Semester of Graduation
Master of Chemical Engineering (MChE)
Over the past few decades, the out-of-equilibrium transport and assembly of colloidal particles have been drawing significant interest due to their myriad applications in biology, engineering, and physics. In the absence of any external force, micro and nanoparticles perform Brownian motion in dispersion and are termed as passive colloids. In contrast, active colloids are a class of particles where a net imbalance of fluid flow around their surface drives their net migration in space when subjected to an external electric field. While several studies have shown the ability to program the dynamics of active colloids using an external electric field, their interactions with passive colloids remain poorly understood and many fundamental questions are unanswered. For example, what is the role of active forces vs interparticle interactions in governing the configuration of the resultant assembly? How do the surface characteristics of the particle influence the interactions and assembly? To answer these questions, in this thesis we report a binary system that takes energy from an external alternating current (AC) electric field to assemble and propel micromachines made of passive “trailers” and active “engines”. To study the dynamics and stability of such a system we start from a homogeneous system made of passive particles and then introduce activity by adding anisotropic particles with triangular metal patches. By changing the electric field strength, we control the long-range interactions between the two types of particles and investigate the competing role of propulsive vs assembly forces on the structural evolution and corresponding pathways. We also do a probabilistic study for the formation of different dimers, trimers, and tetramers at different field conditions. This fundamental investigation on the co-assembly and transport of active and passive colloids lays a foundation to design functional materials capable of performing mechanical work at micron and nanoscale.
Choudhury, Brishty Deb, "ELECTRIC FIELD DRIVEN CO-ASSEMBLY AND TRANSPORT OF COLLOIDS USING ACTIVE-PASSIVE INTERACTION" (2022). LSU Master's Theses. 5633.