True colors

Some may think of turkeys as good for just Thanksgiving dinner, but Berkeley bioengineers found inspiration in the birds for a new type of biosensor that changes color when exposed to chemical vapors. Turkey skin, as it turns out, can shift from red to blue and white, thanks to bundles of collagen that are interspersed with a dense array of blood vessels. Spacing between these collagen fibers changes when the blood vessels swell or contract, which, in turn, affects the way the light waves are scattered and alters the colors we see on the bird’s head. The researchers, led by bioengineering professor Seung-Wuk Lee, found a way to get benign viruses—with a shape that closely resembles collagen fibers—to self-assemble into patterns that could be easily fine-tuned. Like collagen fibers, these nanostructures expanded and contracted, resulting in color changes.

When exposed to a range of volatile organic compounds, the biosensors swelled rapidly, resulting in specific color patterns that distinguished the different chemicals tested. “Our system is convenient, and it is cheap to make,” says Lee. “We also showed that this technology can be adapted so that smartphones can help analyze the color fingerprint of the target chemical. In the future, we could potentially use this same technology to create a breath test to detect cancer and other diseases.”

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