SOMETIMES all it takes is a quick hug, and everything looks different. Now a shape-shifting lens has been developed that alters its focal length when squeezed by an artificial muscle, rather like the lens in a human eye. The muscle, a ring of polymer gel, expands and contracts in response to environmental changes, eliminating the need for electronics to power or control the devices. "The lenses harness the energy around them to control themselves," says lead researcher Hongrui Jiang at the University of Wisconsin-Madison, US, where the device has been developed (Nature, vol 442, p 551). "This would be useful...