Direct Measurements of Adhesion Forces for Water Droplets in Contact with Smooth and Patterned Polymers

Abstract

A microelectronic balance system was employed to measure the force of spreading (snap-in force) during water droplet attachment and spreading on polymer surfaces and the water-polymer adhesion forces (maximum adhesion and pulloff forces) after droplet compression, retreat and detachment. Equipped with a charge-coupled device camera and data acquisition software, the instrument measured directly the forces; monitored droplet-surface separation, including distances over which droplet stretched; and collected optical images simultaneously. The images were used to analyze capillary and surface tension forces based on measured droplet shape, surface curvature, droplet base radius and values of contact angles. The forces measured with the microbalance were compared to calculated capillary/surface tension forces. Nearly excellent agreement between directly measured and calculated forces was verified for polymers with smooth surfaces. Experiments with patterned polymers with pores and pillars revealed that interpretation of forces requires knowledge of a triple-contact-line characteristic. One relevant parameter, named normalized contact line length, was introduced to surface tension forces to quantify forces measured directly with a microbalance.

Water and Ice Adhesion to Solid Surfaces: Common and Specific, the Impact of Temperature and Surface Wettability

“…One more way of characterization of solid/liquid adhesion, which is intensively developing during recent years is based on the measurement of the maximum adhesion and pull-off forces between the solid surface and the suspended droplet using a microelectronic balance system [5,6].…”

Direct measurement of surface adhesion between thin films of nanocellulose and urea–formaldehyde resin adhesives

“…The measurement is divided into four stages: 1) approaching the film surface toward the liquid droplet until the surface of the film makes contact with the surface of the liquid droplet in an equilibrium; 2) retracting the film downward, which changes the state from an advancing to a receding one, and the adhesion force between the droplet and the film surface increases until maximum and the θmax is reached; 3) stretching the film surface from the surface of the droplet by keep moving the solid film down; and 4) final detachment of the surface of the film sample from the surface of the droplet. The force value at the peak of the curve is referred as the maximum adhesion force (Fmax), which represents the surface adhesion between a liquid droplet and a solid film surface (Sun et al 2017). Table S2 shows a summary of the experimental data of the adhesion force measurements.…”

“…However, in this study, the direct adhesion between nanocellulose and UF resins is determined by measuring the adhesion force (Sun et al 2017;Wang et al 2020a) between nanocellulose films and liquid droplets of the UF resins, as well as by calculating the work of adhesion between the films of the nanocelluloses and UF resins using contact angles via the van Oss−Chaudhury−Good (OCG) method (van Oss et al 1988;Gustafsson et al 2012). These two methods were selected because of their convenience and simplicity.…”

“…2) across the liquid-gas interface for a stretched droplet (see Scheme 1 for details). The combination of these two forces can be expressed using the following equation (Sun et al 2017;Wang et al 2020a):…”

Manipulation of the Superhydrophobicity of Plasma-Etched Polymer Nanostructures

“…Another challenge in mimicking natural surface systems with modulated droplet adhesion is how to effectively control the droplet mobility on an artificial surface. The droplet mobility is fundamentally determined by two factors: The intrinsic droplet-solid adhesion force, which is characterized by the advancing and receding CA on a smooth surface, and the microscopic interaction between the liquid and the solid structures, which is essentially determined by the configuration of a three-phase contact line and its dynamics [ 38 , 39 , 40 ]. The first factor can be controlled by modifying the surface energy through methods such as using chemical coating, while the second factor can be controlled by physically regulating the morphological dimensions of the solid surface.…”