Fabrication of Advanced Cellulosic Triboelectric Materials via Dielectric Modulation

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.

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.

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.

The development of nanocarriers for natural products

Natural bioactive compounds from plants exhibit substantial pharmacological potency and therapeutic value. However, the development of most plant bioactive compounds is hindered by low solubility and instability. Conventional pharmaceutical forms, such as tablets and capsules, only partially overcome these limitations, restricting their efficacy. With the recent development of nanotechnology, nanocarriers can enhance the bioavailability, stability, and precise intracellular transport of plant bioactive compounds. Researchers are increasingly integrating nanocarrier-based drug delivery systems (NDDS) into the development of natural plant compounds with significant success. Moreover, natural products benefit from nanotechnological enhancement and contribute to the innovation and optimization of nanocarriers via self-assembly, grafting modifications, and biomimetic designs. This review aims to elucidate the collaborative and reciprocal advancement achieved by integrating nanocarriers with botanical products, such as bioactive compounds, polysaccharides, proteins, and extracellular vesicles. This review underscores the salient challenges in nanomedicine, encompassing long-term safety evaluations of nanomedicine formulations, precise targeting mechanisms, biodistribution complexities, and hurdles in clinical translation. Further, this study provides new perspectives to leverage nanotechnology in promoting the development and optimization of natural plant products for nanomedical applications and guiding the progression of NDDS toward enhanced efficiency, precision, and safety. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Advanced Triboelectric Applications of Biomass-Derived Materials: A Comprehensive Review

The utilization of triboelectric materials has gained considerable attention in recent years, offering a sustainable approach to energy harvesting and sensing technologies. Biomass-derived materials, owing to their abundance, renewability, and biocompatibility, offer promising avenues for enhancing the performance and versatility of triboelectric devices. This paper explores the synthesis and characterization of biomass-derived materials, their integration into triboelectric nanogenerators (TENGs), and their applications in energy harvesting, self-powered sensors, and environmental monitoring. This review presents an overview of the emerging field of advanced triboelectric applications that utilize the unique properties of biomass-derived materials. Additionally, it addresses the challenges and opportunities in employing biomass-derived materials for triboelectric applications, emphasizing the potential for sustainable and eco-friendly energy solutions.

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.

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.

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.

Tribovoltaic Effect: Origin, Interface, Characteristic, Mechanism & Application

Tribovoltaic effect is a phenomenon of the generation of direct voltage and current by the mechanical friction on semiconductor interface, which exhibits a brand-new energy conversion mechanism by the coupling of semiconductor and triboelectrification. Here, the origin, interfaces, characteristics, mechanism, coupling effect and application of the tribovoltaic effect is summarized and reviewed. The tribovoltaic effect is first proposed in 2019, which has developed in various forms tribovoltaic nanogenerator (TVNG) including metal-semiconductor, metal-insulator-semiconductor, semiconductor-semiconductor, liquid-solid and flexible interfaces. Compared with triboelectric nanogenerator, the TVNG has the characteristics of direct-current, high current density (mA-A cm-2) and low impedance (Ω-kΩ). The two mainstream views on the tribovoltaic generation mechanism, one dominated by built-in electric fields and the other dominated by interface electric fields, have been elaborated and summarized in detail. The tribo-photovoltaic effect and tribo-thermoelectric effect are also discovered and introduced because they can easily interact with other multi-physical field effects. The TVNGs are suitable for making energy harvesting and self-powered sensing devices for micro-nano energy applications. This paper not only revisit the development of the tribovoltaic effect, but also makes prospects for mechanism research, device fabrication and integrated application, which can accelerate the evolution of smart wearable electronics and intelligent industrial components.

Adsorbents prepared from epoxy-based porous materials of microcrystalline cellulose for excellent adsorption of anionic and cationic dyes

It reported a porous material prepared from microcrystalline cellulose (MCC), to achieve rapid preparation of adsorbents. The porous material was characterized by several tools including 1H NMR, FTIR, XPS, and SEM. Two adsorbents were prepared and subjected to adsorption experiments. Dye adsorption experiments show that the adsorption driving is electrostatic interactions and the process is chemisorption. The maximum capacity of Microcrystalline cellulose-g-Poly (glycidyl methacrylate)-Tannins (MPT) reached 191.3 (Methylene blue), 123.7 mg g-1 (Rhodamine B), and Microcrystalline cellulose-g-Poly (glycidyl methacrylate)-Lysine (MPL) attained 425.8 (Methylene blue), 480.7 mg g-1 (Methyl orange). The results were followed the pseudo-second-order (PSO) and agreed with the Langmuir fit model. Adsorption-desorption cycling experiments further indicate that the adsorbent possesses outstanding reproducibility. At last, epoxidized bio-porous materials are positive in the preparation of dye adsorbents with critical adsorption properties.

The Recent Advances of Polymer-POSS Nanocomposites With Low Dielectric Constant

This study provides a comprehensive overview of the preparation methods for polyhedral oligomeric silsesquioxane (POSS) monomers and polymer/POSS nanocomposites. It focuses on the latest advancements in using POSS to design polymer nanocomposites with reduced dielectric constants. The study emphasizes exploring the potential of POSS, either alone or in combination with other materials, to decrease the dielectric constant and dielectric loss of various polymers, including polyimides, bismaleimide resins, poly(aryl ether)s, polybenzoxazines, benzocyclobutene resins, polyolefins, cyanate ester resins, and epoxy resins. In addition, the research investigates the impact of incorporating POSS on improving the thermal properties, mechanical properties, surface properties, and other aspects of these polymers. The entire study is divided into two parts, discussing systematically the role of POSS in reducing dielectric constants during the preparation of POSS composites using both physical blending and chemical synthesis methods. The goal of this research is to provide valuable strategies for designing a new generation of low dielectric constant materials suitable for large-scale integrated circuits in the semiconductor materials domain.

Strategies to Improve the Output Performance of Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) can collect and convert random mechanical energy into electric energy, with remarkable advantages including broadly available materials, straightforward preparation, and multiple applications. Over the years, researchers have made substantial advancements in the theoretical and practical aspects of TENG. Nevertheless, the pivotal challenge in realizing full applications of TENG lies in ensuring that the generated output meets the specific application requirements. Consequently, substantial research is dedicated to exploring methods and mechanisms for enhancing the output performance of TENG devices. This review aims to comprehensively examine the influencing factors and corresponding improvement strategies of the output performance based on the contact electrification mechanism and operational principles that underlie TENG technology. This review primarily delves into five key areas of improvement: materials selection, surface modification, component adjustments, structural optimization, and electrode enhancements. These aspects are crucial in tailoring TENG devices to meet the desired performance metrics for various applications.

Bulk Schottky Junctions-Based Flexible Triboelectric Nanogenerators to Power Backscatter Communications in Green 6G Networks

This work introduces a novel method to construct Schottky junctions to boost the output performance of triboelectric nanogenerators (TENGs). Perovskite barium zirconium titanate (BZT) core/metal silver shell nanoparticles are synthesized to be embedded into electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofibers before they are used as tribo-negative layers. The output power of TENGs with composite fiber mat exhibited >600% increase compared to that with neat polymer fiber mat. The best TENG achieved 1339 V in open-circuit voltage, 40 µA in short-circuit current and 47.9 W m-2 in power density. The Schottky junctions increased charge carrier density in tribo-layers, ensuring a high charge transfer rate while keeping the content of conductive fillers low, thus avoiding charge loss and improving performance. These TENGs are utilized to power radio frequency identification (RFID) tags for backscatter communication (BackCom) systems, enabling ultra-massive connectivity in the 6G wireless networks and reducing information communications technology systems' carbon footprint. Specifically, TENGs are used to provide an additional energy source to the passive tags. Results show that TENGs can boost power for BackCom and increase the communication range by 386%. This timely contribution offers a novel route for sustainable 6G applications by exploiting the expanded communication range of BackCom tags.

The Modification of Activated Carbon for the Performance Enhancement of a Natural-Rubber-Based Triboelectric Nanogenerator

Increasing energy demands and growing environmental concerns regarding the consumption of fossil fuels are important motivations for the development of clean and sustainable energy sources. A triboelectric nanogenerator (TENG) is a promising energy technology that harnesses mechanical energy from the ambient environment by converting it into electrical energy. In this work, the enhancement of the energy conversion performance of a natural rubber (NR)-based TENG has been proposed by using modified activated carbon (AC). The effect of surface modification techniques, including acid treatments and plasma treatment for AC material on TENG performance, are investigated. The TENG fabricated from the NR incorporated with the modified AC using N2 plasma showed superior electrical output performance, which was attributed to the modification by N2 plasma introducing changes in the surface chemistry of AC, leading to the improved dielectric property of the NR-AC composite, which contributes to the enhanced triboelectric charge density. The highest power density of 2.65 mW/m2 was obtained from the NR-AC (N2 plasma-treated) TENG. This research provides a key insight into the modification of AC for the development of TENG with high energy conversion performance that could be useful for other future applications such as PM2.5 removal or CO2 capture.

Biomaterial-Based Biomimetic Visual Sensors: Inkjet Patterning of Bacteriorhodopsin

Biomimetic visual sensors utilizing bacteriorhodopsin (bR) were fabricated by using an inkjet method. The inkjet printer facilitated the jetting of the bR suspension, allowing for the deposition of bR films. The resulting inkjet-printed bR film exhibited time-differential photocurrent response characteristics similar to those of a dip-coated bR film. By adjusting the number of printed bR film layers, the intensity of the photocurrent could be easily controlled. Moreover, the inkjet printing technique enabled unconstrained patterning, facilitating the design of various visual information processing functions, such as visual filters. In this study, we successfully fabricated two visual filters, namely, a two-dimensional Difference of Gaussian (DOG) filter and a Gabor filter. The printed DOG filter demonstrated edge detection capabilities corresponding to contour recognition in visual receptive fields. On the other hand, the printed Gabor filter proved effective in detecting objects of specific sizes as well as their motion and orientation. The integration of bR and the inkjet method holds significant potential for the widespread implementation of highly functional biomaterial-based visual sensors. These sensors have the capability to provide real-time visual information while operating in an energy-efficient manner.

Recent developments in nanocellulose-based aerogels as air filters: A review

Today, one of the world's critical environmental issues is air pollution, which is the most important parameter threatening human health and the environment. Synthetic polymers are widely used in industrial air filter production; however, they are incompatible with the environment due to their secondary pollution. Using renewable materials to manufacture air filters is not only environmentally friendly but also essential. Recently, a new generation of biopolymers called cellulose nanofiber (CNF)-based hydrogels have been proposed, with three dimensional (3D) nanofiber networks and unique physical and mechanical properties. CNFs have become a hot research topic for application as air filter materials because they can compete with synthetic nanofibers due to their advantages, such as abundant, renewable, nontoxic, high specific surface area, high reactivity, flexibility, low cost, low density, and network structure formation. The main focus of the current review is the recent progress in the preparation and employment of nanocellulose materials, especially CNF-based hydrogels, to absorb PM and CO2. This study summarizes the preparation methods, modification strategies, fabrications, and further applications of CNF-based aerogels as air filters. Lastly, challenges in the fabrication of CNFs, and trends for future developments are presented.

Biodegradable Electroactive Nanofibrous Air Filters for Long-Term Respiratory Healthcare and Self-Powered Monitoring

The concept of triboelectric nanogenerator (TENG)-based fibrous air filters, in which the electroactive fibers are ready to enhance the electrostatic adsorption by sustainable energy harvesting, is appealing for long-term respiratory protection and in vivo real-time monitoring. This effort discloses a self-reinforcing electroactivity strategy to confer extreme alignment and refinement of the electrospun poly(lactic acid) (PLA) nanofibers, significantly facilitating formation of electroactive phases (i.e., β-phase and highly aligned chains and dipoles) and promotion of polarization and electret properties. It endowed the PLA nanofibrous membranes (NFMs) with largely increased surface potential and filtration performance, as exemplified by efficient removal of PM0.3 and PM2.5 (90.68 and 99.82%, respectively) even at the highest airflow capacity of 85 L/min. With high electroactivity and a well-controlled morphology, the PLA NFMs exhibited superior TENG properties triggered by regular respiratory vibrations, enabling 9.21-fold increase of surface potential (-1.43 kV) and nearly 68% increase of PM0.3 capturing (94.3%) compared to those of conventional PLA membranes. The remarkable TENG mechanisms were examined to elaborately monitor the personal respiration characteristics, particularly those triggered large and rapid variations of output voltages like coughing and tachypnea. Featuring desirable biocompatibility and degradability, the self-powered PLA NFMs permit promising applications in the fabrication of ecofriendly air filters toward high-performance purification and intelligent monitoring.

Electroactive, Antibacterial, and Biodegradable Poly(lactic acid) Nanofibrous Air Filters for Healthcare

Poly(lactic acid) (PLA)-based nanofibrous membranes (NFMs) hold great potential in the field of biodegradable filters for air purification but are largely limited by the relatively low electret properties and high susceptibility to bacteria. Herein, we disclosed a facile approach to the fabrication of electroactive and antibacterial PLA NFMs impregnated with a highly dielectric photocatalyst. In particular, the microwave-assisted doping (MAD) protocol was employed to yield Zn-doped titanium dioxide (Zn-TIO), featuring the well-defined anatase phase, a uniform size of ∼65 nm, and decreased band gap (3.0 eV). The incorporation of Zn-TIO (2, 6, and 10 wt %) into PLA gave rise to a significant refinement of the electrospun nanofibers, decreasing from the highest diameter of 581 nm for pure PLA to the lowest value of 264 nm. More importantly, dramatical improvements in the dielectric constants, surface potential, and electret properties were simultaneously achieved for the composite NFMs, as exemplified by a nearly 94% increase in surface potential for 3-day-aged PLA/Zn-TIO (90/10) compared with that of pure PLA. The well regulation of morphological features and promotion of electroactivity contributed to a distinct increase in the air filtration performance, as demonstrated by 98.7% filtration of PM_0.3 with the highest quality factor of 0.032 Pa^-1 at the airflow velocity of 32 L/min for PLA/Zn-TIO (94/6), largely surpassing pure PLA (89.4%, 0.011 Pa^-1). Benefiting from the effective generation of reactive radicals and gradual release of Zn²⁺ by Zn-TIO, the electroactive PLA NFMs were ready to profoundly inactivate Escherichia coli and Staphylococcus epidermidis. The exceptional combination of remarkable electret properties and excellent antibacterial performance makes the PLA membrane filters promising for healthcare.