Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT)

Abstract

In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT). We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids.

Depletion of carbon nanotube depositions and tube realignment in the spreading of sessile drops

“…Formation of organized flow patterns, similar to those reported in [17], could only be seen after 40-60 s, as the drop had already fully settled on the surface. Adding IPA to the mixture was found to induce a more erratic behavior of the internal currents in the (less viscous) drops, giving rise to chaotic flows that only settled down gradually.…”

Buckling and collapse during drying of a single aqueous dispersion of casein micelle droplet

“…The cap radius decreased substantially while the height tended to be constant. As evaporation progressed, the change in concentration of proteins would have changed the rheological properties of the interface, leading to a solegel transition (Haw, Gillie, & Poon, 2002;Manukyan et al, 2013;Okuzono, Obayashi, & Doi, 2009). It can be supposed that a thin skin would have been formed directly affecting the dynamics of the droplet and causing buckling as the water evaporated Pauchard & Allain, 2003).…”

Deposition and drying dynamics of liquid crystal droplets

“…OCM employs low coherence interferometry to measure reflected back-scattered signals from different depths within thick samples (droplets)52. For flow visualization, the SSY droplets were doped with a very dilute suspension of rinsed micron sized non-functionalized polystyrene particles; note, small numbers of added particles have been shown not to significantly affect the LCLC phases53.…”