Diffusiophoresis of Colloidal Particles in Non-Electrolytic Solutions

Plant vascular systems rely on a gradient of sucrose and water to move necessary nutrients and particles throughout the plant, however a model to quantify how particles, such as proteins, are transported is lacking. Diffusiophoresis, which is the movement of particles in a fluid due to a concentration gradient of a solute, such as sucrose, can serve as an explanation for this trasportation. This research aims to study the diffusiophoresis of varying-sized fluorescent colloidal particles. Microfluidics is used to mimic the plant micro-vascular system to determine if diffusiophoresis can influence particle movement. By utilizing Raman spectroscopy, we monitored the spatiotemporal variation of the sucrose concentration and observed the movement of the particles in a microfluidic chip using fluorescence imaging; these are designed to minimize convection and allow for movement caused by Brownian motion and diffusiophoresis. Through these observations, we mapped the particles' velocities in relation to the concentration gradient of water and sucrose to determine if the movement is correlated to diffusiophoresis. Promising results showing particle movement towards water have been obtained suggesting diffusiophoresis can affect the movement of these particles. The movement of these particles can represent the movement of proteins in plant systems, giving a plausible theory about how physiological nutrients and biological building blocks are transported in plants.