New findings released this week from the University of California, Riverside, report that researchers have constructed liquid crystals that may lead to the next generation of a wide variety of device screens, displays, signs, and more. The novel liquid crystals possess optical properties that can be instantly and reversibly controlled by an external magnetic field.
Old crystals vs. new crystals
Conventional liquid crystals are composed of rod-like or plate-like molecules. When an electric field is applied, the molecules rotate and align themselves along the field direction, resulting in a rapid tuning of transmitted light. Commenting on the new technology, Yadong Yin, the lead researcher on the project explains his team's technology:
"The liquid crystals we developed are essentially a liquid dispersion, a simple aqueous dispersion of magnetic nanorods. We use magnetic nanorods in place of the commercial nonmagnetic rod-like molecules. Optically these magnetic rods work in a similar way to commercial rod-like molecules, with the added advantage of being able to respond rapidly to external magnetic fields."
When a magnetic field is applied, the nanorods spontaneously rotate and realign themselves parallel to the field direction, and influence the transmittance of polarized light.
The advantages of the new liquid crystals are numerous, including that they can be operated remotely by an external magnetic field, without electrodes. Also, the nanorods are much larger than the molecules used in commercial liquid crystals. As a result, their orientation can be conveniently fixed by solidifying the dispersing matrix. Furthermore, the magnetic nanorods can be used to produce thin-film liquid crystals, the orientation of which can be fixed entirely or in just selected areas by combining magnetic alignment and lithographic processes. This allows patterns of different polarizations to be created as well as control over the transmittance of polarized light in select areas.