Autumn Ferns Arcadia National Park – large
Ferns provide model for tiny motors powered by evaporation
Scientists looked to ferns to create a novel energy scavenging device that uses the power of evaporation to move itself — materials that could provide a method for powering micro and nano devices with just water or heat.
“We’ve shown that this idea works,” said Michel Maharbiz, assistant professor of electrical engineering and computer science and principal investigator in the group that built the device. “If you build these things they will move. The key is to show that you can generate electricity from this.”As often happens, the research started while doctoral student Ruba Borno was exploring another idea entirely. Borno was interested in mimicking biological devices, specifically microchannels that plants use to transport water, so Maharbiz gave her a book on plants.
But something else in the book caught her attention – 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.
There is a short video here
Researchers at U-M made this tiny motor, modeled after a fern sporangium, that is propelled when surface tension caused by evaporation caused the ribs to straighten out.
A nice introduction into ferns, What are ferns?. Why are they different from vascular plants, how do they reproduce with a diagram of their life cycle, and some small photos of their parts.
Note: I’ve changed back to the old theme since it seems no matter what I do I still have to play with the photos to get them and the text to look right.
