Butterfly wings inspire light-manipulating surface for medical implants

April 30, 2018, California Institute of Technology

Inspired by tiny nanostructures on transparent butterfly wings, engineers at Caltech have developed a synthetic analogue for eye implants that makes them more effective and longer-lasting. A paper about the research was published in Nature Nanotechnology.

Sections of the wings of a longtail glasswing butterfly are almost perfectly transparent. Three years ago, Caltech postdoctoral researcher Radwanul Hasan Siddique—at the time working on a dissertation involving a glasswing species at Karlsruhe Institute of Technology in Germany—discovered the reason why: the see-through sections of the wings are coated in tiny pillars, each about 100 nanometers in diameter and spaced about 150 nanometers apart. The size of these pillars—50 to 100 times smaller than the width of a human hair—gives them unusual optical properties. The pillars redirect the light that strikes the wings so that the rays pass through regardless of the original angle at which they hit the wings. As a result, there is almost no reflection of the light from the wing's surface.

In effect, the pillars make the wings clearer than if they were made of just plain glass.

That redirection property, known as angle-independent antireflection, attracted the attention of Caltech's Hyuck Choo. For the last few years Choo has been developing an eye implant that would improve the monitoring of intra-eye pressure in glaucoma patients. Glaucoma is the second leading cause of blindness worldwide. Though the exact mechanism by which the disease damages eyesight is still under study, the leading theory suggests that sudden spikes in the pressure inside the eye damages the optic nerve. Medication can reduce the increased eye pressure and prevent damage, but ideally it must be taken at the first signs of a spike in eye pressure.

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Researchers take cells from chrysalis and use them to grow butterfly wings in the lab

A pair of researchers, one from Oxford University, the other with the Natural History Museum in London, has found a way to grow butterfly wings in their lab. In their paper published in Bioinspired, Biomimetic and Nanobiomaterials, Helen Townley and Andrew Parker describe the transparent nature of certain butterfly and beetle wings and their efforts to reproduce them using cell cultures to grow colored materials.

Many butterfly wings, it turns out, are not actually colored by pigments or dyes—instead, their wings are made of transparent three-dimensional structures that only appear to look the color they do because of the way they filter and bend light. Because of the small size and intricate nature of these structures, scientists, despite considerable effort, have been unable to reproduce them—they'd like to be able to do so, however, because it would mean creating coatings that would never fade. In this new effort, the researchers took a more natural route—they took cells from a blue morpho butterfly chrysalis and grew them in a dish in their lab. The effort proved fruitful, as the cells grew into fully formed forewings—the first time it's ever been achieved in a lab.

The pair of researchers were hoping that the cells would continue producing wing structure material as long as they received nutrients, but discovered part of the process resulted in the destruction of the cells. Undeterred, they turned to a type of beetle that creates a shell structure that is in the same form as opal, the gemstone (by producing differing sized nanospherical structures in an array). Those cells kept producing, they found, as long as they were fed, producing a seemingly never ending stream of material.

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How Butterfly Wings Can Inspire New High-Tech Surfaces

Alan McStravick for redOrbit.com – Your Universe Online

Can technology benefit by going green? I’m not talking about retro-fitting buildings for solar power or setting up grey water collection systems. In the recent issue of the journal Soft Matter, a research team out of the Ohio State University is looking at organic materials to aid in the resurfacing of existing technologies and possibly for the manufacture of new products and materials.

The team, comprised primarily of engineers, is taking a detailed look at the structure of butterfly wings and rice leaves. What they found with regard to their microscopic texture could improve a variety of products.

The researchers contend that these items, and their structure specifically, enhance fluid flow and work to prevent surfaces from collecting dirt and dust. Their study, should the structure be able to be mimicked in high-tech surfaces, could be a substantial benefit to the manufacturers of air and watercraft, pipelines and medical equipment.

“Nature has evolved many surfaces that are self-cleaning or reduce drag,” said Bharat Bhushan, Ohio Eminent Scholar and Howard D. Winbigler Professor of mechanical engineering at Ohio State. “Reduced drag is desirable for industry, whether you’re trying to move a few drops of blood through a nano-channel or millions of gallons of crude oil through a pipeline. And self-cleaning surfaces would be useful for medical equipment – catheters, or anything that might harbor bacteria.”

Bhushan, along with doctoral student Gregory Bixler, studied the wings of the Giant Blue Morpho butterfly (Morpho didius) and leaves of the rice plant Oriza sativa. After viewing these two items under an electron microscope and an optical profiler, they cast plastic replicas of both of the microscopic textures. Once completed, they compared their ability to repel dirt and water to replicas of fish scales, shark skin and plain flat surfaces.

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