One of the toughest environments in which to maintain adhesion is underwater. Water is known as the universal solvent. It tends to prevent adhesion between two surfaces by diluting, dissolving, dispersing, or simply forming an interface between adhesive layers. So how do creatures which God created adhere to objects underwater?
Much to the shipbuilder's chagrin, the mussel is God's champion of underwater adhesive systems. When a mussel wants to attach to a surface, it uses its plunger-shaped foot to find the spot that will make the best bond. The foot then cleans the point where the glue will be attached and then presses down upon the surface, forcing all of the water out. Next the mussel lifts the center section of its plungerlike foot, forming a vacuum to hold itself tightly in place. The final step is for the mussel to pump a chemical adhesive down through its foot, depositing the glue into the vacuum area. This adhesive forms a foamy, shock-absorbing foundation, bonded together with individual threads of glue.
The glue itself is made from several different proteins which are mixed in the correct proportions to provide the optimum combination of strength, flexibility, and compressibility for the selected anchor spot. Scientists believe that the specific proteins used change properties as conditions change. This has recently been coined a "smart" material.
Modern science can learn much about glue by examining the mussel. The mussel is both a wonder of God's design and a sophisticated chemist.
And here another fine example of biomimetics, of how solutions adopted in nature serve us as example:
Hydrogel Networks as Underwater Contact Adhesives for Diverse Surfaces
Underwater adhesives with intrinsically tough and stable performance are urgently needed for environmental and engineering applications. Marine organisms have inspired numerous studies on the design and development of wet adhesives. Here we report a facile yet powerful strategy that recapitulates the delivery process of mussel adhesion, to the development of strong and durable hydrogel adhesives. With the hydrogel matrix serving as the interfacial binding sites while the nanocrystal fillers contributing to the strong cohesion, they demonstrate outstanding adhesion abilities to a wide range of wet surfaces including aluminum, ceramic, glass, polymer and wood. Moreover, in contrast with commercial products for underwater bonding, the hydrogel adhesives present continuous strength growth instead of degradation with time due to the hydration effects and intrinsic reinforcement capabilities of ye'elimite. By synergistically combining macroscopic scale architectures and molecular level interactions, this in-situ formation strategy opens a new route to incorporate nanocrystals into hydrogel matrix, leading to a universal bonding solution on diverse surfaces underwater
Natural Underwater Adhesives
A universal glue: underwater adhesion of the secretion of the carnivorous flypaper plant Roridula gorgonias
Natural and bio-inspired underwater adhesives: Current progress and new perspectives
Biochemistry of Barnacle Adhesion: An Updated Review