Researchers have discovered that objects can achieve directed motion within a liquid crystal by periodically changing their sizes, potentially paving the way for advancements in micro-robotics.
A research group from the Ulsan National Institute of Science and Technology (UNIST), led by Professor Jonwoo Jeong of the Department of Physics, has recently discovered a groundbreaking principle of motion at the microscopic scale. Their findings reveal that objects can achieve directed movement simply by periodically changing their sizes within a liquid crystal medium. This innovative discovery holds significant potential for numerous fields of research and could lead to the development of miniature robots in the future.
In their research, the team observed that air bubbles within the liquid crystal could move in one direction by altering their sizes periodically, contrary to the symmetrical growth or contraction typically seen in air bubbles in other mediums. 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.
From left are 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, enabling them to experience a unidirectional force despite their symmetrical shape. As the air bubbles fluctuate in size, pushing and pulling the surrounding liquid crystal, they are propelled in a consistent direction, defying conventional laws of physics.
Sung-Jo Kim, the first author of the study, remarked, “This groundbreaking observation showcases the ability of symmetrical objects to exhibit directed motion through symmetrical movements, a phenomenon previously unseen.” He further highlighted the potential applicability of this principle to a wide range of complex fluids beyond liquid crystals.
Pulsating bubbles dispersed in NLC. Credit: UNIST
Professor Jeong commented, “This intriguing result underscores the significance of symmetry breaking in both time and space in driving motion at the microscopic level. Moreover, it holds promise for advancing research in the development of microscopic robots.”
Reference: “Symmetrically pulsating bubbles swim in an anisotropic fluid by nematodynamics” by Sung-Jo Kim, Žiga Kos, Eujin Um and Joonwoo Jeong, 9 February 2024, Nature Communications.
DOI: 10.1038/s41467-024-45597-1
This research has been supported by the National Research Foundation of Korea (NRF), the Institute of Basic Science (IBS), and the Slovenian Research Agency (ARRS).