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Chemists unveil magnetically-responsive liquid crystals

Posted: 01 Jul 2014 ?? ?Print Version ?Bookmark and Share

Keywords:University of California? liquid crystal? magnetic field? nanorod?

A team of chemists at the University of California, Riverside has developed liquid crystals with optical properties that can be instantly and reversibly controlled by an external magnetic field. According to the, the research opens the path for novel display applications relying on the instantaneous and contactless nature of magnetic manipulation such as signage, posters, writing tablets and billboards.

Commercially available liquid crystals, used in modern electronic displays, 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.

Magnetically-responsive liquid crystals

Top: Scheme showing magnetic control over light transmittance in the novel liquid crystals. B is the alternating magnetic field. The polarised light is seen in yellow. The gray rods represent the polarisers. The magnetic field controls the orientation of the nanorods (seen in orange), which in turn affects the polarisation of the light and, then, the amount of light that can pass through the polarisers. Bottom: Images show how a polarisation-modulated pattern changes darkness/brightness by rotating the direction of the cross polarisers. The circles and background contain magnetic nanorods aligned at different orientations. The research shows that by combining magnetic alignment and lithography processes, it is possible to create patterns of different polarisations in a thin composite film and control over the transmittance of light in particular areas. Image credit: Yin Lab, UC Riverside.

"The liquid crystals we developed are essentially a liquid dispersion, a simple aqueous dispersion of magnetic nanorods," said Yadong Yin, an associate professor of chemistry, who led the research project. "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."

Yin explained that upon the application of a magnetic field, the nanorods spontaneously rotate and realign themselves parallel to the field direction, and influence the transmittance of polarised light.

The magnetically actuated liquid crystals developed by the Yin Lab have several unique advantages.

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