Key Takeaways & Executive Findings
- •• • Two-step solvent displacement (glycerol then water) boosts output current by over 100 times compared to pure PVA hydrogel and PVA-Gly organohydrogel, achieving power density increases up to two orders of magnitude. • • The treated MEGs demonstrate enhanced long-term durability, with glycerol improving water retention capacity, addressing the instability issue of hydrogels in ambient conditions. • • As a self-powered respiratory sensor, the MEG exhibits frequency-dependent response times (0.23–1.15 s) and recovery times (0.33–1.83 s) across breathing rates of 0.24–1.4 Hz, enabling precise monitoring. • • The MEG functions as a non-contact humidity sensor, showing significant relative current changes when a bare finger approaches, but negligible response with a nitrile-gloved finger, confirming moisture-specific detection.
Abstract
Hydrogels, with their hydrophilicity, flexibility, and environmental friendliness, are highly desirable for moisture-electric generators (MEGs) that harness ubiquitous moisture to generate electrical energy. As the active material layer in MEGs, hydrogels play a crucial role in absorbing atmospheric moisture and converting chemical potential energy into electricity. However, the relatively low output current of the device and the instability of hydrogels pose challenges to the development of high-performance hydrogel-based MEGs. Herein, we introduce a straightforward, feasible, cost-effective, and versatile two-step solvent displacement strategy to overcome the barrier associated with the development of MEGs. Through tunable solvent interactions of glycerol and water, the moisture absorption capability and stability of the hydrogel can be improved, while promoting favorable ion migration. Such an effective processing route not only significantly boosts the output performances but also greatly improves the long-term durability of hydrogel-based MEGs. Notably, the current output and power density of the treated MEGs can increase by up to two orders of magnitude. The mechanisms behind the intriguing observation are investigated by various characterizations and theoretical calculations. This universal strategy holds promise to be extended to various hydrogel-based MEGs. Moreover, the MEGs can be used for energy harvesting, self-powered respiratory monitoring, and non-contact humidity detection. This work offers new opportunities for advancing green energy and self-powered technologies.
1. Introduction
Moisture-electric generators (MEGs) offer a promising route for sustainable energy harvesting from ambient humidity, yet their commercial viability is hindered by low output currents and material instability. Conventional MEGs based on carbon or metal oxides suffer from intermittent signals and complex fabrication, while hydrogel-based systems, despite their high water uptake and ion transport, often deliver insufficient power and degrade rapidly under operational conditions. The central bottleneck lies in balancing moisture absorption, ion mobility, and structural integrity within the active layer.
This work introduces a two-step solvent displacement strategy—sequential immersion in glycerol and water—that directly addresses these limitations. By tuning solvent interactions, the approach simultaneously enhances moisture uptake, promotes ion dissociation and migration, and improves water retention, leading to a dramatic increase in output current and power density by up to two orders of magnitude. This universal method, demonstrated on PVA and CA/PAAm hydrogels, not only boosts performance but also extends service lifetime, offering a practical pathway for high-performance, durable MEGs suitable for self-powered sensing applications.
Loading authentic research manuscript (Pages 1–5)...
Xingyi Dai, Jiaxin Han, Yifei Zhao, Weng Fu Io, Xuyang Zhang, Biqin Dong, Long-Biao Huang, Jianhua Hao (2026). Boosting Output Performance in Hydrogel-Based Moisture-Electric Generators via Tunable Solvent Interactions. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4007-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 maximum output current and power density achieved after the two-step solvent displacement, and how does it compare to untreated hydrogels?
The treated PVA hydrogel MEG exhibited more than 100 times higher output current than pure PVA hydrogel and PVA-Gly organohydrogel. Power density increases up to two orders of magnitude were observed, though exact absolute values are not specified in the provided text.
How does the two-step solvent displacement affect the long-term operational stability of the hydrogel-based MEGs?
The treatment significantly improves long-term durability. Glycerol enhances water retention capacity, preventing dehydration and maintaining ionic conductivity over extended periods. The CA/PAAm-Gly-H2O system demonstrated superior overall performance with high output and long service life compared to untreated counterparts.
What are the response and recovery times of the MEG when used as a respiratory sensor at different breathing rates?
At breathing frequencies of 0.35, 0.24, and 1.4 Hz, the sensor exhibits response times of 0.71, 1.15, and 0.23 s, respectively, and recovery times of 1.28, 1.83, and 0.33 s. These frequency-dependent dynamics enable accurate monitoring of respiratory patterns.
Can the MEG distinguish between moisture and other environmental stimuli, such as temperature or mechanical contact?
The MEG shows selective response to moisture. In non-contact humidity sensing, a bare finger approaching causes a significant relative current change, while a nitrile-gloved finger produces almost no change, confirming that the response is moisture-driven rather than due to thermal or proximity effects.
Is the two-step solvent displacement strategy applicable to other hydrogel systems beyond PVA and CA/PAAm?
The authors claim the strategy is universal and holds promise for extension to various hydrogel-based MEGs. The mechanism—glycerol enhancing moisture absorption and water promoting ion migration—is general, though specific performance gains may vary with polymer chemistry.
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.