Gecko tape is a material covered in nanoscopic hairs that maximizes surface area and could allow humans to walk up walls and ceilings like geckos. The adhesive power of gecko tape is similar to that of gecko feet, but it runs out of adhesive power after a few uses due to moisture. Scientists are using biomimicry to create new materials and devices inspired by animals.
Gecko tape is an experimental material developed in 2003 by an international team of scientists from the UK and Russia. It is a tape surface covered with nanoscopic hairs intended to maximize surface area. Gecko tape hasn’t been perfected yet, but when it is, it could allow humans to walk up walls and ceilings like geckos.
The gecko is an impressive creature. He can support his full weight on a horizontal wall with just one finger, which is tiny compared to his body size. It can move faster than a meter per second along a molecularly smooth surface like polished glass. The secret is in the van der Waals force, an intermolecular force that emerges when molecules act like tiny magnets that attract each other. To exploit it well it requires a lot of surface area, which gecko feet have.
The feet of the gecko are covered with small hairs, which use capillary action and the van der Waals force to adhere to the walls. Each hair is 200 to 500 nanometers wide. Only in the last decade or so has it become possible for scientists to fabricate an artificial material like gecko tape with hairs of such tiny size. The adhesive power of one centimeter of gecko foot is approximately 10 Newtons, similar to that of gecko tape.
Gecko hair is made of keratin, but scientists used polyimide fiber to create their gecko tape because that scale is easier to work with. Originally, they used a silicon wafer as a substrate for the hairs in gecko tape, but it has been found that flexible substrates are able to better compensate for uneven surfaces, increasing the adhesion power many times over.
One problem with gecko tape is that, unlike real geckos, it runs out of adhesive power after just a few uses. That’s because polyimide isn’t hydrophobic like keratin, and paper-thin films of moisture on surfaces cause its hairs to eventually get wet and clump together. The keratin hairs on the gecko’s feet allow the animal to run on moist ground and then immediately onto a flat surface like glass, much to the amazement of materials scientists. The gecko ribbon project is part of a larger field called biomimicry, where scientists and engineers use animals as inspiration for new materials and devices.
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