A super-strong adhesive that could stay sticky underwater was inspired by mussels, which use proteins to cling to submerged rocks.
To create these waterproof adhesives MIT researchers engineered bacteria to produce a material that is a hybrid of natural sticky mussel proteins and a protein found in biofilms, which are a slimy layer of bacteria that grow on a surface.
"The ultimate goal for us is to set up a platform where we can start building materials that combine multiple different functional domains together and to see if that gives us better materials performance," Timothy Lu, an associate professor of biological engineering and electrical engineering and computer science (EECS) and the senior author of the paper, said.
The sticky proteins that help mussels attach to underwater surfaces are called "mussel foot proteins." In the past researchers have used E. coli bacteria to produce mussel foot proteins, but these adhesives are far less complex than those produced in the recent study. These new adhesives employ two different mussel foot proteins combined with curli fibers, which are proteins that can clump together and create more complex "meshes."
The researchers purified and incubated these proteins to form dense, fibrous meshes, creating an extremely flexible material that can bind strongly to both dry and wet surfaces.
"The result is a powerful wet adhesive with independently functioning adsorptive and cohesive moieties," said Herbert Waite, a professor of chemistry and biochemistry at the University of California at Santa Barbara who was not part of the research team. "The work is very creative, rigorous and thorough."
The adhesive was tested through a method called atomic force microscopy, which uses a tiny tip to probe the surfaces of the samples. The researchers found the samples bonded well to silica, gold and polystyrene. The adhesives were even sturdier than those naturally occurring in mussels and are the "strongest biologically inspired, protein-based underwater adhesives reported to date."
Using the current method the researchers can only create small batches of the adhesives. In the future the team hopes to figure out a way to produce larger quantities and experiment with a variety of mussel foot proteins.
"We're trying to figure out if by adding other mussel foot proteins, we can increase the adhesive strength even more and improve the material's robustness," Lu said.
The findings were published in the Sept. 21 issue of Nature Nanotechnology.
