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Pumping Fluid With No Moving Parts
RogerRoast writes "In a study published in Physical Review B (abstract; full version is paywalled), researchers demonstrate for the first time an approach that allows ferrofluids to be pumped by magnetic fields alone. The invention could lead to new applications for this mysterious material. Though numerous industrial, commercial, and biomedical applications for ferrofluids have since been created, the original goal — to pump liquids with no machinery — remained elusive, until now. The ferrohydrodynamic pump method works when electrodes wound around a pipe force magnetic nanoparticles within the ferrofluids to rotate at varying speeds. Those particles closest to the electrodes spin faster, and it is this spatial variation in rotation speed that propels the ferrofluid forward."
Magnetohydrodynamics has been around for quite a while and has long been one of the holy grails of submarine propulsion with prototypes existing now for years. During my last visit to a Los Angeles class submarine, this was a hot topic. Movement of ferrofluids is a natural extension of this concept with applications in everything from medical imaging to cooling of large and small objects. Its pretty exciting, though I am surprised that this is the *first* implementation of this.
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When I want to pump my fluids, I like to have my parts moving, nano or not!
Just bought a new quantum computer, but I'm uncertain how it works.
This is a popular problem in microfluidics. For lab-on-a-chip technology it is very difficult to make a pump with moving parts on the micrometre scale, so researchers have turned to more obscure phenomena. Electro-osmosis is commonly used. Essentially, in a channel with dielectric walls, a very thin ionic double layer naturally forms at the solid-liquid interface. If an electric field is applied in the direction of travel, this drags the thin ionic layer, which in turn mobilises the bulk liquid.
Researchers have been playing with magnetic nano-particles in microfluidic systems for years, usually in the context of a separation system. This spinning phenomena is interesting, and could well be used for more than just pumping. In narrow enough channels, if there is only a moderate concentration of these particles then I doubt they would be close enough together to act as described here.
It's a shame the paywall makes it hard for most of us to really RTFA. I'll report back if there's anything interesting...
So if the ferrofluid is stable
That's what I'm wondering too. It is a heterogeneous mixture where the magnets are solid particles, and a surfactant is needed to keep these particles from clogging together. I've dabbled in making some in a chemistry lab, and it was rather tricky getting the result right. There are the issues of both chemical and mechanical stability. Maintaining a constant flow should help with the clogging problem, but even then, there may be spots of low velocity and high pressure where particles start to concentrate.
Escher was the first MC and Giger invented the HR department.
Pumping without moving parts is not news. Liquid metal cooled nuclear reactors, aluminium foundries use this technology, among other things.
Not rocket science, you can go buy yourself a magnetic metal "pump" today: http://www.cminovacast.com/prod/index.html (google 1st for liquid metal cooling pump).
Oh, you talk about magnetically pumping non-metals. Well that's nice.
There does not need to be a shaft seal. Almost all modern small to medium sized mechanical refrigeration compressors are hermetic or semi-hermetic; that is, the motor, drive, and shaft are all contained inside the system along with the refrigerant.
Though there is no explanation of how it works at the link you provided, "Einstein's green refrigerator" seems to be an absorption refrigeration cycle, which was well known at the time, having been around since the mid-1800's. (According to Wikipedia "In 1922 Baltzar von Platen and Carl Munters . . . enhanced the principle with a 3 fluids configuration. This "Platen-Munters" design can operate without a pump." and "In 1926 Albert Einstein and his former student Leó Szilárd proposed an alternative design known as Einstein refrigerator".) Mechanical pumps are usually used in absorption refrigeration, this design "pumps" the fluid using the differences in vapor pressure and density, relying on boiling, condensing, and the force of gravity. The fact that it does not have any mechanical pumps or moving parts, but relies on gravity, probably means it would be impractically tall and/or very inefficient.
Since butane is a Class A3 refrigerant (very flammable) and ammonia is Class B2 (toxic and flammable) it is doubtful that this system would be used in residential settings. It used to be common to use ammonia, butane, or sulfur dioxide in refrigerators, but there were many tragedies like the one described. Ammonia is still very common in industrial refrigeration systems where safety can be monitored and controlled, and butane, and even sulfur dioxide, have their niches. But ammonia systems are no longer sold for residential use, even in sealed systems, for a variety of reasons.
More here.
Anyone who's worked in audio speaker design and used ferrofluid (a common addition to tweeters and small, wide-band drivers, but sometimes used in larger drivers) knows that it will migrate (flow) with the magnetic field applied by the voice coil... In fact, careful attention must be paid to the ratio of voice coil field to static field and the shape of the magnetic gap to keep the ferrofluid from not blowing out of the gap.
Browsing at +1 - no ACs, I ignore their posts. So refreshing!
There does not need to be a shaft seal. Almost all modern small to medium sized mechanical refrigeration compressors are hermetic or semi-hermetic; that is, the motor, drive, and shaft are all contained inside the system along with the refrigerant.
Other options used widely in industrial and laboratory equipment include peristaltic and membrane pumps where the mechanism is separated from the liquid by a flexible barrier. Magnetically coupled pumps of various designs also exist.
Ferrofluid touch interface
Touch interface that uses Ferrofluids to provides tactile feedback
http://www.halfbakery.com/idea/Ferrofluid_20touch_20interface