Air Breakdown Effect Research Articles

Quantifying Dielectric Material Charge Trapping and De-Trapping Ability Via Ultra-Fast Charge Self-Injection Technique.

Recently, utilizing the air breakdown effect in the charge excitation strategy proves as an efficient charge injection technique to increase the surface charge density of dielectric polymers for triboelectric nanogenerators (TENGs). However, quantitative characterization of the ability of dielectric polymers to trap reverse charges and the effect on the startup time of secondary self-charge excitation (SSCE) are essential for extensive applications. Here, an ultra-fast charge self-injection technique based on a self-charge excitation strategy is proposed, and a standard method to quantify the charge trapping and de-trapping abilities of 23 traditional tribo-materials is introduced. Further, the relationship among the distribution of dielectric intrinsic deep, shallow trap states, and transportation of trapped charges is systematically analyzed in this article. It shows that the de-trapping rate of charges directly determines the reactivation and failure of SSCE. Last, independent of TENG contact efficiency, an ultra-high charge density of 2.67 mC m-2 and an ultra-fast startup time of SSCE are obtained using a 15µm poly(vinylidene fluoride-trifluoroethylene) film, breaking the historical record for material modification. As a standard for material selection, this work quantifies the charge trapping and de-trapping ability of the triboelectric dielectric series and provides insights for understanding the charge transport in dielectrics.

Regulation of deep and shallow hole/electron trap states and charge conducting behaviors of dielectric tribo-materials for maximizing retained charges

This work utilizes the UHCSI strategy to quantify the ability of 30 conventional tribo-materials to trap and de-trap positive/negative charges and reveal that the polymer's group composition influences trap states.

A Mutual Boosting Self-Excitation Hybrid Cell for Harvesting High Entropy Energy at 32% Efficiency.

Triboelectric nanogenerators (TENGs) and dielectric elastomer generators (DEGs) are potentially promising energy conversion technologies, but they still have limitations due to their own intrinsic characteristics, including the low energy output of TENGs caused by the air breakdown effect, and external polarization voltage requirement for DEGs, which severely limit their practical applications. Herein, coupling TENG with DEG is proposed to build a mutual beneficial self-excitation hybrid generator (named TDHG) for harvesting distributed and low-quality mechanical energy (high entropy energy). Experimental results demonstrate that the output charges of this TDHG are enhanced by fivefold of that of the conventional charge-excitation TENG, and continuous operation of DEG is also realized by simple mechanical triggering. More importantly, owing to the high peak power contributed by TENG and the long output pulse duration guaranteed by DEG, the TDHG realizes a much higher energy conversion efficiency of 32% in comparison to either the TENG (3.6%) or DEG (13.2%). This work proposes a new design concept for hybridized energy harvester toward highly efficient mechanical energy harvesting.

Improving and Quantifying Surface Charge Density via Charge Injection Enabled by Air Breakdown

AbstractThe modification of triboelectric materials is an important means to improve the output performance of triboelectric nanogenerator (TENG), and the surface charge or ion implantation is an effective way among many modification methods. However, the output enhancement via optimizing triboelectric materials is still limited. Herein, a fast surface charge injection technique based on air breakdown effect is reported, which utilizes an excitation circuit to realize the directional accumulation of charge. Consequently, the output charge density of the Polyimide (PI) film after charge injection reaches 880 µC m‐2, which is the highest of the series of modified triboelectric materials. Moreover, a novel charge transfer mechanism with electrostatic induction competition is proposed, in which significant difference between surface charge density and output charge density is highlighted clearly. Meanwhile, the method of quantifying surface charge density is further given. This work provides a more effective method for the modification of dielectric materials and also offers an important insight towards the charge transfer mechanism in TENG.

Smart Textile Triboelectric Nanogenerators: Prospective Strategies for Improving Electricity Output Performance

By seamlessly integrating the wearing comfortability of textiles with the biomechanical energy harvesting function of a triboelectric nanogenerator (TENG), an emerging and advanced intelligent textile, i.e., smart textile TENG, is developed with remarkable abilities of autonomous power supply and self-powered sensing, which has great development prospects in the next-generation human-oriented wearable electronics. However, due to inadequate interface contact, insufficient electrification of materials, unavoidable air breakdown effect, output capacitance feature, and special textile structure, there are still several bottlenecks in the road towards the practical application of textile TENGs, including low output, high impedance, low integration, poor working durability, and so on. In this review, on the basis of mastering the existing theory of electricity generation mechanism of TENGs, some prospective strategies for improving the mechanical-to-electrical conversion performance of textile TENGs are systematically summarized and comprehensively discussed, including surface/interface physical treatments, atomic-scale chemical modification, structural optimization design, work environmental control, and integrated energy management. The advantages and disadvantages of each approach in output enhancement are further compared at the end of this review. It is hoped that this review can not only provide useful guidance for the research of textile TENGs to select optimization methods but also accelerate their large-scale practical process.

High output direct-current power fabrics based on the air breakdown effect

The finger-sized FDC-TENG can light up 99 commercial bulbs and 1053 LEDs and drive watches and calculators easily and directly by sliding it manually.

Intermediate layer for enhanced triboelectric nanogenerator

Triboelectric nanogenerator (TENG) has shown great advances in converting low-frequency discrete mechanical energy into electricity and multifunctional real-time self-powered sensing systems. It has confirmed that the air breakdown effect is the main factor limiting the maximum effective power output of the TENG. Charges generated on the surface of TENGs diffuse into the atmosphere and internal triboelectric layer, resulting in charge loss and decrease of surface charge density. Breaking through the limitation of air breakdown and prolonging charge decay time are the two priorities for boosting TENG output. By embedding superior intermediate layer into TENG induced output enhancement provides an effective strategy to improve the output performance. Here, the working mechanisms of different materials belonging to the classifications of metals, inorganic non-metal materials, and organic polymers as the intermediate layer are reviewed elaborately. Moreover, the influences of structure parameters, such as thickness of dielectric layer, dielectric layer number, and ground connection design are discussed accordingly. Future challenges and optimizations for improvement of the intermediate layer are finally presented in the review.

Theoretical investigation of air breakdown direct current triboelectric nanogenerator

A triboelectric nanogenerator (TENG), which harvests ubiquitous ambient mechanical energy, is a promising power source for distributed energy. Recently reported new generation direct current TENG (DC-TENG) based on the air breakdown effect exhibits unique advantages over conventional modes of TENG devices, such as free-of-rectification and intrinsic switching behavior. However, owing to different working mechanisms and output characteristics, existing theory and power management strategies are not suitable for in-depth understanding and further advancement of air breakdown DC-TENG. Herein, a theoretical study and experimental verification that systematically investigate the physics, output characteristics, and power management strategy of air breakdown DC-TENG is presented. A general simulation model is then proposed and verified through a statistical analysis method. Contrary to previous understanding of a highly conductive breakdown pathway, a huge resistance is observed and causes inevitable energy loss, which is regarded to be caused by corona discharge. Finally, device optimization and power management strategies are discussed, and fundamental guidance is given for the rational design of air breakdown DC-TENG.

Derivation of analytical equations with experimental verification for working mechanism of triboelectric nanogenerators in contact-separation mode

Abstract Since the invention of triboelectric nanogenerator (TENG) in 2012, various works have attempted to address the basic physical principles of TENG operation such as Maxwell displacement current or air breakdown effect. Nevertheless, physical mechanisms incorporating the measurement system to give a better comprehension of the testing process have not been reported yet. Here, as evidenced by the measurement results of a ZnO-PDMS TENG, we investigate the fundamental mechanisms of short-circuit current and open-circuit voltage output of TENGs in contact-separation mode by analyzing analytical equations based on a capacitor-like and charged-plate model for better comprehension. The analysis can provide deeper insights into the output waveforms of TENGs during contact and separation operations. Moreover, the impact of the testing conditions of a measurement system on the results can be elucidated. The output waveforms could be disguised and misleading to some degree depending on the sampling rate in data collection. More importantly, the inherent resistor associated with the voltmeter dramatically governs the voltage output of TENGs, which is especially sensitive to transfer charge distribution.

Optimization of triboelectric nanogenerator load characteristics considering the air breakdown effect

Working in the ambient environment, the behavior of triboelectric nanogenerator (TENG) is inevitably limited by the air breakdown phenomenon. In this paper, the load characteristics of TENG considering the air breakdown effect are systematically studied. The maximum retainable surface charge density varies with resistive loads, and a saturation state is seen during the capacitive charging process in the TENG due to the air breakdown effect. The optimization criterion to maximize the TENG output was also investigated with the consideration of air breakdown effect. Through theoretical analysis and experimental verification, this work provides a solid criterion to guide the TENG design and operational process.

Maximized Effective Energy Output of Contact‐Separation‐Triggered Triboelectric Nanogenerators as Limited by Air Breakdown

Recent progress in triboelectric nanogenerators (TENGs) has demonstrated their promising potential as a high‐efficiency mechanical energy harvesting technology, and plenty of effort has been devoted to improving the power output by maximizing the triboelectric surface charge density. However, due to high‐voltage air breakdown, most of the enhanced surface charge density brought by material/surface optimization or external ion injection is not retainable or usable for electricity generation during the operation of contact‐separation‐triggered TENGs. Here, the existence of the air breakdown effect in a contact‐separation mode TENG with a low threshold surface charge density of ≈40–50 µC m−2 is first validated under the high impedance external load, and then followed by the theoretical study of the maximized effective energy output as limited by air breakdown for contact‐separation‐triggered TENGs. The effects of air pressure and gas composition are also studied and propose promising solutions for reducing the air breakdown effect. This research provides a crucial fundamental study for TENG technology and its further development and applications.

Effect of air breakdown on microwave pulse energy transmission**Project supported by the National Natural Science Foundation of China (Grant No. 61501358) and the Fundamental Research Funds for the Central Universities,China.

The energy transmission of the long microwave pulse for the frequency of 2.45 GHz and 5.8 GHz is studied by using the electron fluid model, where the rate coefficients are deduced from the Boltzmann equation solver named BOLSIG+. The breakdown thresholds for different air pressures and incident pulse parameters are predicted, which show good agreement with the experimental data. Below the breakdown threshold, the transmitted pulse energy is proportional to the square of the incident electric field amplitude. When the incident electric field amplitude higher than the breakdown threshold increases, the transmitted pulse energy decreases monotonously at a high air pressure, while at a low air pressure it first decreases and then increases. We also compare the pulse energy transmission for the frequency of 2.45 GHz with the case of 5.8 GHz.

Effect of air breakdown in near-field region on maximum power radiated from aperture antenna

The high-power microwave easily causes the air breakdown in the near-field region of an antenna that is one of major factors to limit the enhancement of the radiation power at present. We study the maximum radiation power of a circular aperture antenna at which the maximum electric field in the near-field region equals the breakdown electric field in air, by using the field equivalent principle along with the global model. Results show that, with the pulse width increasing, the maximum radiation power decreases. The larger the antenna radius, the higher power can be radiated. The field distribution on the aperture has an obvious impact on the maximum radiation power.

Effect of air breakdown with a focusing lens on ultrashort laser ablation

The effect of air breakdown on ultrashort laser ablation is investigated in this letter using an integrated simulation method on atomistic level. The generation of air breakdown with different laser peak power densities in the range from 1013 to 1016 W/cm2 and various focusing conditions is analyzed. Air breakdown is generated directly from laser energy absorption through avalanche ionization at a high power density (over 1014 W/cm2), while at a lower power density, air breakdown is assisted by a metal target near the focal region. The laser energy loss due to air breakdown and its effect on laser ablation are studied.