A Dual-Mode Triboelectric Nanogenerator for Efficiently Harvesting Droplet Energy.

Triboelectric nanogenerator (TENG) is a promising solution to harvest the low-frequency, low-actuation-force, and high-entropy droplet energy. Conventional attempts mainly focus on maximizing electrostatic energy harvest on the liquid-solid surface, but enormous kinetic energy of droplet hitting the substrate is directly dissipated, limiting the output performance. Here, a dual-mode TENG (DM-TENG) is proposed to efficiently harvest both electrostatic energy at liquid-solid surface from a droplet TENG (D-TENG) and elastic potential energy of the vibrated cantilever from a contact-separation TENG (CS-TENG). Triggered by small droplets, the flexible cantilever beam, rather than conventional stiff ones, can easily vibrate multiple times with large amplitude, enabling frequency multiplication of CS-TENG and producing amplified output charges. Combining with the top electrode design to sufficiently utilize charges at liquid-solid interface, a record-high output charge of 158 nC is realized by single droplet. The energy conversion efficiency of DM-TENG is 2.66-fold of D-TENG. An array system with the specially designed power management circuit is also demonstrated for building self-powered system, offering promising applications for efficiently harvesting raindrop energy.

Achieving Ultrahigh Effective Surface Charge Density of Direct-Current Triboelectric Nanogenerator in High Humidity.

As an emerging energy-harvesting technology, the triboelectric nanogenerator (TENG) is considered a powerful driving force toward the new-era of Internet of Things and artificial intelligence, but its output performance is dramatically influenced by environmental humidity. Herein, a direct current TENG (DC-TENG) based on the triboelectrification effect and electrostatic breakdown is reported to address the problem of output attenuation in high humidity environments for the conventional TENGs. It is found that high humidity not only enhances the sliding triboelectrification effect of hydrophobic triboelectric materials, but also promotes the electrostatic breakdown process for DC-TENG, thus contributing to the improvement of DC-TENG output. Furthermore, taking poly(vinyl chloride) film as the friction layer, the effective surface charge density of DC-TENG with microstructure-designed electrode achieves a milestone value of ≈2.97 mC m-2 under 90% relative humidity, which is almost 1.42-fold larger than that under 30% RH. This work not only establishes an effective methodology to boost the output performance of TENG in a high humidity environment, but also establishes a foundation for its practical applications in large-scale energy harvesting.

Waste Carton-Derived Nanocomposites for Efficient Removal of Hexavalent Chromium.

A new nanocomposite (SCZ), microspherical carbon (SC) loaded with nanoscale zerovalent iron (ZVI), was fabricated to efficiently remove hexavalent chromium (Cr(VI)) in water. Therein, SC was derived from waste carton through hydrothermal treatment after pretreatment of removing hemicellulose and lignin, and the optimal hydrothermal conditions (200 °C, hydrothermal time of 12 h) for the preparation of SC were obtained. Subsequently, SC could effectively load ZVI nanoparticles which displayed high dispersion on the surface of SC and in the pores among SC particles owing to steric hindrance effect. The obtained SCZ displayed a high removal efficiency of 100% within 5 h on Cr(VI) (20 mg/L), and the resultant SCZ-Cr could be conveniently separated from water because of its magnetism. Importantly, SCZ could be loaded in cardboard, and the obtained system could serve as a stable filter for removal of Cr(VI) in water. This work provides a cheap and effective method for Cr(VI) removal, which also greatly facilitates the recycling of waste carton.

Synthesis of a Multifunctional Graphene Oxide-Based Magnetic Nanocomposite for Efficient Removal of Cr(VI).

A novel magnetic nanocomposite was synthesized using graphene oxide (GO), polyethylenimine (PEI), and Fe3O4 to removal hexavalent chromium (Cr(VI)) from water and soil. Therein, GO was functionalized with plenty of -NH2 by the modification of PEI through an amidation reaction, and the resulting GO/PEI reacted with FeSO4·7H2O and NaBH4 to obtain RGO/PEI/Fe3O4 (the optimal one is designated as ORPF) through an oxidation-reduction reaction. ORPF could effectively adsorb Cr(VI) through electrostatic attraction, and the adsorbed Cr(VI) ions were partially reduced to trivalent chromium (Cr(III)) with low toxicity by RGO (π electron). Afterward, the resulting ORPF-Cr could be conveniently removed from water with a magnet, achieving the maximum Cr(VI) removal capacity of 266.6 mg/g. Importantly, ORPF, once carried by sponge particles, could efficiently remove Cr(VI) from soil, and the resulting mixture could be facilely collected with a magnet on a filter net. Besides, the leaching experiment suggested that, when supported by filter paper, ORPF was able to decrease the number of leached Cr(VI) ions and meanwhile reduce them to Cr(III). This work provides a promising approach to remediate Cr(VI)-contaminated water and soil using a nanocomposite, which has a huge number of application prospects.

Spontaneously established reverse electric field to enhance the performance of triboelectric nanogenerators via improving Coulombic efficiency.

Mechanical energy harvesting using triboelectric nanogenerators is a highly desirable and sustainable method for the reliable power supply of widely distributed electronics in the new era; however, its practical viability is seriously challenged by the limited performance because of the inevitable side-discharge and low Coulombic-efficiency issues arising from electrostatic breakdown. Here, we report an important progress on these fundamental problems that the spontaneously established reverse electric field between the electrode and triboelectric layer can restrict the side-discharge problem in triboelectric nanogenerators. The demonstration employed by direct-current triboelectric nanogenerators leads to a high Coulombic efficiency (increased from 28.2% to 94.8%) and substantial enhancement of output power. More importantly, we demonstrate this strategy is universal for other mode triboelectric nanogenerators, and a record-high average power density of 6.15 W m-2 Hz-1 is realized. Furthermore, Coulombic efficiency is verified as a new figure-of-merit to quantitatively evaluate the practical performance of triboelectric nanogenerators.

Amniotic Fluid Proteomics Analysis and In Vitro Validation to Identify Potential Biomarkers of Preterm Birth.

This study aimed to investigate the regulation of amniotic fibroblast (AFC) function by vitamin K-dependent protein Z (PROZ) during preterm birth (PTB) and its potential role in adverse pregnancy outcomes. Proteomic samples were collected from amniotic fluid in the second trimester, and AFC were isolated from the amniotic membrane and cultured in vitro. The expression of extracellular and intracellular PROZ in AFC was modulated, and their biological properties and functions were evaluated. Clinical analysis revealed a significant upregulation of PROZ expression in amniotic fluid from preterm pregnant women. In vitro experiments demonstrated that PROZ stimulated AFC migration, enhanced their proliferative capacity, and reduced collagen secretion. Overexpression of PROZ further enhanced cell migration and proliferation, while knockdown of PROZ had the opposite effect. PROZ plays a crucial role in promoting the proliferation and migration of amniotic membrane fibroblasts. Increased PROZ expression in amniotic fluid is associated with the occurrence of PTB. These findings shed light on the potential involvement of PROZ in adverse pregnancy outcomes and provide a basis for further research on its regulatory mechanisms during PTB.

Recent Progress of Advanced Materials for Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) have received intense attention due to their broad application prospects in the new era of internet of things (IoTs) as distributed power sources and self-powered sensors. Advanced materials are vital components for TENGs, which decide their comprehensive performance and application scenarios, opening up the opportunity to develop efficient TENGs and expand their potential applications. In this review, a systematic and comprehensive overview of the advanced materials for TENGs is presented, including materials classifications, fabrication methods, and the properties required for applications. In particular, the triboelectric, friction, and dielectric performance of advanced materials is focused upon and their roles in designing the TENGs are analyzed. The recent progress of advanced materials used in TENGs for mechanical energy harvesting and self-powered sensors is also summarized. Finally, an overview of the emerging challenges, strategies, and opportunities for research and development of advanced materials for TENGs is provided.

MXene Lubricated Tribovoltaic Nanogenerator with High Current Output and Long Lifetime.

Tribovoltaic nanogenerators (TVNGs) have the characteristics of high current density, low matched impedance and continuous output, which is expected to solve the problem of power supply for small electronic devices. However, wear occurrence in friction interface will seriously reduce the performance of TVNGs as well as lifetime. Here, we employ MXene solution as lubricate to improve output current density and lifetime of TVNG simultaneously, where a high value of 754 mA m-2 accompanied with a record durability of 90,000 cycles were achieved. By comparing multiple liquid lubricates with different polarity, we show that conductive polar liquid with MXene as additive plays a crucial role in enhancing the electrical output performance and durability of TVNG. Moreover, the universality of MXene solution is well demonstrated in various TVNGs with Cu and P-type Si, and Cu and N-GaAs as material pairs. This work may guide and accelerates the practical application of TVNG in future.

Contact efficiency optimization for tribovoltaic nanogenerators.

Energy harvesters based on the tribovoltaic effect that can convert mechanical energy into electricity offer a potential solution for the energy supply of decentralized sensors. However, a substantial disparity in output current, exceeding 106 times, exists between micro- and macro-contact tribovoltaic nanogenerators (TVNGs). To tackle this challenge, we develop a quantification method to determine the effective contact efficiency of conventional large-scale TVNGs, revealing a mere 0.038% for a TVNG of 1 cm2. Thus, we implement an optimization strategy by contact interface design resulting in a remarkable 65-fold increase in effective contact efficiency, reaching 2.45%. This enhancement leads to a current density of 23 A m-2 and a record-high charge density of 660 mC m-2 for the TVNG based on Cu and p-type silicon. Our study reveals that increasing the effective contact efficiency will not only address the existing disparities but also have the potential to significantly enhance the output current in future advancements of large-scale TVNGs.

mirTools: microRNA profiling and discovery based on high-throughput sequencing.

miRNAs are small, non-coding RNA that negatively regulate gene expression at post-transcriptional level, which play crucial roles in various physiological and pathological processes, such as development and tumorigenesis. Although deep sequencing technologies have been applied to investigate various small RNA transcriptomes, their computational methods are far away from maturation as compared to microarray-based approaches. In this study, a comprehensive web server mirTools was developed to allow researchers to comprehensively characterize small RNA transcriptome. With the aid of mirTools, users can: (i) filter low-quality reads and 3/5' adapters from raw sequenced data; (ii) align large-scale short reads to the reference genome and explore their length distribution; (iii) classify small RNA candidates into known categories, such as known miRNAs, non-coding RNA, genomic repeats and coding sequences; (iv) provide detailed annotation information for known miRNAs, such as miRNA/miRNA*, absolute/relative reads count and the most abundant tag; (v) predict novel miRNAs that have not been characterized before; and (vi) identify differentially expressed miRNAs between samples based on two different counting strategies: total read tag counts and the most abundant tag counts. We believe that the integration of multiple computational approaches in mirTools will greatly facilitate current microRNA researches in multiple ways. mirTools can be accessed at http://centre.bioinformatics.zj.cn/mirtools/ and http://59.79.168.90/mirtools.

MagicViewer: integrated solution for next-generation sequencing data visualization and genetic variation detection and annotation.

New sequencing technologies, such as Roche 454, ABI SOLiD and Illumina, have been increasingly developed at an astounding pace with the advantages of high throughput, reduced time and cost. To satisfy the impending need for deciphering the large-scale data generated from next-generation sequencing, an integrated software MagicViewer is developed to easily visualize short read mapping, identify and annotate genetic variation based on the reference genome. MagicViewer provides a user-friendly environment in which large-scale short reads can be displayed in a zoomable interface under user-defined color scheme through an operating system-independent manner. Meanwhile, it also holds a versatile computational pipeline for genetic variation detection, filtration, annotation and visualization, providing details of search option, functional classification, subset selection, sequence association and primer design. In conclusion, MagicViewer is a sophisticated assembly visualization and genetic variation annotation tool for next-generation sequencing data, which can be widely used in a variety of sequencing-based researches, including genome re-sequencing and transcriptome studies. MagicViewer is freely available at http://bioinformatics.zj.cn/magicviewer/.

Highly Stable and Eco-friendly Marine Self-Charging Power Systems Composed of Conductive Polymer Supercapacitors with Seawater as an Electrolyte.

A self-charging power system harvesting random and low-frequency wave energy into electricity provides a promising strategy for the construction of smart oceans. However, the system faces huge challenges of easy corrosion in the marine environment and the utilization of toxic organic electrolytes in energy storage devices. To address the issues above, a seawater supercapacitor (SWSC) for the marine self-charging power system is rationally proposed by using a conductive polymer, polypyrrole with hollow morphology (h-PPy), to enhance the stability and capacitance while using seawater as an eco-friendly electrolyte to reduce the cost and achieve sustainability. The hollow design provides a shortcut for the ion transportation of seawater into the h-PPy electrode, and the SWSC achieves a high power density of 4.32 kW kg-1 under an energy density of 5.12 W h kg-1. Even after 180 days in seawater, h-PPy still endows a mass retention of 99.9%, enabling the SWSC to maintain a stability of 99.3% after 6000 cycles. More importantly, when combined with a TENG module as the marine self-charging power system to harvest wave energy, the system provides a stable output in water wave to drive electronics and sensors, which shows a competitive potential in the smart ocean and marine internet of things.

A Self-Powered Dual-Type Signal Vector Sensor for Smart Robotics and Automatic Vehicles.

Automatic control systems are the most efficient technology for reducing labor cost while improving work efficiency. Vector motion monitoring is indispensable for the normal operation of automatic control systems. Here, a self-powered dual-type signal triboelectric nanogenerator (DS-TENG) is designed through integrating an alternating-current TENG and a direct-current TENG, which can monitor vector movement in real time based on pulse signal counts. As a result, the DS-TENG avoids the shortcoming of traditional self-powered sensors based on signal amplitude that is sensitive to the working environment, achieves a high sensing precision, and maintains stability after reciprocating motion of 500 000 cycles. Moreover, it realizes effective movement direction recognition by self-powered switching of signal type in reverse movement. This dual-type signal TENG exhibits high precision and automatic direction recognition in vector motion monitor and trajectory tracker, paving the way for the application of the self-powered TENG sensor in automatic control systems in the future.

Seawater-Based Triboelectric Nanogenerators for Marine Anticorrosion.

The liquid-solid triboelectric nanogenerator is broadly studied for its self-powered sensing and blue energy harvesting, thanks to its low wear and highly efficient contact. However, the corresponding research studies focusing on deionized-water liquid-solid triboelectric nanogenerators (DL-TENGs) and seawater-type liquid-solid TENGs (SL-TENGs) are rarely being carried out at present. Here, a SL-TENG is fabricated by applying a dielectric film as the organic coating and coated and uncoated steel hull as the two electrodes. Based on the reasonable material selection of the dielectric film, the SL-TENG showed excellent performance, which benefits from the good triboelectrification performance and weak ion adsorption effect. In addition, compared with commercial marine anticorrosive coatings, the friction coefficient of the SL-TENG with the seawater can be reduced 43.8%, which is significantly beneficial to reduce the sailing resistance of ships. More importantly, the uncoated steel electrode can obtain a high potential in highly corrosive seawater, which can enable it to perform the function of marine anticorrosive agents. Our finding provides a potential strategy to evade the marine anticorrosion of ships.

A Tuning-Fork Triboelectric Nanogenerator with Frequency Multiplication for Efficient Mechanical Energy Harvesting.

As a new technology for high-entropy energy harvesting, a triboelectric nanogenerator (TENG) has broad applications in sensor networks and internet of things as a power source, but its average power density is limited by the fixed low-frequency output. Here, a frequency-multiplication TENG based on intrinsic high frequency of tuning fork is proposed which enables converting low-frequency mechanical energy into high-frequency electric energy. A tuning-fork TENG is used to systematically study the effects of intrinsic frequency, dielectric's thickness, and gap distance on its electric performance, and a total transferred charges of 4.3 µC and an average power density of 9.42 mW m-2 are realized at the triggering frequency of 0.2 Hz, which are 71 times and 5.7 times than that of the single-cycle output of conventional contact-separation TENG, respectively. Moreover, the crest factor also decreases from 3.5 to around 1.5. Then, a homemade tuning fork-like TENG is reasonably designed for harvesting ambient wind energy, achieving an average power density of 20.02 mW m-2 at a wind speed of 7 m s-1 . Specially, its impedance resistance is independent of the mechanical triggering frequency, simplifying the back-end power management circuit design. Therefore, the frequency-multiplication TENG shows a great potential for efficient distributed energy harvesting.

A Dual-Mode Triboelectric Nanogenerator for Wind Energy Harvesting and Self-Powered Wind Speed Monitoring.

The triboelectric nanogenerator shows a broad application potential in wind energy collection and wind speed sensing. However, it is difficult to realize wind energy collection and real-time wind speed monitoring in one simple device without external power support. Here, a high-performance dual-mode triboelectric nanogenerator is proposed to simultaneously collect wind energy efficiently and monitor wind speed in real time, which is composed by an alternating current triboelectric nanogenerator (AC-TENG) and a direct-current triboelectric nanogenerator (DC-TENG). Based on the material optimization, the charge density of the AC-TENG improves by a factor of 1 compared with previous works. Moreover, benefiting from the elastic structure and material optimization to realize a low friction force, the AC-TENG shows an excellent durability and obtains a retention of 87% electric output after 1 200 000 operation cycles. Meanwhile, thanks to the high charge density and low friction force, the energy-harvesting efficiency of the AC-TENG is doubled. In addition, the DC-TENG not only displays an excellent real-time sensing performance but also can provide gale warning. Our finding exhibits a strategy for efficiently collecting wind energy and achieving fully self-powered and real-time wind speed monitoring.

Self-Powered Seawater Electrolysis Based on a Triboelectric Nanogenerator for Hydrogen Production.

Water splitting for yielding high-purity hydrogen represents the ultimate choice to reduce carbon dioxide emission owing to the superior energy density and zero-pollution emission after combustion. However, the high electricity consumption and requirement of large quantities of pure water impede its large-scale application. Here, a triboelectric nanogenerator (W-TENG) converting offshore wind energy into electricity is proposed for commercial electric energy saving and cost reduction. By introducing PTFE/POM dielectric pairs with matched HOMO/LUMO band gap energy, a high charge density is achieved to promote the output of W-TENG. With the impedance matching design of transformers with the internal resistance of W-TENG, the output current is further enhanced from 1.42 mA to 54.5 mA with a conversion efficiency of more than 92.0%. Furthermore, benefiting from the high electrocatalytic activity (overpotential = 166 mV and Tafel slope = 181.2 mV dec-1) of a carbon paper supported NiCoP-MOF catalyst, natural seawater can be adopted as a resource for in situ hydrogen production without acid or alkaline additives. Therefore, the self-powered seawater electrolysis system achieves a H2 production rate as high as 1273.9 µL min-1 m-2 with a conversion efficiency of 78.9%, demonstrating a more practical strategy for conversion of wind energy into renewable hydrogen energy.

Standardized measurement of dielectric materials' intrinsic triboelectric charge density through the suppression of air breakdown.

Triboelectric charge density and energy density are two crucial factors to assess the output capability of dielectric materials in a triboelectric nanogenerator (TENG). However, they are commonly limited by the breakdown effect, structural parameters, and environmental factors, failing to reflect the intrinsic triboelectric behavior of these materials. Moreover, a standardized strategy for quantifying their maximum values is needed. Here, by circumventing these limitations, we propose a standardized strategy employing a contact-separation TENG for assessing a dielectric material's maximum triboelectric charge and energy densities based on both theoretical analyses and experimental results. We find that a material's vacuum triboelectric charge density can be far higher than previously reported values, reaching a record-high of 1250 µC m-2 between polyvinyl chloride and copper. More importantly, the obtained values for a dielectric material through this method represent its intrinsic properties and correlates with its work function. This study provides a fundamental methodology for quantifying the triboelectric capability of dielectric materials and further highlights TENG's promising applications for energy harvesting.

Triboelectric nanogenerator: from alternating current to direct current.

Triboelectric nanogenerator (TENG) is considered as a potential solution to harvest distributed energy for the sustainable and reliable power supply of the internet of things. Although numerous researches on alternating current (AC) output TENG from fundamental physics to potential applications have been widely promoted in recent years, the studies about direct current (DC) output TENG is just beginning, especially for a constant current output. This work gives the summary of recent key researches from AC-TENG to DC-TENG, especially a constant current TENG, as well as the design of AC/DC-TENG. In addition, some new DC generators will also be summarized toward a wide range of readers. This study presents the similarities and differences between AC-TENG and DC-TENG, so that their impact and uniqueness can be clearly understood. Finally, the major challenges and the future outlooks in this rapidly emerging research field will be discussed as a guideline for future research.

Recent Advances in Self-Powered Electrochemical Systems.

Electrochemistry, one of the most important research and production technology, has been widely applicated in various fields. However, the requirement of external power source is a major challenge to its development. To solve this issue, developing self-powered electrochemical system (SPES) that can work by collecting energy from the environment is highly desired. The invention of triboelectric nanogenerator (TENG), which can transform mechanical energy into electricity, is a promising approach to build SPES by integrating with electrochemistry. In this view, the latest representative achievements of SPES based on TENG are comprehensively reviewed. By harvesting various mechanical energy, five SPESs are built, including electrochemical pollutants treatment, electrochemical synthesis, electrochemical sensor, electrochromic reaction, and anticorrosion system, according to the application domain. Additionally, the perspective for promoting the development of SPES is discussed.