Contact Angle

 Contact angle is a measure of the wetting of a liquid on a solid surface. It is expressed in degrees, with 0 degrees being complete wetting and 180 degrees being absolute non-wetting.  It is a useful measurement for researchers interested in wetting, adhesion and other phenomena where liquids contact solids. It can also be used to characterize the solid surface itself when contact angles for various wetting liquids are compared. For more on theory click this link.

Methods of Measurement

Goniometry

A drop of the wetting liquid is placed on the solid sample. The image of the drop shape is investigated with the contact angle being the tangent between the drop edge and the solid surface.                                      For more on theory click this link.

Instruments which use goniometry to measure contact angles:

CAM 200research quality computerized goniometer. Strobed monochromatic LED light source, telecentric optics and high speed camera yield exceptional quality images. Data reduction software includes profile fitting to Young-Laplace equation for most accurate contact angle measurements available.

CAM100 low-priced goniometer with computer assisted data reduction. Uses 50mm USB camera and LED lighting. Get the power of sophisticated computer image analysis in an economical package.

Tensiometry

A sample of the solid is hung on a force balance and brought into contact with the wetting liquid.  The change in forces when the solid contacts the liquid are used to calculate contact angles.                            For more on theory click this link.

Instruments which use tensiometry to measure contact angles

Sigma 70 the finest tensiometer available. Fiber range microbalance accurate to 1 microgram. Experiments included in expansive software package allow study of wide range of solid substrates including fibersof less than 10 micron diameters.

Sigma 701(with software upgrade) computer controlled research quality tensiometer. Capable of full range of Wilhelmy method contact angle measurements except very small samples. Modular construction allows upgrade to full  Sigma 70 capabilities. Accurate to 0.01 mN/m.

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