Ferns provide model for nanodevice power

Filed in archive Research on September 19, 2006

A constant challenge in nanotechnology is how to power all those tiny devices. Getting electricity to them the way we power most appliances today, for instance, is extremely impractical. Nanodevices need to draw power from immediate, local sources. But how?

Scientists at the University of Michigan are definitely thinking outside the box by looking at ferns to use light or heat to generate power. Yes, ferns. It started when assistant professor Michel Maharbiz gave doctoral student Ruba Borno a book on plants for her research on biomimicry. In studying it, Borno became fascinated with the section on how ferns spread their spores.

"It's essentially a microactuator," said Maharbiz, meaning that 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 were water logged, the sporangium remained closed like a fist, storing the spores safely inside. But when the water in the outer wall evaporated, it caused the sporangium to unfurl and eject the spores into the environment.

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.

"Once we saw that, we thought, 'Oh, we have to build that,'" Maharbiz said.
The group plans to add electrical components to the device in an attempt to generate electricity. They predict that the device will be able to generate the same amount of electricity as other scavenging devices, say, a solar cell in a calculator.

They have also posted a nice short video of the ferns in action. (photo University of Michigan)