Tunable 'metasurface' is akin to optical swiss army knife

MIT engineers and colleagues report important new advances on a tunable metasurface, or flat optical device patterned with nanoscale structures, that they compare to a Swiss army knife while its passive predecessor can be thought of as just one tool, like a flat-bladed screwdriver. Key to the work is a transparent material discovered by the team that quickly and reversibly changes its atomic structure in response to heat.