Dynamics of wetting: from inertial spreading to viscous imbibition

Abstract

We report the influence of the nature of boundaries on the dynamics of wetting. We review some work recently published and highlight new experimental observations. Our paper begins with the spreading of drops on substrates and demonstrates how the exponents of the spreading laws are affected either by the surface chemistry or by the droplet shape. We then discuss the imbibition of completely and partially wetting fluids into channels and over microtextured surfaces. Starting with the one-dimensional imbibition of completely wetting liquids in tubes and surface textures, we show that (i) shape variations of channels change the power-law response of the imbibition and (ii) the geometrical parameters of a surface roughness change the spreading behavior. For partially wetting fluids, we observe directionally dependent spreading: polygonal wetted domains can be obtained. We conclude with a tabular summary of our findings, allowing us to draw connections between the different systems investigated, and shed light on open questions that remain to be addressed.

High-resolution liquid patterns via three-dimensional droplet shape control

“…On the basis of our understanding of the reason droplets demonstrate dissimilar contact angles along different directions (line-of-sight), we developed a geometric model to predict the side-length ratio 31 B/A of the octagonal droplets in our experiments. Different depinning contact angles along the two directions, but with the same droplet height (Fig.…”

Short time dynamics of viscous drop spreading

“…This approach has proven very successful in the low-viscosity limit. The coalescence of water drops 13 shows the same dynamics as water drops spreading in total wetting conditions 12,[18][19][20] . In both cases it was found that r ∼ t 1/2 , with prefactors in agreement with potential flow calculations 21 .…”

Wetting of Hydrophilic Electrospun Mats Produced by Blending SEBS with PEO–PPO–PEO Copolymers of Different Molecular Weight

“…Wicking experiments with mat strips were performed to evaluate another aspect of the wetting behavior 31 of electrospun materials. The results are presented in Figure 3a for 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13 capillaries with an equivalent radius of the capillary structure r. Neglecting the hydrostatic pressure, the relation between the height h and time t can be described as 33 :…”