Butterfly wings + nanotubes = new optical material

Caren B. Les, caren.les@photonics.com

Butterflies have always been beautiful, but it turns out they’re useful, too: Combining butterfly wings with carbon nanotubes (CNTs) could lead to new biotech tools such as soft, wearable devices, high-sensitivity photosensors and sustainable light batteries.

A honeycomb-shaped network containing CNTs can be readily formed on a Morpho sulkowskyi butterfly wing using a simple self-assembly technology, according to Eijiro Miyako and his colleagues at the National Institute of Advanced Industrial Science and Technology in Osaka, Japan. The CNT-butterfly wing composite material has multiple functions, such as laser-induced remote heating and high electrical conductivity, and the light-driven composite allows for repetitive DNA amplification, Miyako said.

A new nanobiocomposite material that can be activated by a laser was formed by growing a honeycomb network of carbon nanotubes on butterfly wings. Courtesy of Eijiro Miyako.

Making the composite was not particularly complicated, he said. The researchers put a small amount of a well-dispersed polymer-CNT complex in organic solvent on a real butterfly wing and waited several minutes for the process to complete. At this point, Miyako said, they could see the natural pattern of CNTs on the butterfly wing by electron microscopy. They irradiated the composite with an ordinary CW laser.

Individually, each material has worthy properties: The thin, lightweight, flexible butterfly wings are self-cleaning and can absorb solar energy and shed water quickly; the CNTs offer unique electrical, mechanical, thermal and optical properties.

“The most important optical [characteristic] of our composite is the powerful photothermal conversion effect of carbon nanotubes expressed by laser light,” Miyako said. The self-assembled CNT pattern creates a large light-receiving surface area, and the nanocarbons produce heat through vibrational energy, he explained. “Indeed, we could confirm that the nano- tubes generate heat when they are exposed [to] laser light, and the composite material heats faster than its two components would by themselves.”

Miyako wants to develop functional nanobiomaterials that surpass biomimetics, using the synergy effect between natural and artificial materials to go beyond the properties of nature. “I believe that it is the best way to make an innovative nanobiocomposite,” he said.

Next, the researchers need to combine the CNT-butterfly hybrid with nanoelectronic devices to develop high-performance photosensors and photovoltaic cells, Miyako said. The work appears in ACS Nano (doi: 10.1021/nn403083v).