Triboelectric nanogenerators are an energy harvesting technology that relies on the coupling effects of contact electrification and electrostatic induction between two solids or a liquid and a solid. ...Here, we present a triboelectric nanogenerator that can work based on the interaction between two pure liquids. A liquid-liquid triboelectric nanogenerator is achieved by passing a liquid droplet through a freely suspended liquid membrane. We investigate two kinds of liquid membranes: a grounded membrane and a pre-charged membrane. The falling of a droplet (about 40 μL) can generate a peak power of 137.4 nW by passing through a pre-charged membrane. Moreover, this membrane electrode can also remove and collect electrostatic charges from solid objects, indicating a permeable sensor or charge filter for electronic applications. The liquid-liquid triboelectric nanogenerator can harvest mechanical energy without changing the object motion and it can work for many targets, including raindrops, irrigation currents, microfluidics, and tiny particles.
Polymers are commonly used to fabricate triboelectric nanogenerators (TENGs). Here, several polymer films with similar main chains but different functional groups on the side chain are employed to ...clarify the contributions of each functional group to contact electrification (CE). The results show that the electron‐withdrawing (EW) ability and density of these functional groups on the main chain can determine both the polarity and density of CE‐induced surface charges. Similar results are obtained for CE in both the polymer–polymer and polymer–liquid modes. A theoretical mechanism involving electron cloud overlap is proposed to explain all of these results. More importantly, the unsaturated groups on poly(tetrafluoroethylene) molecular chain are proved to have a much stronger EW ability than the saturated groups. The density of these unsaturated groups can be increased using a sputtering technique, suggesting that this is a facile and effective method of enhancing the performance of TENGs. These results clarify the correlation between the molecular structure and macroscopic electrification behavior of polymers.
A series of polymer films with different functional groups on the side chain are employed for clarifying the contribution of functional groups to their contact electrification (CE) processes with both solids and liquids. The unsaturated groups of PTFE can enhance the electronegativity of the whole functional group.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
As a well‐known phenomenon, contact electrification (CE) has been studied for decades. Although recent studies have proven that CE between two solids is primarily due to electron transfer, the ...mechanism for CE between liquid and solid remains controversial. The CE process between different liquids and polytetrafluoroethylene (PTFE) film is systematically studied to clarify the electrification mechanism of the solid–liquid interface. The CE between deionized water and PTFE can produce a surface charges density in the scale of 1 nC cm−2, which is ten times higher than the calculation based on the pure ion‐transfer model. Hence, electron transfer is likely the dominating effect for this liquid–solid electrification process. Meanwhile, as ion concentration increases, the ion adsorption on the PTFE hinders electron transfer and results in the suppression of the transferred charge amount. Furthermore, there is an obvious charge transfer between oil and PTFE, which further confirms the presence of electron transfer between liquid and solid, simply because there are no ions in oil droplets. It is demonstrated that electron transfer plays the dominant role during CE between liquids and solids, which directly impacts the traditional understanding of the formation of an electric double layer (EDL) at a liquid–solid interface in physical chemistry.
The mechanism behind the contact electrification between liquid and solid remains controversial. According to experimental results and theoretical calculations, the contact electrification of ionic liquids and solids is caused by both electron transfer and ion transfer. Furthermore, the contact electrification between nonionic liquids and solids is mainly due to electron transfer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
As the dominant component for precise motion measurement, angle sensors play a vital role in robotics, machine control, and personalized rehabilitation. Various forms of angle sensors have been ...developed and optimized over the past decades, but none of them would function without an electric power. Here, a highly sensitive triboelectric self‐powered angle sensor (SPAS) exhibiting the highest resolution (2.03 nano‐radian) after a comprehensive optimization is reported. In addition, the SPAS holds merits of light weight and thin thickness, which enables its extensive integrated applications with minimized energy consumption: a palletizing robotic arm equipped with the SPAS can precisely reproduce traditional Chinese calligraphy via angular data it collects. In addition, the SPAS can be assembled in a medicare brace to record the flexion/extension of joints, which may benefit personalized orthopedic recuperation. The SPAS paves a new approach for applications in the emerging fields of robotics, sensing, personalized medicare, and artificial intelligence.
Sensing angular information via the most energy‐efficient method is vitally important. After systematic optimization, a triboelectric self‐powered angle sensor provides high‐quality sensing signals while itself needing neither electric power supply nor a signal‐amplification module. In addition, its feasibility is proved by practical application in a robotic arm, precisely duplicating traditional Chinese calligraphy as well as medical brace monitoring joint motions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Triboelectric materials and their modification methods are the cornerstones for fabricating triboelectric nanogenerators (TENGs). Numerous modification methods have been proposed for TENGs, while a ...highly effective and long-term stable method is still under exploration. Here, a surface modification method using low-energy ion irradiation has been proposed for tuning the chemical structures and functional groups of triboelectric polymers at the molecular level. The low-energy ion irradiation brings negligible change to the surface roughness at the micro-scale and mechanical flexibility of the target polymer, while it can provide a stable modification of the electrification performance. Systematic studies about the chemical structure changes in four different polymers induced by ion irradiation can bring insight into the interaction between different chemical groups and electrification performance. A Kapton film modified by ion irradiation shows several unprecedented characteristics, such as high surface charge density, excellent stability and ultrahigh electron-donating capability, and not only creates a new record in the tribo series, but also provides a good demonstration for regulating electrification behavior based on controllable chemical structure change. This study can open up a series of possible breakthroughs in the production of triboelectric materials with diversified properties, which can promote the study of TENGs from a very fundamental level.
Electrowetting technique is an actuation method for manipulating position and velocity of fluids in the microchannels. By combining electrowetting technique and a freestanding mode triboelectric ...nanogenerator (TENG), we have designed a self-powered microfluidic transport system. In this system, a mini vehicle is fabricated by using four droplets to carry a pallet (6 mm × 8 mm), and it can transport some tiny object on the track electrodes under the drive of TENG. The motion of TENG can provide both driving power and control signal for the mini vehicle. The maximum load for this mini vehicle is 500 mg, and its highest controllable velocity can reach 1 m/s. Freestanding TENG has shown excellent capability to manipulate microfluid. Under the drive of TENG, the minimum volume of the droplet can reach 70–80 nL, while the tiny droplet can freely move on both horizontal and vertical planes. Finally, another strategy for delivering nanoparticles to the designated position has also been demonstrated. This proposed self-powered transport technique may have great applications in the field of microsolid/liquid manipulators, drug delivery systems, microrobotics, and human-machine interactions.
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IJS, KILJ, NUK, PNG, UL, UM
Water pollution is one of the most severe environmental issues nowadays. For sustainably and autonomously monitoring water quality, in-situ self-powered sensing systems which can harvest local wave ...energy are highly desired. Here, a high-performance tandem disk triboelectric nanogenerator (TD-TENG) for self-powered water quality monitoring is demonstrated. By surface modification and optimized design, a radial grating structure which can be effectively agitated by slow water waves is realized, boosting the peak and average power of wave-energy-harvesting TENG devices to 45.0 mW and 7.5 mW respectively, which are roughly 35 and 24 folds of the typical ball-shell structured device. The average power density reaches 7.3 W m−3, setting up a new record. The short-circuit current is greatly enhanced to 11 mA through a facile power management circuit. The high output enables a self-powered total dissolved solids testing system, which can be scaled up into networks for in-situ, real-time mapping water quality in a large area. The TD-TENG as a high-power wave energy harvesting device also opens up an avenue to solve the bottleneck of power supply for versatile sensing platforms that need to work autonomously in water, providing a fundamental technology for smart environmental and ocean science.
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•A novel expandable tandem disk TENG for water wave energy harvesting is designed.•High peak power of 45.0 mW and average power of 7.5 mW are achieved.•The average power density reaches 7.3 W m−3, setting up a new record.•Facile power management circuit enables self-powered TDS testing system.•Self-powered networks for in-situ, real-time mapping water quality can be expected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Miniaturized or microscale generators that can effectively convert weak and random mechanical energy into electricity have significant potential to provide solutions for the power supply problem of ...distributed devices. However, owing to the common occurrence of friction and wear, all such generators developed so far have failed to simultaneously achieve sufficiently high current density and sufficiently long lifetime, which are crucial for real-world applications. To address this issue, we invent a microscale Schottky superlubric generator (S-SLG), such that the sliding contact between microsized graphite flakes and n-type silicon is in a structural superlubric state (an ultra-low friction and wearless state). The S-SLG not only generates high current (~210 Am
) and power (~7 Wm
) densities, but also achieves a long lifetime of at least 5,000 cycles, while maintaining stable high electrical current density (~119 Am
). No current decay and wear are observed during the experiment, indicating that the actual persistence of the S-SLG is enduring or virtually unlimited. By excluding the mechanism of friction-induced excitation in the S-SLG, we further demonstrate an electronic drift process during relative sliding using a quasi-static semiconductor finite element simulation. Our work may guide and accelerate the future use of S-SLGs in real-world applications.
Triboelectric nanogenerators (TENGs) have been widely applied for energy harvesting and self-powered sensing, whereas smart deformable materials can be combined with the TENG to acquire a more ...intelligent and self-adaptive system. Here, based on the vapor-driven actuation material of a perfluorosulfonic acid ionomer (PFSA), we propose a type of humidity-responsive TENG. The integrated TENG array can automatically bend to the desired angles in response to different humidity conditions, and thus, it can effectively collect energy from both wind and rain drops, where the power density can reach 1.6 W m–2 at a wind speed of 25 m s–1 and 230 mW m–2 under rainy conditions. Meanwhile, this TENG array can fully lay down in dry weather, using the reflective surface to reflect sunlight and heat radiation. The vapor absorption process of the PSFA film can also result in the charge accumulation process. Accordingly, relying on the strong absorption capability of PFSA, a TENG-based vapor sensor with high sensitivity has been developed for monitoring chemical vapor leakage and humidity change. This work opens up a promising approach for the application of the humidity-responsive materials in the field of energy harvesting and self-powered sensors. It can also promote the development of TENG toward a more intelligent direction.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
Structural superlubricity, a state of nearly zero friction and no wear between two contact surfaces under relative sliding, holds immense potential for research and application prospects in ...micro-electro-mechanical systems devices, mechanical engineering, and energy resources. A critical step towards the practical application of structural superlubricity is the mass transfer and high throughput performance evaluation. Limited by the yield rate of material preparation, existing automated systems, such as roll printing or massive stamping, are inadequate for this task. In this paper, a machine learning-assisted system is proposed to realize fully automated selective transfer and tribological performance measurement for structural superlubricity materials. Specifically, the system has a judgment accuracy of over 98% for the selection of micro-scale graphite flakes with structural superlubricity properties and complete the 100 graphite flakes assembly array to form various pre-designed patterns within 100 mins, which is 15 times faster than manual operation. Besides, the system is capable of automatically measuring the tribological performance of over 100 selected flakes on Si
3
N
4
, delivering statistical results for new interface which is beyond the reach of traditional methods. With its high accuracy, efficiency, and robustness, this machine learning-assisted system promotes the fundamental research and practical application of structural superlubricity.
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