Microactuator design unfurls

University of Michigan Scientists took ferns as their inspiration to create an energy scavenging device that uses the power of evaporation to move itself.

To spread its spores, the fern sporangium transforms one form of energy, in this case heat via the evaporation of water, into motion. When the cells in the outer wall of the sporangium are water logged, the sporangium remains closed like a fist, storing the spores safely inside. But when the water in the outer wall evaporates, it causes the sporangium to unfurl and eject the spores into the environment.

‘It's essentially a microactuator,’ said Michel Maharbiz, assistant professor of electrical engineering and computer science.

The researchers examined some fern leaves under a microscope. They found that when exposed to light or heat or any evaporation-inducing event, the sporangia opened and released the spores.

The method for making the material is simple. A wafer is coated with silicone and then hit with light, causing a pattern. The residual pattern is lifted off and that is used for the device. It resembles a curved spine with equally spaced ribs fanning outward from the spine.