Monday, 27 May 2013

Spheres can form squares

Spheres can form squares

How to make fit a square peg into a round hole?  If you are using spherical micrometer sized particles that are colloids and have an oil water interface you might want to adjust the surface tension.  You can minimize the surface of these spherical particles to make a more compact square like stackable structure by placing these particles on a curved oil-water surface e.g. the meniscus.  The same effect is observed in your bowl of Cheerios (cereal) and is called the Cheerio effect.  It has been suggested to be used to see the self assembly of small structures (likely how evolution first started in reactions of dirty volcanic ponds).

Thursday, 23 May 2013

Better understanding of water's freezing behavior at nanoscale

Better understanding of water's freezing behavior at nanoscale

They say that 'engineering approaches may be able to be taken to tune the surface tension of water so that the ice crystallization rate can be controlled.'  How would that be?  Adding an external current, nucleation, what....?

Tuesday, 21 May 2013

Soft matter offers new ways to study how ordered materials arrange themselves

Soft matter offers new ways to study how ordered materials arrange themselves

"When you are making the toroid, the forces on the needle are large enough that the surrounding material behaves as a fluid," he explained. "Once you stop, the elasticity of the outside fluid overcomes surface tension and that freezes the structure in place."

Making Doughnuts shape droplets out of liquids is really cool... mmmmmm...Doughnuts.  

Fabric channels lab-on-a-chip ideas to remove sweat | News | The Engineer

Fabric channels lab-on-a-chip ideas to remove sweat | News | The Engineer

They made smaller sewer channels in the fabric where sweat runs to keep people dry.  Capillary action at its finest...

Wednesday, 15 May 2013

A Better Surfactant for Counteracting the Coffee Ring Effect: Marangoni vs. The Bacterium

The particles are coffee.  The edge to the right is the coffee ring.  It gets 

If you are reading this you may be drinking a cup of coffee.  Or if you are not drinking some coffee you have likely experienced this in your lifetime.  The coffee ring effect is the so named effect of how coffee or other materials move to the edge of the ring (see above video).  This effect occurs when a puddle with particles (it does not matter if they are coffee or not) evaporates leaving a characteristic ring around the perimeter.  This should be renamed to the red wine effect as it is more commonly seen after spilling wine (likely wine is more spilled because of the alcohol).  This effect is also seen with other materials like paint and adhesives.

Evaporation induces a Marangoni flow occurs inside the droplet.  If the Marangoni flow is strong can do the opposite redistributing the particles back to the centre instead of to the edges.  For the coffee ring (or red wine ring) to take place it is suggested that the Marangoni flow must be weak.  Water which composes both wine and coffee has a weak Marangoni flow.  In order to disrupt this flow surfactants can be added which lower the surface tension and stop the Marangoni flow likely leaving a even surface.  But what kinds of surfactants?

Recently researchers from KU Leuven found a bacterium that produces natural surfactants that counteracts the Marangoni flow and the spreads out the material causing the coffee ring effect more evenly.   The bacterium does this naturally...

Pseudomonas aeruginosa is a dangerous bacterium that can cause infections in open wounds. "A Pseudomonas aeruginosabacteria colony wants to find as large a breeding ground as possible. To avoid overconcentration on the edges of a wound when spreading itself during the drying-out process, the bacterium produces substances that counteract the coffee ring effect."

Interestingly the researchers took one extra step and genetically modified the bacterium so they would not produce surfactants.  The coffee ring effect was visible with these genetically modified bacterium.

Better surfactants are needed in all kinds of projects from inks, paints, adhesives to cleaning the surface of your table.  So the next time you are drinking coffee or wine and produce the a unsatisfactory visible ring think about the Marangoni effect and the bacterium that can fight it.

Making surfactant formulations from this natural surfactants from this bacterium can be made better with the only High Throughput Device, The Kibron Delta-8.    In only 12 minutes you will have an answer which Surfactant formula is better to get rid of the coffee stains.  

Tuesday, 14 May 2013

Multi-scale Foam Computer Simulation and Why more Scientists Should Take Bubble Baths

Foams, Foams, Foams 

People like to blow bubbles.  This starts off when you are a child and blowing bubbles with soap.  It is fun.  I once won 500 euros (700 US dollars) in travel money because of blowing bubbles to show how they are related to other membranes.  Mathematician Thomas Young (and other scientists that predate him) studied bubbles in the 18th century to show how elastic.  The surface tension and elastic properties of the bubble and the surrounding environment cause it not to pop.  With a single bubble it is easier to understand.  With clustered bubbles physicists from Berkley recently figured out how they pop and why they produce a complex bunch of physical events.  Overall this effects the overall stability of all the bubbles.  (One for all and all for one in bubble bath terms I suppose).  After one bubbles pops the other bubbles can quickly rearrange to balance the overall cluster.  A cascade like a fission bomb occurs with a number of sequential pops.  

Mathematicians and scientists have pondered about this. What they did is slow down the time and divide it into steps...Scientists like to break things down into simple solvable problems.  These scientists from Berkley  broke the lifecycle into three phases that can be mathematically modelled:

1) rearrangement - the bubble reorient themselves after a pop
2) drainage - accounts for the effect of gravity and likely the water being drained
3) rupture - the moment when the bubble pops 

They say it in this eloquent yet nerdy statement:
'Liquid drains from the bubbles' thin walls until they rupture, after which the remaining bubbles rearrange, often destabilizing other bubbles, which subsequently pop. Note the sunset reflections. The research could help in modeling industrial processes in which liquids mix or in the formation of solid foams such as those used to cushion bicycle helmets.'  

These of course could help with other foams like bubble baths....

This is a scale-separated approach where important physics is done in each of the distinct scales.  The researchers at Berkley took the expressed equations within a computer simulation and for added realism (what is this a comic book) added the way the sunset would look on the reflected bubbles.  

Many of these problems could have been solved if more scientists took bubble baths like Archemedes.  These problems could help to make better solid foams for bike helmets, the safety foam in Judge Dredd or potentially liquid foams for uhhh well better bubbles baths.

See the whole article in Science

These steps can be seen in this video:


Monday, 13 May 2013

What happens when you wring out a washcloth in zero-G?

What happens when you wring out a washcloth in zero-G? 

The surface tension of water was originally studied by Agnes Pockles while she did her dishes.  While now Chris Hadfield takes this physical concept that is still not totally understood to space using washing dishes as an example.  When people are frustrated that they cannot study science in a University or do not have access to the materials you might be able to take a look around and wash some dishes.  Who knows you may do what Agnes did and publish her findings in Nature.

Friday, 10 May 2013

Changing the Surface Tension of Electronic Inks

For years people have wanted to make circuits using a printer like in their home on paper.  The possiblibilities in the near future to make 'rapid-prototyping circuits, integrated circuit on paper, sensors, functional RFID tags on books, even daily life personal electronics and educational training are endless. This concept is called Printed-Circuits-on-Paper (PCP).  The idea is to make new devices, faster, cheaper and potentially disposable.  Conventionally metal is deposited on a surface using a number of complex methods.    But can you make this faster and do this with a regular desktop printer?  The answer is yes!

There is a problem with doing this.  The main problem people face in this field is to get the material they are printing with to the correct surface tension.  The surface tension of the metal has to be correct in order to spray in the right size on the substrate.  Now scientists in China have made  developed a method to print flexible electronic circuits on paper using liquid metal ink.  Electronic inks are more difficult because they have an extremely large surface tension.  

How did this team from Beijing do this?  Firstly, the scientists improved the adhesion of liquid metal alloy ink by an oxidation strategy.  The team designed new print machinery to overcome the high surface tension of the ink.  Generally you would want the surface tension to be from 37-60 mN/m depending on the substrate and the properties of the ink.  This new machinery has a brush-like porous pinhead (looks a little bit like a mascara brush).  The last step involved a specially coated paper (changing the substrate) that offered this special ink to attach easier. The scientists tested a number of different papers and used AFM to compare their properties.  They mention that the whole printing process can be done at room temperature using an office printer.  This is the future!  

Develop Inks Easier with Kibron Delta-8.  A faster Surface Tensiometer.

Tuesday, 7 May 2013

Columbia engineers manipulate a buckyball by inserting a single water molecule

Columbia engineers manipulate a buckyball by inserting a single water molecule

It will help solve a surface tension problem by understanding a single water molecule and see how it interacts with hydrogen bonds.  "The important role of hydrogen bonds in the properties of water, like surface tension and viscosity, and the precise interactions between a single water molecule and hydrogen bonds, are still unclear," Chen notes, "so our new technique to isolate a single water molecule free from any hydrogen bonds provides an opportunity for answering these questions."

Thursday, 2 May 2013

Blood Spatter Solving Crimes

You may have seen the last episode of CSI, Monk, The Shield, Dexter, Criminal Minds or some other crime show that I am not aware.  The technology is advanced for understanding blood splattering?  Right?  Wrong.

You can understand blood stain pattern analysis to help you recreate the scene of the crime which may interpret the origin or help with identifying the weapon.  

Several kinds of information can be found from blood stain analysis.  For example:

1. Distance from the blood source to the target
2. Direction of travel and impact angles
3. Nature of the force used to cause the bloodshed
4. The object used to cause the bloodshed
5. Sequencing of multiple bloodshed events
6.Interpretation of contact or transfer patterns
When properly documented, bloodstain patterns found at the crime scene, or on a particular person's clothing, can be used to:

What does this have to do with surface tension?  Since blood is an aqueous fluid information information would apply like viscosity and surface tension as well as gravity acting on the fluid (not in space).  Blood can spray like ink around a room and depending on the outgoing force.  Like ink from an ink jet nozzle spraying on paper a bullet passed through the body at a high enough speed can create a similar spray that can flow onto the carpet.  With both the droplet size is important.  For ink the droplet size relates to the pixelation and to get a certain size droplet a specific surface tension needs to be reached.  In the same way the droplet size of a blood stain relates to smaller and smaller droplets like an atomized spray or mist which may relate to faster and faster speeds.  The blood will not break up unless it is acted upon by a force like a bullet.  For the blood to break up the force must be great enough to overcome the surface tension of blood ( 56  mN/m).  The blood when sprayed across the carpet forms a nearly perfect circular shape due to the surface tension of the blood.  This spherical shape will be maintained until the blood droplets hit the surface of the carpet.  The blood spray would depend on the size, and speed of the bullet.    One might be able to calculate the speed and size of the bullet and likely the location of the shooter.  Bullets can reach speeds from 180-1500 m/s.    So with that range you likely would have different blood stains from an exit wound.