Measuring contact angle and meniscus shape with a reflected laser beam

Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact ang...

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Bibliographic Details
Published in:arXiv.org 2013-06
Main Authors: Eibach, T F, Fell, D, Nguyen, H, Butt, H J, Auernhammer, G K
Format: Article
Language:English
Subjects:
Ammonium bromides
Angle of reflection
Contact angle
Cylinders
Image reconstruction
Laser arrays
Laser beams
Lasers
Liquid surfaces
Measurement techniques
Polystyrene resins
Rotating cylinders
Solid surfaces
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Description
Summary:Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle \(\varphi\) to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.
ISSN:2331-8422
DOI:10.48550/arxiv.1306.0506