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Description
Recently, reflection interference fringe (RIF) and transmission fringe techniques (TIF) have been introduced to investigate the origin of far-field interference fringe formation and to determine a droplet’s contact angle and thickness. In this study, an integrated analysis of the interference fringe (IF) technique is conducted by varying the schematics, including configuration (transmission/reflection), the droplet’s side (left-hand side/right-hand side), and the substrate types (flat/prism). Additionally, the effect of refraction at the droplet edge is considered in relation to the droplet contact angle (sizes), the droplet’s refractive index, the zero fringe radius (FR), and the working distance (WD). Moreover, the effects of the maximum incidence angle and the maximum contact angle are investigated. This integrative study demonstrates that a large contact angle range can be measured using a transmission configuration and the droplet’s right-hand side. Furthermore, the increasing contact angle trend with the incidence angle on the prism substrate for the droplet’s left-hand side is explained through geometric analysis. It is also revealed that the IF technique can determine nanometer-scale thicknesses below 100 nm, corresponding to an ultra-small contact angle of less than 2 micro-radians, with an extended working distance of 3,000 mm. This finding is remarkable, as it shows that nanoscale thickness can be determined using a simple optical configuration under ambient conditions, without requiring a sophisticated setup such as a microscope. It is anticipated that the IF technique can be combined with other nanoscale thickness measurement techniques to enhance its measurement reliability.
| Country | United States |
|---|---|
| Water & Porous Media Focused Abstracts | This abstract is related to Water |
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