Experimental and numerical study of an evaporating capillary bridge of a binary liquid*

We numerically and experimentally study the evaporating capillary bridges of pure and binary liquids between poly-dimethylsiloxane (PDMS) coated surfaces. The temporal evolution of the bridge is captured using side visualization. The numerical model uses the Galerkin finite element method (FEM), for diffusion-limited species transport equation in cylindrical coordinates. Modified Roult's law is used for the binary liquid, and the ``Aerosol Inorganic-Organic Mixtures Functional Groups Activity Coefficient'' model approximates the activity coefficients. The model was validated using published experimental data for sessile droplets and in-house measurements for capillary bridges. Results reveal longer evaporation periods for capillary bridges than sessile droplets with identical initial parameters attributed to the confined space. Volume evolution for binary liquids is non-linear, dependent on the remaining alcohol percentage. The model accurately predicts observed non-linear evaporation rates for binary liquids. A reduced order model is developed for binary capillary bridges, which shows a good prediction for volume variation and evaporation time with the FEM model. The applications of this research are in rheometers, roller printing, and other areas.