Condensation dynamics at the solid-liquid interface on micro- and nano-structured surfaces by Total Internal Reflection method

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A new experimental setup combining Total Internal Reflection methodology coupled with optical microscopy was proposed to observe closely the dynamic interactions between condensing drops and solid surfaces. Visualisation setup consisting of a long working distance optical microscope lens Keyence VH-Z50L (spatial resolutions 6.1 x 4.6 mm^2 at 50x, 610 x 460 microns^2 at 500x coupled with a CCD camera (500 frames per seconds) was built.Optical microscopy was applied to image condensation of drops on lubricant infused surfaces LIS. By shifting the plane of view/focus using a micrometer x-y stage the first experimental observations looking directly at the solid-liquid/gas interface were acquired. Observations at the solid-liquid/gas interface reveal the intimate interactions between condensing drops and the solid structures as well as the intimate interactions between the condensing drops and the oil. Observations put forward the lower solid-condensate direct interactions in the case of hierarchical micro-/nano-structured LIS when compared to solely nano-structured LIS. The lower direct drop-solid interactions offer in turn lower adhesion of the condensate to the lubricant infused hierarchical surface inducing the shedding of smaller drops when compared to nano-structured LIS, which is characteristic of high heat transfer.Due to short duration of the grant since the PI moved to a new academic position at The University of Edinburgh, the second part of the setup comprising; laser, sapphire cooling stage, halogen lamps, optical microscopy side view, was not completely finalised.