Vertically-Oriented-Capillary Video-Microscopy: Drops Levitated by a (Reacting) Fluid

Microscopy in a vertical capillary provided the ability to continuously observe the dynamic particle phenomena on microscopic objects levitated by an imposed flow. Such a technique was developed and used to monitor flow-levitated droplets, by manually regulating the imposed flow so as to keep the droplets suspended in the area of view. Local sudden increases and decreases in temperature were achieved with an external heating filament, which produced rapid changes in the fluids’ properties (viscosity and density). Even in such cases it was possible to control the levitated drop’s position in the microscope’s field of vision by adjusting the levitating fluid’s vertical flow. The shrinkage and alteration of levitated acid drops that react with the basic nanoparticles of levitating oil, verified that, when compared to static conditions, fluid flow significantly accelerated the neutralization of the acid drop by the oil’s basic nanoparticles. Allowing droplets to levitate and rotate due to the flow of another fluid in high-temperature regions, this technique may be used as an improved way to mix contents in suspended microscopic droplets.