stretchable TENG are elaborated.
文摘Nanogenerator technologies have gained significant attention as sustainable methods for harvesting energy and powering various applications.We review the research progress and obstacles related to triboelectric and piezoelectric nanogenerators utilized for wind energy extraction.This is crucial given the increasing demand for clean energy sources and the importance of technologies that can efficiently harvest such energy.We highlight the role of triboelectric and piezoelectric nanogenerators as promising solutions for capturing mechanical energy from wind sources.First,the fundamental physics modes of triboelectric and piezoelectric nanogenerators are discussed.The mechanisms underlying the triboelectric effect and the piezoelectric effect are explained,emphasizing their relevance to energy harvesting applications.An overview of energy harvesting using triboelectric and piezoelectric nanogenerators is then provided,encompassing the latest developments in the field.This review encompasses the design principles,materials,and fabrication techniques employed in the construction of triboelectric and piezoelectric nanogenerators.Specifically,we delve into how nanogenerators are utilized for wind energy harvesting.Various approaches for optimizing the performance of these devices are examined,along with methods of integration into wind energy harvesting systems.The potential applications of these devices are highlighted,along with the challenges that may come with their implementation.We conclude by discussing the current state of research,future perspectives,and insights into wind energy harvesting using triboelectric and piezoelectric nanogenerators.Accordingly,we recommend that future research addresses issues such as scalability,durability,and system integration.This review provides a comprehensive analysis of the use of triboelectric and piezoelectric nanogenerators for wind energy harvesting.It serves as a reference for researchers and engineers working in wind engineering,offering insights and directions for future advancements.
基金funded by National Natural Science Foundation of China(Nos.:62225308 and 62001281)Shanghai Science and Technology Committee(22dz1204300)
文摘In engineering practice,the output performance of contact separation TENGs(CS-TENGs)increases with the increase of tribo-pair area,which includes increasing the size of single layer CS-TENGs(SCS-TENGs)or the number of units(zigzag TENGs).However,such two strategies show significant differences in output power and power density.In this study,to seek a universal CS-TENG design solution,the output performance of a SCS-TENG and a zigzag TENG(Z-TENG)is systematically compared,including voltage,current,transferred charge,instantaneous power density,and charging power density.The relationship between contact area and output voltages is explored,and the output voltage equation is fitted.The experimental results reveal that SCS-TENGs yield better performance than Z-TENGs in terms of voltage,power,and power density under the same total contact area.Z-TENGs show energy loss during the transfer of mechanical energy,and such loss is aggravated by the increasing number of units.The instantaneous peak power of the SCS-TENG is up to 22 times that of the Z-TENG(45 cm^(2)).Furthermore,the power density of capacitor charging of SCS-TENGs is 131%of that of Z-TENGs,which are relatively close.Z-TENG is a feasible alternative when the working space is limited.
基金supported by the National Natural Science Foundation of China(12104249,11804313 and 11847135)the Youth Innovation Team Project of Shandong Provincial Education Department(2021KJ013,2020KJN015)by State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(GZRC202011&ZKT46)。
文摘In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.
