University of Northern Iowa Research Foundation

The University of Arizona

Feredoon Behroozi

Peter Behroozi

Various examples are provided related to determination of contact angle of sessile drops. In one example, a method includes determining a volume of a sessile drop of fluid disposed on a test surface; determining a height of the sessile drop of fluid; and determining a contact angle of the sessile drop of fluid based upon the volume and the height of the sessile drop. In another example, a system includes a volume sensing, a height sensing, and computing that can determine a volume and height of a sessile drop using volume and height data from the sensing, and determine a contact angle of the sessile drop with the volume and the height. The contact angle and surface tension can be determined with at least three of volume, a height, a footprint radius, a radius of maximum horizontal extent, and/or an apex radius of curvature of the drop.

Reliable determination of contact angle of sessile drops

A method and apparatus for determining the contact angle and/or surface tension of a liquid on a solid surface is described. The method involves placing a fluid drop on a solid surface, and gradually increasing its volume by adding more fluid, while continuing to determine the corresponding increase in fluid height, until the drop attains maximum height beyond which additional fluid only increases the drop footprint and not height, and determining the equilibrium height and in turn the contact angle by means of an equation that correlates contact angle with depth below the fluid surface, together with the fluid surface tension and liquid density. The method may in turn be used to determine the fluid surface tension from the equilibrium height when the contact angle and density of the fluid are known.

Method and apparatus for measurement of fluid properties

A non-contact apparatus and method for mapping the wave profile of capillary waves on a fluid surface to determine viscosity of the fluid. Two conducting blades coupled to a sine wave generator are positioned spaced laterally above and near the surface of the fluid to generate a standing capillary wave on the fluid surface between the blades. A laterally moveable fiber optic probe is coupled to a laser to transmit laser light toward the fluid surface and to receive reflected light from the fluid surface. Part of the laser light reflects from the end of the probe and creates an interference pattern with the light reflected from the fluid surface. The light reflected from the end of the probe and from the fluid surface are combined to form an interference signal which is analyzed to obtain the amplitude of the wave directly under the probe. By moving the probe laterally, nodes on the standing wave may be detected to find the wavelength of the capillary wave. One blade may be decoupled from the sine wave generator and the fiber optic probe moved laterally to determine the wave amplitude of a traveling wave as a function of distance which is then used to determine viscosity.

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Cedar Falls, IA, United States of America

Feredoon Behroozi