It's not Harry Potter's invisibility cloak, but new findings could enable a chameleon-like style of camouflage.
Researchers at the University of Michigan have devised a technique as part of a study that can change the color of a crystal structure by manipulating its particles with ultraviolet light, a process that has the potential to be used for concealment.
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The colors of a crystal structure are based on the space between its particles. This space (or lack thereof) decides what light the crystals will absorb, and what it will reflect, a process that manifests itself in visible color. Knowing this, researchers realized that if they manipulated the space between the particles, they would be able to control the color of the crystals.
This change occurs thanks to a chemical reaction set off by ultraviolet light. Latex-paint microparticles were submerged in a kerosene-like fluid while a metallic sheet of indium tin oxide (a transparent solid solution) was placed at the bottom of this pool. When the light was shone on the microparticles, it created a current of ions. If the current had a negative charge, the particles would be attracted to the illuminated area; but if it had a positive one, they would steer clear, creating a shape with negative space. In the absence of light, the particles would simply dissolve into the solution. Researchers demonstrated the effectiveness of this technique by having particles create the university's trademark "M" — part of the school's logo.
"We can shine the light in a certain region, and the particles create a crystalline region where they all come together and create this crystal structure," Youngri Kim, a chemical-engineering doctoral student who led the study, said in a statement.
"We have understood why this happens in a way that is not specific to this one system," Mike Solomon, Kim's advisor and a University of Michigan chemical-engineering professor, said in a statement. "Anyone who wants to work on these materials now can use light to manipulate them without a template."
This phenomenon has clear benefits when it comes to camouflaging techniques, but it also has other potential applications. For example, it could be used to develop new technology for devices such as e-readers and billboards — electronics that consistently change what is displayed on their screens.
Camouflage technology has also been explored in real-life invisibility cloaks, which cannot be seen in certain types of light. The possibilities for this discovery are far-reaching. For example, future research could lead to sensors that would change change color to identify specific molecules — a process that could be used in medical or environmental monitoring.
The University of Michigan study was published last month in Nature Communications.
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