Droplet evaporation on soft solid substrates

Abstract

Droplet evaporation on soft solid substrates is relevant to applications such as fabrication of microlenses and controlled particle deposition. Here, we develop a lubrication-theory-based model to advance fundamental understanding of...

Influence of Surface Roughness on Droplet Evaporation and Absorption: Insights into Experiments from Lubrication-Theory-Based Models

“…73,74 With soft substrates, deformation of an initially flat solid near the droplet contact line creates surface topography that can pin the contact line during droplet evaporation, leading to predicted behavior consistent with experimental observations. 74 Important open issues in this area include threedimensional effects, the role of nonlinear elasticity, the nature of the solid−liquid interfacial tension, and the fate of suspended solute particles. • Vertical concentration gradients: The rapid-verticaldiffusion approximation, used in the model predictions presented here, cannot describe vertical concentration gradients of the solute, which are important under some conditions, e.g., when a "skin" of particles forms at the liquid−air interface.…”

“…Similarly, wettability (equilibrium contact angle) variations can also be incorporated by using a spatially varying disjoining pressure. Such detailed modeling would allow for more quantitative comparisons between theory and experiment and provide insight into how to design surface topography and wettability to influence droplet dynamics. Soft substrates: While we have focused in this feature article on substrates that are rigid, substrates that are deformable (e.g., polymer gels) are also important for some of the applications mentioned in the Introduction as well as others. − By coupling mass and momentum conservation equations for a deformable solid to the equations governing droplet height, the influence of substrate deformability on droplet height can be systematically investigated. Charitatos and Kumar have developed such models, allowing for disentanglement of the effects of substrate wettability and deformability on droplet spreading and evaporation. , With soft substrates, deformation of an initially flat solid near the droplet contact line creates surface topography that can pin the contact line during droplet evaporation, leading to predicted behavior consistent with experimental observations .…”

“…Such detailed modeling would allow for more quantitative comparisons between theory and experiment and provide insight into how to design surface topography and wettability to influence droplet dynamics. Soft substrates: While we have focused in this feature article on substrates that are rigid, substrates that are deformable (e.g., polymer gels) are also important for some of the applications mentioned in the Introduction as well as others. − By coupling mass and momentum conservation equations for a deformable solid to the equations governing droplet height, the influence of substrate deformability on droplet height can be systematically investigated. Charitatos and Kumar have developed such models, allowing for disentanglement of the effects of substrate wettability and deformability on droplet spreading and evaporation. , With soft substrates, deformation of an initially flat solid near the droplet contact line creates surface topography that can pin the contact line during droplet evaporation, leading to predicted behavior consistent with experimental observations . Important open issues in this area include three-dimensional effects, the role of nonlinear elasticity, the nature of the solid–liquid interfacial tension, and the fate of suspended solute particles. Vertical concentration gradients: The rapid-vertical-diffusion approximation, used in the model predictions presented here, cannot describe vertical concentration gradients of the solute, which are important under some conditions, e.g., when a “skin” of particles forms at the liquid–air interface .…”

“…Soft substrates: While we have focused in this feature article on substrates that are rigid, substrates that are deformable (e.g., polymer gels) are also important for some of the applications mentioned in the Introduction as well as others. − By coupling mass and momentum conservation equations for a deformable solid to the equations governing droplet height, the influence of substrate deformability on droplet height can be systematically investigated. Charitatos and Kumar have developed such models, allowing for disentanglement of the effects of substrate wettability and deformability on droplet spreading and evaporation. , With soft substrates, deformation of an initially flat solid near the droplet contact line creates surface topography that can pin the contact line during droplet evaporation, leading to predicted behavior consistent with experimental observations . Important open issues in this area include three-dimensional effects, the role of nonlinear elasticity, the nature of the solid–liquid interfacial tension, and the fate of suspended solute particles.…”

Size-Dependent Dried Colloidal Deposit and Particle Sorting via Saturated Alcohol Vapor-Mediated Sessile Droplet Spreading

“…6 Because of the coupled energy and mass transfer, and the complex physics involved, 15 evaporation of sessile droplets on solid surfaces exhibits intriguing features, such as surface tension gradient-induced flowerlike patterning of an evaporation droplet spreading on a liquid surface, 16 contraction of evaporating binary-liquid sessile, 17 modulation of evaporationaffected crystal motion in drying saline droplets by varying the saline and surfactant concentrations, 18 hollow rim formation on salt substrates due to droplet evaporation, 19 with nonuniform width mediated by substrate heating with a temperature gradient, 20 to name a few. Recently, researchers have also taken a keen interest in looking at sessile droplet evaporation dynamics on inclined substrates 21,22 and soft substrates. 23 The complex physics associated with a drying sessile droplet has triggered several efforts to tailor and suppress the CRE pattern of drying sessile droplets.…”