Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Let there be light: Chemists develop magnetically responsive liquid crystals

27.06.2014

UC Riverside discovery has applications in signage, posters, writing tablets, billboards and anti-counterfeit technology

Chemists at the University of California, Riverside have constructed liquid crystals with optical properties that can be instantly and reversibly controlled by an external magnetic field. The research paves the way for novel display applications relying on the instantaneous and contactless nature of magnetic manipulation-such as signage, posters, writing tablets, and billboards.

Magnetically Actuated Liquid Crystals

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

Credit: Yin Lab, UC Riverside.

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.

"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."

... more about:
»UCR »crystals »magnetically »orientation »synthesis

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 polarized light.

Study results appear online in Nano Letters. How light passing through the magnetic liquid crystal is controlled simply by altering the direction of an external magnetic field can be seen here and here.

The magnetically actuated liquid crystals developed by the Yin Lab have several unique advantages. First, they can be operated remotely by an external magnetic field, with no electrodes needed. (Electrical switching of commercial liquid crystals requires transparent electrodes which are very expensive to make.) Second, 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.

Further, 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.

"Such a thin film does not display visual information under normal light, but shows high contrast patterns under polarized light, making it immediately very useful for anti-counterfeit applications," Yin said. "This is not possible with commercial liquid crystals. In addition, the materials involved in our magnetic liquid crystals are made of iron oxide and silica, which are much cheaper and more eco-friendly than the commercial organic molecules-based liquid crystals."

The liquid crystals may also find applications as optical modulators— optical communication devices for controlling the amplitude, phase, polarization, propagation direction of light.

The discovery came about when Yin's lab first had the idea of using magnetic nanorods to replace rod-shaped molecules in commercial systems to produce liquid crystals that can be magnetically controlled. After looking into the literature, the research team realized that the main challenge in producing practically useful magnetic liquid crystals was in the synthesis of magnetic nanorods.

"Prior attempts had been limited to materials with very limited magnetic responses," Yin said. "We utilized our expertise in colloidal nanostructure synthesis to produce magnetite nanorods that can form liquid crystals and respond strongly to even very weak magnetic fields – even a fridge magnet can operate our liquid crystals."

###

The research was supported by grants to Yin by the National Science Foundation and the U.S. Army Research Laboratory.

Yin was joined in the research by Mingsheng Wang and Le He at UCR; and Serkan Zorba at Whittier College, Calif.

The UCR Office of Technology Commercialization has filed a patent on the technology reported in the research paper.

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion. A broadcast studio with fiber cable to the AT&T Hollywood hub is available for live or taped interviews. UCR also has ISDN for radio interviews. To learn more, call (951) UCR-NEWS.

Iqbal Pittalwala | Eurek Alert!

Further reports about: UCR crystals magnetically orientation synthesis

More articles from Life Sciences:

nachricht Cells cling and spiral 'like vines' in first 3-D tissue scaffold for plants
27.08.2015 | University of Cambridge

nachricht Cellular contamination pathway for plutonium, other heavy elements, identified
27.08.2015 | DOE/Lawrence Berkeley National Laboratory

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

Im Focus: FIC Proteins Send Bacteria Into Hibernation

Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.

For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...

Im Focus: Fraunhofer IPA develops prototype of intelligent care cart

It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.

Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...

Im Focus: A Grand Voyage for Tiny Organisms

Climate and Ecosystem Change in the Mediterranean

Since the opening of the Suez Canal in 1869 many hundreds of marine animal and plant species from the Red Sea have invaded the eastern Mediterranean, leading...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Cells cling and spiral 'like vines' in first 3-D tissue scaffold for plants

27.08.2015 | Life Sciences

Hypoallergenic parks: Coming soon?

27.08.2015 | Health and Medicine

Stiffer breast tissue in obese women promotes tumors

27.08.2015 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>