| Actual images (top) and a schematic illustration (bottom) show the color change of a plasmonic film after experiencing different amounts of pressure. (Credit: Yin Lab, UC Riverside) |
University of California, Riverside (UCR) researchers have created a pressure-sensing substance based on a self-assembled color-changing surface-plasmonic material.1 A polymer film contains embedded gold nanoparticles that create a color based on plasmonic interactions between the particles. When pressure is applied, the particle spacing changes, changing the color also.
Potential applications range from stress sensors for engineering (for example, a coating applied to crash-test dummies that allow testers to determine exactly what impacts the dummies endure in an automobile crash) to gloves that, when worn in a baseball game by batters, show the batters if they are using the appropriate amount of pressure to grip their bats.
"When linked together, the gold nanoparticles originally appear blue," says Yadong Yin, an associate professor of chemistry, whose lab led the research. "But they gradually change to red with increasing pressure as the nanoparticles start disassembling. This easily and visually helps us figure out how much pressure has been applied."
The new sensor differs from commercially available pressure-sensor films. that indicate pressure by changing the intensity of just one color (for example, a pale red to a darker red). They tend to be difficult to interpret and have low resolution and contrast.
Can be used on complex surfaces
The new technology produces a mosaic of easy-to-distinguish colors and has the benefit of higher contrast and resolution. It can potentially be used in many safety devices for revealing pressure distribution over even very complex surfaces.
While Yin's lab used gold in the experiments, silver and copper could also work, he says. The sensor the lab developed is a solid plastic film. Under stress, it deforms like conventional plastics. The new color that arises persists after the stress is removed. "This is why we are calling it a 'colorimetric stress memory sensor,'" Yin says.
The UCR Office of Technology Commercialization has filed a patent on the technology reported in the research paper.
REFERENCE:
1. Xiaogang Han et al., Nano Letters (2014); http://pubs.acs.org/doi/abs/10.1021/nl500144k