Imagine repairing the scratches in your car's paint finish just by shining a special light on them. Or using the same technology to make your scratched-up mobile phone look as good as new. How about removing the unsightly flaws on a varnished tabletop with the glow of a black-light lamp?
These scenarios may sound like the start of a late-night infomercial, but they're actually among the possibilities raised by the development of a new type of "healable" polymer.
"You can think about different ways to realize this technology," Christoph Weder, a materials-science researcher at Switzerland's University of Fribourg, told reporters. "If you think about cars, yes, you can think about your own little fix-it-up tool, but you can also think about combining the instrumentation with car washes."
AMI / CWRU / USARL
Scratches on this polymer can be fixed by shining ultraviolet light on them.
You can't get this stuff at your body shop just yet, though. The material is still years away from commercialization. "Our study is really a fundamental research study. ... We really provide a toolbox to developers who hopefully will take this to the next level," Weder said.
Weder and other researchers describe their molecular "toolbox" in a paper published in this week's issue of the journal Nature. The researchers, led by Case Western Reserve University's Stuart Rowan, say they have developed a new class of materials known as "metallo-supramolecular polymers."
"These polymers have a Napoleon Complex," Rowan explained in a news release. "In reality, they're pretty small, but are designed to behave like they're big by taking advantage of specific weak molecular interactions."
Most polymers consist of long molecular chains, but these metallo-supramolecular polymers consist of short chains that are glued together with metal ions.
If the material is scratched, cut or cracked, that breaks up the polymer. But researchers can "heal" the damage by shining intense ultraviolet light on the material. The irradiation heats up the polymer, causing the molecules to come unglued and flow back together like a liquid. That fills in the cracks and smooths out the surface. When the light is switched off, the material reassembles and solidifies again within seconds.
Zina Deretsky / NSF
This schematic shows how the molecules making up the polymer can be temporarily disassembled under UV light. When the light is turned off, the molecules reassemble themselves.
The light can be focused on a particular area of the polymer surface to fix a defect, while the rest of the finish remains intact and unaffected. The research team also found that the material could be "healed" repeatedly with no ill effects.
Although the experiments were conducted exclusively with ultraviolet light, the researchers are looking into tweaking the technology so that other wavelengths can be used, such as a specific kind of blue light. During the experiments, the team came across some instances where the material was discolored in the course of being healed, but Weder said that was probably due to molecular defects in the material.
Weder said the main ingredients of the polymer are "relatively inexpensive" chemicals.
"I don't think that ultimately cost will be a showstopper," he said, "but I should say again, what we have reported is not something that I expect to be commercialized tomorrow or next year. It's really a first generation of a class of materials that need further refinement."
In a Nature commentary on the research, Nancy Sottos and Jeffrey Moore of the University of Illinois at Urbana said that healable polymers "offer an alternative to the damage-and-discard cycle" that is seen so often in today's consumer society, and represent a first step toward products "that have much greater lifespans than currently available materials."
Andrew Lovinger, polymers program director in the National Science Foundation's Division of Materials Research, said the quest for healable materials was part of a wider initiative to create "matter by design."
"There are people working both on the chemistry of creating this kind of matter, on the propoerties and the processing ... and even on the theoretical [side] and cybertools to make that possible," he said. "Having scientists and engineers all working together in all of these areas with that vision may one day lead us to any kind of material or matter we will be able to design from scratch — pardon the pun — and may be able to design for any kind of property."
More on materials science:
- Metals with memory could fix dents
- Self-healing car coating repairs scratches
- Rubber-like material can mend itself
- Bendy antennas could reshape electronics
- Airplanes of the future could be self-healing
- 'Programmable matter' may shape future tools
- Water-blocking material mimics spider hair
- Graphene: Thin stuff is a big fat deal
- The latest fashion in invisibility
- Solar cells that heal themselves
In addition to Rowan and Weder, co-authors of "Optically Healable Supramolecular Polymers" include Mark Burnworth, Liming Tang and Justin R. Kumpfer of Case Western Reserve University; Andrew J. Duncan and Frederick L. Beyer of the U.S. Army Research Laboratory; and Gina L. Fiore of the Adolphe Merkle Institute and Fribourg Center for Nanomaterlais, University of Fribourg. The reearch paper was based on work supported by the U.S. Army Research Office, the National Science Foundation, the Adolphe Merkle Foundation and the U.S. Army Research Laboratory.
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