A coacervate is a unique liquid phase rich in polymers or molecules that separate from an aqueous solution, forming a dense, sticky phase capable of adhering to surfaces. By ingeniously conjugating terminal butyl groups to poly(propylene glycol) (PPG), the researchers have successfully engineered a system that undergoes liquid–liquid phase separation under water. This process results in the formation of a PPG-based coacervate stabilized by a combination of hydrogen bonding and hydrophobic interactions. The coacervate’s physical properties are tailored to promote not only adhesion but also exceptional spreading behavior, enabling it to infiltrate the surface irregularities and porous structures of substrates that typically repel adhesives.

The standout feature of this adhesive system is its “superspreading” ability, which refers to the coacervate’s capacity to rapidly and extensively wet a surface. This property is critical underwater, where the presence of water films, hydration layers, or lipid coatings can prevent conventional adhesives from establishing intimate contact. The superspreading coacervate overcomes these hurdles by efficiently wetting and infiltrating the substrate’s surface, enabling a molecular-level intertwining that anchors the adhesive securely. The resulting interface is markedly robust and durable, addressing a long-standing gap in underwater adhesion technology.

Beyond merely forming an interfacial bond, the system encapsulates hydrophilic curing agents within the coacervate phase. Upon application, these curing agents are concentrated and retained within the coacervate matrix, enabling rapid, in situ photocuring once exposed to light. This swift curing process solidifies the adhesive bond quickly, minimizing the risks of adhesive dilution or displacement by water. The integration of this curing mechanism ensures that the adhesive bond is not only strong but also long-lasting and resilient in diverse aqueous conditions, including saline seawater or complex biological fluids.

The versatility of the coacervate adhesive is exemplified by its efficacy on a wide array of substrate types. From highly hydrated biomaterials, which typically pose significant adhesion challenges due to their water-rich nature, to lipid-rich surfaces common in biological tissues, the coacervate demonstrates impressive adaptability. Additionally, it successfully adheres to substrates exhibiting multiscale porosity—a feature that often diminishes adhesive performance due to the complex physical landscape that adhesives must navigate and bind within. Such versatility portends broad applications in both industrial and biomedical settings.

Industrial underwater repair and sealing applications stand to benefit greatly from this technology. The coacervate adhesive’s rapid curing and robust bonding capacities make it ideal for sealing underwater leakages, a common and costly challenge in marine infrastructure, pipelines, and fluid transport systems. Its capacity to infiltrate porous and irregular surfaces ensures effective sealing performance, which is crucial for maintaining structural integrity in harsh marine environments over extended periods.

In the biomedical domain, the implications of this technology are equally profound. The coacervate adhesive has been successfully used in adhesion-mediated assembly of hydrogels and organogels, which are materials widely employed for tissue engineering and regenerative medicine. Its ability to bond hydrated and lipidic substrates opens avenues for repairing tissue perforations and sealing wounds underwater, such as during surgical procedures involving fluid-filled or moist tissue environments. This capability is particularly critical for developing minimally invasive surgical adhesives that can operate reliably within the human body, where hydration and lipidic components abound.

From a material’s science perspective, the study underscores the importance of combining hydrophobic and hydrogen bonding interactions to drive phase separation and coacervate formation. The terminal butyl groups on PPG play a pivotal role by introducing hydrophobic domains that interact favorably with the aqueous environment and substrate surfaces. This molecular design strategy could inspire future efforts aimed at customizing adhesive materials for specific environmental or substrate challenges, using phase behavior and chemical functionality as key tuning parameters.

The liquid–liquid phase separation phenomenon exploited in this work serves not only to concentrate adhesive components but also to endow the system with remarkable resistance to dilution—a common problem faced by adhesives applied in aqueous settings. Conventional adhesives tend to lose efficacy as water dilutes reactive species or interferes with molecular interactions, but the coacervate’s dense phase effectively isolates and protects these species until curing. This innovation addresses one of the core challenges in underwater adhesion science and points toward a paradigm shift in designing adhesives for wet environments.

Moreover, this research emphasizes the dynamic interaction at the interface—the infiltration and intertwining of polymer chains with the substrate surface at multiple scales. This intimate interaction at molecular and microstructural levels is key to the adhesive strength and durability observed. It marks a departure from mere surface coating or physical contact, moving toward a more integrated and mechanistic understanding of underwater adhesion where the substrate and adhesive coalesce into an interpenetrated network.

The study also highlights the coacervate’s stability and functionality across complex aqueous milieus, ranging from pure water to biologically relevant saline solutions. This robustness signifies potential for real-world deployment where environmental conditions can vary widely and unpredictably. It enables confidence that the adhesive system could be adapted for diverse ecosystems, from marine conservation efforts to medical applications in human and veterinary medicine.

Researchers demonstrated the coacervate adhesive’s practical utility by assembling hydrogel and organogel constructs underwater, showcasing its ability to create strong bonds even in soft and pliable materials. Such demonstrations are crucial for translating laboratory breakthroughs into tangible technologies that solve pressing problems related to wet adhesion. The capacity to assemble hybrid materials underwater offers exciting prospects for soft robotics, flexible electronics, and biologically inspired materials science.

Another compelling advantage of this adhesive system lies in its biocompatibility potential. The use of PPG, a polymer already employed in medical contexts, coupled with rapid photocuring of common hydrophilic agents, suggests a pathway toward safe, effective adhesives for clinical use. This aligns with broader trends in developing materials that blend performance with environmental and biological safety, addressing growing demands for sustainable and healthcare-compatible technologies.

The evolutionary inspiration behind this innovation—barnacle adhesion to living marine surfaces—exemplifies the power of biomimetic approaches in material science. By decoding and emulating nature’s solutions to adhesion under difficult conditions, the study not only advances the technical field but also enriches our understanding of biological interfaces. This interdisciplinary approach, melding chemistry, biology, and materials engineering, is a beacon for future research focused on overcoming intractable challenges via nature-inspired design.

In summary, this pioneering research introduces a superspreading and ultra-infiltrative coacervate adhesive that addresses fundamental challenges in underwater adhesion to hydrated and lipidic substrates. Through molecular engineering, phase behavior exploitation, and synergistic curing strategies, the adhesive achieves durable, rapid, and versatile bonding under conditions previously considered prohibitive. The implications stretch across multiple fields, from marine science and industry to emergent biomedical technologies, potentially sparking a wave of innovation in how adhesives are conceptualized and applied in aqueous environments.

Subject of Research: Underwater adhesives; biomimetic coacervates; phase-separated polymer systems; adhesion on hydrated and lipidic substrates; photocurable underwater bonding.

Article Title: Superspreading and ultra-infiltrative coacervate mediates strong underwater adhesion on hydrated and lipidic substrates

Article References:
Yi, B., Li, H., Chen, S. et al. Superspreading and ultra-infiltrative coacervate mediates strong underwater adhesion on hydrated and lipidic substrates. Nat. Chem. (2026). https://doi.org/10.1038/s41557-026-02087-9

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41557-026-02087-9

The foundation of this breakthrough lies in a meticulously engineered synthesis process, wherein multiple functional monomers were copolymerized in a single step via free-radical polymerization. By fine-tuning the ratio of chemical crosslinkers relative to monomer content, the researchers optimized each hydrogel’s balance of elasticity and deformability. Notably, gels were synthesized using dimethyl sulfoxide (DMSO) solutions containing functional monomers at a high total molarity, ensuring robust polymer networks amenable to adhesive functionality. Ultraviolet (UV) irradiation initiated polymerization, achieving nearly complete monomer conversion within hours.

Following synthesis, the organogel precursors were immersed in physiological saline solutions to remove residual solvents and unreacted chemicals, stabilizing the hydrogels into their functional aqueous states. This meticulous post-processing step not only ensured biocompatibility but also locked in the gels’ swelling equilibrium. Storage in saline stabilized the materials, setting the stage for precise adhesion characterization under reproducible conditions.

To quantitatively assess adhesion, the team employed a battery of mechanical tests, including tack assays and lap shear measurements, conducted entirely underwater to simulate real-world conditions pertinent to biomedical and marine interfaces. Adhesion tests utilized custom instrumentation calibrated for gentle yet firm application of forces, ensuring accurate measurement of adhesive strength without overstressing the materials. Repeated attachment-detachment cycles highlighted the hydrogels’ remarkable durability, while peeling assays characterized interfacial toughness — a critical parameter for applications demanding sustained adhesion.

The design strategy extended beyond traditional polymer chemistry, incorporating a large-scale bioinformatics effort to decode adhesive protein sequences from nature. By mining over 24,000 adhesive protein sequences across thousands of species, the researchers generated consensus sequences that distilled the most conserved and functionally relevant motifs. This natural blueprint guided monomer selection and formulation parameters, creating synthetic hydrogels inspired yet optimized beyond biological templates.

Central to the endeavor was the implementation of sophisticated machine learning (ML) techniques to correlate hydrogel composition with adhesive performance. Six key monomers defined a multidimensional feature space, within which adhesive strength served as the target variable. The team exhaustively evaluated a suite of linear and non-linear regression models, including ridge regression, support vector machines, Gaussian processes, and ensemble tree methods. Cross-validation identified Gaussian process regression and random forest algorithms as the most accurate predictors.

Yet, the true power of the ML integration manifested in the iterative, closed-loop optimization of hydrogel formulations. By leveraging Bayesian optimization strategies, the researchers navigated the vast compositional space with both exploitation of known high-performing areas and exploration of uncharted territories. This included batch evaluations of predicted compositions, and the use of hybrid surrogate models that dynamically balanced the uncertainty and expected improvements in adhesion. Such sampling efficiency was critical given the protracted two-week synthesis and equilibration times inherent to hydrogel fabrication.

Through successive rounds of prediction, synthesis, and validation, the data set expanded from an initial 180 hydrogels to over 340 unique formulations. This expansive dataset not only enhanced model fidelity but also unearthed novel compositions exhibiting adhesion strengths surpassing those of natural protein adhesives. The approach demonstrated a powerful paradigm for material discovery by marrying high-dimensional data analytics with experimental rigor.

This research sets a precedent for smart material design, showcasing how integrating bioinspired heuristics and advanced algorithms can circumvent traditional trial-and-error limitations. The resultant super-adhesive hydrogels possess tunable mechanical and adhesive properties, opening avenues for wound closure materials, underwater repair adhesives, and bioelectronic interfaces. Their stability under physiological saline and repeated mechanical stress further underscores their translational potential.

Moreover, this work illuminates the utility of consensus sequence analysis in translating complex biological information into actionable design variables for synthetic systems. By bridging disciplines — polymer chemistry, bioinformatics, and machine learning — the study exemplifies the power of interdisciplinary strategies in addressing formidable scientific challenges.

The meticulous characterization protocols established herein provide a reproducible framework for future studies targeting material adhesion phenomena. Standardized testing parameters, including contact times, loading rates, and environmental conditions, enable rigorous comparison across samples and formulations. Such precision ensures that improvements in performance are due to intrinsic material properties rather than measurement artifacts.

Intriguingly, the study’s machine learning methodology incorporated not only predictive modeling but also uncertainty quantification, facilitating strategic experimentation that maximized information gain. Techniques such as expected improvement acquisition functions allowed for efficient prioritization of formulations to synthesize, minimizing wasted effort and accelerating discovery cycles.

In sum, this research presents a compelling vision for the future of material innovation, where intelligent algorithms guide molecular design toward unprecedented capabilities. The capacity to customize adhesion properties precisely and rapidly, even under challenging conditions like underwater environments, is poised to impact a host of technological domains. Ongoing and future exploration informed by this work may well redefine what is achievable in synthetic adhesives.

Subject of Research: Data-driven design and synthesis of super-adhesive hydrogels inspired by adhesive proteins.

Article Title: Data-driven de novo design of super-adhesive hydrogels.

Article References:
Liao, H., Hu, S., Yang, H. et al. Data-driven de novo design of super-adhesive hydrogels. Nature 644, 89–95 (2025). https://doi.org/10.1038/s41586-025-09269-4

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41586-025-09269-4