The first artificial material that follows sunlight may upgrade solar panels
By Sofie Bates
As the sun moves across the sky, sunflowers continually orient themselves to soak up the most light (SN: 8/4/16). Now a type of human-made material can do that, too.
This is the first artificial material capable of phototropism, researchers report November 4 in Nature Nanotechnology. Stemlike cylinders of the material, dubbed SunBOTs, can maneuver to capture about 90 percent of available sunlight, even when the sun comes in at an oblique angle, materials scientist Ximin He of UCLA and her colleagues found. The technology could someday be used to optimize solar panels, desalinate water or move robots, the researchers say.
Other scientists have made artificial substances that can bend toward light, but those materials stop arbitrarily. SunBOTs can self-regulate, moving into the optimal position needed to absorb the sun’s rays, then making small adjustments to stay there as the sun shifts.
That ability comes from a SunBOTs’ configuration: a stemlike polymer about 1 millimeter in diameter embedded with a nanomaterial that responds to light. The nanomaterial absorbs light and converts it into heat; the polymer shrinks in response to increased temperatures.
When He and colleagues trained a beam of light on one of these artificial stems, the illuminated side heated up and contracted. That caused its top to bend toward the light. The newly shaded underside of the stem then cooled, stopping the SunBOT’s movement in a position best oriented to soak up the light. The process repeated as the angle of the light beam changed.