Dynamics of Drying Process of Polymer Solution Droplets: Analysis of Polymer Transport and Control of Film Profiles

Abstract

We report a series of experimental works about the drying process of polymer solution droplets. Our aims are to analyze the local polymer transport in the drying droplet and to precisely control the profile of polymer film formed after the droplet dries up. For the analysis of the polymer transport, we have established a dynamical observation method for the polymer concentration field by combining the fluorescence microscopy with the lateral profile observation. We observed that a large spatial inhomogeneity of the polymer concentration grows inside the droplet which is caused by the outward capillary flow. For the control of the film profile, we proposed two methods: adding the small amount of surfactant and switching between the solvent evaporation and condensation. These two processes enable us to make a polymer film having a flat profile. Our results propose effective suggestions for controlling the fabrication process of polymer films in inkjet-printing technologies.

Concentration Field Evolution during the Drying of a Thin Polymer Solution Film near the Contact Line

“…In fact, the species inside the thin film (dye and polymer) are transported by two mechanismsconvection and diffusion (eq 3) while convection typically occurs at a much higher rate for both species, as can be shown through the associated Pećlet numbers. 9 As a result, both polymer and dye are expected to be transported together by evaporation-induced convection while diffusion is negligible. This will be confirmed by the calculation of the Pećlet numbers for the dye and polymer throughout the evaporation process.…”

Inkjet printing of uniform dielectric oxide structures from sol–gel inks by adjusting the solvent composition

“…3 reveals a weak and broad endothermic peak appearing at B260 1C, the intensity of which increased with the increasing fraction of PD and was associated with its evaporation. Even though several reports on the drying of polymer solutions 16,[27][28][29][30][31] and colloidal suspensions 17,[32][33][34] emphasize the importance of the flow direction and the velocity on the shape of the dried deposits, the topology of the deposit is not necessarily determined by the flows present in the early stage of drying. In general, there are two flows competing when a binary-solvent ink is drying: the capillary flow towards the periphery of the drying feature and the recirculating Marangoni flow.…”

Simultaneous amplitude-contrast and phase-contrast surface plasmon resonance imaging by use of digital holography

“…The detailed theoretical analysis and an experiment of monitoring the evaporation process of a drop of NaCl injection in real time by use of this method are shown. Evaporation of droplets on a flat substrate, a commonly observed phenomenon in our everyday life, has been a topic of continued interest for several decades because of its important role in the nature and in various engineering fields [15–17]. For the analysis of droplet evaporation, it would be beneficial in models for complex devices or systems that incorporate various sub-processes for which simplified descriptions are needed [18].…”