Butterfly wing structure informs the design of solar panels

Mimicking the airy architecture of the Rose butterfly’s wings, a team of researchers at the California Institute of Technology and the Karlsruhe Institute of Technology have created ultra-efficient thin-film solar cells.Mimicking the airy architecture of the Rose butterfly’s wings, a team of researchers at the California Institute of Technology and the Karlsruhe Institute of Technology have created ultra-efficient thin-film solar cells.

Traditional crystal-based solar panels are made of thick, rigid solar cells, mounted to hardware which can follow the sun’s movement as it tracks across the sky.

While this maximises the capture of sunlight, the motion hardware which tilts the heavy panels puts a significant dent in the efficiency of solar energy.

Solar panels found in watches and calculators, which can be just a few nanometres thick, are cheaper and lighter than their crystal predecessors but even less efficient.

Butterflies need sunlight in order to fly. In the researchers’ novel approach, they examine the secrets of the soft black wings that keep the cold-blooded butterfly warm during the cooler months.

After collecting samples, researchers examined each sample under an electron microscope and discovered some astonishing features.

The wings are covered in scales and shot through with tiny holes. In addition to making the wings lighter, these holes scatter the sunlight wherever it strikes, allowing the butterfly to collect more of the sun’s heat.

Unlike the erstwhile solar cells, these wings can absorb a great deal of light regardless of the sun’s angle, and take about 10 minutes to reabsorb light.

The team, led by Dr Radwanul Siddique, a bioengineer at CalTech, created a 3D model of the wings’ nanostructures out of extremely thin sheets of hydrogenated amorphous silicon. A top layer, comprising tiny holes less than a millionth of a metre wide, causes light to scatter and strike the silicon base below. This design picked up roughly twice as much light as previous designs.

“The really interesting thing is that the butterflies, which have evolved these complex structures as a result of selection over millions of years, are still way outperforming our engineering,” says Yale Biology professor Vinod Saranathan. (Saranathan was not involved in the study.)

The group explains their inspiration for studying the butterfly wings and the details of their improved solar cells in their journal Science Advances paper.

Image: J. M. Garg

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