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ramé-hart instrument co. January 2014 Newsletter |
| Upstream Contamination |
|
Sebastian Bianchini, an undergraduate
Latin-American college student, observed that particles of mate (a type
of tea from Argentina) appeared to flow upstream when pouring hot water
into a cup of mate.1 Additional experimentation has resulted
in the observation of other particles which can be made to seemingly
float upstream and against the forces of gravity as shown in the video
below.
Troy Shinbrot, a researcher at Rutgers University in New Jersey, has been able to replicate the behavior by observing random and small numbers of particles flowing against gravity and current flow to move upstream in a number of different systems when the surface tension of the water is higher upstream than it is downstream.2 Surface tension produces an elastic film-like shell on the outside surface which is what causes raindrops to bead up on a waxed car, for example. In fact, if it were not for surface tension, then the water drop would not bead up at all but wet out as the contact angle approaches zero. Small particles, however, interact with this elastic film-like surface and disturb the delicate balance resulting in some random particles being pushed upstream toward less contaminated water. Some particles can be seen moving upstream and against the forces of gravity to move to water with higher surface tension. In order to replicate this phenomenon, certain conditions must exist. For example, the waterfall cannot be more than about 1 cm high. And while particles may be able to travel several meters upstream, a surface tension gradient condition must exist in which the water is progressively cleaner (and increasing in surface tension) as the particles move upstream.3 Dr. Shinbrot has suggested that further research may conclude that certain pollutants may flow upstream and that dispensing systems that use pipette tips can become contaminated if contaminants flow upstream into the source liquid. 1 See
http://arxiv.org/abs/1105.2585 |
| Happy New Year |
|
2014 is destined to be an exciting year
for goniometry and surface science. Researchers on a variety of fronts
are working on numerous ways to make the world more hydrophobic. We've
reported on a few of these developments in recent issues of this
newsletter. The development of Self-Assembled Monolayers (SAM), new
adhesive technologies, bioinspired nanostructures, microfluidic and
biomedical applications, oleophobic coatings for tablets, electrowetting
methods, antifouling and biocompatible coatings for marine
surfaces, and myriad other developing technologies are on our list of
things to watch for in 2014.
We look forward to beginning our 53rd year of providing the research community with specialized tools that help answer questions of wetting behavior, contact angle, and surface tension, and that open the doors to discoveries that make the world a better place. |
|
Regards,
Carl Clegg |
