Pinning, Retraction, and Terracing of Evaporating Droplets Containing Nanoparticles

Abstract

We consider the dynamics of a slender, evaporating droplet containing nanoparticles. We use lubrication theory to derive a coupled system of equations that govern the film thickness and the concentration of nanoparticles. These equations account for capillarity, Marangoni stresses, evaporation and disjoining pressure; the nanoparticles-induced structural component of the disjoining pressure is also considered. Contact line singularities are avoided through the adsorption of ultrathin films wherein evaporation is suppressed by the disjoining pressure; a similar approach has recently been used by Ajaev [J. Fluid Mech., 528, 279-296, 2005] who has built on the previous work of Moosman and Homsy [J. Colloid Interface Sci., 73, 212-223, 1980]. The results of our numerical simulations indicate that, depending on the value of system parameters, the droplet exhibits a variety of different behaviours, which include spreading, evaporation-driven retraction, contact line pinning, and 'terrace'-formation.

The Flow Characteristics of an Evaporating Ethanol Water Mixture Droplet on a Glass Substrate

“…This interest is driven by many technological and biological applications, e.g. the evaporation of blood serum drops has recently been introduced as a diagnostic tool for certain diseases (5) , Craster et al have proposed the use of drying droplets for nanopatterning deposition (6) and Dugas et al have proposed its use in DNA stretching (7) .…”

Modification of the Young–Laplace equation and prediction of bubble interface in the presence of nanoparticles

“…In a separated study, the evaporating droplets containing nanoparticles were studied theoretically based on the lubrication theory, by deriving a system of equations that govern the film thickness and concentration of nanoparticles [21].…”

“…The modification of the effective thermophysical properties influences the pressure drop and heat transfer coefficient in macro/microchannels [2]. The modification of liquid-gas and solid surface tensions would change the force balance at the triple line and consequently affect its dynamic behavior [7][8] including the radius of triple line [9] and the bubble contact angle [5,10], which has significant effects on the bubble growth and departure process [11][12][13][14][15][16], as well as the boiling heat transfer [6,[17][18][19][20][21][22][23][24].…”

Evaporation of Sessile Water Droplets in Presence of Contact Angle Hysteresis

“…Their results indicated that evaporative flux is not diverging at the three phase contact line, but still has a maximum over there. Craster et al [9] demonstrated also a variety of different behaviours of the system in question: spreading, retraction, contact line pinning, and "terrace" formation.…”

“…Craster et al [9] studied evaporation of sessile droplets to ambient vapour. They used kinetic model of evaporation.…”