Researchers discovered ferroelectricity in 2D vermiculite, boosting electric field responsivity in liquid crystals and paving the way for innovative large-scale displays.
Electro-optical liquid crystal (LC) device with wide applications is a cornerstone of the information society, which can continuously and dynamically modulate the light intensity, polarization, and phase retardation. An ancient theoretical insight proposes that a LC material with both an extremely large geometrical anisotropy and an inherent electric dipole is highly expected to improve the electric field responsivity of LCs.
However, neither commercial organic LC molecules nor R&D LC nanomaterials meet both aforementioned perquisites, while such LCs have not been reported so far. As for now, they are open questions for LC community about whether such an LC exists and the upper limit of its electric field responsivity.
Discovery of Ferroelectricity in Vermiculite
In response to these questions, for the first time, the research team led by Professor Bilu Liu from Tsinghua Shenzhen International Graduate School, Tsinghua University reveal the ferroelectricity in a century-old clay mineral, vermiculite, in its monolayer limit. The two-dimensional (2D) vermiculite possesses an extremely large geometrical anisotropy and the ferroelectricity endows an inherent electric dipole.
By dispersing 2D vermiculite in deionized water, the research team prepares a LC dispersion with 2D ferroelectric moieties. Its electric field responsivity, i.e., the Kerr coefficient, raises the record value of Kerr coefficient by an order of magnitude.
Considering that the 2D vermiculite LC represents a new class of inorganic lyotropic LC with 2D ferroelectric materials, the physical insights provided in this work, such as the relationship between the responsivity and geometrical anisotropy of LC materials, have universality to other potential similar LCs.
Technological Advancements and Future Applications
The breakthrough of the electric field responsivity enables an ultra-low operational electric field and the fabrication of electro-optical LC devices with an inch-level electrode separation, which is not practical previously. A large-scale and energy-efficient prototypical displayable billboard with inch-scale pixels has been fabricated for outdoor interactive scenes, where the letters and digits can be shown on it controlled by smartphone software or human gestures.
“Scientifically, we give a new strategy to design advanced inorganic LCs or LC-like systems with sensitive electric field responsivity. The key is to prepare 2D ferroelectric materials dispersion from layered bulk.” Prof. Bilu Liu said, “From another perspective, the inspiring evidence on 2D ferroelectricity in layered natural minerals brings new opportunities for scalable production and practical application of van der Waals ferroelectric materials.”
Reference: “An inorganic liquid crystalline dispersion with 2D ferroelectric moieties” by Ziyang Huang, Zehao Zhang, Rongjie Zhang, Baofu Ding, Liu Yang, Keyou Wu, Youan Xu, Gaokuo Zhong, Chuanlai Ren, Jiarong Liu, Yugan Hao, Menghao Wu, Teng Ma and Bilu Liu, 21 March 2024, National Science Review.
DOI: 10.1093/nsr/nwae108
The research receive funding from National Natural Science Foundation of China, Department of Education of Guangdong Province, Shenzhen Municipal Science and Technology Innovation Council, Tsinghua Shenzhen International Graduate School
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