Phase-Directed Assembly of Triboelectric Nanopaper for Self-Powered Noncontact Sensing.

Noncontact sensing technology serves as a pivotal medium for seamless data acquisition and intelligent perception in the era of the Internet of Things (IoT), bringing innovative interactive experiences to wearable human-machine interaction perception networks. However, the pervasive limitations of current noncontact sensing devices posed by harsh environmental conditions hinder the precision and stability of signals. In this study, the triboelectric nanopaper prepared by a phase-directed assembly strategy is presented, which possesses low charge transfer mobility (1618 cm2 V-1 s-1) and exceptional high-temperature stability. Wearable self-powered noncontact sensors constructed from triboelectric nanopaper operate stably under high temperatures (200 °C). Furthermore, a temperature warning system for workers in hazardous environments is demonstrated, capable of nonintrusively identifying harmful thermal stimuli and detecting motion status. This research not only establishes a technological foundation for accurate and stable noncontact sensing under high temperatures but also promotes the sustainable intelligent development of wearable IoT devices under extreme environments.

Gel-Based Triboelectric Nanogenerators for Flexible Sensing: Principles, Properties, and Applications.

The rapid development of the Internet of Things and artificial intelligence technologies has increased the need for wearable, portable, and self-powered flexible sensing devices. Triboelectric nanogenerators (TENGs) based on gel materials (with excellent conductivity, mechanical tunability, environmental adaptability, and biocompatibility) are considered an advanced approach for developing a new generation of flexible sensors. This review comprehensively summarizes the recent advances in gel-based TENGs for flexible sensors, covering their principles, properties, and applications. Based on the development requirements for flexible sensors, the working mechanism of gel-based TENGs and the characteristic advantages of gels are introduced. Design strategies for the performance optimization of hydrogel-, organogel-, and aerogel-based TENGs are systematically summarized. In addition, the applications of gel-based TENGs in human motion sensing, tactile sensing, health monitoring, environmental monitoring, human-machine interaction, and other related fields are summarized. Finally, the challenges of gel-based TENGs for flexible sensing are discussed, and feasible strategies are proposed to guide future research.

Directional Moisture-Wicking Triboelectric Materials Enabled by Laplace Pressure Differences.

Wearable sensors are experiencing vibrant growth in the fields of health monitoring systems and human motion detection, with comfort becoming a significant research direction for wearable sensing devices. However, the weak moisture-wicking capability of sensor materials leads to liquid retention, severely restricting the comfort of the wearable sensors. This study employs a pattern-guided alignment strategy to construct microhill arrays, endowing triboelectric materials with directional moisture-wicking capability. Within 2.25 s, triboelectric materials can quickly and directionally remove the droplets, driven by the Laplace pressure differences and the wettability gradient. The directional moisture-wicking triboelectric materials exhibit excellent pressure sensing performance, enabling rapid response/recovery (29.1/37.0 ms), thereby achieving real-time online monitoring of human respiration and movement states. This work addresses the long-standing challenge of insufficient moisture-wicking driving force in flexible electronic sensing materials, holding significant implications for enhancing the comfort and application potential of electronic skin and wearable electronic devices.

Compliant Iontronic Triboelectric Gels with Phase-Locked Structure Enabled by Competitive Hydrogen Bonding.

Rapid advancements in flexible electronics technology propel soft tactile sensing devices toward high-level biointegration, even attaining tactile perception capabilities surpassing human skin. However, the inherent mechanical mismatch resulting from deficient biomimetic mechanical properties of sensing materials poses a challenge to the application of wearable tactile sensing devices in human-machine interaction. Inspired by the innate biphasic structure of human subcutaneous tissue, this study discloses a skin-compliant wearable iontronic triboelectric gel via phase separation induced by competitive hydrogen bonding. Solvent-nonsolvent interactions are used to construct competitive hydrogen bonding systems to trigger phase separation, and the resulting soft-hard alternating phase-locked structure confers the iontronic triboelectric gel with Young's modulus (6.8-281.9 kPa) and high tensile properties (880%) compatible with human skin. The abundance of reactive hydroxyl groups gives the gel excellent tribopositive and self-adhesive properties (peel strength > 70 N m-1). The self-powered tactile sensing skin based on this gel maintains favorable interface and mechanical stability with the working object, which greatly ensures the high fidelity and reliability of soft tactile sensing signals. This strategy, enabling skin-compliant design and broad dynamic tunability of the mechanical properties of sensing materials, presents a universal platform for broad applications from soft robots to wearable electronics.

High Strength and Toughness Polymeric Triboelectric Materials Enabled by Dense Crystal-Domain Cross-Linking.

Lightweight, easily processed, and durable polymeric materials play a crucial role in wearable sensor devices. However, achieving simultaneously high strength and toughness remains a challenge. This study addresses this by utilizing an ion-specific effect to control crystalline domains, enabling the fabrication of a polymeric triboelectric material with tunable mechanical properties. The dense crystal-domain cross-linking enhances energy dissipation, resulting in a material boasting both high tensile strength (58.0 MPa) and toughness (198.8 MJ m-3), alongside a remarkable 416.7% fracture elongation and 545.0 MPa modulus. Leveraging these properties, the material is successfully integrated into wearable self-powered devices, enabling real-time feedback on human joint movement. This work presents a valuable strategy for overcoming the strength-toughness trade-off in polymeric materials, paving the way for their enhanced applicability and broader use in diverse sensing applications.

Lightweight and Strong Cellulosic Triboelectric Materials Enabled by Cell Wall Nanoengineering.

As intelligent technology surges forward, wearable electronics have emerged as versatile tools for monitoring health and sensing our surroundings. Among these advancements, porous triboelectric materials have garnered significant attention for their lightness. However, these materials face the challenge of improving structural stability to further enhance the sensing accuracy of triboelectric sensors. In this study, a lightweight and strong porous cellulosic triboelectric material is designed by cell wall nanoengineering. By tailoring of the cell wall structure, the material shows a high mechanical strength of 51.8 MPa. The self-powered sensor constructed by this material has a high sensitivity of 33.61 kPa-1, a fast response time of 36 ms, and excellent pressure detection durability. Notably, the sensor still enables a high sensing performance after the porous cellulosic triboelectric material exposure to 200 °C and achieves real-time feedback of human motion, thereby demonstrating great potential in the field of wearable electronic devices.

A Tough Monolithic-Integrated Triboelectric Bioplastic Enabled by Dynamic Covalent Chemistry.

Electronic waste is a growing threat to the global environment and human health, raising particular concerns. Triboelectric devices synthesized from sustainable and degradable materials are a promising electronic alternative, but the mechanical mismatch at the interface between the polymer substrate and the electrodes remains unresolved in practical applications. This study uses the sulfhydryl silanization reaction and the chemical selectivity and site specificity of the thiol-disulfide exchange reaction in dynamic covalent chemistry to prepare a tough monolithic-integrated triboelectric bioplastic. The stress is dissipated by covalent bond adaptation to the interface interaction, which makes the polymer dielectric layer to the conductive layer have a good interface adhesion effect (220.55 kPa). The interfacial interlocking of the polymer substrate with the conductive layer gives the triboelectric bioplastic excellent tensile strength (87.4 MPa) and fracture toughness (33.3 MJ m-3). Even when subjected to a tension force of 10 000 times its weight, it still maintains a stable triboelectric output with no visible cracks. This study provides new insights into the design of reliable and environmentally friendly self-powered devices, which is significant for the development of flexible wearable electronics.

Dynamic Thermostable Cellulosic Triboelectric Materials from Multilevel-Non-Covalent Interactions.

Triboelectric materials present great potential for harvesting huge amounts of dispersed energy, and converting them directly into useful electricity, a process that generates power more sustainably. Triboelectric nanogenerators (TENGs) have emerged as a technology to power electronics and sensors, and it is expected to solve the problem of energy harvesting and self-powered sensing from extreme environments. In this paper, a high-temperature-resistant triboelectric material is designed based on multilevel non-covalent bonding interactions, which achieves an ultra-high surface charge density of 192 µC m-2 at high temperatures. TENGs based on the triboelectric material exhibit more than an order of magnitude higher power output (2750 mW m-2 at 200 °C) than the existing devices at high temperatures. These remarkable properties are achieved based on enthalpy-driven molecular assembly in highly unbonded states. Thus, the material maintains bond strength and ultra-high surface charge density in entropy-dominated high-temperature environments. This molecular design concept points out a promising direction for the preparation of polymers with excellent triboelectric properties.

Bioinspired asymmetric amphiphilic surface for triboelectric enhanced efficient water harvesting.

The effective acquisition of clean water from atmospheric water offers a potential sustainable solution for increasing global water and energy shortages. In this study, an asymmetric amphiphilic surface incorporating self-driven triboelectric adsorption was developed to obtain clean water from the atmosphere. Inspired by cactus spines and beetle elytra, the asymmetric amphiphilic surface was constructed by synthesizing amphiphilic cellulose ester coatings followed by coating on laser-engraved spines of fluorinated ethylene propylene. Notably, the spontaneous interfacial triboelectric charge between the droplet and the collector was exploited for electrostatic adsorption. Additionally, the droplet triboelectric nanogenerator converts the mechanical energy generated by droplets falling into electrical energy through the volume effect, achieving an excellent output performance, and further enhancing the electrostatic adsorption by means of external charges, which achieved a water harvesting efficiency of 93.18 kg/m2 h. This strategy provides insights for the design of water harvesting system.

Fabrication of Lignin-Based Nano Carbon Film-Copper Foil Composite with Enhanced Thermal Conductivity.

Technical lignin from pulping, an aromatic polymer with ~59% carbon content, was employed to develop novel lignin-based nano carbon thin film (LCF)-copper foil composite films for thermal management applications. A highly graphitized, nanoscale LCF (~80-100 nm in thickness) was successfully deposited on both sides of copper foil by spin coating followed by annealing treatment at 1000 °C in an argon atmosphere. The conditions of annealing significantly impacted the morphology and graphitization of LCF and the thermal conductivity of LCF-copper foil composite films. The LCF-modified copper foil exhibited an enhanced thermal conductivity of 478 W m-1 K-1 at 333 K, which was 43% higher than the copper foil counterpart. The enhanced thermal conductivity of the composite films compared with that of the copper foil was characterized by thermal infrared imaging. The thermal properties of the copper foil enhanced by LCF reveals its potential applications in the thermal management of advanced electronic products and highlights the potential high-value utility of lignin, the waste of pulping.

Solar light induced synthesis of silver nanoparticles by using lignin as a reductant, and their application to ultrasensitive spectrophotometric determination of mercury(II).

Lignin nanoparticles (LNPs) were employed as the reducing and stabilizing agent in the preparation of silver nanoparticles (Ag NPs) from silver nitrate under solar light. The Ag NPs were characterized by spectrophotometry, TEM, HRTEM, element mapping, XRD and XPS. The formation of Ag NPs and the structural changes of lignin during the reaction was monitored by analysis via 31P NMR, 1H NMR and 13C NMR. The Ag NPs have uniform shape and an average size of ~14 nm. They were loaded onto the surface of LNPs and entangled in lignin. The resulting Ag NP-LNP suspension displays an ultrasensitive and selective optical response to Hg (II) in giving a color change from yellow to colorless. The assay was performed by spectrophotometry at 450 nm. The analytically useful range extends from 5 nM to 100 nM of Hg (II), and the limit of detection is 1.4 nM in deionized water and 1.8 nM in spiked tap water. This is lower than the threshold level (10 nM) in drinking water specified by the US Environmental Protection Agency. Graphical abstract Schematic representation of the solar light induced synthesis of sliver nanoparticles (Ag NPs) by lignin nanoparticles (LNPs) and their application to colorimetric determination of Hg2+.