MeasurementPrinciples
Experimental approaches for determining surface and interfacial tension from forces, pressures, interface shapes and detachment conditions.
No single tensiometric method is universally valid.
Surface and interfacial tension can be determined from forces, pressures, interface shapes or detachment conditions. These observables describe the same interfacial thermodynamics, but the experimental assumptions differ between methods.
Method selection must therefore begin with the experimental question. Relevant factors include interfacial age, phase combination, expected tension range, density difference, sample volume, temperature, viscosity and susceptibility to contamination.
Explore experimental routes to interfacial tension.
Shape-, pressure-, force- and detachment-based approaches each provide access to different experimental conditions and time windows.
How to Select a Tensiometric Method
Method selection begins with the experimental question and must consider interfacial age, phase combination, expected tension range, density difference, sample volume, temperature, viscosity and susceptibility to contamination.
Profile Analysis Tensiometry
Profile analysis determines surface or interfacial tension from the shape of an axisymmetric pendant or sessile drop or from an attached bubble by fitting the measured contour to the Young–Laplace equation.
Pendant Drops at Liquid–Gas & Liquid–Liquid Interfaces
Pendant-drop profile analysis can be applied to liquid–gas and liquid–liquid interfaces, with the density difference between the phases entering directly into the evaluation.
Oscillating Drops & Dilational Response
Periodic variation of drop volume changes interfacial area and produces an oscillatory tension response that can be used to characterize dilational elasticity and viscosity of adsorption layers.
Maximum Bubble Pressure Tensiometry
Maximum bubble pressure tensiometry determines dynamic surface tension at short surface ages from the pressure evolution of a growing bubble at a submerged capillary.
Wilhelmy Plate Tensiometry
The Wilhelmy method measures the vertical force acting on a thin plate intersecting the interface, with the interfacial contribution depending on wetted perimeter and contact angle.
Du Noüy Ring Method
The Du Noüy ring method measures a force maximum while a ring is drawn through an interface, with correction factors required because the meniscus geometry changes during withdrawal.
Drop Volume & Drop Weight
Drop-volume methods infer interfacial tension from drop detachment at a capillary and can access time windows between rapid bubble-pressure measurements and long-time static methods.
Capillary Pressure Methods
Pressure-based approaches determine interfacial tension from known or simultaneously observed interface curvature and are particularly useful when density differences are too small for strong gravitational deformation.
Different observables, one interfacial quantity.
Tension can be determined from interface shape, pressure, force or detachment. Each route has its own experimental assumptions and operating range.