Effects of quantum dots on the properties of ferroelectric liquid crystals
Mukherjee, Prabir K. ‘Effects of quantum dots on the properties of ferroelectric liquid crystal’. Liquid Crystals (2023): 1–6.
In this theoretical study, the authors consider mixtures of ferroelectric liquid crystals (FLC) and quantum dots to study the effects of quantum dot concentration on pitch length, spontaneous polarisation and tilt angle of the chiral smectic-C* phase of materials with the smectic-A* to chiral smectic-C* transition. The theory is modelled using Flory-Huggins and Landau theories. It was found that in the quantum dots doped FLC systems, an increase in the quantum dot concentration leads to a subsequent increase in the pitch length, spontaneous polarisation and tilt angle of the material. After a qualitative analysis, the authors found agreement between the theoretical and experimental results.
Geometry of focal conics in sessile cholesteric droplets
Kamien, Randall D., Yuriy Nastishin, and Brigitte Pansu. ‘Geometry of focal conics in sessile cholesteric droplets’. Proceedings of the National Academy of Sciences 120, no. 46 (2023): e2311957120.
There is an array of complex textures that can be found in liquid crystal phases, especially those that display one-dimensional periodicity, such as smectic and cholesteric phases. In this work, the authors work with a cholesteric system with a very precise geometry – a sessile cholesteric droplet sitting on a glass substrate and surrounded by glycerol. Via optical microscopy, they uncover focal conic flowers, the petals of which form ellipses of Duplin cyclides. By observing the droplets from different directions, the authors are able to work out the 3D architecture of the flower. Furthermore, they also studied the effects of the droplet size and the value of the pitch.
Chiral active membrane: odd mechanics, spotless flows, and shape instabilities
Al-Izzi, Sami C., and Gareth P. Alexander. ‘Chiral active membranes: Odd mechanics, spontaneous flows, and shape instabilities’. Physical Review Research 5, no. 4 (2023): 043227.
Chirality can be found in numerous living systems and the active mechanics of these systems are not only driven by these chiral components but also generate chiral morphologies. In this paper, the mechanics of active fluid membranes are described in a coordinate-free form, with a particular focus being on the contributions to the stress by chirality. These result in the generation of ‘odd elastic’ forces that are geometric in nature and are formed in response to mean curvature gradients. Consequently, tangential membrane flows circulating the maxima and minima of the membrane curvature are induced. Shape instabilities arise when the membrane shape becomes linearly unstable due to the normal viscous forces amplifying perturbations. These shape instabilities are controlled by an active Scriven-Love number. Examples of spheroids, membrane tubes and helicoids are described with a focus on the relevance and predictions of the aforementioned examples for a number of biological systems.
Minimal model of solitons in nematic liquid crystals
Atzin, Noe, Ali Mozaffari, Xingzhou Tang, Soumik Das, Nicholas L. Abbott, and Juan J. de Pablo. ‘Minimal Model of Solitons in Nematic Liquid Crystals’. Physical Review Letters 131, no. 18 (2023): 188101.
Liquid crystal solitons have been the subject of interest for quite some time; however, their mechanisms of formation, as well as their structure are not well understood. In this paper, the authors describe a minimal model for achiral nematic liquid crystal solitons. This model reveals the essential requirements of soliton generation in the absence of added charges. These requirements are inhomogeneity of the surface which consists of an adsorbed particle capable of producing a twist in the director structure, the presence of an applied AC field to couple the director’s orientation to flexoelectricity and dielectric constant. The basis of the model consists of a tensorial representation of confined liquid crystals and predicts the formation of solitons shaped as ‘butterflies’. It was noted that upon increasing the applied field, the ‘bullet’ solitons detach from the butterfly wings and move freely through the system. All of these observations from the model are in agreement with experimental data for confined nematics between chemically treated parallel plates.