Liquid crystals go 3D

Researchers from Sheffield University in England and the University of Pennsylvania have unlocked some of the secrets of liquid crystals, materials that self-assemble into lattices of geometric shapes that are neither solid nor liquid, but somewhere between.

They have also discovered a type of liquid crystal that is bigger than any known before.

The researchers developed a geometrical model that relates the shape of molecules to the way they grow. The model allows researchers to form liquid crystals that self-assemble into desired shapes.

Such self-assembly at the molecular scale could lead to photonic crystals that guide certain wavelengths of light and crystal templates that yield ceramics with specific patterns of nanoscale pores. These could be used in chemical and biological sensors.

Using the model, the researchers constructed a new type of liquid crystal that is four times bigger, and more complicated, than any other type known. The liquid crystal is a three-dimensional array of spherical supramolecules, or molecules linked by weak chemical bonds, aggregated into unit cells. Each unit cell contains 30 spheres totaling a quarter million atoms.

The method could be used to make practical designer liquid crystals in five to ten years, according to the researchers. The work appeared in the February 21 issue of Science.