Biomedicine

Mixing Darks with Lights

Because most recycling centers don’t accept dark-colored plastics, more than four billion kilograms of car bumpers, cell phones and other materials clog U.S. landfills each year. Black plastic could easily be recycled. The problem: the polymers used in different plastics are incompatible, and melting them together yields an unusable glop. But the conventional plastic-identification method of analyzing reflected laser light doesn’t work well with black plastic, which chars under the bright beam.

SpectraCode of West Lafayette, IN, may have solved the problem. The key is a laser beam that hops around. The beam can be bright enough to produce an identifying signal rapidly; by dancing from point to point roughly every tenth of a second, it never dwells on one spot long enough to burn it. SpectraCode CEO Edward Grant expects the probe to be used in commercial products by early 2002.

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