Liquid crystals: potential energy source

Ariel Lev

Imagine a world in which people can constantly charge cell phones, iPods and computers simply by walking. Thanks to new technology called the bent-core liquid crystal, this world is not far away.

“Imagine harvesting your legs’ energy during walking to charge your cell phone,” said James Gleeson, professor and assistant chair of the physics department. “These liquid crystals can generate electricity in something the size of a postage stamp. The stamp-sized generators can then be stacked to add more power.”

With the help of two grants from the National Science Foundation and the Office of Naval Research, researchers in the Liquid Crystal Institute are currently investigating the applications of the bent-core liquid crystal.

Bent-core liquid crystals are commonly called boomerang or banana liquid crystals because of their crooked shape. Normal liquid crystals appear as long cylinders. Two normal liquid crystals combine to form the bent-core liquid crystal and a curve forms at the joint in the middle.

The bent-core liquid crystal is special because it rotates on its axis much faster than a normal liquid crystal. This is important because it allows the liquid crystals to generate much more energy than what can be created by the slower rotation of a normal liquid crystal.

“The reaction we get from normal liquid crystals is too small to generate electricity,” said Antal Jakli, assistant professor in the chemical physics interdisciplinary program. “But the banana liquid crystal lets us generate electricity on a much larger scale.”

The increased rotation speed of the bent-core liquid crystal might also be used to improve the quality of televisions with liquid crystal displays. The human eye requires about four milliseconds of switching time, the time it takes the eye to perceive changes in its surroundings.

Televisions take longer than that to refresh the picture, but using the bent-core liquid crystal could reduce that time to as little as three milliseconds. This reduction in the refresh rate of the television would make changes in the picture almost impossible to detect. This would improve the perceived quality of the image because the picture could change faster than the human eye.

Bent-core liquid crystals must use energy to make energy. This initial reaction can be created in different ways.

One way to generate the necessary electricity is to place bent-core liquid crystals between thin sheets of plastic material. The material is then placed on the body where bending occurs such as the knees or elbows. Body movement creates energy in the material and the energy is sent through a cord to the device the user wants to charge, Gleeson said.

“The small plastic film bends while walking and generates electricity from the liquid crystals,” Jakli said. “This electricity can be used to power up your cell phone, iPod or computer.”

Electricity can also be generated in the liquid crystals through electromagnets. Research staff and graduate students use the magnets at National High Magnetic Field Laboratory in Tallahassee, Fla.

“We go to the magnet lab because we can’t create magnetic fields that strong here,” Gleeson said. “The lab’s enormous electromagnets each use as much electricity as a small town.”

The magnets at the lab apply forces on the liquid crystals that cannot be used under normal circumstances. The liquid crystals respond weakly to external force, so the lab’s large electromagnets are used to create the necessary force.

Although it is not practical for individuals to use such magnets for power, the large force that can be created in the lab is perfect for researchers who study the properties of the liquid crystals.

Current research is focused on the possibility of using bent-core liquid crystals for a process known as beam steering, and to improve the quality of televisions with liquid crystal displays.

In this case, beam steering is the process of using thin sheets of liquid crystals to redirect beams of light from different sources. This technology could be used to guide telecommunications satellites in space and it could be used by the military when operating laser-guided weapons because the process is extremely accurate.

Currently, many of these applications are only concepts. However, researchers speculate that all of these applications will be made possible by the use of bent-core liquid crystals.

More research is required before these items will be available to the public. Studies by Kent State faculty and graduate students are being done now. More grants to continue research into bent-core liquid crystals are pending.

Contact sciences reporter Ariel Lev at [email protected].