A closeup image shows a unique polymer turning into a gel and expanding as it is exposed to electricity. Photo by Thor Balkhed
Oct. 30 (UPI) -- Scientists have discovered a new material that dramatically expands or contracts when exposed to a weak electrical signal.
Many materials expand and contract in response to changes in temperature and pH levels. Materials in greenhouse windows, for example, automatically open and close to help regulate the temperature. Similar materials, both solids and gels, are used in robots and biomedicine applications.
Until now, however, scientists had failed to find a material that can dramatically alter its volume -- ideally, triggering a phase change -- in response to electricity.
While making and testing experimental materials in the lab, researchers in Sweden and Britain synthesized a polymer that can both expand and contract in response to a weak electrical signal.
Scientists described the novel material this week in the journal Advanced Science.
When placed in an electrolyte solution, the material expands by a factor of 100 in response to a weak positive electrical pulse. A negatively charged pulse causes the material to return to its original volume.
In follow up experiments, scientists insulated a wire with the new material. When electricity was run through the wire, the thin film of polymer absorbed water and converted to a rapidly expanding gel. When scientists repeated stronger electrical pulses, the gel expanded to a volume 300 percent larger than the film's original size.
If integrated into a sponge or filter, scientists suggest the new material can manipulate via electricity to control the passage of different sized particles.
"We can control the pore size of a filter electronically, and potentially actively control the size of particles that pass through," Magnus Berggren, professor in organic electronics and director of the Laboratory of Organic Electronics at Linköping University, said in a news release.
"This means that the properties of this smart filter can be dynamically changed to allow different types or different sizes of particle to pass through. This function can be used for sieving, filtration, purification, and in process chemistry. It may also have applications in medicine and biochemistry," Berggren said.