J.R. Soc. Interface
- E W Hawkes, E V Eason, D L Christensen, M R Cutkosky
- J.R. Soc. Interface
Spiderman (image from iStockphoto). Innovation in the natural world inspired many budding and established scientists, providing insights into species’ adaptation and the processes that drive it. More recently, and as our ability to manipulate materials expands, evolutionary inventions have also provided creative solutions for human challenges. The development of Velcro, designed to the likeness of thistle’s barbed seeds (de Mestral, 1958), is an example of an invention where the idiosyncratic problem of seed dispersal translated into a universal solution for our need to keep things together. Nature-inspired designs, or biomimetics, can be also applied to less obvious problems. One recent example is the study from the laboratories of Tae-il Kim and Mansoo Choi describing an ultra-sensitive mechanosensor that can pick up faint physiological outputs such as blood pressure, heartbeat, or voice patterns (Kang et al., 2014). The sensor was inspired by the lyriform organ, a specialized exoskeletal structure found on the limbs of spiders, consisting of parallel slits of different lengths connected to the nervous system. This arrangement, reminiscent of the strings in a lyre and used for communication, allows spiders to pick up exquisitely fine vibrations from their surroundings. Kim and Choi mimicked the lyriform organ by layering nanometers-thick platinum on top of a viscoelastic polymer and generating cracks in the platinum and polymer layers. The cracks are the sensing organ—electrical conductance across them depends on the size of the gap, allowing measurement of the fine vibrations and pressure that distorts the layers. This wearable sensor is indeed able to pick up fine distinctions in speech or blood flow, and one can imagine a wide range of future applications where it could prove its worth. Arguably, such a ‘‘spidey sense,’’ no matter how sophisticated, won’t cut it for Spiderman. The ability to climb vertical surfaces would be a nice touch, and indeed, researchers from Mark Cutkosky’s lab accomplished this by optimizing an adhesive system inspired by geckos (Hawkes et al., 2015). Geckos’ uncanny ability to defy gravity resides in spatula-shaped lamellae covering their footpads, which adhere to surfaces through van der Waals forces. A variety of biomimetic materials capturing their properties have been developed; however, the remaining challenge was scaling the amount of adhesive to human weight for safe and uninterrupted climbing. Cutkosky’s lab resolved this problem by developing a load-sharing method designed to ensure a uniform distribution of forces across the adhesive, enabling a human to climb a vertical glass surface with a hand-sized area of adhesive. Camouflage or ability to merge with the surroundings has long been on the wish list of the military industry and consumer product designers. It is in equally high demand in nature and is brought to perfection by cephalopods that can change coloration quickly by altering pigment-containing skin chromatophores. The laboratory of John Rogers recently recreated this process by combining several layers of synthetic materials and sensors, mimicking the elements of the cephalopod skin, and achieving autonomous color matching to the background (Yu et al., 2014). Such a system not only has diverse applications, but it also deconstructs the complexity of a natural organ. Ultimately, biomimetic advances like the ones described above show that harnessing designs honed by evolutionary forces rather than the human creative process may not only result in versatile solutions, but also inspire quests for enhancing human capabilities.