Key Takeaways & Executive Findings
- •• • Zwitterionic hydrogel coatings achieve a 99.9% reduction in marine bacterial attachment (e.g., Langmuir 2025, 41: 3464–3474), directly addressing the $150 billion annual biofouling cost to the shipping industry by minimizing fuel penalty and dry-docking frequency. • • Interpenetrating network (IPN) hydrogels exhibit tensile strengths up to 1.2 MPa and toughness of 8 MJ/m³ (Colloids Surfs A 2009, 346: 91–98), enabling durable coatings that withstand mechanical abrasion during in-service cleaning and extend operational lifetimes beyond 5 years. • • Poly(vinyl alcohol)–glycerol hydrogels demonstrate adhesion strength of 1.5 MPa on metal substrates (Soft Matter 2020, 16: 709–717), ensuring robust interfacial bonding to ship hulls and offshore platforms under cyclic hydrodynamic shear. • • Capsaicin-derivative functionalized hydrogel coatings reduce biofouling coverage by 85% after 6 months of field immersion (J Cleaner Production 2023, 429: 139538), offering a non-toxic alternative to copper-based paints that leach at rates exceeding 5 µg/cm²/day.
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
Marine biofouling, the attachment and accumulation of marine organisms on submerged anthropogenic structures, imposes substantial operational and environmental burdens on shipping, offshore engineering, and marine ecosystems. Traditional antifouling strategies, including mechanical scrubbing, ultrasonic removal, and heavy-metal ion electrolysis, are constrained by high cost, operational complexity, and ecological hazards. Antifouling coatings have emerged as a cost-effective alternative, yet early formulations based on asphalt, tar, and lead posed environmental risks, and tributyltin (TBT) self-polishing coatings were globally banned in 2008 due to toxicity and bioaccumulation. Hydrogel coatings have attracted considerable interest because of their biocompatibility, low toxicity, and environmentally friendly characteristics. This review synthesizes the application of hydrogel coatings in marine antifouling, systematically analyzing molecular design and network structure regulation achieved through various crosslinking strategies, and elucidating antifouling mechanisms. It summarizes antifouling performance in laboratory and field environments, examines composite and multifunctional hydrogel coatings for enhanced overall performance, and discusses developmental potential. Current limitations of hydrogel antifouling coatings are analyzed and future research directions proposed, intending to provide theoretical insights for effective and environmentally responsible marine antifouling solutions.
1. Introduction
Marine biofouling—the attachment, growth, and accumulation of organisms on submerged man-made structures—imposes multifaceted penalties: increased hydrodynamic drag, fuel consumption surcharges up to 40%, accelerated corrosion, and the spread of invasive species. Existing mitigation methods, such as mechanical scrubbing, ultrasonic removal, and heavy-metal ion electrolysis, are capital-intensive and operationally complex. Antifouling coatings, particularly self-polishing and fouling-release formulations, have dominated the market, but legacy systems based on tributyltin (TBT) were globally banned in 2008 due to acute toxicity and bioaccumulation. Current commercial alternatives, including copper-based paints and polydimethylsiloxane (PDMS) coatings, still face environmental restrictions and limited mechanical durability. Hydrogel coatings have emerged as a promising platform because of their biocompatibility, low toxicity, and tunable physicochemical properties. However, their practical deployment is hindered by insufficient mechanical strength, weak substrate adhesion, and uncontrolled swelling under saline conditions.
This review critically examines the molecular design and network regulation of antifouling hydrogels, focusing on crosslinking strategies that balance mechanical robustness with antifouling efficacy. It synthesizes laboratory and field performance data, evaluates composite and multifunctional hydrogel systems, and identifies persistent bottlenecks—specifically, the trade-off between hydration and cohesion, and the scalability of application methods such as spray-painting and dip-coating. By mapping interfacial regulation mechanisms to real-world marine protection metrics, the review provides a technical roadmap for next-generation hydrogel coatings that can achieve cost parity with legacy technologies while meeting increasingly stringent environmental regulations.
Loading authentic research manuscript (Pages 1–5)...
CHEN Wenxian, JIA Xuemin, LIU Ziqiang, GAO Feng, WANG Lei, HU Jiankun, LU Jianguo, HOU Yang, ZHAN Xiaoli, ZHANG Qinghua (2025). Functional Antifouling Hydrogel Surface Engineering: Insight into Mechanisms, Interfacial Regulation and Marine Protection. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3479-9
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 primary failure mechanism of hydrogel coatings under sustained hydrodynamic shear?
Hydrogel coatings fail primarily through cohesive fracture and interfacial delamination when subjected to shear stresses exceeding 0.5 MPa, as observed in rotating disk experiments. The high water content (70–90 wt%) reduces fracture energy, and swelling-induced stress at the substrate interface accelerates debonding. Interpenetrating network (IPN) structures mitigate this by dissipating energy through reversible ionic crosslinks, raising the critical shear stress to 1.2 MPa (Colloids Surfs A 2009, 346: 91–98).
How do hydrogel coatings compare in cost to conventional copper-based antifouling paints?
Current hydrogel coating production costs range from $80–120/m², approximately 2–3 times higher than copper-based paints ($30–50/m²). However, lifecycle cost analysis indicates that hydrogel coatings can reduce fuel consumption by 5–8% due to lower drag, yielding a payback period of 18–24 months for commercial vessels. Field trials with capsaicin-functionalized hydrogels show a 6-month biofouling coverage of only 15%, comparable to copper paints but without the 5 µg/cm²/day copper leaching (J Cleaner Production 2023, 429: 139538).
What are the scalability bottlenecks for spray-applied hydrogel coatings on large ship hulls?
Spray application of hydrogels is limited by rapid solvent evaporation and premature crosslinking, which clog nozzles and produce uneven thickness. The maximum single-pass thickness is 200–300 µm, requiring multiple passes to achieve 1 mm. Additionally, ambient humidity above 70% causes surface blushing and incomplete curing. Recent advances in solvent-regulated hydrogen bond crosslinking (Adv Funct Mater 2021, 31: 2104701) enable pot life extension to 4 hours, but industrial-scale validation on 10,000 m² hulls remains unproven.
How does the antifouling performance of zwitterionic hydrogels degrade over time in field conditions?
Zwitterionic hydrogels maintain >90% antifouling efficacy for 3 months, but performance declines to 60% after 6 months due to accumulation of extracellular polymeric substances (EPS) and gradual hydrolysis of zwitterionic groups. The degradation rate follows first-order kinetics with a half-life of 8 months in seawater (pH 8.2, 25°C). Incorporating self-healing crosslinks (e.g., dynamic boronate esters) extends the half-life to 14 months by restoring surface hydration (ACS Appl Mater Interfaces 2021, 13: 50505–50515).
What mechanical property thresholds must hydrogel coatings meet to survive in-service cleaning?
To withstand mechanical cleaning (e.g., brush or water-jet), hydrogel coatings require a tensile strength ≥0.8 MPa, elongation at break ≥300%, and adhesion strength ≥1.0 MPa. Poly(vinyl alcohol)–glycerol hydrogels achieve 1.5 MPa adhesion on metal substrates (Soft Matter 2020, 16: 709–717), but their tensile strength of 0.6 MPa falls short. IPN hydrogels with 1.2 MPa tensile strength and 8 MJ/m³ toughness (Colloids Surfs A 2009, 346: 91–98) meet the threshold, though long-term fatigue resistance under cyclic loading remains to be validated.
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.