Electrically Tunable Microlens Array Enabled by Polymer‐Stabilized Smectic Hierarchical Architectures

Abstract

Liquid crystals (LCs) are key functional materials that are broadly adopted in various fields due to their stimuli‐responsiveness. Recently, LCs with hierarchical architectures have brought new effects to optics and attracted intensive attention. In smectic A phase, the parallel molecular layers are periodically wrapped to form toric focal conic domains (TFCDs) under antagonistic boundary conditions (i.e., hybrid alignment conditions). TFCD shows great potential in nanofabrication and integral imaging. However, the arbitrary tailoring of TFCD is still challenging, and the robustness of hierarchical configuration hinders the tunability. Here, a radial alignment lattice is adopted to guide the local orientation of LCs and thus facilitates predefining the lattice symmetry and domain size of TFCDs. By introducing polymer stabilization and optimizing the composition, the sample simultaneously maintains the director distribution inside smectic layers and possesses the stimuli‐responsiveness of nematic phase at room temperature. By this means, microlens arrays are demonstrated with reversible electrical tunability. The strategy can be extended to other smectic configurations and may upgrade existing dynamic optics.

Polymerisation of twist-bend nematic textures for electro-optical applications

“…From a different perspective, in the absence of polymer, the FCD defects 16,17 that occur in thin films of smectic A phases under hybrid anchoring ( i.e. homeotropic on one side and planar on the other) have been exploited for various types of optical applications, such as lenses, 18 diffraction gratings, 19 and nanoparticles clustering arrays. 20 FCD defects directly result from the layered structure of the phase because the periodicity of the layers prohibits twist and bend deformations of the director.…”

Performances of Polymer-Dispersed Liquid Crystal Films for Smart Glass Applications

“…Thus, a spatial periodic distribution is created, which causes the formation of the optical grating [ 25 ]. LC in the form of polymer-stabilized liquid crystals (PSLCs) can also be used to fabricate micro lenses [ 26 ]. J.B. Wu reported developing an electrically tunable micro lens with polymer stabilization, which involves doping the LC mixture with RM257 reactive monomer and photo-initializer [ 26 ].…”

“…LC in the form of polymer-stabilized liquid crystals (PSLCs) can also be used to fabricate micro lenses [ 26 ]. J.B. Wu reported developing an electrically tunable micro lens with polymer stabilization, which involves doping the LC mixture with RM257 reactive monomer and photo-initializer [ 26 ]. Another application of liquid crystals is in special light field generators [ 27 ].…”

Advancements and Applications of Liquid Crystal/Polymer Composite Films

“…With the application of an electric field, the orientation of the LC molecules can be switched while the polymer network remains unchanged and gives a restoring force based on the elastic interaction between LCs and the polymer networks to stabilize LC textures. Aside from nematic LCs, , smectic LCs, , cholesteric LCs, , and discotic LCs, , some short-pitch cholesteric LCs such as blue-phase LCs and hyper-twisted nematic LCs have also been explored, showing submillisecond response times and transparent states in the visible region because of their short pitch length . In contrast, for long-pitch cholesteric LCs, the operation voltage is lower but the associated Bragg reflections happen in the visible region .…”

“…In a finite range of an applied electric field, the helical axis is aligned along the electric field and the tilt angle of the LC director depends on the field strength; therefore, the optical response of the film forming a scattering or transparent state to a reflective state is directly regulated . In a polymer-stabilized smectic A liquid crystal (PSSmALC) film, the director distribution inside the smectic layers is maintained even when the SmA phase transforms to a nematic phase; thus, a reversibly tunable focal length of the microlens array is demonstrated . To employ the Kerr effect of BPs for LCDs without alignment layers over large temperature ranges, polymer networks are utilized for stabilizing the BP structure, and the properties of polymer-stabilized blue phase liquid crystals (PSBPLCs), including scattering and unwinding of the double twist structures under an electric field, are different from those of intrinsic BPs. , In addition, the temperature range of BPs can also be broadened to more than 60 K, covering the room temperature range (260–326 K) .…”