Solar stems developed
Researchers in the US have developed a material that bends and moves to face the light, just like sunflowers.
The new material, which is formed into small cylindrical stem-like shapes, is able to perfectly align with the direction of a light beam, according to a new paper in Nature Nanotechnology.
The device has been dubbed SunBOT.
Widely observed in nature, phototropism is when organisms follow a light source for foraging or reproductive purposes.
However, artificial phototropism has been challenging to achieve, as it is difficult to find the right balance between the material composition and its properties.
Researchers at the University of California have made a breakthrough by combining a photoresponsive nanomaterial that can absorb light efficiently and transform it into heat, with a thermoresponsive polymer that contracts when heated.
The team then shaped the resulting material into small cylinders.
When illuminated, the cylinder absorbs light and becomes hotter, but only on the side facing the light source. As the material contracts on the illuminated side, the cylinder bends towards the light beam.
Once the top of the cylinder aligns with the beam, the underside of the shaft, now in the shadow of the light, cools down, expands and stops the motion of the cylinder.
The cylinders can follow a light beam continuously in a wide range of directions.
The authors suggest this research could be used to improve the efficiency of light-harvesting materials, such as solar cells, as the cylinders bend autonomously to expose the tip to the maximum amount of light.