Ultrahigh Kerr Coefficient of Two-Dimensional MXene Liquid Crystals

MXene liquid crystals (LCs) demonstrate remarkable characteristics, making them promising for applications in flexible electronics, energy storage, and biomedicine. Although MXene LCs are known to exhibit field-responsive behavior, their electro-optical (EO) properties, particularly the quantitative Kerr coefficient, its physical origin, and dynamic switching capabilities, remain unexplored, limiting their application in photonics. Here, we systematically investigate electric-field-induced ordering, response kinetics, and the giant EO Kerr effect in MXene LCs. A remarkable Kerr coefficient of up to 4.9 × 10–6 m/V2 is achieved, surpassing conventional LCs by 2 orders of magnitude and ranking among the highest reported for two-dimensional LC systems. This outstanding performance originates from the high geometric anisotropy, giant electric polarizability anisotropy, and large optical anisotropy of the MXene flakes. Furthermore, we demonstrate a proof-of-concept and dynamically switchable anticounterfeiting device enabled by this fast and reversible EO response. This work bridges the fundamental EO mechanisms of MXene LCs with their functional device potential, providing a foundation for their use in next-generation, tunable photonic technologies.