Collimated light

Quantum mechanics

Reflection (computer programming)

Beam (structure)

Materials science

Total internal reflection

Computer science

Contact angle

Laser

Physics

Laser beams

Optics

Composite material

Programming language

Wetting

Surface tension

Beam expander

Angle of incidence (optics)

Optics Express

We present an optical method of simultaneous measurement of liquid surface tension, contact angle, and the curved liquid surface shape, which uses the light reflection from this liquid surface due to the wettability. When an expanded and collimated laser beam is incident upon the curved liquid surfaces vertically, the special light reflection pattern, which includes a dark central region and a bright field outside, was observed. A critical spot on the curved liquid surface was found, and the dark field distribution is related to both the width of incidence beam and this critical spot. In our experiment, the different dark field distribution patterns were recorded when the width of the incidence beam changed. The liquid surface tension, contact angle, and the liquid surface shape were measured simultaneously. The proposed method is a new effective tool for present wetting characterization methods.

Simultaneous measurement of liquid surface tension and contact angle by light reflection