Once again advancing the field of precious metal-based nanotechnology, chemists at the University of California, Riverside have filed a patent for a new type of pressure sensor that uses color changing gold nanoparticles.
While experimenting with methods to assemble gold nanoparticles into specific structures (such as rods, disks, or a thin film), the scientists noticed that handling the structures caused them to change color. But, they weren’t sure why. After deeper investigation, they determined that handling the nanoparticles caused their delicate structure to warp, changing how they reflect and absorb light. From there, the idea for a new type of pressure sensor was born.
Gold nanoparticles are assembled in a liquid form that looks blue. This solution of nanoparticles are then applied to a thin and flexible polymer film. When the film is stretched by being pressed or hit, the layer of gold nanoparticles shifts, separates, and changes color. The more the particles shift, the more red they appear. For example, a light press changes the color to purple, while a hard press changes the sensor to red.
The sensors use gold in amounts that are small enough to make them practical for a wide variety of applications. However, the UC researchers are already working on developing a sensor that uses silver nanoparticles instead. Although silver is less chemically stable than gold, it could produce a broader spectrum of colors for less cost.
Photo credit: Yin Lab, UC Riverside.
Published April 30, 2014 in New Revolutionary Sensor Links Pressure to Color Change