Triboelectric Film Research Articles

Magnetic Levitation Type Double Helix Self‐Powered Acceleration Sensor Based on ZnO‐RTV Film

AbstractTraditional accelerometers rely on batteries to provide energy, and the massive use of batteries caused great pressure on the natural environment. In this paper, a self‐powered acceleration sensor is designed. To more easily harvest weak vibration signals and effectively improve the sensitivity, this sensor is built on a magnetic levitation type double helix structure and ZnO‐doped triboelectric film. Experiments indicated that the open‐circuit voltage and short circuit current of the triboelectric nanogenerator (TENG) doped with ZnO are increased by 2.51 times and 2.07 times, respectively. Under shaking table test for simulating machine vibration environment, the sensor's sensitivity reaches 16.31 V (m s−2)−1 and its linearity is 0.993. The sensor power generation is 110 μW and its test range is ≈1–7 m s−2. Also, the sensor can be applied for monitoring human's movement state by installing in a sole. This design provides a new idea for the development of TENG‐based sensors.

Surface-microengineering for high-performance triboelectric tactile sensor via dynamically assembled ferrofluid template

Surface-microengineering of the active layer in triboelectric tactile sensor enables to effectively reduce the surface stiffness of the non-ideal planar triboelectric film and increase the contact area during the triboelectric process. In this work, a facile and dynamically controllable two-step method based on the unique characteristic of ferrofluid has been proposed to fabricate a high-performance self-powered triboelectric tactile sensor. Through adjusting the distance and rotating angle of magnet, ferrofluid spikes with different lengths and inclination angles ranging from 30° to 90° can be obtained. The adjustable microstructures distributed on the active layer were analyzed theoretically and verified experimentally, indicating the inclined and high microstructures can effectively facilitate the sensing performance. When the inclination angle of the microstructure is 30°, the sensitivity delivers 6.75 kPa −1 with pressure lower than 44 kPa, and keeps excellent linearity with the sensitivity of 3.01 kPa −1 even the detection pressure reaches 250 kPa. Simultaneously, the tactile sensor has a fast response/recovery time of 75 ms and 56 ms, respectively. Finally, it was demonstrated to adopt in the bionics robotic hands for weight perception and attached to various parts of the human body for detecting physiological activities with outstanding repeatability and stability. A facile and dynamically controllable two-step method based on the unique characteristic of ferrofluid has been proposed to fabricate a high-performance self-powered triboelectric tactile sensor. The inclined and high microstructures can effectively facilitate the sensing performance. This sensor can be adopted in the bionics robotic hands or detect physiological activities with outstanding repeatability and stability. • Micro-engineered the dielectric surface of the tactile sensor with different inclination angles and length. • The smaller inclination angle and more height are beneficial to the sensitivity and high sensitivity detection range. • When the inclination angle is 30°, the sensitivity delivers 6.75 kPa −1 with pressure lower than 44 kPa.

Theoretical investigation and experiment of a disc-shaped triboelectric energy harvester with a magnetic bistable mechanism

Triboelectric energy harvesting has emerged as a promising route to scavenge ambient mechanical energy for cost-effective, clean and sustainable electricity. Disc-shaped triboelectric energy harvesters are suitable for two kinds of mechanical energy sources: continuous rotation and vibration. A majority of current studies about disc-shaped triboelectric energy harvesters focus on scavenging energy in continuous rotation, but there is a lack of investigations on angular vibration, especially in structural dynamics. In this work, a new disc-shaped triboelectric energy harvester with a bistable mechanism enabled by two repulsive magnets is developed for harvesting vibration energy. There are two discs in the harvester, one stationary and the other undergoing angular oscillation. Both have segmented triboelectric films on their contact surfaces. The magnetic bistable mechanism is utilized for the first time in a disc-shaped triboelectric energy harvester for efficiency enhancement. A comprehensive theoretical model coupling both structural dynamic and electric dynamic domains is established. A comparison between the coupled and uncoupled models reveals that the ET between electrodes can be ignored. Numerical simulations are carried out to investigate the effect of the potential wells due to the two magnets, basins of attractors and the influence of damping from the perspective of structural dynamics. A prototype is fabricated for experimental investigations, which demonstrate that the harvester with the bistable mechanism can achieve a better performance than the corresponding harvester without the bistable mechanism, and the output voltage of the harvester increases with the increase of excitation amplitude. Theoretical and experimental comparisons about the electric outputs between the triboelectric films with different segmentation structures reveal that increasing the number of sectors on the films effectively improves the harvesting efficiency. This work establishes a link between the structural dynamics and electric dynamics for the vibration-based disc-shaped triboelectric energy harvester, providing guidelines for its design and fabrication.

Scalable fabrication of hierarchically structured graphite/polydimethylsiloxane composite films for large-area triboelectric nanogenerators and self-powered tactile sensing

Abstract Health monitoring, e-skin, and soft robotics call for large-area and robust energy-harvesting strategy to powering their embedded sensors and peripheral electronics. Triboelectric nanogenerator (TENG) is an optimum option to energizing self-powered sensors and self-charging systems. Herein, a large-scale facile and compatible bar-assisted printing method is presented to achieve hierarchically microstructured polymer composite triboelectric film with good hydrophobicity to improve the electrical output performance and achieve the robustness of TENG. The electrical outputs of the TENG devices are tuned by imparting the graphite fillers into polydimethylsiloxane (PDMS) with optimal concentration. The achieved microstructured graphite/PDMS composite based TENG supplies high and stable short-circuit current of 42 µA, open-circuit voltage of 410 V, and transferred charges of 160 nC under an applied force of 1.2 N, which are sufficient enough to power wearable sensors or charge the energy storage devices. The TENG devices can charge a 2.2 µf capacitor to 1.5 V within 2 s, lighten 30 commercial green LEDs, and drive an electronic watch as well. Self-powered tactile sensing has also been demonstrated by attaching the TENG devices onto a rubber glove to monitor the process in grasping objects. Furthermore, a large-scale self-powered sensor array is fabricated and utilized to map the spatial pressure distributions. This work not only demonstrates a scalable fabrication of the hierarchically microstructured polymer composite films for high-performance TENGs with high electrical outputs, excellent durability and ambient stability, but also brings insight into the development of future cost-effective and self-powered electronics.

A Triboelectric Nanogenerator Exploiting the Bernoulli Effect for Scavenging Wind Energy

Summary Wind energy is one of the most cost-effective energy sources available today. Some techniques have been developed to scavenge wind energy, but making use of lower flutter velocity while maintaining high conversion efficiency remains challenging. Here, we report a triboelectric nanogenerator composed of two interacting triboelectric films with four flapping modes, enabling an effective work wind velocity as low as 1.6 ms−1 and a high conversion efficiency of 3.23%, which, to our knowledge, are better than previously reported values of wind energy scavenging. The output performance of B-TENG can be determined by device size and flow velocity; the optimized device exhibits an output voltage, current, and power of 175 V, 43 μA, and 2.5 mW, respectively, with dimensions of 3 × 8 × 2 cm3 at a flow velocity of 8 ms−1. The B-TENG may pave the way for future wind scavenging devices for a range of point-of-use applications.

Triboelectric nanogenerators with porous and hierarchically structured silk fibroin films via water electrospray-etching technology

Abstract Triboelectric nanogenerator (TENG) has great potential applications in self-powered electronic devices, especially in flexible and wearable applications. Currently, to improve the performances, micro/nano structured surfaces are constructed in TENGs using complicated, costly, and toxic processes. Herein, a cost-effective and versatile water electrospray-etching (ESE) process for fabrication micro/nano structured silk fibroin (SF) triboelectric film has been presented. The water-soluble SF film could be easily dissolved by the atomized water droplets, meanwhile, as the residual charges on the droplets transferred and accumulated on to the SF surface, a patterned electrical field emerged due to the peak effect on the etched crater-like structures and manipulated the positions of deposition of the charged droplets. Our ESE strategy, which was different from the randomly distributed deposition by conventional electrospray deposition (ESD) process, could obtain quasi-periodical and porous structures, providing significantly increased surface roughness. The structural features, such as period and depth of the micropores, could be controlled by adjusting the spray parameters. The maximum output voltage and power density of the TENGs with porous structures were obviously increased by 180%, compared to 100 V obtained for a planar device. Furthermore, hierarchical micro/nano structures could be simply obtained by mixing SiO2 nanospheres in the aqueous precursor solution as nano-electrets. With this, the output voltage was up to 260 V, representing an overall 260% increase over the value of a planar device. The highest total power and peak power density were 0.65 mW and 161.5 μW/cm2 at a driving force of 18 N and frequency of 1 Hz. Meanwhile, the porous SF based TENG exhibited higher transmittance due to light scattering effects. The proposed water ESE strategy has advantages such as low cost, large area applications, bio-compatibility and nontoxicity, showing great promise as a technology in practical use.

Integrated Design of Highly Porous Cellulose-Loaded Polymer-Based Triboelectric Films toward Flexible, Humidity-Resistant, and Sustainable Mechanical Energy Harvesters

A wearable and humidity-resistant cellulose-based flexible triboelectric nanogenerator (FTENG) device with high performance is proposed here. In this regard, cellulose extracted from cotton was com...

Normally Transparent Tribo-Induced Smart Window.

Self-powered smart windows are desirable with the expectations of their energy-saving, weather-independent, user-controllable, and miniature performance. Recently developed solar- or thermal-powered smart windows largely depend on the weather conditions and have an extremely slow response, and only a certain portion of thesaved energy can be utilized by the external circuit for mode conversion. In this work, a self-powered normally transparent smart window was developed by the conjunction of a rotary freestanding sliding triboelectric nanogenerator (RFS-TENG) and a polymer network liquid crystal (PNLC) cell. To fabricate the PNLC cell, the alignment layer with randomly distributed microdomains was constructed to encapsulate a mixture of LC polymers and nematic LCs. The opacity of the smart window exposed to an alternating electric field was considerably improved owing to the embedded microdomains and a dense web of LC polymers. The ultrahigh haziness greatly alleviates the charge density required for the LC actuation and thus enables the driving by the TENG where the charge amount is usually limited. The RFS-TENG was elaborately designed with six periodic bent triboelectric films and Ag electrodes, which presented an ultralow friction wear and met the frequency requirement to achieve the steady opacity. By harvesting the mechanical energies from ambient environments, the tribo-induced smart window can benefit a wide variety of fields, such as self-powered sunroofs, wind-driven smart farming systems etc.

Non-resonant and low-frequency triboelectric-electromagnetic hybridized nanogenerator for vibration energy

As the age of the internet of everything begins, the demand for various sensors to communicate with each other is soaring. As the lifeblood of the sensing system, reliable energy supply is the key consideration. Environmental mechanical energy harvesting has been a key technology for self-powering sensing system, which can convert mechanical energy into electric energy. Here, we present a non-resonant triboelectric-electromagnetic hybridized nanogenerator, which can scavenge low-frequency vibration energy from environmental vibration. In the device a rotating gyro is used as a core component. An embedded magnet and four coils arranged evenly around at the bottom of the shell form an electromagnetic generator (EMG), and a piece of triboelectric film pasted on the outer surface of the gyro together with a bottom electrode constitutes a triboelectric nanogenerator, (TENG). With the design of rotating gyro, a high sensitive energy capture can be realized under low frequency and irregular vibration. Under the rotation and revolution of the gyro, the triboelectric and electromagnetic energy will be generated. Through theoretical analysis and software simulation, the working principle of the device is expounded. Based on a linear motor platform, the influences of oscillation frequency and amplitude are systematically studied, and the maximum power of 0.084 mW under a loading resistance of 20 MΩ and 4.61 mW under 800 Ω are obtained at a driving frequency of 2 Hz by the TENG and EMG, respectively. The energy conversion efficiency of the system is 0.45%. Moreover, by placing the devices on the legs and arms of the human body respectively, the ability of the hybridized nanogenerator to capture the simple movement energy of the human body is further verified. After that, a self-powering pedometer module is successfully integrated with the energy storage unit. Under the excitation provided by running a body, the hybridized nanogenerator can provide a 20-s pedometer normal operation after charging a capacitance of 100 μF to 3.2 V. This research not only provides a new idea for the efficient acquisition of vibration energy, but also has potential applications in the energy supply of self-powered sensors.

Triboelectric freestanding flapping film generator for energy harvesting from gas flow in pipes

We are reporting on the conversion of gas/air flow energy in pipes to electrical signals using the triboelectric effect. A flapping triboelectric generator design with all freestanding flexible films is introduced in this regard. The generator can be integrated within a regular pipe infrastructure, as it is independent of the pipe material, for implementing the triboelectric effect. All flexible materials are used to develop the triboelectric generator, utilizing a simple fabrication process that is easily scalable. The performance of the triboelectric device was influenced by several physical parameters, as well as by the gas flow speed, which has been optimized here for a pipe diameter of 5 cm. The triboelectric generator implementing a flexible silver material in combination with polytetrafluoroethylene (PTFE) exhibits 100% higher optimum average power output compared to a generator made of PTFE and polyurethane. A harvester unit with two pairs of triboelectric films with an active film area of 5 × 3.3 cm2 with 6 mm gaps was demonstrated. The device produced total average power of 1.64 mW across an optimum load resistance of 16.7 MΩ under the air flow speed of 9.8 ± 0.2 m s−1.

Engineering squandered cotton into eco-benign microarchitectured triboelectric films for sustainable and highly efficient mechanical energy harvesting

Harvesting mechanical energy from daily life human activities has gained tremendous interest, along with the concept of waste to wealth which has been also a major concern from a few decades. In this regards, firstly, we fabricated microcrystalline cellulose (MCC) particles from the squandered cotton and they were further dissolved into biocompatible polyvinyl alcohol (PVA) to develop a triboelectric material. The resultant cellulose loaded PVA film (CPF) was employed as a positive triboelectric material to design a coin-cell type TENG, whereas the Kapton was used as a negative material. Design of such TENG using CPF can reduce the processing cost and is also significant to incorporate the waste cotton into an energy harvesting device. Besides, the effect of electrical output performance of CPF-based prototype TENG (CPF-pTENG) as a function of the concentration of MCC particles loaded into PVA was also systematically studied and optimized. Thus, the CPF-pTENG with the 2.5 wt% of cellulose added into PVA exhibited a stable and high electrical output. The electrical performance of CPF-pTENG was further enhanced by introducing the microarchitectures on the surface of CPF, and it exhibited comparatively very high voltage, current and power density values of ∼600 V, 50 μA and 84.5 W/m2, respectively. Finally, to demonstrate the practical or commercial applications, a MACPF-based coin-cell type TENG (i.e., MACPF-ccTENG) was developed to harvest the mechanical energies available in daily human life by placing it under the human-foot medial arch, which can be further utilized as a self-power system to drive various portable electronics.

Layer-by-layer assembly for ultrathin energy-harvesting films: Piezoelectric and triboelectric nanocomposite films

Energy-harvesting devices such as piezoelectric and triboelectric nanogenerators (NGs), which can convert mechanical energy into electricity, are under development to be combined with various electronics. In particular, the rapid progress in microscale electronics such as nanorobotics or microelectromechanical devices has strongly increased the demand for ultrathin film devices. Therefore, the thickness, highly uniform structure, chemical composition, interfacial adhesion/interactions, and electrical performance of electrically active films should be carefully considered for high-performance ultrathin energy-harvesting devices. This review focuses on how layer-by-layer (LbL) assembly as a kind of thin film technology can be effectively applied to ultrathin piezoelectric and triboelectric films, and furthermore enhance device performance. First, we introduce the basics of various LbL assemblies using electrostatic, hydrogen-bonding, and covalent-bonding interactions. Then, the LbL-assembly-assisted piezoelectric and triboelectric NGs reported to date are reviewed. Finally, we briefly present perspectives on the direction of LbL assembly for the realization of various ultrathin piezoelectric and triboelectric NGs with high performance.

Self-sustainable wind speed sensor system with omni-directional wind based triboelectric generator

A stable power supply is critical for wireless sensor systems. While various energy harvesting devices have been studied, there has been limited discussion of circuit design for a self-powered sensor system. This study introduces a self-sustainable wind speed sensor system (SSWSSS) with an omni-directional wind-based triboelectric generator (OW-TEG) along with a 2-dimensional co-planar surface. The OW-TEG simultaneously provides both signal sensing and energy harvesting without interference. The SSWSSS consists of an OW-TEG and a control circuit that senses wind speed and manages the harvested energy storage. Wind speed is extracted from the frequency of the electrical signals from the OW-TEG, which operates by wind actuation of a flat triboelectric film which flutters between two electrodes. The frequency is characterized by counting the number of induced voltage peaks above a reference voltage. Meanwhile, omni-directional energy harvesting is accomplished by using control circuit functions to count frequency, convert power, and store energy. Realization of this self-sustainable sensor system represents a forward step towards achieving a self-powered sensor platform.

Field-effect enhanced triboelectric colloidal quantum dot flexible sensor

Flexible electronics, which is of great importance as fundamental sensor and communication technologies for many internet-of-things applications, has established a huge market encroaching into the trillion-dollar market of solid state electronics. For the capability of being processed by printing or spraying, colloidal quantum dots (CQDs) play an increasingly important role in flexible electronics. Although the electrical properties of CQD thin-films are expected to be stable on flexible substrates, their electrical performance could be tuned for applications in flexible touch sensors. Here, we report CQD touch sensors employing polydimethylsiloxane (PDMS) triboelectric films. The electrical response of touching activity is enhanced by incorporating CQD field-effect transistors into the device architecture. Thanks to the use of the CQD thin film as a current amplifier, the field-effect CQD touch sensor shows a fast response to various touching materials, even being bent to a large curvature. It also shows a much higher output current density compared to a PDMS triboelectric touch sensor.