Pretty Liquid Crystal Experiments Could Reorganize Electronic Displays
A new approach to electrophoresis is giving researchers more control over how they play with small particles.
Electrophoresis is the movement of particles in solution under a current–a phenomenon that can be exploited for use in everything from ePaper to DNA separating gels. Instead of using a normal fluid to conduct current, researchers led by Oleg Lavrentovich tried using liquid crystals as their conductive fluid.
Liquid crystals, like those seen in the first three pictures above (which might look similar to the patterns you’ve seen when you push on the screen of some of your electronics), act like a fluid. But instead of being a disorganized jumble of molecules, the individual rod-shaped particles line up parallel to each other. When they take on different orientations, they refract different colors of light, a phenomenon called birefringence.
The last picture in the set shows a 10 micron glass sphere moving in a liquid crystal carrier. You can see the “tail” of unorganized liquid crystal around and above the object (it would be moving in a plane with the screen, from top to bottom). This tail is what propels the object through the charged liquid crystal.
The liquid crystal can be used to propel small objects (anything bigger than about a half a micron wide) in a variety of ways and trajectories based on how the crystals are aligned. The parallel lines of molecules can be set up in such a way that when a current is applied, the object moves through the liquid crystal, following the track, and being propelled by the “tail” of deformed liquid crystals behind it. In this way, the liquid crystal can also move non-charged particles and those with symmetrical structures, which were troublesome when using non-crystalline carriers.
From the paper, which was published in Nature:
The phenomenon offers new perspectives for practical applications where highly flexible, precise and simple control of particle (or cargo) placement, delivery, mixing or sorting is needed. Examples include microfluidic devices and electrophoretic displays.
Images: Nature / O. Lavrentovich