Dragonfly-like lenses grown with liquid crystals

Scientists have successfully grown liquid crystal flowers with grains of sand, that resemble insect eyes and could be used as complex lenses.
A team of scientists from the University of Pennsylvania has made another advance in their effort to use liquid crystals as a medium for assembling structures.
In their earlier studies, the team produced patterns of "defects," useful disruptions in the repeating patterns found in liquid crystals, in nanoscale grids and rings.
The new study adds a more complex pattern out of an even simpler template: a three-dimensional array in the shape of a flower.
And because the petals of this "flower" are made of transparent liquid crystal and radiate out in a circle from a central point, the ensemble resembles a compound eye and can thus be used as a lens.

"Before we were growing these liquid crystals on something like a trellis, a template with precisely ordered features. Here, we are just planting a seed," Kamien said.

The seed, in this case, were silica beads - essentially, polished grains of sand. Planted at the top of a pool of liquid crystal flower-like patterns of defects grow around each bead.
The key difference between the template in this experiment and ones in the earlier work was the shape of the interface between the template and the liquid crystal.
In their experiment that generated grid patterns of defects, those patterns stemmed from cues generated by the templates' microposts.

Domains of elastic energy originated on the flat tops and edges of these posts and travelled up the liquid crystal's layers, culminating in defects.
Using a bead instead of a post makes it so that the interface is no longer flat.
Surface tension on the bead also makes it so these petals are arranged in a tiered, convex fashion. And because the liquid crystal can interact with light, the entire assembly can function as a lens, focusing light to a point underneath the bead.
"It's like an insect's compound eye, or the mirrors on the biggest telescopes," said Kamien.
The study was published in Physical Review X.