Nature is an excellent designer. Today, faced with ever more complex challenges, scientists and researchers are increasingly turning to the natural world for inspiration when designing and creating new technologies. This is known as “biomimicry,” which is essentially a scientific approach that imitates natural models, systems, or elements in order to solve human challenges.
While examples of biomimicry at work exist in all kinds of fields—the classic biomimicry example is the story of Velcro, which was inspired by the grappling hook-style mechanism burrs use to attach and cling persistently to fur or clothing—the medical world is one of the areas where biomimicry innovations are most commonly seen. Read on to learn how three very different animals are providing scientists with ideas for helping wounds heal more effectively, making injections easier and less painful, and developing a better kind of medical adhesive material.
How to grip: geckos
Geckos may be tiny, but they have evolved to make the absolute most of their miniature size. In order to defy gravity while climbing up walls and skittering across ceilings, geckos have developed incredible feet. A dense mat of projections (like minuscule fingers, each far thinner than a human hair and no more than a few thousandths of an inch in length) covers the bottom of a gecko’s foot. From the end of each of these, a tuft of hundreds of nanoscale fibers protrudes, and the end of each of these fibers (which are known as “spatulae”) is shaped like a broad, flat, rounded triangle, very similar to a kitchen spatula. Thanks to these spatulae, a gecko’s foot has a hugely increased surface area which makes it easier for the creature to grip and maintain contact with different surfaces as it moves.
These same properties that make gecko feet so grippy are ideal qualities for medical adhesives, which need to be able to stick to many different tissue surfaces, including ones that are irregular or inconsistently-shaped. Some medical researchers, notably Jeffrey Karp and Robert Langer of Harvard and MIT, are experimenting with designs for a new type of medical tape that incorporates a pattern of nanoscale pillars in order to maximize contact area. Furthermore, when combined with a thin layer of medical-grade glue, the tape is strong, tight, and sensitive enough to be used on internal organs (for example, in repairing blood vessels or in sealing holes in the digestive tract) without causing irritation to delicate tissues.
How to puncture: porcupines
We all know that porcupines are best avoided because of their ability to shoot quills that are agonizing to remove once they penetrate flesh. But, while these quills might make most of us want to run in the other direction, their unique properties are proving very intriguing to medical researchers.
Rather than being pointed and smooth-sided, like a dart, porcupine quills are covered in layers of microscopic barbs, 700 to 800 per quill. Clearly, these barbs make it very difficult to remove quills that have become lodged in skin or flesh, but what fascinates researchers about these barbs is that they actually make it easier to pierce flesh in the first place. We might expect the presence of barbs to make the puncturing process more difficult, but in fact, the barbed tips of quills operate like the ridged teeth of a serrated knife; by concentrating pressure onto small areas, it’s easier for the barbs to penetrate skin with less force.
Less force in turn means less pain, and that’s why medical researchers like Karp and Langer are now experimenting with barbed designs for needles and syringes, which could potentially make injections less painful. As for the problem of how to withdraw these barb-tipped needles, possible solutions include creating barbs from synthetic material that softens or dissolves after the injection has been made, or positioning barbs on the needle only in places where they would make entry easier but not impede a smooth exit.
How to stick (or not): spiders
Spider silk has a number of truly remarkable properties that make it a rich source of inspiration for medical scientists. Not only is it lightweight, stretchy, and very strong (when compared by weight with steel, spider silk is five times stronger!), it’s also sometimes sticky and sometimes not: certain strands of a spider’s web are adhesive in order to trap prey, but others are smooth to allow the spider to move around easily.
Together with their postdoctoral associate Bryan Laulicht, researchers Karp and Langer turned to spider silk as the inspiration for a pliable and easily detachable medical adhesive that doesn’t cause damage to the underlying surface when it’s removed. This could serve to keep tubes or sensors in position on infants, the elderly, or other patients with sensitive or delicate skin.
Experiments yielded a type of medical tape composed of thin backing, a layer of silicon-based film, and a coating layer of sticky adhesive, but with a microscopic grid pattern etched onto the film by a laser. The grid pattern means that on some parts of the tape (where the silicon film was burned away by the laser), the backing touches the adhesive and the tape behaves like regular sticky tape, while the silicon film still present on other parts of the tape provides a floating barrier from which the adhesive can be easily detached. The result is a product that is sticky in some places but not in others, just like a spider’s web.