Optical tensiometers (also known as goniometers or contact angle meters) allow direct measurements of surface tension, interfacial tension and contact angles. Optical tensiometry is an extremely versatile technique used for characterization of both liquids and solids. Applications range from developing engineered surfaces and technical liquids to controlling the purity of semiconductors.
Measuring surface tension, interfacial tension or contact angles provides information on material properties such as wettability, absorption, surface free energy, adsorption, spreading, cleanliness, surface heterogeneity and interfacial rheology. These properties are pivotal when studying and developing engineered surfaces and technical liquids. They are also valued information when controlling solid surface and liquid quality.
An optical tensiometer captures drop images and automatically analyzes the drop shape as a function of time. The drop shape is function of surface tension of liquid, gravity and the density difference between sample liquid and surrounding medium. On a solid the liquid forms a drop with a contact angle that also depends on the solid’s surface free energy. The captured image is analyzed with a drop profile fitting method in order to determine contact angle and surface tension.