The video (played in real time) shows a mineral oil jet (black) passing over a solid inner core (a single optical fiber obscured by the oil) surrounded by a background flow of glycerol. The image is roughly 1mm in height. The high viscosity of the fluids ensures that the Reynolds number is low despite the somewhat large size and serendipitously keeps the oscillation frequency low enough to observe at 30 fps. These particular oscillations appear spontaneously and are being observed at a spatial station a few centimeters downstream from the nozzle that introduces the heavy mineral oil into the glycerol stream. The oscillations grow in amplitude and far downstream result in a train of droplets that appear to be nearly unduloidal in shape.
What it is: A still from this video of a C. elegans nematode encapsulated in a water drop, surrounded by oil, floating atop a water bath. The specimen was inserted into the droplet using hydrodynamic flow focusing. Originally, the intent was to isolate specimens for high through-put screening; surfactant at the oil-water interface renders the individual droplets resistance to coalescing.
What it could be: It turns out that the system may be interesting for more fundamental reasons. Colloids and emulsions can be used as model systems to study crystallization, glasses, and the dynamics of defects. Here is an example of droplets (empty) shifting around, trying to form a perfect lattice (again, these are water drops, surrounded by oil, floating atop water). In this case, capillary action (the "cheerio" effect) provides an attractive potential. It would be interesting to dope such an emulsion with some active nematode laden drops to see how the lattice responds to local, periodic, and anisotropic distortions. While applying bulk forces to such systems has been done in the past, such a local probe would be very interesting to explore.
This is a snapshot of the fuel cell setup I helped design in conjunction with General Motors scientists as a research intern in Dr. Satish Kandlikar's lab at RIT in 2007. The main design goal was to fabricate a fully functional fuel cell that would feature transparent flow channels to allow the observation of water transport during operation. Water management is crucial to proper FC operation: too little and the PEM ceases to function; too much and flooding prevents fresh hydrogen and oxygen from being introduced. As of 2014, the cell was still in operation.
(1) End Plate, (2) Die Springs, (3) Viewing Window, (4) Metal Case, (5) Air/Hydrogen In/Out, (6) Heating/Cooling Water In/Out, (7) Flow Field Lexan Plates, (8) Cathode & Anode Channels.
When an electrically neutral, dielectric sphere is placed in a symmetric binary electrolyte, and subjected to an electric field, polarization of the particle and the electrolyte surrounding it results. The polarization of the electrolyte takes place within a relatively thin layer around the particle known as the electric double layer (or Debye layer). For micron-scale colloids, this layer is thin compared to the radius of the particle; the disparity in length scales can be used to find tractable analytical solutions for the electric potential and charge distributions around the particle. For nano-particles, this assumption is not valid. Instead, I assume that the electric field is weak and use it as a regular perturbation parameter.
At first order in E*, I find the electric potential and charge distribution. At second order, I find the streamlines for the electro-osmotically induced flow and spatial distribution of total charge carriers (pictured). The electric field is directed from south to north; the contours show that the total number of charge carriers or "excess electrolyte" is greater than the bulk around the equator of the particles, and less than the bulk at the poles.