AUTOMATION OF THE CAPILLARY RISE TECHNIQUE FOR MEASURING CONTACT ANGLES

The measurement of the capillary rise at a vertical surface enables one to measure static and dynamic contact angles. The advantage of this technique is that the measurement of an angle has been reduced to the measurement of a length. To attain high accuracy in the contact angle (±0.2°), the capillary rise measurement has to be made to a precision of about 4·10-4 cm. To date, these measurements have been performed using a conventional optical device, a cathetometer. This procedure is not only time consuming and laborious but also somewhat susceptible to human error. A new approach of measuring the capillary rise is described, using digital image analysis in conjunction with high precision translational stages (resolution of 0.1·10-4 cm). Methodology and results of contact angle measurements will be discussed. © 1990.