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Liquid crystal compound lenses function like the eyes of insects

16 May 2015

Engineers and physicists at the University of Pennsylvania show how liquid crystals can help create compound lenses similar to those found in nature.

An array of microlenses self-assemble around a central pillar (image: University of Pennsylvania)

By 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. Each 'petal' of these flowers is a 'focal conic domain', a structure that other researchers had shown could be used as a simple lens.

To make the lenses, the researchers used photolithography to create a sheet of micro-pillars, 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.

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

An article describing the work is published in the journal, Advanced Optical Materials.

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