Top down imaging is used to extract the contact angle, θ, of drops on surfaces greatly relaxing the requirements and limits demanded by side imaging. The method is compared between two standard lateral measurement techniques (the tangent method and the height/diameter method) for the hydrophilic contact angle of a droplet of water (20 drops of 2 μl each) on borosilicate slide: θ= (52 ± 7)° and (52 ± 6)°, respectively, and (53 ± 8)°, for the proposed method, agreeing within experimental error. This technique can be applied on multiple contact angle measurements, depression, between electronic components and on concave surfaces. The top down method has the potential to revolutionize diagnostics by making contact angle measurements ubiquitous and accessible to low cost imaging.
The feasibility of optically detecting air and water bubbles flowing through the oil is presented. By scanning wavelengths it is possible to add functionalities by implementing a spectroscopy based chemical detection that can directly lead to chemical detection and imaging and/or chemical species tomography of flowing fluids. In this article, a halogen lamp (175 - 1000 W and centered at 1.2 mm) and an IR-array camera (8-12 μm, 31 x 32 pixels and 10 fps) is used to observe the three-phase flow involving oil, air and water.