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Manufactured adhesives — used in products from bandages to sticky notes — cannot out-stick those of nature. Phillip Messersmith of Northwestern University in Evanston, Illinois, and his colleagues found success by merging mimics of two natural adhesives. They combined a nanometre-scale structure inspired by the feet of geckos — which can cling to vertical and inverted surfaces — with an adhesive protein similar to those used by mussels to stick to rocks (see page 338). This achieved a first — a strong yet reversible adhesive that works in wet conditions. Messersmith spoke to Nature about the material, dubbed 'geckel'.

What made you think of combining mussel- and gecko-like adhesives?

We started mimicking gecko adhesives about two years ago, but our discovery that a component of mussel adhesive protein provides strong, reversible bonds to wet surfaces really accelerated our work. Others had already achieved gecko-like dry adhesion, but none was able to maintain stickiness with repeated use. And gecko-type adhesion is known to perform poorly under water. These factors got me thinking about combining both adhesive strategies in one material.

How was your nanometre-scale gecko-foot design different from previous ones?

We used a silicone elastic polymer — chosen not for its adhesive properties but for its compatibility with the nanofabrication technique — to design nanometre-scale pillars that mimic gecko foot hairs. We also applied a thin layer of mussel-like polymer to the pillar surface.

Is gecko-like adhesion the ultimate objective of engineered adhesives?

Probably not. Several natural biological adhesives remain open frontiers. For example, certain bacteria live in turbulent waters and use remarkably strong adhesives. Their mechanisms are largely unknown. Another classic wet adhesive is that of barnacles, which use different proteins from mussels.

How might geckel be used?

Geckel works well as a dry adhesive, but it is the wet adhesive component that captivates us. For example, bandages often come off in the shower. Another medical use for geckel might be in dermal patches for drug delivery.

What challenges remain for commercialization?

We are now fine-tuning the pillar tip shape to mimic gecko foot hairs more closely. One huge challenge will be finding a cost-effective way to scale up production to make large amounts of this adhesive. Don't expect geckel sticky notes anytime soon.