ცისანა ზურაბიშვილი

A new type of flexible cholesteric liquid crystal mirror is presented. The simple and effective method for the deposition of a cholesteric mixture on a paper substrate and the particular design of the device give a homogeneous alignment of the cholesteric texture providing mirrors with an intense and uniform light reflectance. A desired polarization state for the reflected light, linear or circular, can be easily obtained varying the thickness and optical anisotropy of the polymer cover film. By using non-azobenzene based photosensitive materials a permanent array of RGB mirrors with high reflectivity can be obtained on the same device. Paper like reflective mirrors are versatile and they can find applications in reflective displays, adaptive optics, UV detectors and dosimeters, information recording, medicine and IR converters.

We have developed a novel, light activated drug delivery containers, based on spiropyran doped liquid crystal micro spheres. Upon exposure to UV/violet light, the spiropyran molecules entrapped inside the nematic liquid crystal micro spheres, interconvert from the hydrophobic, oil soluble form, to the hydrophilic, water soluble merocyanine one, which stimulates the translocation of the merocyanine molecules across the nematic liquid crystal-water barrier and results their homogeneous distribution throughout in an aqueous environment. Light controllable switching property and extremely high solubility of spiropyran in the nematic liquid crystal, promise to elaborate a novel and reliable vehicles for the drug delivery systems.

Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. 

With the rapid development of modern information technology, massive amounts of data are stored that require an information security. Here, we introduce a spiropyran doped polymer dispersed cholesteric liquid crystal film based rewritable medium that can produce high quality visual two-dimensional barcodes for anti-counterfeiting, authentication and security purposes. The prepared film exhibits excellent photochromic properties, improved photosensitivity, high spatial resolution, and numerous rapid write/erase capabilities. Such rewritable material can be efficiently printed over 70 cycles without compromising its readability. Furthermore, the fabricated film is mechanically resistant to small stresses and, hence, it can be directly handled.

A thin layer of the photosensitive cholesteric liquid crystal possessing a high value of the optical activity is studied. Reversible change in the optical activity controlled by two light emission diodes (LEDs) with different emission wavelengths is applied for information recording. The behavior of this structure under exposure to UV and blue light is investigated. A smooth decrease in optical activity caused by the UV light resulting in a change in the color of the structure between crossed polarizers is obtained. The reverse process occurs under exposure to the blue light. On the basis of the obtained results, two methods of optical information recording in such a layer have been demonstrated.

In this work, we demonstrate micro resonators made of liquid crystal blue phase (BP) microspheres, embedded in a polymer/water matrix. The omnidirectional 3D lasing from BPII and BPI microspheres and the temperature-controlled laser tuning within the range of 55 nm from the BPI microspheres were observed for the first time. The potential applications of BPs microlasers range from temperature-controllable, omnidirectional, coherent light micro sources to informational displays and micro sensing devices.

We have prepared the liquid crystal blue phase (BP) microdroplets emulsified in the glycerol environment and investigated their electro-optical properties upon the applied electric field. We showed that the lasing from the supercooled luminescent dye-doped BPI microdroplets can be controlled electrically. When the electric field intensity is increased, the lasing intensity is increased too along with the linewidth that decreases from 6 to 2.5 nm. Besides, the laser lines were shifted toward the shorter wavelength by 11 nm. All effects were achieved via electric field-stimulated structural and symmetrical modification of BPI microdroplets, resulting in their optical anisotropy and birefringence. Luminescent dye-doped liquid crystal blue phase-based microdroplets can find applications as electrically controlled microlaser sources for microphotonics and environmental sensing.