News Release 

First real-time observation of the chaos within 3D liquid crystals

American Association for the Advancement of Science

A new study offers the opportunity to watch dynamic 3D liquid crystal systems and the chaotic motion within that until now have largely been studied through theory and simulations. By both synthesizing and characterizing 3D active matter, the study achieves two major milestones in the field and offers a "formidable experimental platform" for future observation of complex active materials, says Denis Bartolo in a related Perspective. Active matter can be defined as any system, from flocks of birds to artificial particles, that -- in response to energy input--forms large organized regions through local interactions. Seeking to better understand and capture the movements of active matter in lab, scientists have studied liquid crystals called nematics - rod-shaped molecules that prefer to point in the same overall direction but can also face structural turbulence via the formation of defects. When subject to flow, through a source of energy, the lines of defects in active matter can grow, pinch off or shrink. While well-understood from theory, it is challenging to observe 3D active nematics at high temporal resolution because the molecules are usually too small to be viewed and move too quickly to be tracked over a significant volume of space. Now, Guillaume Duclos and colleagues created a 3D nematic system out of bacteriophage virus particles (rigid rods that provide a nematic phase at room temperature) and microtubules (which can be fed an energy source to create flow throughout the entire sample). Using polarized sheet microscopy, the researchers could rapidly scan the nematic material to track the motion of defects in real time. From this, they found excitations in 3D nematics were primarily disclination lines and loops, including those in the form of Möbius strips, that can nucleate, shrink, open and merge. This discovery may someday help propel the practical applications of smart active materials, the researchers say.

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