Tuning Electronic Friction in Structural Superlubric Schottky Junctions.

Friction at sliding interfaces, even in the atomistically smooth limit, can proceed through many energy dissipation channels, such as phononic and electronic excitation. These processes are often entangled and difficult to distinguish, eliminate, and control, especially in the presence of wear. Structural superlubricity (SSL) is a wear-free state with ultralow friction that closes most of the dissipation channels, except for electronic friction, which raises a critical concern of how to effectively eliminate and control such a channel.

Loading Mode-Induced Enhancement in Friction for Microscale Graphite/Hexagonal Boron Nitride Heterojunction.

Classical friction laws traditionally assume that the friction between solid pairs remains constant with a given normal load. However, our study has unveiled a remarkable deviation from conventional wisdom. In this paper, we discovered that altering the loading mode of micro graphite flakes led to significant changes in the lateral friction under identical normal loads.

Fully automatic transfer and measurement system for structural superlubric materials.

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.

Architecting Nanostructured Co-BTC@GO Composites for Supercapacitor Electrode Application.

Herein, we present an innovative graphene oxide (GO)-induced strategy for synthesizing GO-based metal-organic-framework composites (Co-BTC@GO) for high-performance supercapacitors. 1,3,5-Benzene tricarboxylic acid (BTC) is used as an inexpensive organic ligand for the synthesis of composites. An optimal GO dosage was ascertained by the combined analysis of morphology characterization and electrochemical measurement.

Effect of Photo-Excitation on Contact Electrification at Liquid-Solid Interface.

Liquid-solid triboelectric nanogenerator (L-S TENG) is one of the major techniques to collect energy from tiny liquids, while the saturated charge density at the L-S interface is the key element to decide its performance. Here, we found that the saturated charge density of L-S contact electrification (CE) can be further increased under the illumination of an ultraviolet (UV) light. The fluorine-containing polymers and SiO are chosen as the electrification materials and with and without UV illumination on the L-S TENG.

Microscale Schottky superlubric generator with high direct-current density and ultralong life.

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).

Self-powered electro-tactile system for virtual tactile experiences.

Tactile sensation plays important roles in virtual reality and augmented reality systems. Here, a self-powered, painless, and highly sensitive electro-tactile (ET) system for achieving virtual tactile experiences is proposed on the basis of triboelectric nanogenerator (TENG) and ET interface formed of ball-shaped electrode array. Electrostatic discharge triggered by TENG can induce notable ET stimulation, while controlled distance between the ET electrodes and human skin can regulate the induced discharge current.

A Self-Powered Angle Sensor at Nanoradian-Resolution for Robotic Arms and Personalized Medicare.

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.

Probing Contact-Electrification-Induced Electron and Ion Transfers at a Liquid-Solid Interface.

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.

Dual-Stimulus Smart Actuator and Robot Hand Based on a Vapor-Responsive PDMS Film and Triboelectric Nanogenerator.

Intelligent actuating materials with vapor-stimulated mechanical response usually require complicated synthesizing processes or have a high cost. Here, we found that the UV/O-modified poly(dimethylsiloxane) PDMS) film can show spontaneous curling deformation when it encounters small alcohol molecules such as ethanol vapor. Based on the coupling of the vapor-responsive PDMS film and triboelectric nanogenerator (TENG), a flexible actuator for object transport and a double-finger gripper for loading small objects are designed.

Power generation from the interaction of a liquid droplet and a liquid membrane.

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.

Self-Powered Intracellular Drug Delivery by a Biomechanical Energy-Driven Triboelectric Nanogenerator.

Nondestructive, high-efficiency, and on-demand intracellular drug/biomacromolecule delivery for therapeutic purposes remains a great challenge. Herein, a biomechanical-energy-powered triboelectric nanogenerator (TENG)-driven electroporation system is developed for intracellular drug delivery with high efficiency and minimal cell damage in vitro and in vivo. In the integrated system, a self-powered TENG as a stable voltage pulse source triggers the increase of plasma membrane potential and membrane permeability.

Environmental Energy Harvesting Adapting to Different Weather Conditions and Self-Powered Vapor Sensor Based on Humidity-Responsive Triboelectric Nanogenerators.

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.

Stretchable VO/PEDOT supercapacitors: a modular fabrication process and charging with triboelectric nanogenerators.

Stretchable energy storage devices are of great importance for the viable applications of wearable/stretchable electronics. Studies on stretchable energy storage devices, especially supercapacitors (SCs), have shown encouraging progress. However, challenges still remain in the pursuit of high specific capacitances and facile fabrication methods.

Stretchable Triboelectric-Photonic Smart Skin for Tactile and Gesture Sensing.

Smart skin is expected to be stretchable and tactile for bionic robots as the medium with the ambient environment. Here, a stretchable triboelectric-photonic smart skin (STPS) is reported that enables multidimensional tactile and gesture sensing for a robotic hand. With a grating-structured metal film as the bioinspired skin stripe, the STPS exhibits a tunable aggregation-induced emission in a lateral tensile range of 0-160%.

Self-Powered Electrostatic Adsorption Face Mask Based on a Triboelectric Nanogenerator.

The physical filtration mechanism of a traditional face mask has a low removal efficiency of ultrafine particulates in the size range of 10-1000 nm, which are badly harmful to human health. Herein, a novel self-powered electrostatic adsorption face mask (SEA-FM) based on the poly(vinylidene fluoride) electrospun nanofiber film (PVDF-ESNF) and a triboelectric nanogenerator (TENG) driven by respiration (R-TENG) is developed. The ultrafine particulates are electrostatically adsorbed by the PVDF-ESNF, and the R-TENG can continually provide electrostatic charges in this adsorption process by respiration.

Self-Powered Microfluidic Transport System Based on Triboelectric Nanogenerator and Electrowetting Technique.

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.

Self-Powered Electrostatic Filter with Enhanced Photocatalytic Degradation of Formaldehyde Based on Built-in Triboelectric Nanogenerators.

Recently, atmospheric pollution caused by particulate matter or volatile organic compounds (VOCs) has become a serious issue to threaten human health. Consequently, it is highly desirable to develop an efficient purifying technique with simple structure and low cost. In this study, by combining a triboelectric nanogenerator (TENG) and a photocatalysis technique, we demonstrated a concept of a self-powered filtering method for removing pollutants from indoor atmosphere.

A Nanostructured Molybdenum Disulfide Film for Promoting Neural Stem Cell Neuronal Differentiation: toward a Nerve Tissue-Engineered 3D Scaffold.

Physical cues from nanostructured biomaterials have been shown to possess regulating effects on stem cell fate. In this study, nanostructured molybdenum disulfide (MoS ) thin films (MTFs) are prepared by assembling MoS nanosheets on a flat substrate. These films are used as a new biocompatible platform for promoting neural stem cell (NSC) differentiation.