Bioinspired Metamaterial Shows Potential for Optical Devices, Energy Harvesting, Signature Management

Ultra-antireflective synthetic brochosomes (false colored).

Ultra-antireflective synthetic brochosomes (false colored).

December 4, 2017 | Source: Penn State News, news.psu.edu, 3 Nov 2017, Walt Mills

Synthetic microspheres with nanoscale holes can absorb light from all directions across a wide range of frequencies, making them a candidate for antireflective coatings, according to a team of Penn State engineers. The synthetic spheres also explain how the leaf hopper insect uses similar particles to hide from predators in its environment.

"We knew our synthetic particles might be interesting optically because of their structure," said Tak-Sing Wong, assistant professor of mechanical engineering and the Wormely Family Early Career Professor in Engineering. "We didn't know, until my former postdoc and lead author of the study Shikuan Yang brought it up in a group meeting, that the leaf hopper made these non-sticky coatings with a natural structure very similar to our synthetic ones. That led us to wonder how the leaf hopper used these particles in nature."

The synthetic microspheres are produced via a rather complex five-step process using electrochemical deposition. However, the process can be scaled up and many different materials can be used to make the synthetic brochosomes, such as gold, silver, manganese oxide or even a conductive polymer.

As an antireflective coating, this material could have applications in sensors, cameras and telescopes. For solar cell applications, a coating of synthetic brochosomes could increase light capture at multiple wavelengths and from every angle due to the 3D soccer-ball-shaped structure, making it unnecessary to build devices to track the sun. In the future, we may try to extend the structure to longer wavelengths. If we made the structure a little larger, could it absorb longer electromagnetic waves such as mid-infrared and open up further applications in sensing, energy harvesting, or even signature management?