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A groundbreaking new principle – Korean researchers discover a revolutionary phenomenon in liquid crystals

Materials Science Crystal Art Concept

Researchers have discovered that objects can achieve directed motion within a liquid crystal by periodically changing their dimensions, potentially paving the way for advances in microrobotics.

A research group from the Ulsan National Institute of Science and Technology (UNIST), led by Professor Jonwoo Jeong from the Department of Physics, recently discovered a groundbreaking principle of motion on a microscopic scale. Their findings show that objects can achieve directed motion simply by periodically changing their dimensions within a liquid crystal medium. This innovative discovery offers significant potential for numerous areas of research and could lead to the development of miniature robots in the future.

In their research, the team observed that air bubbles in the liquid crystal could move in one direction by periodically changing their size, unlike the symmetrical growth or contraction typically observed in air bubbles in other media. By introducing air bubbles, comparable in size to a human hair, into the liquid crystal and manipulating the pressure, the researchers were able to demonstrate this extraordinary phenomenon.

Sung by Jo Kim, Joonwoo Jeong and Eujin Um

From left to right Sung-Jo Kim, Professor Joonwoo Jeong and Research Professor Eujin Um. Credit: UNIST

The key to this phenomenon lies in the creation of phase defects within the liquid crystal structure next to the air bubbles. These defects disrupt the symmetrical nature of the bubbles, causing them to experience a unidirectional force despite their symmetrical shape. As the bubbles fluctuate in size and push and pull the surrounding liquid crystal, they are propelled in a consistent direction, defying the conventional laws of physics.

Sung-Jo Kim, the study’s first author, noted: “This groundbreaking observation demonstrates the ability of symmetrical objects to exhibit directional motion through symmetrical movements, a phenomenon previously unseen.” He further emphasized the potential applicability of this principle to a wide range of complex liquids in addition to liquid crystals.

Pulsating bubbles spread in NLC

Pulsating bubbles spread in NLC. Credit: UNIST

Professor Jeong commented: “This intriguing result underlines the importance of breaking symmetry in both time and space in driving motion at the microscopic level. Moreover, it is promising for advancing research into the development of microscopic robots.”

Reference: “Symmetrically Pulsating Bubbles Swimming in an Anisotropic Fluid by Nematodynamics” by Sung-Jo Kim, Žiga Kos, Eujin Um and Joonwoo Jeong, February 9, 2024, Nature communication.
DOI: 10.1038/s41467-024-45597-1

This research was supported by the National Research Foundation of Korea (NRF), the Institute of Basic Science (IBS) and the Slovenian Research Agency (ARRS).