Electrically Controllable Fingerprint Texture and Diffraction Pattern of Polymer-Stabilized Cholesteric Liquid Crystals

Fingerprint textures formed in chiral nematic liquid crystals can interact with light to generate complex, random transmitted or reflective patterns and can be used in several applications, optical devices, anticounterfeiting measures, tunable diffractive optics, and microfluidic devices. Here, we report the fabrication and properties of electrically controllable fingerprint textures and their associated diffraction patterns using polymer-stabilized cholesteric liquid crystals (FP-PSCLCs). While FP-CLCs exhibit different fingerprint textures each time an electric field is applied and removed, FP-PSCLCs stabilized with a small amount of polymer show the same fingerprint texture upon application and removal of a low AC voltage. Applying a sufficiently high AC voltage to FP-PSCLCs can induce random movement of ionic charges (i.e., hydrodynamic instability), leading to a different FP texture. The application of mechanical force to the FP-PSCLC sample can also induce a temporary texture independent of the electrically induced FP texture. In the absence of external stimulation, both the initial FP texture and the deformed temporary FP texture were observed to remain unchanged for several months, demonstrating a bistable behavior due to the memory effect of the polymer network of the FP-PSCLC.