Dynamics of structural transformation for liquid crystalline blue phases

Liquid crystals are materials that have properties of both liquid and solid. They flow like liquids but can also form ordered structures like solids. Liquid crystals are widely used in devices such as digital displays, light-responsive materials, and sensors. However, despite their widespread use, understanding how they reorganize at the microscopic level has long been a scientific challenge, and the underlying mechanisms remain unclear.

Professor Jun-ichi Fukuda of Kyushu University’s Department of Physics, in collaboration with Dr. Kazuaki Z. Takahashi of the Japan Institute of Industrial Technology (AIST) and the Japan Science and Technology Agency (JST), conducted a study focusing on the cholesteric blue phase , a special type of liquid crystal with unique cubic symmetry. These blue phases form complex three-dimensional structures with unique properties, making them a topic of great interest in basic science and materials engineering.

The research team studied the transition from one blue phase, BP II, to another blue phase, BP I. Previous experimental studies have failed to capture the detailed mechanism of the blue phase transition involving the formation of twin structures.

To gain a deeper understanding of this process, the team used computer simulations conducted by Fukuda and MALIO, a machine learning tool designed by Takahashi to analyze and distinguish the local structure of the BP I and BP II liquid crystal phases. Using the latter machine learning approach, it is possible to distinguish BP II and BP I structures and analyze their evolution over time. The strategy developed by the team can track the transition in real time, revealing key stages in the transition, such as the formation of small BP I domains that grow and eventually form twin boundaries. Their method provides valuable insights into the formation and growth of twin structures during transformation.

“The dynamics of soft materials such as liquid crystals are very complex,” Fukuda said. “This work gives us a deeper understanding of how these materials transform at the microscopic level.”

The method presented in this study could also reveal how layered structures in soft materials, such as polymers and biological systems, undergo similar phase transitions. “Our approach is not limited to LCD,” Fukuda explains. “It can be applied to other complex materials, which could provide new insights into how structures form and change in systems.”