(490a) Temperature Dependence of Diffusiophoresis Using a Novel Microfluidic Approach.

Diffusiophoresis (DP) is being explored for targeted delivery applications such as for drug delivery or transporting sensing and recovery agents to hidden oil in reservoirs. Although these applications involve temperatures higher than room temperature, most experimental studies of DP to date have been carried out at room temperature, and only one theoretical study has considered temperature dependence. Based on theory, DP mobility (D_DP) depends on zeta potential of colloids, viscosity and permittivity of solvent and diffusivities of ions. Since, all these parameters depend on temperature, D_DP does as well.

In this work, we performed systematic DP measurements at a range of temperatures to test theoretical predictions. To do so, we developed a novel microfluidic approach that allows us to impose truly steady state gradients and make direct and repeatable D_DP measurements at a range of temperatures. As a model system, we performed experiments with negatively charged polystyrene particles under NaCl gradients and validated the approach at room temperature. We carried out experiments at temperatures ranging from 20⁰C to 70⁰C and found DP velocities and D_DP to monotonically increase with temperature in relatively good quantitative agreement with theoretical predictions. Our results give further confidence to DP theory to predict DP mobilities under high temperature conditions.