Photoactivated Langmuir Monolayers as an Active Polar Fluid

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dc.contributor.advisor Baskaran, Aparna en_US Elif, Demirbas 2012-06-11T19:37:56Z 2012-06-11T19:37:56Z 2012
dc.description Joint BS/MS Program en_US
dc.description.abstract We consider a continuum theoretical description of a Smectic C monolayer made of molecules that can undergo cis-trans isomerization when subject to photo-activation. We use analytical and numerical methods to investigate the dynamics of this system. We show that this system exhibits self-regulation and the existence of propagating solitary waves, central features of an active fluid. Thus we demonstrate that this system can serve as an experimental platform to investigate the physics of this inherently out-of-equilibrium class of materials. The specific results obtained in this study are as follows : a) An equilibrium Smectic C monolayer can exist in one of two states - a homogeneous state and a striped state. b) In the presence of photo-activation the system develops propagating orientation waves. These waves are not a pattern but are rather solitary waves resulting from the self-regulating nature of the dynamics of the system. c) The properties of these waves are characterized as a function of two system parameters, the strength of spontaneous splay and the relaxation rate for the equilibration process of the molecular isomerization. We find that the speed of propagation increases as a function of both these parameters. c) We localize the activation by illuminating the monolayer using slits of various widths. In this case we find that the localization leads to the formation of a domain wall at the edge of the activated region and propagating waves are set up moving away from this domain wall. In the absence of diffusion, the waves remain confined to the slit of illumination. When diffusion is ramped up, the waves penetrate into the dark regions of the system and hence can potentially serve for controlled pattern generation and stabilization in this liquid crystal system. en_US
dc.description.sponsorship Brandeis University, Graduate School of Arts and Sciences en_US
dc.format.mimetype application/pdf en_US
dc.language English en_US
dc.language.iso eng en_US
dc.publisher Brandeis University en_US
dc.rights Copyright by Elif Demirbas 2012 en_US
dc.subject Langmuir Monolayers en_US
dc.subject Photoactive en_US
dc.subject Orientational Waves en_US
dc.subject Traveling Waves en_US
dc.subject Active Polar Fluid en_US
dc.title Photoactivated Langmuir Monolayers as an Active Polar Fluid en_US
dc.type Thesis en_US
dc.contributor.department Department of Physics en_US MS en_US Masters en_US Physics en_US Brandeis University, Graduate School of Arts and Sciences en_US

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