In the demanding arena of underwater adhesion technology, a breakthrough study has emerged that promises to transform how we bond materials beneath aquatic environments. Developing adhesives that maintain robust adhesion on a variety of substrates submerged underwater has long challenged scientists, particularly when dealing with substrates that are highly hydrated or lipidic. Recently, researchers have drawn inspiration from the natural world, focusing on the extraordinary adhesiveness of barnacles, which effortlessly cling to marine creatures despite constant exposure to water and biological complexity. This biomimicry has led to the creation of a novel adhesive system centered on a dilution-resistant and superspreading coacervate, designed to penetrate and bond with challenging underwater surfaces.
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
