A stretchy material developed for holograms and an obsolete photography technique from the 19th century have already been combined to produce a material that changes colour as its tension changes
An obsolete photographic technique that won a Nobel prize greater than a century ago has been resurrected to produce a novel material that changes colour when stretched. It may be used to create bandages that warn medics if they’re being wrapped too loosely, or mechanical sensors that want no electronics.
Materials that change colour under tension have already been created before in laboratories, but scaling the procedure up has proved tricky and expensive. The precision with which different colours could be printed on these materials in addition has been poor generally.
Now, Benjamin Harvey Miller at the Massachusetts Institute of Technology (MIT) and his colleagues have revived a method called Lippmann photography, named after physicist Gabriel Lippmann, to produce a cheap method which could print even probably the most intricate designs in multicolour onto a stretchable material. When this material is put under strain, the colours move across the spectral range of visible light, with red sections first getting into greens and blues.
Lippman never saw commercial success with the color photography technique he developed in the 1890s which involved coating a glass plate having an emulsion of fine grains because exposure times of photographs often reached into hours and images couldnt be replicated from negatives. But his work nonetheless won him the Nobel prize in physics in 1908.
Harvey Miller realised that the technique could possibly be used to print onto a material called a photoelastomer that may change in reaction to light being shone onto it rather than glass slides, by beaming the required image about it with an electronic projector.
He says the material the team used was made for holograms, where its elasticity can be an undesirable property which makes it normally mounted on a rigid backing plate.
On a whim, I acquired one of these brilliant high-school hologram kits you could buy in a museum or something, says Harvey Miller. Also it proved that I had most stuff inside it that people needed. Now, having spent 3 years of my PhD trying different ways to do this, I was almost annoyed, actually.
It had been a surprise a mix of materials developed for holographics and an obsolete photography technique could possibly be combined to generate materials with novel characteristics, he says. This system was sat there for a long time without really being touched, says Harvey Miller. Whenever we figured this out and started considering writing a paper, for the initial month or two, we were like surely someone did this, that is type of there in plain sight, however they just hadnt.
The team says that certain application for the material could possibly be mechanical sensors that may show stress and strain visibly, with no need for electronics. It might also be utilized in medical bandages showing how tightly they’re being applied, or incorporated into clothing for fun.
Team member Mathias Kolle, also at MIT, says similar advances could be possible by combining old scientific techniques and materials that werent offered by the time. I believe more folks in science should consider the 50s and 60s, as well as two centuries back, and say hey, what did people do this was way before their time? Do you know the things that that they had as conceptions, however the materials were not there?’
Journal reference: Nature Materials, DOI: 10.1038/s41563-022-01318-x
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