| Popis: |
The main purpose of this thesis is the development of a new methodology of contact angle measurement called ADSA-NA (Axisymmetric Drop Shape Analysis - No Apex) that analyzes drop shape configurations with no apex. Thus ADSA-NA facilitates contact angle measurements on drops with a capillary protruding into the drop. This development is desirable because the original ADSA has some limitations for contact angle measurement, and there is a need for the improvement of the accuracy of contact angle measurement. To develop ADSA-NA, a new reference point other than the apex and a new set of optimization parameters different from those of ADSA had to be defined. The three main modules of ADSA had also to be modified; the image analysis, the numerical integration of the Laplace equation for generating theoretical curves, and the optimization procedure. It was shown that ADSA-NA significantly enhances the precision of contact angle and surface tension measurements (by at least a factor of 5) compared to those obtained from sessile drops using ADSA. Computational as well as design aspects of ADSA-NA were scrutinized in depth, well beyond the level of scrutiny in the original ADSA. On the computational side, the results obtained from one and the same drop image were compared using different gradient and non-gradient edge detection strategies and different gradient and non-gradient optimization methods. It was found that the difference between the results of different edge detection strategies is minimal. It was also found that all the optimization methods yield the same answer with eight significant figures for one and the same image. The determination of the location of the solid surface in the drop image was also further refined. On the design side, the effect of controllable experimental factors such as drop height and drop volume on the accuracy of surface tension measurement was studied. It was shown that drop height is the dominant experimental factor, and larger drop heights yield lower surface tension errors. |
