Wednesday, 31 October 2012

MOF based motorboat

MOF based motorboat 

Basically they structured peptides in a metal organic framework (MOF).  A cage where peptide (small proteins).  When a salt that chelates and degrades the MOF is introduced the peptide leaks out make a hydrophobic aggregate on the surface of the water.  This reduces the surface tension of the water at that point and makes a surface tension gradient propelling the boat forward a phenomenon known as the Maragoni effect (tears in wine).  Cool right?  We have seen similar boats like this before (like that kid in the science fair and Robin Ras at Aalto) where they use some hydrophobic substance to propel the boat.  The peptide aggregation is something interesting mainly because you might be able to use different peptides or perhaps other biochemicals like nucleotides to get a more hydrophobic effect.

Check out the original article from chemistry world.

Still cannot help you when you are stranded at sea.

Monday, 22 October 2012

The Hummingbirds Tongue and Capillary Action

The hummingbird (Archilochus colubris) drinking from a transparent feeder; Credit: © Wonjung Kim, Franc¸ois Peaudecerf, Maude W. Baldwin, and John W. M. Bush

If you are drinking from a straw this weekend you may notice that some of the water or whatever you are drinking using a straw rises in the straw more than the water in the glass.   This occurs because the surface tension of the water and its attraction to the straw are stronger than gravity.  The same effect will also occur if you place a sponge in water so the water rises through the different bubbles of the sponge defying gravity.  This movement through a thin tube and through bubbles is called capillary action.

So it is no surprise that plants use this for their root system and animals use it.  Capillary action in hummingbird's tongues was recently found to do the same thing by researchers at MIT :

they use 'an incredible self-assembling capillary siphon. Because nectar is stored in shallow, small scale areas in flowers, the tongue is not under the surface but rather adopts capillary action as its preferred method of taking out the "juice."' (as EarthTimes reports)

This is likely how the small hummingbird has survived.  It has exploited this small niche allowing itself to drink the nectar other birds cannot reach.  Surface tension properties allows the hummingbird to be awesome!

See full article here.

Tuesday, 16 October 2012

Drugs, Acoustics and Surface Tension

With the right music you can change the world.  With the right drugs you can change the world.  With the right drugs and right music you have Motley Crue.

Well.....Actually if you put a certain frequency of sound you move a liquid.  Some people thought how to use this for science and they came up with Labcyte.  Labcyte is a liquid handler that moves liquids not with a traditional pump and pipette robots but with acoustics.  It is innovative because this tool changes liquid handling overall without cross contamination from pipette tips.  It is allowing for drug companies to get better results than traditional handling procedures due to concentration effects.  If they could figure out how to accurately determine the surface tension using acoustics  they might be able to compete with companies that make tensiometers.

However, what is even more interesting than Labcyte and handling drugs is actually making drugs using acoustical waves or crystallizing drugs using inverse acoustics.

Drugs when made can fall into two categories: amorphous or crystalline.  For some reason the crystalline drugs do not get absorbed as well.  Amorphous drugs get absorbed in the body better and in lower quantities.   The Department of Energy in the US has found that using acoustics, drugs can be levitated to make amorphous drugs.  The surface tension of the aqueous solution allows the drug to stay in tact when levitating (like in zero gravity).  Likely, the drugs on the surface of the liquid probably form different hydrogen bonds or other types of bonds with each other to form the amorphous drug than in a crystallized form.  For some reason (not sure why) the membranes in the body like these antigravity amorphous drugs more.

Monday, 15 October 2012

My Surface Energy Reducing Non-Stick Pan: A Salute to Teflon

I love cooking.  Cooking to me is the Jeux de vie.  Lately, I have been learning how to cook French and Italian food.  Both require either butter or a lot of olive oil.    In old times part of the reason people use oil or butter was partly for taste and partly to make the things you are cooking not stick to the pan.  If you are cooking pasta and you do not add oil the hydrophobic parts of the starch will make the pasta stick together.  If you are cooking eggs likely part of the eggs will be stuck to the pan.  This is mostly evident if you are using an old cast iron pan.  People know that you need much more oil in order for the food not to stick to the pan.   The non-stick pan was invented for this purpose.  To make eggs and everything else not stick while requiring the need for less oil and fats.  The non-stick pan also saves a little time and frustration when cooking and cleaning up afterwards. 

Tefal Pots and Pans

Around seventy years ago non-stick pans were not available.  The main part of the non-stick pan did not exist.  At the time there was no thermoplastics (or none that I am aware of) that existed to reduce the surface of energy of pans.  So butter, oil, wax and spam were widely the best way to do this before teflon was invented.  The interesting thing about teflon was it was a nice accident.

This is described in Plunkett's own words:

 'On the morning of April 6, 1938, Jack Rebok, my assistant, selected one of the TFE cylinders that we had been using the previous day and set up the apparatus ready to go. When he opened the valve — to let the TFE gas flow under its own pressure from the cylinder — nothing happened. Jack called me over and asked whether we had used all the TFE from that cylinder. I said, I don't think so. We both tinkered with the valve a bit, and then thinking it might be stuck or closed in some way, we disconnected the cylinder from the line and pushed a wire through the valve opening. Still no TFE came out, although the weight of the cylinder showed that there was material inside. We were in a quandary. I couldn't think of anything else to do under the circumstances, so we unscrewed the valve from the cylinder. By this time it was pretty clear that there wasn't any gas left. I carefully tipped the cylinder upside down, and out came a whitish powder down onto the lab bench. We scraped around some with the wire inside the cylinder — or maybe I tapped it — I don't remember which — to get some more of the powder. What I got out that way certainly didn't, add up, so 1 knew there must be more, inside. Finally, more out of curiosity I suppose than anything else, we decided to cut open the cylinder. When we did, we found more of the powder packed onto the bottom and lower sides of the cylinder.'

 Sometimes a happy accident happens. I called the guys at Dupont one time and they told me a similar story.  It is quite funny but science is sometimes an accident.  Without Fleming leaving his bread out on the table we would not have had penicillin.  However, the people making these ´´discoveries´´ like Plunkett or Fleming need to fulfill to secondary need that it is an actual discovery.  So with Plunkett´s discovery that this white stuff was actually a valuable he could reproduce it in the lab and help to make DuPont billions and billions of dollars.  Dupont would go on to use it for a number of applicatons it thought about.  The material allows water and oil to not absorb due to the low surface energy of teflon and the surface tension of water and oil is too high to stick to the pan.  If one were to put water on a teflon pan you would see a surface energy creates nearly a 180 degree angle between the air-water and surface of the teflon  coated pan.  Put another way the water molecules are more attracted to themselves than to the teflon molecules in the pan. 

Other inventions for a great material come from the public.  Fourteen years after Plunkett´s discovery of teflon a French engineer named Marc Gregoire created the first pan (likely he knew that the French tradition of using a lot of butter for cooking was not healthy).  Actually his wife urged the engineer to use the material he was using on fishing tackle on her cooking pans.  That company called Tefal is still around today.  The first US made Teflon pan had less success as the ´´The Happy Pan´´ (not really sure why a pan should be happy but it is some 1950´s bad marketing gimmick).

So due to a few industrious people by accident and coincidence made teflon pans.  Now I am going to use my Tefal pan to cook some pancakes. 

Saturday, 13 October 2012

Bouncing Water Droplet

Still amazed on what you can do with a high speed camera, water and a needle.  Noah Philips shows that water droplets bounce.  Surface tension is amazing....

Wednesday, 10 October 2012

Sailing Last Summer

I went sailing last summer and was thinking about how to explain the difference in buoyancy to surface tension.  To a person they could seem like similar things.  However, they are not.  For buoyancy there is an upward force on the object from the water.  The boat is buoyant and is maintained floating because of this upward force from the particles on the bottom of the boat.  With surface tension there is only the particles on the surface of the water that affect the thing floating.  Since this has less force mostly small things like paper clips can float on the surface of the water and be maintained solely from the surface tension of the water.  Adding soap this surface tension and the small bonds maintaining the paperclip are broken and the paperclip sinks.  Here is a similar explanation from science blogs.

Friday, 5 October 2012

Wednesday, 3 October 2012

K-Y Jelly- the Lubricant of the Century

K-Y Jelly is an awesome lubricant that is unparalleled by other lubricants.  It is used at hospitals and other practical uses (like making Arnold Schwarzenegger glow in the dark green blood) or wrestling.  One scientific use is to use it as a gonioscopic fluid.  It is like the Duct tape of lubricants.  However, most people use it just for sex.  Johnson & Johnson caught onto this trend and started making this into a  significant brand.  Here are a bunch of commercials that are funny and it all started with a good lubricant that reduced the skin's surface tension....

-Y Jelly was made by Johnson & Johnson.  glycerol BP, propylene glycol BP, hydroxyethyl cellulose,
hydrogen phosphate buffer, and water.  Although it would seem desirable to use natural products like mud, cream corn, Vaseline or other products they are not so good.. One thing that K-Y Jelly does really well is to "surface tension" of the skin without being appreciably absorbed. Vegetable oils do make the skin feel slippery, but do so weakly as compared to glycerin based, (water based) lubricants.  The surface tension of lubricants like K-Y Jelly and ability to reduce the surface tension of the things skin is really important.  

There is a actually a theory called lubrication theory in fluid dynamics which describes the flow of fluids (liquids or gases) in a geometry in which one dimension is significantly smaller than the other.  The interior flow parameter needs to be known and the pressure distribution of volume need to be solved.  In the case of K-Y Jelly on skin however a free film lubrication theory is used.  This theory involves one of the surfaces to be a free surface and the surface tension is a dominant factor in understanding the position of this free surface.  I do not understand the last sentence I just wrote.....and should look up more on this theory.

Anyways, I know that when you use K-Y jelly you will notice that it makes you feel like your skin is more wet and allows a thin film to cover whichever part you are using the K-Y jelly with.  This allows less Van der Waals, hydrogen bonds and less adjoining forces to come in contact with the skin surface.

One excellent instrument to help test the surface tension to make better lubricants would be the EZ-Pi Plus.  It offers both static and dynamic surface tension to help researchers make the best formulations.  This and other instruments are used at 4/5 of the major cosmetic and toiletry companies. 

Monday, 1 October 2012

How Can Scorpions Save Us?

I am not talking about the 80's band the Scorpions with classic hits like:     I am talking about the the little ectotherm canibals, with a nasty stinger that live in the dessert, give people nightmares and occasionally give people a larger sting of a giant hospital bill. 

However, the venom from scorpion bites could be a double edged sword since it could also people against drug resistant bacteria.  Scorpion venom has phospholipase A2 a enzyme protein that destroys fat or lipid molecules and small proteins or peptides that have an antimicrobial effects.  Antimicrobial means that it can destroy microbes e.g. bacteria.  Why is this awesome?  Well these bacteria do not react any sort of antibody so there is little doctors have at their disposal.  Scorpion venom could easily help.  (Likely they could just order the peptide in large quantities) and be very effective to destroy the bacteria as shown in this Wired (July 11th) by Robert Hancock of the University of British Columbia.

In the video this is one way that antimicrobial peptides can penetrate and destroy bacterial cell walls.  There are actually several ways e.g. carpet model, leaky slit model, barrel-stave, or toroidal pore model. 

What does this have to do with surface tension?  The lipid molecules in a bacterial membrane (or normal membrane for that matter) have a tensile strength that prevents substances from getting into the membrane.  Several bacterial membranes have a net positive charge and the antimicrobial peptides can bind and destroy the membrane without 1) any disruption of normal human cells 2) use of antibiotics

There are a nearly infinite number of combinations that can make good antimicrobial peptides.  Several of the best ones are evolved from nature and are listed on this database.  A good way to test them before subjecting the antimicrobial peptides and yourself to deadly bacteria is to use a Delta-Pi or Delta-Pi 4 surface tension device.  Both of these units have helped researchers to understand the penetration and effectiveness of antimicrobial peptide to disrupt the bacterial membrane.