Key Takeaways & Executive Findings
- •• • The device generates 500 mV and 790 pA under 3.47 N compressive force, enabling self-powered operation for wearable sensors without external bias. • • Long-term functionality over 1500 cycles demonstrates mechanical robustness, critical for continuous monitoring in bioelectronics. • • Output power reaches 110.76 pW, sufficient for low-power wearable devices, though higher power density is needed for broader applications. • • HF-free etching ensures biocompatibility and safety, addressing toxicity concerns of conventional HF etching for clinical translation.
China Clean Energy & Battery Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
MXene exhibits notable piezoelectric properties, making it a promising material for high-performance piezoelectric nanogenerators (PENGs) in next-generation smart wearable devices and bioelectronics. However, current MXene-based PENGs face challenges such as insufficient mechanical robustness, low piezoelectric response, and limited long-term functionality. These limitations primarily stem from the small effective area and low strain levels of MXene nanosheets. Here, we constructed a high-entropy TiVCrMoC3Tx MXene composite film by leveraging strong hydrogen bonding interactions between MXene and polyvinyl alcohol (PVA), which was further developed into a self-powered flexible nanogenerator. The resulting device exhibited a significant piezoresponse with output signals of 500 mV and 790 pA under a compressive force of 3.47 N, along with considerable long-term functionality over 1500 cycles. Moreover, a hydrofluoric-free etching approach was employed to synthesize the high-entropy MXene nanosheets, which ensures the safety and biocompatibility for bioelectronics applications. This work highlights the potential of high-entropy MXene for sustainable applications in wearable electronics and energy harvesting.
1. Introduction
MXene, a class of two-dimensional materials, has emerged as a versatile material with exceptional characteristics, including vast surface area, excellent catalytic performance, impressive mechanical properties, high tunability, and notable piezoelectric sensitivity. These attributes have propelled MXene into the spotlight across diverse applications, such as catalysis, sensing technologies, and energy devices. Notably, MXene exhibits strong piezoelectric properties due to the non-centrosymmetric lattice from the multi-atomic lattice structure and tunable functional groups, enabling practical applications in flexible nanogenerators. However, current MXene-based piezoelectric nanogenerators (PENGs) face challenges such as insufficient mechanical robustness, low piezoelectric response, and limited long-term functionality. These limitations primarily stem from the small effective area and low strain levels of MXene nanosheets.
Recently, high-entropy MXenes incorporating multiple transition metallic elements have garnered attention for their superior physiochemical properties compared to their conventional counterparts. The asymmetric interlayer segregation of atoms in high-entropy MXenes underscores their unique electrical behavior, which is crucial for their piezoelectric characteristics. While conventional hydrofluoric acid (HF) etching remains a common method for layered MXene synthesis due to its efficient delamination and high yields, concerns persist regarding safety and environmental impact owing to its corrosiveness and toxicity. Alternatively, HF-free etching routes, such as alkali etching, molten salt etching, and electrochemical etching, offer safer approaches for MXene production. Despite these advancements, achieving piezotronic applications for MXene nanosheets remains challenging due to size limitations and low strain levels. To address this, MXene nanosheets can be engineered into self-supporting thin films through facile methods like vacuum filtration, which could consolidate the exceptional properties of individual MXene nanosheets and enable their development in large-scale and array-based applications. However, their inherent random stacking would undermine stability and strain tolerance under external conditions like mechanical stress, thereby hindering their practical applicability. The MXene films, capable of preserving structural integrity and performance stability, are highly desirable. One effective strategy involves the integration of polymers into MXene matrices through robust interactions, leveraging dynamic covalent or non-covalent bonds to tailor the physical and chemical properties.
Loading authentic research manuscript (Pages 1–5)...
YANG Fumei, CHAN Kam Lin, WU Zehan, ZHAO Fangqing, WONG Man Chung, PANG Sin-Yi, HAO Jianhua (2025). HF-Free Synthesis of High-Entropy MXene-PVA Composite Film and Its Flexible Nanogenerator. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3445-x
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the failure mechanism under cyclic mechanical stress, and how does the device maintain performance over 1500 cycles?
The strong hydrogen bonding between MXene and PVA enhances structural integrity, preventing delamination and random stacking. Over 1500 cycles, the device retains output stability, with no significant degradation in voltage (500 mV) or current (790 pA), indicating robust mechanical resilience.
How does the HF-free etching approach compare in cost and scalability to conventional HF etching for MXene synthesis?
The thermal-assisted electrochemical etching method avoids toxic HF, reducing safety costs and environmental hazards. While exact cost parity data is not provided, the method yields highly crystalline TiVCrMoC3Tx nanosheets, and the process is amenable to scaling, though optimization for mass production is required.
What are the operational thresholds for the nanogenerator in terms of force and output, and how do they align with wearable applications?
Under a compressive force of 3.47 N, the device outputs 500 mV and 790 pA, sufficient for self-powered motion monitoring (e.g., finger bending generates 10 mV and 85 pA). These thresholds are compatible with human motion, but higher force may be needed for certain applications.
What is the power density and efficiency of the MXene/PVA-PENG, and how does it compare to existing piezoelectric nanogenerators?
The output power reaches 110.76 pW, which is modest compared to some PENGs but adequate for low-power sensors. Efficiency is not explicitly quantified, but the self-powered operation and durability over 1500 cycles highlight its potential for continuous wearable monitoring.
How does the biocompatibility of the HF-free MXene-PVA composite film address clinical translation challenges?
The HF-free synthesis eliminates toxic residues, and PVA is biocompatible. The composite film exhibits good flexibility and stability, making it suitable for bioelectronics, though in vivo biocompatibility and long-term implantation studies are still needed.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.