Parientes-Sánchez, Deyvi A.

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    Single particle dynamics around the boundaries of nematic media
    (2018-10-31) Parientes-Sánchez, Deyvi A.; Acevedo-Rullán, Aldo; College of Engineering; Córdova Figueroa, Ubaldo M.; Suleiman Rosado, David; Department of Chemical Engineering; Zapata Medina, Rocío
    Brownian motion of a colloid suspended in a lyotropic chromonic liquid crystal (LCLC's) leads to the description of the transport properties of the medium through a unification of theories where the confinement effect is included. The understanding of the phenomenology of the system using a fluid considered a living liquid, with potential for multiple bioengineering applications, allows us to imitate natural systems, design new devices, and validate stochastic, empirical and virtual models. In this thesis the system is discretized by a mathematical conjecture which catalogs the information of the colloidal dynamics in relation to the stress by confinement of the colloidal system. Significant structural changes of the environment are described due to hydrodynamic disturbances caused by the presence of the colloid, which are in the order of the elastic forces and induce the fluid to behave in different ways. The bulk has similar properties as infinity, where there are no hydrodynamic disturbances caused by confinement and the isodesmic aggregation does not have a considerable impact on the colloidal dynamics. Outside the bulk where the colloid interacts with a surface, the structure of the medium reduces colloidal mobility as a function of the hydrodynamic distance, which is reflected in the increase in the size of the aggregates. Polymeric spherical colloids with radius (R) of 390 nm suspended in an LCLC's shows a similar behavior to gold colloids (R = 50 nm), relating these experiments to the confinement index, this being a third way outside the bulk: colloids between two plates. This discretization of the colloidal dynamics leads us to reveal the viscosity coefficients twist (ȠTwist) and splay (ȠSplay) for each mode, which can be obtained from the Leslie coefficients. However, the viscosity bend (ȠBend) is obtained with a mathematical model that depends on the aspect ratio of the aggregate. The values found for each of the coefficients ȠTwist, ȠSplay, and ȠBend from the colloidal dynamics in a nematic medium with the uniform director in confinement are in the same order as those found in literature.