Manipulation enhancement of terahertz liquid crystal phase shifter magnetically induced by ferromagnetic nanoparticles by Y. Ji et al., Nanoscale, vol. 11, p. 4933, (2019).
There is an increasing demand for high-performance functional devices with liquid crystals to control and modulate THz waves. In such cases, liquid crystal devices employing external magnetic field to control optical effects are preferred as they do not require ITO electrodes which are polarization selective. Ji et al. report the optical and magneto-optical properties of mixtures of liquid crystals having ferromagnetic nanoparticles in the THz regime. Particularly, magnetically induced birefringence characteristics of the composite systems for THz liquid crystal phase shifter are discussed. A phase shift range between ne and no, by changing the magnitude of the external magnetic field without changing its direction has been achieved. The interaction between magnetic cluster chains formed by the ferroparticles, with the liquid crystal director and the external magnetic field, is explained theoretically by comparing the surface anchoring force and the magnetic moment in the dynamic system.
Phase calibration of liquid crystal based spatial light modulators using the spatial structure of focussed optical fields by L. Turquet, Phys. Rev. Appl., vol. 11, p. 044050 (2019).
Turquet et al. present a diffraction-based in situ technique to calibrate the phase response of liquid crystal spatial light modulators (SLMs). SLMs are useful optical components, and the manufacturers usually provide typical phase response curves for these elements to calibrate the response of liquid crystal SLMs when used in various set-ups. However, the relationship between input and output phase delays of a 2D SLM is unknown. In this paper, the authors show that a phase response curve achieved by modulating the phase of one half of the incident beam and correlating the variations in the corresponding intensity distributions/spatial structure of the focal fields is necessary to understand the output phase delays of SLMs. The accuracy of the technique is illustrated by performing calibrations considering theoretical focal fields. The technique is demonstrated to be useful for any microscopy set-up that utilizes a liquid crystal SLM in the excitation path.
Self-assembly of fractal liquid crystal colloids by N. V. Solodkov et al., Nat. Commun. vol. 10, p. 198 (2019).
Self-assembly of intrusions in liquid crystals due to their interaction with the director field is a topic of massive research interest in recent years. Solodkov et al. present the spontaneous formation of complex structures in double emulsion of water droplets inside a nematic droplet. The properties and the mechanisms of formation of these structures are explained by considering topological rules of creation and annihilation of defects. Numerical analysis is carried out to understand the experimentally observed results, which shows that the ratio between the core of the droplet and inclusions plays a key role in deciding the nature of the resulting self-assembled structure.
Bioinspired synthesis of aqueous nanoapatite liquid crystals by J. Tan et al., Scientific Reports, vol. 9, p. 466 (2019).
Apatite crystals are basic building blocks of bone tissues, and considerable research has been done on the synthesis of apatite nanocomposites. Such synthesis procedures are highly advantageous for applications in bone repair and fixation, however, developing a scalable assembly method is an issue. Tan et al., report the synthesis of aqueous liquid crystal from rod-like nanoapatites with the aid of sodium citrate. The citrate molecules are known to play important roles in facilitating the dispersion of nanoapatites in bone tissue and in controlling the growth of apatite crystals. Detailed synthesis procedures and characterisation of the liquid crystal properties are provided. The results are expected to open up new avenues for the fabrication of macroscopically assembled inorganic liquid crystals for biomedical applications.
Self-powered optical switch based on triboelectrification triggered liquid crystal alignment for wireless sensing by C. Zhang et al., Adv. Funct. Mater. vol. 29, p. 1808633 (2019).
Zhang et al. reports the fabrication and functioning of an optical switch based on polymer dispersed liquid crystals. The switch switches its optical states from its light scattering OFF state to light transmitting ON state, in response to a mechanical force applied to a single electrode nanogenerator, without any extra optical elements or external power supplies. The optical switch is integrated into a visible light operated processing circuit to obtain a wireless sensing and power-free sensing node. Details of the configuration of the liquid crystal films, demonstrations of hand touching and foot stepping triggered wireless alarms are provided. Numerical calculation by finite element method is carried out to understand the electric output from the nanogenerator.