Liquid crystals are used for just about everything – from small digital watches to large TV screens, from optical equipment to biological sensors. Nevertheless relatively little is known about the exact molecular structure of such crystals at the boundary surface with the air.

Recent research under the leadership of professor Juan de Pablo from the Institute for Molecular Engineering (University of Chicago) has brought to light previously unknown characteristics of this boundary between air and many commonly used liquid crystals.

'The effectiveness relies on controlling their molecular orientation at an interface,' says De Pablo. 'The precise understanding of this interface gained from our research will enable the design of better liquid crystal sensors and displays.'

Liquid crystals are in a state between liquid and solid – they can flow like a liquid, but have also a few characteristics of solids. The molecules have the shape of rods which can be oriented in different directions. Certain liquid crystals go through a phase change as a reaction to a change in temperature. In the so-called nematic phase, the rod-shaped molecules are aligned in parallel but are layered in an unorganized fashion. In the smectic phase, the molecules are also aligned in parallel but are also clearly organized in layers.

The research by De Pablo has revealed that the boundary of a liquid crystal forces a very ordered structure (like that of a solid) to occur in the liquid crystal which continues deep into the crystal mass, particularly in the nematic and smectic phases This discovery can open the road to developments of sensitive liquid crystal interfaces to detect chemicals and biological molecules.