Whether you're manufacturing cars, phones, sports equipment or pretty much anything else, a key part of the design process involves measuring the amount of mechanical stress experienced by different parts of the product. Thanks to research being conducted at the University of California, Riverside, doing so may soon be much easier. Scientists there have created a film that changes color when subjected to pressure, making it easy to see where objects coated with the film may need reinforcement.

While other pressure sensor films do already exist, they all work by changing the intensity of just one color. Because the UC Riverside film actually changes between different colors, however, it is reportedly much easier for the unaided eye to "read."

It's made by stringing gold nanoparticles together, which are then embedded in a polymer film. When little or no pressure is applied to the film, the closely-spaced particles reflect light in a blue color. As pressure is applied and the film stretches, however, the spaces between the particles become larger. This causes them to gradually change in color, until they appear completely red.

Even once the source of pressure is removed, the stressed sections of the film remain red, allowing researchers to see which areas need attention.

Lead scientist Yadong Yin states that the film can be painted onto objects, allowing it to conform to curved and uneven surfaces – this is not the case with many existing alternatives, that only work when laid flat. He says that it could also be made using nanoparticles composed of less expensive metals, such as silver or copper.

A paper on his research was recently published in the journal Nano Letters.