Learning from the living
Even in a lab, of course, making a self-regulating material is no small feat. How did the scientists do it? Inspired by the feedback loops organisms use to maintain their internal environments, they've strung together a series of actions and reactions that interconnect like pieces of a Rube Goldberg machine. Instead of making a contraption that might start with, say, knocking over a domino and end with hammering in a nail, researchers have tied up mechanical and chemical reactions so that each responds to the other in an endless loop.
The hydrogel, for example, is made of two separate layers. The lower layer contains tiny hair-like microstructures made of a material that automatically swells -- causing them to stand up -- when the temperature drops below a set point. When that happens, the tips deliver a substance from that lower layer to the top layer, setting off a chemical reaction that creates heat. As the temperature rises, the microstructures lie back down, ending the heat-creating reaction.
This concept could work with a broad range of heat-producing chemical reactions, giving developers the flexibility to choose the reactions -- and chemicals -- that make the most sense for various applications. It seems the scientific possibilities are, well, if not endless, then only limited by what chemical reactions can accomplish. "This design can serve as a blueprint for a whole generation of self-regulating materials," He said.
She expects the lab will produce other materials with different abilities -- such as keeping cool when outside temperatures rise, creating light when darkness falls or maintaining specific pH or glucose levels -- in the next year. That could lead to all kinds of potential applications beyond temperature control in buildings.
Imagine materials that could help keep electronics cool without fans or other external cooling; that could enable biomedical devices -- many of which require specific pH levels, temperatures or other conditions -- to work in places they can't be used today, potentially helping far more people; and that could help purify water, such as in -- perhaps -- a self-cleaning water bottle. Those are just a few of the ideas that He envisions. "We have a lot of follow-up research to do," she said.