Aristotle started it. His musings on how woodpeckers and geckos “can run up and down a tree in any way even with the head downward” got scientists wondering not only how nature does it but whether it was possible to steal a few tricks. Now we have “biomimetic” suspension bridges whose cable tension and capability to self-repair mimic features found in muscles. We have Velcro, modelled on seed burrs. And we have robots that climb walls like geckos.
At the end of this month, researchers from all over the world will gather at the Royal Society in London to discuss the latest innovations. The University of Sheffield researcher Neil Hunter, for instance, will share his group’s insights into photosynthesis, the process by which plants harvest sunlight. Plants rely on what are, in essence, solar-charged batteries. When sunlight hits the light-harvesting antennae in leaves, energy is transferred to electrons in the antennae’s molecules. This is the same process that occurs in silicon solar panels. However, the electrons released in silicon end up transferring relatively little solar energy. In plants, evolved arrangements of protein molecules move the electrons with extraordinary efficiency through to areas known as “reaction centres”. Here, a series of chemical reactions ends with most of the energy stored inside biological cells.
Prof Hunter’s team is building computer models of this process in the hope of borrowing from evolution’s success. That will be a long road. The same is true of the wall-climbing technology that Stanford University’s Mark Cutkosky will be discussing. The extraordinary skills of lizards did not arrive overnight – they evolved over millions of years of not-quite-there product development and we are treading the same path, though with more purpose.
We now know that a gecko’s feet are covered in microscopic hairs. All the gecko has to do is put these hairs as close as possible to the wall. The position of the electrons in the molecules at the end of each hair causes shifts in the electrical charges in the molecules of the wall’s surface. The result is an attraction known as the van der Waals force. With so many hairs in play, it’s a force that can hold up the gecko’s weight.
It turns out that beetles are even better suited for this than geckos. The presentation by Kiel University’s Stanislav Gorb at the Royal Society meeting will be about the mushroom-shaped ends of the hairs on the feet of male chrysomelid beetles. These outperform the spatula-shaped hairs that keep geckos clinging to vertical surfaces. The beetle’s adhesion even works underwater and on dirty surfaces that would disrupt the sticking power of geckos.
Such discoveries are certain to lead to technological applications but there is a sting in the tail: this discipline is awash with military money. Evolution is a kind of arms race and the products of an arms race will always be useful to generals. Biomimetic research will give us gadget-encumbered soldiers carrying high-efficiency solar panels and perfect the art of camouflage, among other applications. Yes, we’ll get better picture-hanging technology, but the intelligence services will get spy bots that scuttle or fly into buildings, eavesdropping while perched on walls and ceilings, unlikely to be noticed.
It creates a dilemma for researchers. Nature’s tricks are compelling but the people who want to mimic them most are not always those you want to work for. At least one of the Royal Society presenters – Stephen Hyde of the Australian National University – once quit a research position to avoid involvement in military research, a choice that Aristotle never had to consider.