Measurement and analysis of forces in bubble and droplet systems using AFM

Measuring Forces and Spatiotemporal Evolution of Thin Water Films between an Air Bubble and Solid Surfaces of Different Hydrophobicity

“…The air bubble was immobilized on a well-defined circular gold patch (diameter 65 μm, thickness 30 nm) at one end of the cantilever that was hydrophobized with a layer of self-assembled 1-dodecanethiol. 48,55 The position of the cantilever and hence the air bubble was accurately controlled by a piezo-electric transducer and variation of the actual displacement, ΔX(t) of the www.acsnano.org 97 cantilever with time t, was measured and recorded with a linear variable differential transformer (LVDT) that is an integral part of the AFM. 56,57 The timedependent interaction force was measured by monitoring the deflection of the cantilever with a known spring constant through changes in the position of a laser beam reflected from the cantilever on a photodiode detector.…”

Modulating the zeta potential of cellulose nanocrystals using salts and surfactants

“…This is corroborated by the insensitivity of the measured zeta potential to pH when salts are not present, and this result also indicates that the application of the Smoluchowski and Grahame equations (see below) to convert mobility to zeta potential and surface charge respectively [14] are valid approximations for the CNC system. However, it is well known for other interfaces that have some hydrophobic characteristics -air/water, oil/water, gold/water, for example -that surface charge arises from the spontaneous adsorption of ions from solution -likely hydroxide in the case where no electrolyte is present [31]. It is therefore a logical question as to whether celluloseknown to have hydrophobic adsorption sites [32] -can also experience this phenomenon in addition to any charges arising from the surface-bound sulfate ester groups.…”

Measurement of surface and interfacial tension using pendant drop tensiometry

“…Holistic models that account for interfacial deformation, fluid flow and interfacial tension must therefore be developed to access shorter time-scale information. Such modelling is now commonplace in understanding flows in microfluidics [51], colloidal atomic force microscopy [52] and film interferometry experiments [53], and as such could potentially be extended to dynamic pendant drop studies.…”