Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 7 of 7

Full-Text Articles in Physics

Statistical Mechanics Of Bend Flexoelectricity And The Twist-Bend Phase In Bent-Core Liquid Crystals, Shaikh M. Shamid, Subas Dhakal, Jonathan V. Selinger May 2013

Statistical Mechanics Of Bend Flexoelectricity And The Twist-Bend Phase In Bent-Core Liquid Crystals, Shaikh M. Shamid, Subas Dhakal, Jonathan V. Selinger

Chemical Physics Publications

We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second-order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters.


Direct Piezoelectric Responses Of Soft Composite Fiber Mats, M. Varga, J. Morvan, Nicholas Diorio, E. Buyuktanir, John Harden, John L. West, Antal Jákli Apr 2013

Direct Piezoelectric Responses Of Soft Composite Fiber Mats, M. Varga, J. Morvan, Nicholas Diorio, E. Buyuktanir, John Harden, John L. West, Antal Jákli

Chemical Physics Publications

Recently soft fiber mats electrospun from solutions of Barium Titanate (BT) ferroelectric ceramics particles and polylactic acid (PLA) were found to have large (d(33) similar to 1 nm/V) converse piezoelectric signals offering a myriad of applications ranging from active implants to smart textiles. Here, we report direct piezoelectric measurements (electric signals due to mechanical stress) of the BT/PLA composite fiber mats at several BT concentrations. A homemade testing apparatus provided AC stresses in the 50 Hz-1.5 kHz-frequency range. The piezoelectric constant d(33) similar to 0.5 nC/N and the compression modulus Y similar to ...


Characterization Of Cellular Uptake And Toxicity Of Aminosilane-Coated Iron Oxide Nanoparticles With Different Charges In Central Nervous System-Relevant Cell Culture Models, Zhizhi Sun, Vinith Yathindranath, Matthew Worden, James A. Thliveris, Stephanie Chu, Fiona E. Parkinson, Torsten Hegmann, Donald W. Miller Mar 2013

Characterization Of Cellular Uptake And Toxicity Of Aminosilane-Coated Iron Oxide Nanoparticles With Different Charges In Central Nervous System-Relevant Cell Culture Models, Zhizhi Sun, Vinith Yathindranath, Matthew Worden, James A. Thliveris, Stephanie Chu, Fiona E. Parkinson, Torsten Hegmann, Donald W. Miller

Chemical Physics Publications

Background: Aminosilane-coated iron oxide nanoparticles (AmS-IONPs) have been widely used in constructing complex and multifunctional drug delivery systems. However, the biocompatibility and uptake characteristics of AmS-IONPs in central nervous system (CNS)-relevant cells are unknown. The purpose of this study was to determine the effect of surface charge and magnetic field on toxicity and uptake of AmS-IONPs in CNS-relevant cell types.


Surface Induced Phase Separation And Pattern Formation At The Isotropic Interface In Chiral Nematic Liquid Crystals, Rafael S. Zola, L. R. Evangelista, Y.-C Yang, Deng-Ke Yang Jan 2013

Surface Induced Phase Separation And Pattern Formation At The Isotropic Interface In Chiral Nematic Liquid Crystals, Rafael S. Zola, L. R. Evangelista, Y.-C Yang, Deng-Ke Yang

Chemical Physics Publications

We study the pattern formation of a chiral nematic liquid crystal under a wetting transition. In the isotropic-liquid crystal transition, a surface-enhanced effect happens and a thin liquid crystal layer forms at the substrates of the cell. In this confined system, chirality, elastic anisotropy, surface anchoring, and wetting strength interplay. A striped pattern is formed due to the chiral nature of the material and the tilted anchoring at the isotropic boundary. As the wetting layer grows from cooling the sample, first the stripes rotate through a process where dislocation defects are formed. As the wetting layer grows further, the periodicity ...


Simulation Study Of Seemingly Fickian But Heterogeneous Dynamics Of Two Dimensional Colloids, Jeongmin Kim, Chanjoong Kim, Bong June Sung Jan 2013

Simulation Study Of Seemingly Fickian But Heterogeneous Dynamics Of Two Dimensional Colloids, Jeongmin Kim, Chanjoong Kim, Bong June Sung

Chemical Physics Publications

A two-dimensional (2D) solid lacks long-range positional order and is diffusive by means of the cooperative motion of particles. We find from molecular dynamics simulations of hard discs that 2D colloids in solid and hexatic phases show seemingly Fickian but strongly heterogeneous dynamics. Beyond translational relaxation time, the mean-square displacement is linear with time, t, implying that discs would undergo Brownian diffusion and the self-part of the van Hove correlation function [G(s)(r, t)] might be Gaussian. But dynamics is still heterogeneous and G(s)(r, t) is exponential at large r and oscillatory with multiple peaks at intermediate ...


Comment On "The Limits Of Flexoelectricity In Liquid Crystals", Peter Palffy-Muhoray Jan 2013

Comment On "The Limits Of Flexoelectricity In Liquid Crystals", Peter Palffy-Muhoray

Chemical Physics Publications

In their paper, using the principle of energy conservation, F. Castles, S. M. Morris, and H. J. Coles [AIP Advances 1, 032120 (2011)] establish inequalities involving the elastic and dielectric constants and flexoelectric coefficients of liquid crystals. They then argue that recently measured values of flexoelectric coefficients by Harden et al. do not obey these inequalities, hence they violate the principle of energy conservation. In this comment, we point out that in their calculation, Castles et al. use an inappropriate value for an elastic constant, hence their conclusions, predicated on the outcome of this calculation, are not justified. Copyright 2013 ...


A Cellulose Liquid Crystal Motor: A Steam Engine Of The Second Kind, Yong Geng, Pedro Lucio Almeida, Cheng Cheng, Peter Palffy-Muhoray, Maria Helena Godinho, Susete Nogueira Fernandes Jan 2013

A Cellulose Liquid Crystal Motor: A Steam Engine Of The Second Kind, Yong Geng, Pedro Lucio Almeida, Cheng Cheng, Peter Palffy-Muhoray, Maria Helena Godinho, Susete Nogueira Fernandes

Chemical Physics Publications

The salient feature of liquid crystal elastomers and networks is strong coupling between orientational order and mechanical strain. Orientational order can be changed by a wide variety of stimuli, including the presence of moisture. Changes in the orientation of constituents give rise to stresses and strains, which result in changes in sample shape. We have utilized this effect to build soft cellulose-based motor driven by humidity. The motor consists of a circular loop of cellulose film, which passes over two wheels. When humid air is present near one of the wheels on one side of the film, with drier air ...