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Monday, 27 January 2020

Scientists create Crystal inside a crystal to improve screens and more

The beautiful patterns created by blue liquid phase crystals have a number of technological applications.

Liquid crystals have enabled new technologies, such as LCD screens, thanks to their ability to reflect certain wavelengths of light, or colors, and to be very easy to manipulate.

Researchers have now developed an innovative way to sculpt a crystal inside a liquid crystal.
Because these crystals within crystals can reflect light at certain wavelengths that others cannot, they can be used to improve screen and monitor technologies.



They can also be manipulated with temperature, electrical voltage or chemicals, which makes them valuable for detection applications. Temperature changes, for example, would result in color changes. And since these changes require only small temperature variations or small voltages, the devices would consume very little energy.

Creating an interface between crystals

The molecular orientation of liquid crystals makes them useful in key functions of various display technologies. They can also form "blue phase crystals", in which the molecules are arranged in highly regular patterns, which reflect visible light.

To design a blue phase crystal interface, Xiao Li and his colleagues at the University of Chicago, USA, developed a method that is based on chemically patterned surfaces, on which liquid crystals are deposited, thus providing a means of manipulating their orientation molecular. This orientation is then amplified by the liquid crystal itself, allowing a specific blue phase crystal to be carved into another blue phase crystal.



The process, the result of theoretical predictions and experimentation to arrive at the right design, allowed the creation of specific crystal forms within the liquid crystals - something unprecedented.

Not only that: The newly sculpted crystal can be manipulated with temperature and electricity to change from a blue phase to another type of blue phase, thus changing color.

"This means that the material can change its optical characteristics very precisely," said Professor Juan de Pablo, from the Argonne National Laboratory. "We now have material that can respond to external stimuli and reflect light at specific wavelengths, for which we had no good alternatives before."

This ability to manipulate crystals on such a small scale also makes it possible to use them as models to manufacture perfectly uniform structures at the nanoscale.

Details of the manufacturing process and the interfaces inside the crystal.

Blue phase crystals

Blue phase crystals have the properties of liquids and crystals, which means that they can flow and are flexible, while having highly regular characteristics that transmit or reflect visible light.

They also have better optical properties and a faster response time than traditional liquid crystals, making them good candidates for optical technologies.

In addition, the projections responsible for reflecting light in the blue phase crystals are separated by relatively large distances compared to traditional crystals, such as quartz. The larger size of these projections facilitates the engineering of the interfaces between them, a process notoriously difficult in traditional crystalline materials.

These interfaces are important because they provide ideal locations for chemical reactions and mechanical transformations, and because they can make it difficult to transport sound, energy or light.





Bibliography:

Article: Sculpted grain boundaries in soft crystals

Authors: Xiao Li, José A. Martínez-González, Orlando Guzmán, Xuedan Ma, Kangho Park, Chun Zhou, Yu Kambe, Hyeong Min Jin, James A. Dolan, Paul F. Nealey , Juan J. de Pablo

Magazine: Science Advances

Vol .: 5, no. 11, eaax9112

DOI: 10.1126 / sciadv.aax9112

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