Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List

Full text release has been delayed at the author's request until June 30, 2025

ETD Abstract Container

Abstract Header

Dynamics of Liquid Crystal Based Active Matter

Baza, Hend M
http://orcid.org/0000-0002-0445-1672
http://rave.ohiolink.edu/etdc/view?acc_num=kent1713956403375386

Abstract Details

2024, PHD, Kent State University, College of Arts and Sciences / Department of Physics.
Science of active matter is a multidisciplinary field that focuses on systems that consist of a large number of units converting the energy of the environment into motion. The main goals of this rapidly growing field are: (1) to understand the pattern formation in active systems, and (2) to design the environment to streamline the chaotic motion of active units into useful work. In this work, we pursue these goals through experimental studies of a living nematic (LN) representing dispersions of swimming bacteria B. Subtilis in a lyotropic chromonic liquid crystal (LCLC). LCLC is a biocompatible liquid crystal formed by an aqueous dispersion of disk-like organic molecules such as disodium cromoglycate (DSCG) Since the swimming bacteria impose shear on the surrounding LCLC, the first task of the dissertation is to explore how the externally imposed shear affects the LCLC director, by employing in-situ polarizing optical microscopy (POM), small-angle and wide-angle X-ray scattering (SAXS/WAXS). The LCLC response to shear depends on the shear rate, with the director realigning along the vorticity axis at low rates and parallel to the shear direction at higher shear rates. We use the higher-rate regime to uniformly align the LN. We demonstrate experimentally that upon shear cessation, the activity of the bacteria results in a cascade of structural transformations, which start with the enhancement and growth of bend fluctuations and continue with nucleation and proliferation of topological defects-disclinations, which drive the system to topological turbulence. To address the challenge of useful work extraction, we explore active droplets formed by bacterial dispersions and placed in a thermotropic liquid crystal. The surface anchoring of the droplet is designed to produce a fore-aft asymmetric director field around the droplet, which rectifies the chaotic flows inside the droplet into directional flows outside the droplet, which results in a ballistic unidirectional propulsion of the droplet. We demonstrate that the viscosity and orientational order of the swimming medium of the bacteria can be used for the propulsion optimization.
Oleg Lavrentovich (Advisor)
Sergij Shiyanovskii (Committee Member)
John Portman (Committee Member)
Elizabeth Mann (Committee Member)
Elda Hegmann (Committee Member)
Min-Ho Kim (Committee Chair)
134 p.
Physics
Liquid Crystal, active matter, active droplets, rheology, active suspension, active turbulence, Self-locomotion, Swimming Microorganisms, Bacteria, swimming bacteria

Recommended Citations

Citations

  • Baza, H. M. (2024). Dynamics of Liquid Crystal Based Active Matter [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1713956403375386

    APA Style (7th edition)

  • Baza, Hend. Dynamics of Liquid Crystal Based Active Matter. 2024. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1713956403375386.

    MLA Style (8th edition)

  • Baza, Hend. "Dynamics of Liquid Crystal Based Active Matter." Doctoral dissertation, Kent State University, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=kent1713956403375386

    Chicago Manual of Style (17th edition)

kent1713956403375386
© 2024, all rights reserved.
This open access ETD is published by Kent State University and OhioLINK.