Machine Vision Based Measurement of Dynamic Contact Angle in Microchannel Flows

When characterizing flows in miniaturized channels, determination of the dynamic contact angle is important. By measuring the dynamic contact angle, the flow properties of the flowing liquid and the effect of material properties on the flow can be characterized. A machine vision based system to measure the contact angle of a front or rear meniscus of a moving liquid plug is described in this paper. In this research, transparent MABS-based flow channel structures, sealed with adhesive tapes are used. The transparency of the channels enables image based monitoring and measurements of flow variables, including the dynamic contact angle. It is shown that the dynamic angle can be measured from a liquid flow in a channel using the image based measurement system. The image processing algorithm has been developed in a MATLAB environment. Imaging is done using a CCD camera (Firewire connection) and illumination is created using a custom made ring light.