Fluorinated smectics – New liquid crystalline medium for smart windows and memory displays

2020

Nanomaterials

Nanomaterials in liquid crystals are a hot topic of contemporary liquid crystal research. An understanding of the possible effects of nanodopants on the properties of liquid crystals is critical for the development of novel mesogenic materials with improved functionalities. This paper focuses on the electrical behavior of contaminated nanoparticles in liquid crystals. More specifically, an analogy between electrolytes and ion-generating nanomaterials in liquid crystals is established. The physical consequences of this analogy are analyzed. Under comparable conditions, the number of ions generated by nanomaterials in liquid crystals can be substantially greater than the number of ions generated by electrolytes of similar concentration.

Section: Introductionmentioning

confidence: 99%

On the Analogy between Electrolytes and Ion-Generating Nanomaterials in Liquid Crystals

2020

Nanomaterials

“…As a result, their physical properties can be tuned in a desirable way. This fact enabled numerous applications of liquid crystals including ubiquitous liquid crystal displays (LCD) [1] and liquid crystal on silicon (LCoS) displays for virtual and augmented reality [2], tunable components of biomedical equipment (lenses, filters for hyperspectral imaging) [3,4], polarization and phase control devices (waveplates and retarders) [5,6], diffractive optical elements [7], spatial light modulators and beam-steering devices [8], light shutters [9,10], smart windows [11,12,13], various tunable signal processing devices operating at microwave and millimeter wave frequencies [14,15], and countless others.…”

Section: Introduction: Ions In Liquid Crystalsmentioning

confidence: 99%

Evaluating the concentration of ions in liquid crystal cells: hidden factors and useful techniques

Proceedings of the 2nd International Online Conference on Crystals

2020

Many of the liquid crystal devices are driven by electric fields. Ions, typically present in molecular liquid crystal materials in minute quantities, can compromise the performance of mesogenic materials (in the simplest case, through a well-known screening effect). Even highly purified liquid crystals can be contaminated with ions during their production and handling.Therefore, measurements of the concentration of ions became an important part of the material characterization of liquid crystals. Interestingly, even a brief analysis of existing publications can reveal a quite broad variability of the values of the concentration of ions measured by different research groups for the same liquid crystals. It reflects the complexity of ion generation mechanisms in liquid crystal materials and their dependence on numerous factors. In this paper, an overview of ion generation mechanisms in liquid crystals and modern ion measurement techniques is followed by the discussion of frequently overlooked factors affecting the measured values of the ion concentration. Ion-generating and ion-capturing properties of the alignment layers (or substrates) of liquid crystal cells are considered and used to evaluate a true concentration of ions in liquid crystals. In addition, practical recommendations aimed at improving the measurements of the ion density in liquid crystals are also discussed.

“…Thermotropic liquid crystals are widely used in the design of tunable electro-optical devices. They include liquid crystal displays (LCD) [1], tunable lenses [2], filters [3], wave plates [3], retarders [3], diffractive optical elements [4], optical shutters [5,6], and smart windows [7], to name a few. In the majority of cases, all of them are driven by electric fields [8].…”

Section: Introductionmentioning

confidence: 99%

“…This type of liquid crystal based applications considers ions a nuisance because of many negative side effects caused by ions in liquid crystal devices (image sticking, image flickering, reduced voltage holding ratio, overall slow response) [9][10][11][12]. There are also electro-optical devices relying on ions in liquid crystals (optical shutters and smart windows) [5][6][7]. That is why an understanding of possible sources of ion generation in liquid crystals is very important [13].…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle-Enabled Ion Trapping and Ion Generation in Liquid Crystals

Advances in Condensed Matter Physics

2018

Nowadays, nanomaterials in liquid crystals and their possible applications in the design of tunable, responsive, and wearable devices are among the most promising research directions. In the majority of cases, all liquid crystal based devices have one thing in common; namely, they are driven by electric fields. This type of device driving can be altered by minor amounts of ions typically present in liquid crystal materials. Therefore, it is very important to understand how nanodopants can affect ions in liquid crystals. In this paper, a recently developed model of contaminated nanoparticles is applied to existing experimental data. The presented analysis unambiguously indicates that, in general, nanomaterials in liquid crystals can behave as a source of ions or as ion traps. Physical factors determining the type of the nanoparticle behaviour and their effects on the concentration of ions in liquid crystals are discussed.