Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids

Abstract

The growing interest in integrating liquid crystals (LCs) into flexible and miniaturized technologies brings about the need to understand the interplay between spatially curved geometry, surface anchoring, and the order associated with these materials. Here, we integrate experimental methods and computational simulations to explore the competition between surface-induced orientation and the effects of deformable curved boundaries in uniaxially and biaxially stretched nematic and smectic microdroplets. We find that the director field of the nematic LCs upon uniaxial strain reorients and forms a larger twisted defect ring to adjust to the new deformed geometry of the stretched droplet. Upon biaxial extension, the director field initially twists in the now oblate geometry and subsequently transitions into a uniform vertical orientation at high strains. In smectic microdroplets, on the other hand, LC alignment transforms from a radial smectic layering to a quasi-flat layering in a compromise between interfacial and dilatation forces. Upon removing the mechanical strain, the smectic LC recovers its initial radial configuration; however, the oblate geometry traps the nematic LC in the metastable vertical state. These findings offer a basis for the rational design of LC-based flexible devices, including wearable sensors, flexible displays, and smart windows.

Virtual Special Issue Honoring the Legacy of Dr. Bettye Washington Greene

“…Edgehouse et al and Han et al both describe the characterization of various ionic liquids, Darlington et al report on the use of biocompatible ionic liquids to improve blood detection, and Birrer et al describe ionic liquid-in-water emulsions. Wang et al and Norouzi et al report on liquid crystals, while Piñeres-Quiñones et al characterize emulsions of thermotropic liquid crystals. Hu et al, Neibloom et al, Smith, Tran and Richmond, and Langevin all describe recent advances in emulsions.…”

“…Dr. Phillips’ reflection provides a unique perspective on the lasting influence and legacy of Dr. Greene. Following this personal reflection, we present invited research articles submitted to this VSI to honor Dr. Greene and further recognize the importance of her work in advancing the discipline. − We then include selected recent articles published in Langmuir that showcase advances within research areas related to those that Dr. Greene devoted her scientific career to advancing. − This collection of articles is divided into four sections that reflect the breadth of topics influenced by Dr. Greene’s accomplishments (Table ).…”

LCPOM: Precise Reconstruction of Polarized Optical Microscopy Images of Liquid Crystals

“…The substantial color changes that accompany such transitions are rarely exploited. 15,18 Understanding how the POM color patterns of LCs correspond to a particular molecular alignment is of interest not only from a fundamental perspective, but also for development of next-generation optical and sensing devices. 19,20 One method to understand the color texture of POM images is to rely on the Michel−Levy chart, which tabulates the interference color as a function of thickness and birefringence.…”

“…The realignment of a confined LC can be triggered by altering the balance between elastic and surface energies; a minute change in the external environment can completely change the material’s appearance under POM. ,, Optical and sensing devices often rely solely on the transition between configurations that exhibit different topological defects (such as bipolar and radial) that are identifiable through the brightness profile. The substantial color changes that accompany such transitions are rarely exploited. , Understanding how the POM color patterns of LCs correspond to a particular molecular alignment is of interest not only from a fundamental perspective, but also for development of next-generation optical and sensing devices. , …”

Phase transitions and topological defects in discotic liquid crystal droplets with planar anchoring: a Monte Carlo simulation study

“…Under such conditions, the morphology of the liquid crystal becomes highly responsive to external stimuli, particularly to those that modify the interfacial conditions such as surfactant adsorption phenomena and mechanical strain. [23][24][25] Recent studies have shown that the properties of liquid crystal nanodroplets can be tuned by changing their size and shape. 26,27 In ref.…”