Understanding exactly how droplets and bubbles stick to surfaces is a “100-year-old problem”. People love working with water. It is cheap, bountiful and still a mystery. These guys at MIT used Scanning Electron Microscope and adapted a weaker vacuum that has the ability to change the surface angle and to push and pull droplets across the surface with a tiny wire. Then they can investigate how these droplets of water stick to the surface at the droplets leading and trailing edges.
“People have only been able to make sketches” of how droplet adhesion works, Paxson says. With the new high-resolution imagery, it is now clear that as a droplet peels away from a rough surface, the round droplet forms a series of tiny “necks” adhering to each of the high points on the surface; these necks (which the researchers call “capillary bridges”) then gradually stretch, thin and break. The more high spots on the surface, the more of these tiny necks form. “That’s where all the adhesion occurs,” Paxson says.
This research on surface tension and adhesion could have implications on cooling of power plants, ink & coating research, fabrics, packages and medical devices. Maybe it might even make a better supersuit.
It might also help in us to understand several biological process like the lotus effect.
Using lasers and Marangoni effect to control liquids at the microscale is awesome. This is concentrated in two projects by a scientist at Wayne State University. The first is Optofluidic Tweezers that manipulate particles. This technique uses the not compelely understood Marangoni flow, which is a surface tension-driven phenomenon that becomes more powerful at a small scale. Why are people spending money on this?
He can use these droplets for liquid handling. This important for all sorts of applications that I won't mention because some of them have not been invented. It is also just really cool to move water with lasers. That kind of ability currently only belongs to Superman.
The second project is called "Tensiophoresis: Label Free Droplet Sorting in Surfactant Microgradients," To make better cell sort droplets based on their chemical composition but without the use of labels. Tensiophoresis uses the phenomenon of capillary migration to sort droplets based on their chemical composition, without the fluorescent labels typically required in such assays. There are again a range of things to do with this technique from cell sorting to understanding biology better. Find out more here: http://phys.org/wire-news/122908381/new-techniques-enable-more-faster-testing-of-biological-liquids.html
There is a whole bunch of science in food. I find learning about science while eating is delightful. The chef/ inventor/economist/food extraordinaire Nathan Myhrvold is a true polymath and has amalgamated the world of food and the world of science. As this blog deals with surface tension I took the clause out from the article here that talks about surface tension. 'Mayonnaise is not just a sandwich spread, but a wonder of surface tension between droplets of oil.' This is nicely explained here. Basically the mayonnaise is a unique emulsion which contains the mixture of water and oil and thus called a colloid. One of the the major components in the mayonnaise is oil. The oil is dispersed throughout the lesser amount of continuous aqueous phase (water). However, the interesting part about mayonnaise is that the structure can be easily disrupted because of this unusual relationship between the oil and aqueous phase. Integration of processing and colloid chemistry is essential to understanding the formation and stabilization of the mayonnaise. An emulsifier needs to be added (in this case egg yolk lecithin) in order to get them to mix the two phases properly. And that is why it is a wonder of surface tension. Without an emulsifier breaking the interfacial tension between the oil and water phase there would just phase separation of water and oil. This happens when these emulsifiers go rancid. Learn more about mayonnaise here before shoving that mayo dripping burger into your mouth. http://1chemistry.blogspot.fi/2012/03/mayonnaise-production-method.html
To meet these requirements,
the researchers used a fabrication technique called the
Langmuir-Schaefer method, which involves dispersing pre-enriched
semiconducting nanotubes on a water surface. The floating nanotubes
spread out to cover the whole surface as a result of the surface
tension. Applying a compressive force assembles the nanotubes into
well-ordered arrays, and the compression is stopped when the nanotube
film becomes incompressible, which indicates that nanotube arrays have
covered the entire surface. The resulting nanotube arrays have a 99%
semiconducting purity and are aligned within 17° of one another.
To meet these requirements,
the researchers used a fabrication technique called the
Langmuir-Schaefer method, which involves dispersing pre-enriched
semiconducting nanotubes on a water surface. The floating nanotubes
spread out to cover the whole surface as a result of the surface
tension. Applying a compressive force assembles the nanotubes into
well-ordered arrays, and the compression is stopped when the nanotube
film becomes incompressible, which indicates that nanotube arrays have
covered the entire surface. The resulting nanotube arrays have a 99%
semiconducting purity and are aligned within 17° of one another.
See the compression from the top to the bottom frame.
Kibron MTX-LB has arriers that can do this simply and accurately.
Researchers are doing really cool stuff at IBM (especially at the Thomas J. Watson Research Center). Besides their feats on Jeopardy they are building dense array nanotubes. They want to make carbon nanotubes that are purely semiconducting, well-aligned and cover the entire substrate. You would have thought that would have been done already. Right? Not so...
The Langmuir Schaefer technique is employed here. A Langmuir-Schaefer film is when one or more monolayers of material (in this case nanotubes) is deposited from a liquid surface onto a solid substrate. It can be done by dipping the substrate horizontally through a floating monolayer at a constant molecular density) or by placing the substrate in contact with the monolayer. Here they used method involves dispersing pre-enriched semiconducting nanotubes on a water surface. Due to the high surface tension of water the nanotubes float and spread over the surface. Using something like the Kibron MTX-LB you can compress these nanotubes into well-ordered arrays. This is similar to compressing lipid films. When the nanotube film becomes incompressible this is an indication that the nanotube arrays are maximized.
So what has improved? This method allows an increased density of 10 x more. This array covers 500 tubes per micrometer on 100% of the surface whereas the previous array only covered 50 tubes per micrometer on 10% of the surface. Not only that but these tubes can be double packed!
With the increased density better lower cost electronics can be built from the nanotubes. For example that new thin film mobile device that is flexible, economically disposable and possibly optically transparent can be built with ease. This kind of technology may not go into the AppleiWatch but in the future we might be able to see them in other wearable electronic devices. These wearable devices would be substantially better than previous thin-film materials because the more dense equals faster operating speed and lower output resistance.
Last Tuesday was Pancake day or Laskiaistiistai in Finland which precedes Ash Wednesday. It is usually the on the second week of February and in Finland it is a day where kids go outside to sled and hangout in the snow. This could be good with a superhydrophobic coating and bad if their were the off chance of an avalanche. In both cases surface tension is a contributing factor since it involves frozen water.
Making a Faster Sled
However, this snow day could become dangerously awesome if a superhydrophobic coating from Ultraeverdry was applied to the bottom of a sled. (This has the Dudesons written all over it). The super hydrophobic coating repels water and makes the bottom have less friction. Waxing does the same. However, the spray coating from is both superhydrophobic (repelling water like a lotus leaf with a high contact angle) and quite oleophobic (lacking affinity for oils). This makes it quite different than wax.
On a microscopic level the nanomaterial is rough working like the Lotus effect to repel droplets so it is easier for the droplets to maintain their shape with the help of surface tension than it is to wet the surface. One interesting thing about the nanomaterial is that it prevents icing too. However, it probably won't be used for sledding as it is both toxic and expensive.
If one is using this material and going down the hill this fast it could cause an avalanche. This is the case in Luckily, in Finland they have little chance of avalanche (not lucky if you like the mountains). Avalanche are caused by the different levels of the snow changing their properties so one level might be hard packed but the upper level is soft packed and loose. Snow grains are held together by surface tension and air bubbles.
Wet snow grains held together by surface tension from Juneau Empire
If there is unusually warm air or rain it likely will only affect the top pack of snow. As more water trickles down through the snow grains are not bound together by air bubbles and the water's surface tension but rather just suspended in the water. This causes the top snow pack to lose its strength and with some sort of small force like Clark W. Griswold going down the hill on a superhydrophobic sled at super fast speeds this could cause an avalanche (of one of the different kinds shown in the picture).
A new technique to measure surface tension in soft surfaces. A new technique is required because Young's Law fails on soft surfaces because the liquid’s surface tension is able to significantly deform a soft solid.
But should use a Kibron EZ-Pi Plus for a direct observation of surface tension. The one they suggest in their article is an indirect approach and can lead to trouble if it is not clean.
So you are in a place where there is water. This could be on an island, on a dock, on a lake or possibly even a swimming pool. Suddenly someone pools a gun. You think about all the action movies like Lethal Weapon 3 where the hero dives into the water to escape being shot to death.
Can the surface tension of water help you to survive?
The water can probably help you depending on the speed of the bullet fired in the gun. It might not have anything to do with the surface tension of the water although that may help slow the bullet down on first impact.. If you fire a bullet into water one of two things are sure to happen:
1. the bullet ricochets of the surface due to the surface tension of the water.
2. the bullet shatters on the force of impact trying to break the surface tension. even an aluminum bullet will shatter.
However, sometimes a situation may arise that the bullet does not shatter and will break the surface tension in one piece. The bullet might get a little bit destroyed so ballistics test could not identify it. It also might still penetrate your body if it is one piece. However, the surface tension will redirect the bullet and make it more difficult for the person shooting to take an accurate shot. That is how people who are being shot at and take refuge in water don’t getting fatally wounded.
How can water be that bullet proof? Mythbusters does an alright albeit (layman) job at showing how the bullet proof water actually works. Here is a video.
What did I learn? If I’m ever being shot at, I’m looking for the nearest body of water!
Shooting into water at an angle of 23 degrees you need to only be two feet under and three feet away to survive being shot at, even by something as big as a 0.50 caliber weapon. Most of the bullets would disintegrate into a handful of shrapnel on water impact and fall harmlessly to the bottom. Even with very powerful weapons like the M1 the 223 you only need to be in 3 ft of water in order to escape the bullet. So the stronger the gun the less water you need. Modern bullets move much faster that
the water by comparison moves much more like a solid than a liquid, causing
the bullet to self-destruct. So the much slower civil war bullet gave the
water in front of it enough time to move out of the way. This allowed the
bullet to go much farther.
The Mythbusters, as in many of their shows, do not really explain what the forces are behind their experiment though. Although it might seem at first that this has something to do with surface tension. It has less to do about surface tension than the overall surface pressure of the bulk water. To test whether surface tension has an affect one solution would be to raise and lower the temperature of the water or to add a surfactant. Likely this has little impact and the surface pressure might be the larger effect. To test the latter the pool size could be changed.
I was watching old episodes of the Big Bang Theory. Howard Walowitz is on the International Space Station. He is crying to his newlywed wife and to his exhausting and overprotective mother. His crying is unnoticed by his fellow astronauts because of the adhesive forces of surface tension of the water in the tears (also some proteins and fats in there) as well as the absence of gravity make his tears fly up in a ball from his floating into the air. Where they land nobody knows. He could possibly drink his own tears if he wishes.
By the way Canadian astronaut Chris Hadfield (seen in the above video) does not cry in space. Guys with moustaches do not ever cry. Ever see Tom Selleck cry? Nope.
A middle school project about surface and surfactant cleaning ability beats out some project about biomass farts (methane gas in biomass). These girls should work for P&G.
As you know from reading this blog surface tension is like a trampoline. It is like a thin coating of elastic fabric that can hold a particular force (like a child) in the vertical plane and a held by springs supporting that weight in the horizontal plane. We still have a lot to learn about surface tension and its properties though from the Marangoni effect to what they are doing at SLAC National Accelerator Laboratory and at the Lawrence Berkley National Laboratory. There scientists started working with dense water which remained liquid well beyond its typical freezing point.
These researchers then applied a superthin coating to the surface of a barium fluoride crystal. Superthin means in this case no deeper than a few molecules (that is pretty thin).
What did they expect?
They expected to stimulate ice formation when they lowered the temperature below 0 C. However, that would be boring and not worth writing about. Even when lowering the temperature to -14.2 C the water on the surface of the barium fluoride crystal remained liquid. Then things got a little crazy. The molecular structure of the crystal surface transformed into a high density form in a broad temperature range. This mimicked the density that water achieves at higher pressure. This research took three years (three years of trying to explain to your husband or wife of how interesting surface tension is) and included experiments with synchotrons laboratory and computer simulations with Swedish collaborators (det ar jattebra!) What does this mean though? It gives us a better understanding of how water exhibits exotic properties under a range of conditions (said by Anders Nilsson one of the lead authors). Water is exotic and is still the one of the only molecules known to sustain life. Its properties, as shown in this paper published in Nature Scientific Reports, shows how scientists intense fascination with this wonderful simple molecule.
With this information it might help scientist design materials that can 'steer the water structure and properties' like new membranes in water purification, fake rain clouds and efficient hydrogen fuel cells (I made the last two up). These nerds from the SLAC are also exploring other unique unusual properties of water under a range of conditions from understanding the typical freezing point and the solid vs. the liquid form. They are refuting "widely believed concepts" that the pattern
of the crystal's surface, which is similar to the latticed molecular
structure of ice, can greatly impact ice formation by serving as a sort
of artificial template, he says.
First seen here:
http://www.rdmag.com/news/2013/02/synchrotrons-explore-waters-molecular-mysteries
Eating your vegetables today? Nice that you have vegetables to eat. Crops and the agriculture industry has improved significantly over the last 60 years. Everything from better machinery, rotating crops, genetically modified (I hate GMO foods), crop optimization, and crop protection. Crop protection is important. Without proper crop protection many of the vegetables would be ruined by insects, fungus, and disease. Formulators that make crop protection agrosolutions for companies like Bayer, BASF and Dow use surface tension as a critical factor in making sure the formulation is correct. Otherwise the formulation may hit the target but not just slide off into the soil doing nothing for the crop.
Excerpt from Formulation vs. Generics
'To ensure that the product stays on the leaf is then a further
challenge. Scientists add other substances to cushion the impact or
reduce the surface tension. This ensures that the spray mist of droplets
adheres firmly to the leaves and that, by creating large wet areas, the
active substance can penetrate quickly.
"Without the right formulation, even the best active ingredient is useless," notes Dorin''
One device which has helped formulators in agrosolutions is the Kibron Delta-8. The surface tension of eight different solutions can be tested at once. This allows a high throughput and high impact solution so formulators can pinpoint one formulation that works. It saves time to go from research and developing a interesting formulation to actually spraying it on the vegetables that you eat.
Can’t Burst This Bubble Blown a soap bubble? The smaller the radius of curvature causes the bubble to leak gas and collapse easier due to the surface tension. However, putting the bubble on a solid surface (like on a glass slide) cover it with water, nanobubbles can live as much as ten orders of magnitude longer than free bubbles (up to days). The reason for this is unclear. These Dutch researchers say they solved the riddle....
