UC Researchers Create Color-Changing, Touch-Sensitive Nanomaterial Film

Scientists at the University of California, Riverside (Riverside, Calif.) have created a film of gold nanoparticles that can change color in response to movement. The material does more than emulate color-changing capabilities — it’s formulated to respond to any type of movement, including bending and twisting. The film can be used for surface coating, and practical applications include displays, mechanical sensors, security devices, smart windows and bionic robots. The film could act as a color-changing skin on robots, enabling them to mimic animals like chameleons.

The basis of the film’s color-changing capacity is its structure. When materials like gold are small enough, they change color depending on their orientation, size and shape. Researcher Yadong Yin explains, “In our case, we reduced gold to nano-sized rods. We knew that, if we could make the rods point in a particular direction, we could control their color. Facing one way, they might appear red. Move them 45 degrees, and they change to green.”

The difficulty was getting all the nanoparticles to be oriented in the same direction to display the desired color. To achieve that, researchers fused smaller magnetic nanorods onto the larger gold ones. At this stage, orientation can be controlled and programmed magnetically. The rods are then encapsulated in a polymer shield to maintain their orientation but enable flexibility.

Researchers published their process in an article in the research journal Nature Communications.