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Direct Observation of Liquid Crystal Droplet Configurational Transitions using Optical Tweezers
Version 2 2020-05-22, 17:35
Version 1 2020-02-10, 19:39
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posted on 2020-05-22, 17:35 authored by Jake Shechter, Noe Atzin, Ali Mozaffari, Rui Zhang, Ye Zhou, Benjamin Strain, Linda M. Oster, Juan J. de Pablo, Jennifer L. RossLiquid
crystals (LCs) are easily influenced by external interactions,
particularly at interfaces. When rod-like LC molecules are confined
to spherical droplets, they experience a competition between interfacial
tension and elastic deformations. The configuration of LCs inside
a droplet can be controlled using surfactants that influence the interfacial
orientation of the LC molecules in the oil-phase of an oil in water
emulsion. Here, we used the surfactant sodium dodecyl sulfate (SDS)
to manipulate the orientation of 5CB molecules in a polydisperse emulsion
and examined the configuration of the droplets as a function of SDS
concentration. We triggered pronounced morphological transitions by
altering the SDS concentration while observing an individual LC droplet
held in place using an optical tweezer. We compared the experimental
configuration changes to predictions from simulations. We observed
a hysteresis in the SDS concentration that induced the morphological
transition from radial to bipolar and back as well as a fluctuations
in the configuration during the transition.