Sea mussels to inspire offshore wind farm solutions

The team is investigating how sea mussels grip onto wet rocks using collagen-rich sticky threads, ending in adhesive pads known as plaques. It is hoped that the findings will provide insight into how best to anchor the floating foundations of an offshore wind farm to the sea bed.

Engineers are yet to find a reliable way to fix cables from the foundation into the ground in a system that can withstand the weight of turbines and the forces of rough oceans and high winds.

Researchers believe that the design principles of the mussels’ multiple thread-plaque system could inspire new ways to securely join dissimilar man-made materials, preventing them from pulling apart when subjected to stress and weight.

“Mussels can achieve a steadfast grip on pretty much any material surface even while being pounded by the sea,” said Nottingham University’s professor Tao Liu, project leader. “Their adhesive pads demonstrate an incredible load-bearing capacity, and the stiffness and the surface texture pattern of the material they stick to play important roles in that behaviour.”

An engineer's view: over 40 years in offshore wind and infrastructure

The £320k Leverhulme Trust-funded project will run for three years and aims to bio-mimic the characteristics of sea mussel plaques to inform the design of new, ultra-lightweight and porous yet durable materials for use in aerospace and transportation manufacturing.

An outer, dense protective layer and a low-density porous plaque core work cooperatively to form the adhesive structure of a mussel plaque. The plaque core consists of a foamy network of pores at different lengths and reinforced by fibre bundles.

Existing research has demonstrated that a plaque core can achieve good load-bearing capacity and strength under tension and shear (forces that cause layers or parts to slide against each other in opposite directions). In contrast, manmade porous materials such as foams or honeycombs have very limited load-bearing capacity and strength under the same forces.

Using a type of 3D printing technology known as electron beam lithography, the team will recreate surface texture patterns of materials such as silica glass, silicone rubber and polycarbonate down to the micro-scale. The findings will be used to manipulate the stiffness and surface texture patterns of materials to understand how this can influence plaque adherence, researchers said.

Test samples copying the internal structures of a mussel plaque core formed under various forces will be manufactured using 3D printing, as will material joints inspired by this behaviour. Researchers said a test rig will be built to analyse the way the plaque responds to various loading scenarios when attached to different materials, and Traction Force Microscopy (TFM) will be adopted for the study to measure the forces exerted by a mussel plaque on a surface it is gripping.