Active colloids are widely used to understand phase behavior and phase transformations of various classical systems. These processes can be thermodynamically driven due to changes in concentration, pressure, or temperature. Additionally, active colloids have gained attention in modeling molecular systems to explain the origins of physical properties at the nanoscale. This presentation will explore the use of superparamagnetic colloids in a time-varying magnetic field to characterize phase behavior and bulk properties using a classical approach.
System of superparamagnetic colloids in high frequency rotating magnetic fields generate a phase map as a function of particle density and field strength. Paramagnetic colloidal interactions mimic Lennard-Jones potential; thus, the phase behavior exhibits properties of a molecular system. Phase transformation dynamics and diffident morphologies under the binodal and spinodal curves are analyzed using Minkowski functionals. These characterization techniques provide a better understanding of the spatiotemporal evolution of different phases.
Additionally, we explain the coexistence between the particle sparse (bulk)- particle rich (clusters) phases under a binodal curve using a classical nucleation theory and vapor-liquid equilibrium model. With this approach, one can define the equivalent vapor pressure for the system of interacting colloids, which shows an exponential relationship with the effective temperature of the system. Additionally, this equivalent vapor pressure follows Kelvin's equation that depends on the average size of particle clusters. Thus, this novel approach of applying classical theory to a system of particles helps tie up bulk properties to individual interactions, which is crucial in exploring physical properties such as vapor pressure, surface tension, etc., at the nanoscale.
About the speaker :
Kedar received his bachelor's degree in chemical engineering from the Institute of Chemical Technology (ICT), Mumbai, India, in 2012. He then moved to the US and earned his doctorate in 2017 from Lehigh University, under the supervision of Prof. James Gilchrist. His research was mainly focused on the colloidal assembly using a convective deposition. He is currently working as a postdoctoral researcher at Rice University with Prof. Lisa Biswal. Kedar's work preliminary interests in understanding colloidal bulk behavior using classical and statistical thermodynamics.