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Crystal-forming microparticles could lead to color-changing tanks and planes

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April 23, 2014

The University of Michigan M, formed by exposing the microparticles to light

The University of Michigan M, formed by exposing the microparticles to light

Military vehicles that change color to be dark at night, and camo-green in the daylight ... could such a thing be possible? Well, it's certainly closer to reality, thanks to research being conducted at the University of Michigan. Scientists there have created a solution that changes color when exposed to light, then changes back when the light is removed. If incorporated into a thin film coating, the result could be chameleon-like surfaces.

The solution consists of negatively- or positively-charged latex paint microparticles suspended in a kerosene-like fluid, pooled on an indium tin oxide substrate.

When light is shone onto a section of that pool, it causes a localized chemical reaction to take place between the fluid and the substrate, creating a current of ions in the fluid. This in turn causes the negatively-charged microparticles to draw together in that area and form crystals, which reflect the light in a given color. The color is determined by the spacing between the particles within the crystals, and that spacing is determined by the wavelength of the light that is being shone on the liquid.

Once the light is turned off, the crystals dissolve, and the liquid returns to its previous color. The process can be repeated indefinitely. If the microparticles are positively charged, incidentally, they will move away from the illuminated area, which still results in a localized color change.

Along with its possible use for camouflaging vehicles, it is hoped that once developed, a film incorporating the technology could also be used for applications such as e-readers and dynamic billboards.

A paper on the research was published today in the journal Nature Communications. In the videos below, you can see the liquid displaying the University of Michigan's M logo as it's exposed to ultraviolet light in the shape of the letter – in the first clip, the logo is formed as negatively-charged microparticles form into crystals, while in the second, the M is created when positively-charged particles retreat from the light.

Source: University of Michigan

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
3 Comments

We see in black and white at night. So a dark green would look black to us any way. With new cameras able to see colour at night a tank would stand out like a sore thumb being black.

I remember I was being evaluated in my spotting skills. Small objects were placed in a field at night and I had to count them. I was the only person to spot the camo hat on the ground, every one else missed it, about 20 other people. They all seen the other things.

Camo works about 10 times better at night imo.

fenshwey
23rd April, 2014 @ 05:49 pm PDT

Never mind military applications! I want a car with this stuff on it! Bright white during the night, glossy black during the day perhaps?

Bryan Paschke
24th April, 2014 @ 08:38 am PDT

I think that would be cool on a car. One could change the color when ones mood changes or one feels like having a different color car but not wanting to buy another one.

BigGoofyGuy
25th April, 2014 @ 06:33 am PDT
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