Publications

In article number 1807450, Khaled N. Salama, Husam N. Alshareef, and co-workers describe the integration of on-chip electrochemical microsupercapacitors with thin-film electronics at the transistor level using a single electrode material (RuO2) for both. The functionality of the integrated devices is successfully demonstrated using alternating signals, which are properly stored, and used to power several electronic devices. Highly miniaturized microsupercapacitor–rectifier micropower units are produced as a result, which are suitable for self-powered sensor applications.

Wave energy collector based on triboelectric nanogenerator (TENG) (W-TENG) is excellent candidate in complex marine environments. However, the improvement of energy conversion efficiency and understanding of motion mechanisms of W-TENG were limited due to the lack of theoretical basis. Here, based on the theory of hydromechanics, an energy conversion model is proposed to unveil the energy conversion mechanism and interaction mechanism between W-TENG (solid) and water wave (liquid) during the wave energy harvesting process. An inverted pendulum-typed multilayer triboelectric nanogenerator (IPM-TENG) is developed to capture water wave energy in weak wave environment (wave height: 2-13 cm, wave frequency: 0.5-1.25 Hz). Based on the theoretical model and hydrodynamic experiments, the structural parameters and output performance of the device are further optimized. Most importantly, the available energy conversion efficiency of the optimized device is up to 14.5 %. Furthermore, the optimized IPM-TENG can serve as a console for the ‘on demand’ release of pesticides to promote the development of self-powered smart agriculture. This work can not only provide guidance for the design and energy conversion efficiency improvement of future blue energy harvesting devices, but also accelerate the commercial rollout and practical application of W-TENG.

A hybrid-fiber nanogenerator comprising a ZnO nanowire array, PVDF polymer and two electrodes is presented. Depending on the bending or spreading action of the human arm, at an angle of ∼90°, the hybrid fiber reaches electrical outputs of ∼0.1 V and ∼10 nA cm−2. The unique structure of the hybrid fiber may inspire future research in wearable energy-harvesting technology.

Energiespeicher aus Papier: Papierbasierte, flexible Festkörpersuperkondensatoren wurden erzeugt, die mit einem piezoelektrischen Biegewandler oder einer Solarzelle geladen und durch Betreiben eines Spannungssensors oder einer blau emittierenden Diode entladen werden. Die Kondensatoren können in energieautarken Nanosystemen eingesetzt werden (siehe Bild). Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Enhancing the output performance of triboelectric nanogenerators through surface modification, mechanical design and power management.

Triboelectric nanogenerators (TENGs) have emerged as a highly effective and easily scalable technology for harvesting mechanical energy. Recently, standards and figure‐of‐merits have been defined to quantify the performance of TENGs. In this work, the figure‐of‐merits of rolling‐friction‐based TENGs are investigated through a theoretical model based on the rolling freestanding mode, including the conductor‐to‐dielectric and dielectric‐to‐dielectric cases. By combining finite‐element simulations and semi‐analytical derivations, the basic properties and resistive load output characteristics of rolling TENGs are calculated for various structural parameters, such as the electrode gap or rod diameter. The average output power is optimized by maximizing the structural figure‐of‐merit, which depends on the structural parameters. The results gained in this work could provide useful guidance for optimizing the performance of rolling‐friction‐based TENGs toward practical self‐powered systems.

Recent studies have suggested a potential correlation between ecological dysregulation of the gut microbiota (GM) and the onset and development of postpartum depression (PPD). In addition, inflammatory factors (IFs) have been reported to play an important role in the development of PPD. However, the causal connections among GM, IFs, and PPD remain to be understood. This study sought to determine if genetically predicted GM and IFs exert a causal effect on PPD and to study whether IFs mediate the causal effect of GM on PPD. Two-step and two-sample Mendelian randomization (MR) analyses, primarily employing the inverse variance weighted (IVW) method, were conducted to evaluate the causal relationship between GM, IFs, and PPD, and to assess potential mediating effects. Heterogeneity and horizontal pleiotropy tests were performed to evaluate the robustness of the findings and the strength of the causal associations. Class Alphaproteobacteria, genus Family XIII AD3011 group exhibited a positive association with PPD risk; whereas, the family Clostridiales vadin BB60 group, family Veillonellaceae, genus Ruminococcaceae UCG011, and the inflammatory factors C–C motif chemokine ligand 5 (CCL5) and C–C motif chemokine ligand 3 (CCL3) demonstrated negative correlations with PPD risk. IFs did not exhibit a mediating role. No heterogeneity or horizontal pleiotropy was observed. Our MR study offered genetic evidence that GM and IFs contribute to the pathogenesis of PPD, with no mediating effect of IFs. This enhances our understanding of PPD's pathological mechanisms and offers new perspectives for developing novel preventative and therapeutic strategies.

Deep ultraviolet light-emitting diodes (DUV LEDs) are promising light sources for disinfection, especially during the pandemic of novel coronavirus (COVID-19). Despite much effort in the development of DUV LEDs, the device temperature and ideality factor are key parameters of devices, which are often neglected. Here, we developed a simple and convenient method to study the behavior of a 280 nm AlGaN-based DUV LED, obtaining the electrical, optical, and thermal properties within one measurement. From the experimental results, we find that the light output power and wall-plug efficiency of the AlGaN-based DUV LED are strongly affected by device temperature, ideality factor (β), and series resistance (Rs). β decreases from 9.3 to 8.1 at 40 mA when the temperature increases from 302 to 317 K. We compared these results with simulations and found that the high potential barriers inside the device and the carrier concentration in n-type or p-type layers, especially the hole concentration in p-type layers, are the two key factors for the high value of the ideality factor from the LED structure. As the device temperature increases, carriers with higher energy would overcome some potential barriers and Mg acceptor activation would be more efficient, which are beneficial for carrier transportation. However, these also lead to the carrier overflow and weaken the radiative recombination rate. The trade-off role of device temperature in carriers between transportation and overflow is needed to be considered in the future development of DUV LEDs with higher efficiency and higher brightness.

Ocean wave energy is one of the important renewable energy sources. However, random, low‐frequency, and micro‐amplitude characteristics of ocean waves make it difficult for traditional electromagnetic generators to collect wave energy efficiently. The emergence of triboelectric nanogenerator (TENG) provides an extremely effective technical means for the collection of low‐frequency and micro‐amplitude wave energy. In this work, a non‐contact turntable‐structured oscillating water column TENG (OWC‐TENG) is designed by combining an OWC wave energy conversion mechanism with a TENG for the first time. The OWC is optimized through simulation experiments according to the principles of ship hydrostatics and wave theory. The output performances of the OWC‐TENGs with different structural parameters under different water wave excitation conditions are then tested. The TENG delivers a maximum output current of 55.45 µA and an output power of 5.28 mW, which corresponds to a power density of 114.8 W m −3 , enabling a stable power supply for small sensors at sea. This work provides a new solution to the efficient collection of low‐frequency micro‐amplitude ocean wave energy for powering various offshore equipments, presenting broad application prospects in ocean blue energy development and offshore Internet of Things.

We demonstrate the design, fabrication, evaluation, and use of a self-powered microphone that is thin, flexible, and easily manufactured. Our technology is referred to as a Self-powered Audio Triboelectric Ultra-thin Rollable Nanogenerator (SATURN) microphone. This acoustic sensor takes advantage of the triboelectric nanogenerator (TENG) to transform vibrations into an electric signal without applying an external power source. The sound quality of the SATURN mic, in terms of acoustic sensitivity, frequency response, and directivity, is affected by a set of design parameters that we explore based on both theoretical simulation and empirical evaluation. The major advantage of this audio material sensor is that it can be manufactured simply and deployed easily to convert every-day objects and physical surfaces into microphones which can sense audio. We explore the space of potential applications for such a material as part of a self-sustainable interactive system.

As an energy harvester that converts mechanical power into electrical energy, a triboelectric nanogenerator (TENG) with a pair of metallic and insulating electrodes can generate only the displacement current (Idis) in the electrodes, whereas a chemical potential difference generator (CPG) with a pair of semiconducting or/and metallic electrodes can generate both Idis and conduction current (Icon). Considering the effects of motion parameters on Idis and Icon is important for harvesting different mechanical energies in practical scenarios; the output characteristics of CPGs and traditional TENGs under different external resistance (R), contact-separation frequency (f), and maximum separation distance (xm) were systematically studied for the first time in this work. More interestingly, a direct current (DC) output can be generated directly by CPGs under R > 10 MΩ or f > 100 Hz. This work not only provides a guideline for collecting different mechanical energies but also promotes the development of CPGs as an energy harvester and self-powered vibration sensor in the semiconductor industry.

In the above paper one of the author's names was misspelled as Yong Jun Park. The correct spelling is Young Jun Park.

Dielectric elastomers are a type of actuator materials that exhibit excellent performance as artificial muscles, but a high driving voltage is required for their operation. By using the amazingly high output voltage generated from a triboelectric nanogenerator (TENG), a thin film dielectric elastomer actuator (DEA) can be directly driven by the contact‐separation motion of TENG, demonstrating a self‐powered actuation system. A TENG with a tribo surface area of 100 cm 2 can induce an expansion strain of 14.5% for the DEA samples (electrode diameter of 0.6 cm) when the system works stably within the contact‐separation velocity ranging from 0.1 to 10 cm s −1 . Finally, two simple prototypes of an intelligent switch and a self‐powered clamper based on the TENG and DEA are demonstrated. These results prove that the dielectric elastomer is an ideal material to work together with TENG and thereby the fabricated actuation system can potentially be applied to the field of electronic skin and soft robotics.

In article number 1807560, Yubo Fan, Hao Zhang, Zhong Lin Wang, Zhou Li, and co-workers present a miniaturized flexible self-powered endocardial pressure sensor (SEPS) based on a triboelectric nanogenerator. The SEPS achieves ultra-sensitive, real-time monitoring and mechanical stability in vivo. Atrial fibrillation and ventricular premature contraction are also detected by the SEPS. This device may promote the development of miniature implantable medical sensors for monitoring and diagnosis of cardiovascular diseases.