Phoretic Phenomena of Colloidal Particles in a Dead-end Pore Microfluidic Channel

Journal Title
Journal ISSN
Volume Title
Colloidal particles can be manipulated under the gradient of an external field to transport them in the system toward desired locations. The motion of colloidal particles resulting from an imposed or self-generated concentration gradient is called diffusiophoresis which has been used in a wide range of applications such as drug delivery, wastewater treatment, and enhanced oil recovery. This phenomenon provides a low-cost and easy portable method to manipulate particles. Previous works investigated the diffusiophoretic motion of non-porous particles in microfluidic channels both experimentally and theoretically. However, the migration of porous particles under the effect of concentration gradient has not been studied experimentally. In this work, we have used a dead-end pore microfluidic channel to explore the diffusiophoretic motion of porous particles. For this purpose, we first study the migration of non-porous particles in the dead-end pore channel with and without the presence of background concentration gradients. Our results indicate a temporary self-generated concentration gradient is generated in the channel resulting from the interfacial interaction of PDMS walls with the ions present in DI water without introducing any background concentration gradient. In the presence of an electrolyte concentration gradient, the relative difference in the ions' diffusivity (β) and particles’ zeta potential are two main effective factors on the diffusiophoretic motion of non-porous particles. In the next section, we study the diffusiophoretic motion of porous particles, and differences in the case of non-porous particles are investigated. In contrast to non-porous particles, porous particles’ migration under the influence of concentration gradient is a function of pore size, surface area, and surface charge density. The surface charge density of porous particles can change significantly because of counterions diffusion into the porous particles which can result in inversion of motion direction. Therefore, the effect of the interior microstructure of colloidal particles is crucial in controlling their diffusiophoretic motion.
Microfluidics, Phoretic phenomena, Colloidal particles, porous particles, Fluid mechanics
Nooryani, M. (2023). Phoretic phenomena of colloidal particles in a dead-end pore microfluidic channel (Unpublished master's thesis). University of Calgary, Calgary, AB.