Liquid crystal lenses work like insect eyes

New York, May 19:

Not many are aware that in an insects eyes, thousands of lenses work together to provide a sophisticated image. And the same technique can be used for 3D imaging, scientists say.


However, to replicate these structures artificially would require elaborate, painstaking manufacturing techniques.

Now, engineers and physicists at the University of Pennsylvania have shown how liquid crystals can be employed to create compound lenses similar to those found in nature.

Taking advantage of the geometry in which these liquid crystals like to arrange themselves, the researchers are able to grow compound lenses with controllable sizes.

These lenses produce sets of images with different focal lengths, a property that could be used for three-dimensional imaging.

They are also sensitive to the polarization of light, one of the qualities that are thought to help bees navigate their environments.

Previous work by the group had shown how smectic liquid crystal, a transparent, soap-like class of the material, naturally self-assembled into flower-like structures when placed around a central silica bead.

“Given the liquid crystal flower’s outward similarity to a compound lens, we were curious about its optical properties,” said lead researcher Mohamed Amine Gharbi.

To make the lenses, the researchers used photolithography to fashion a sheet of micropillars, then spread the liquid crystal on the sheet.

At room temperature, the liquid crystal adheres to the top edges of the posts, transmitting an elastic energy cue that causes the crystal’s focal conic domains to line up in concentric circles around the posts.

Answering fundamental questions about how these microlenses work extends this area of research in the direction of practical applications.

With an understanding on the geometric relationships between the size of the pillars, the arrangement of the focal conic domains and the focal lengths of the microlenses they produce, the team has shown how to grow these compound lenses to order.

“Last time we had tiny flowers. Now they are 10 times bigger. If we ever wanted to mass-produce these lenses, we can use the same technique on arbitrarily large surfaces,” said co-researcher Kathleen Stebe.

The study was published in Advanced Optical Materials. (IANS)

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