Synthetic glue that combines dry, wet adhesive properties of gecko and mussel

Washington, July 19: Researchers have designed a synthetic glue that combines the dry and wet adhesive properties of the gecko lizard and the underwater mussel.

Researchers said the hybrid material, which has been named 'geckel nanoadhesive', proved in initial testing to be adherent under both dry and wet conditions.

It also adhered much longer under both extremes than previous gecko-based synthetic adhesives, they said.

The team led by Dr. Phillip Messersmith, a scientist at Northwestern University in Evanston, Illinois, designed a small nanopolymer array that mimicked the natural spatial patterns of the hair on the foot of a gecko.

They then coated it with a thin layer of a synthetic compound, which mimicked the reversible bonding action of a mussel adhesive protein the scientists have been studying for the past several years.

In initial experiments, the team found that the wet adhesive force of each pillar increased nearly 15 times when coated with the mussel mimetic and applied to titanium oxide, gold, and other surfaces.

The dry adhesive force of the pillars also improved when coated with the compound, the experiment revealed.

"That actually wasn't so surprising to us. The mussel-inspired adhesive is extremely versatile in that it can bond reversibly to inorganic surfaces under wet and dry conditions," said graduate student Haeshin Lee, lead author on the study.

Findings further revealed that the geckel hybrid maintained 85 percent of its adherence under wet conditions after 1,100 contacts with the tip. Under dry conditions, the level of adherence was 98 percent.

"This isn't quite a home run, but it's somewhere in between a double and a triple," said Lee, who devised on his own a special imaging devise to visualize individual pillars during the experiments.

Dr. Messersmith said that while the results are extremely promising, his group still must tackle several practical problems before it can scale up its research.

"Any time that you fabricate an array of nano pillars of this type over large areas, you must have a very effective way of doing it without losing the efficacy of the approach. We'll also need to reduce the fabrication costs to make geckel commercially viable," said Dr. Messersmith.

"But, this is the first time that two polar opposite adhesion strategies in nature have been merged into a man-made reversible adhesive.

I should add that the essential component of the wet adhesive polymer on the pillars contains a chemical that we have discovered last year adheres well to mucosal surfaces, such as those inside our mouth.

It may be possible to develop patches in the future that can be applied on the inside of the cheek to cover damaged tissue," he said.

According to Dr. Messersmith, their invention could lead to more durable and longer-lasting bandages, patches, and surgical materials.

"Band aids already adhere well, except if you go swimming, take a shower, or somehow expose it to a lot of water. So I think the most important thing with this adhesive is the added value of resisting immersion in water," said Dr. Messersmith.

The findings appear in this week's issue of the journal Nature.


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