Validating contact angle algorithms for droplets in parallel-plate

Parallel-plate channels, defined as two closely spaced plates confining fluid motion, are widely used in microfluidics. Optical contact angle measurement techniques are particularly suited for analyzing capillary phenomena in such configurations. While prior studies have utilized these methods to evaluate contact angle in electrowetting-on-dielectric systems with stationary droplets, a comprehensive validation of the measurement accuracy remains insufficiently explored. Therefore, in order to verify the accuracy of the observation results, the theoretical value of the contact angle between the two parallel hydrophobic surfaces is calculated by using the two-parameter ellipsoid segment model, and the actual measured value obtained by the mainstream technology is compared. Experimental results demonstrate exceptional agreement between theory and observation: distilled water exhibits a negligible percentage error of 0.548%, while phosphate-buffered saline (PBS) buffer shows a deviation of merely 1.102%. This systematic comparison of theoretical and empirical data for both water and PBS conclusively validates the precision of contemporary parallel-plate contact angle measurement methodologies.