Artificial-muscle diffraction grating

Manuel Aschwanden and Andreas Stemmer of ETH Zürich in Switzerland molded a soft, electroactive polymer into a shape resembling a microscopic pleated window shade and bonded it onto a prestretched elastic polymer. The result is an artificial muscle that contracts when a voltage is applied. With no voltage, the grating’s lines are spaced 1 µm apart. But when a voltage is applied to the ETH device, the line spacing can change by up to a whopping 32%—compared with less than 1% for tunable gratings made of hard materials. When white light strikes a diffraction grating, different wavelengths fan out at different angles; a small aperture placed within the fan can isolate any of the colors. Changed line spacing means changed angles, and a different color sweeps across the aperture. With different voltages, the test device isolated different wavelengths over a range of 139 nm starting at 446 nm, as shown...