Monday, 23 April 2012

Could bubbles be the future of the lightbulb?


The history of lightbulbs is only two hundred years old starting with Humphry Davy an English chemist in 1809. That said there have been very similar consisting: a filament, a gas or under vacuum and a glass bulb.  So they all share one important trait: they're all solid.  A new design has changed this a little using surface tension of a bubble.  So it can pop and reform making a hazy bubble light.

The Surface Tension Lamp, is a design by Italian designers Spazio Rossana Orlandi from Netherland's company Front and Boo.  It replaces the lightbulb's glass with liquid water.  In the middle an LED lamp shines through a bubble as it expands.  The light is reflected to create luminescence. Then POP!  The surface tension bulb pops.  However when this bubble pops a new on takes its place. Three million bubbles will expand and explod over the LED lamp's lifespan of 50000 hours.  

Check them out in the video below:

Possibly this is not the most practical idea since it does not give out so much light.  Maybe a it will give a hazy glow.  It might be good for certain applications like outside because the liquid might spray out in a mist when the bubbles pop.  It would be interesting also to see whether the surface tension can be altered to make the bulb last longer. 

Friday, 20 April 2012

Geek Dad and Geek Mom Blog about Surface Tension

They are not my parents but they talk about Nanoscience and surface tension in The Secret World of Arrietty.  It is a Disney movie.

 Check it out the post here:

Wednesday, 18 April 2012

Clean up Oil Spills by Floating Water on Oil

If you made lasagna recently and had a oily film on the casserole dish you probably can see that oil and water do not mix.  From the time you were small people were telling you 'oil and water don't mix!'  You learn in general chemistry later in life more about why they do not mix.  Oil molecules are non-polar (the charge is spread evenly among the structure).  On the other hand water molecules are polar (their oxygen and hydrogen have a specific charge this relates to how surface tension forces are made).  Also oil particles are less dense because of their non-polarity and float on the surface of the water like in your casserole dish.  Oil molecules 'float' on top of water.  Right?  Well sometimes they do not and water can float on oil.

Science's Jon Cartright gives a nice explanation the conditions necessary for water to 'float' on oil.  This was published recently in the surface chemistry journal Langmuir by an Australian team:

So researchers dropped water onto a surface of oil.  They calculated the forces acting on the water.  They showed that from the surface tension the water droplet can 'hang' on the oil's surface.  The surface of the oil droops- like when you stand on a trampoline- allowing air to extend beneath the surface's average level.  The surface tension helps this air pocket to balance the weight of the water droplet, preventing it from sinking.  You can try this at home.

When they tested this in real-world experimental trials, the researchers found that water droplets could accommodate up to 170 microliters of water before losing "bouyancy."  This is not a lot of room but it could be enough space to make some interesting changes in the world.  How?  The researchers believe it's enough space to house oil-munching microbes. The microbe could be spread in droplets of water and aerosolized.  The aerosilized microbe could be sprayed easily to help efforts like oil spills.

A tensiometer would be needed to also measure the surface tension of the microbes in the bulk spray solution to get that perfect droplet size.  The perfect droplet size would help to optimize the solution and see if the microbe will float or sink.

Sunday, 1 April 2012

Surface tension of Soap Bubbles


I won a travel grant during the first three months of my PhD. One of my colleagues suggested that we make bubbles to help people understand membranes.  Membrane's are the core study in our laboratory.  With a poster in the University of Helsinki open house we started blowing soap bubbles illuminated by a black light.  This was compared to liposomal or cell membranes being illuminated by fluorescent light.

The surface tension of bubbles is still different than liposomal membranes.  Firstly, they have air in the middle and are not aqueous.  Soap bubbles are also composed of surfactants rather (think of a single chained lipid) rather than a double chain.  Lastly, their lipid tails point outwards towards the air with a thin layer of water present in the middle of surfactant layers.   

From Soap Bubbles to Science

This thin layer of water between the soap is critical for the bubbles.  The surface tension provides necessary wall tension.  The bubble tends to minimize this wall tension pulling the bubble into a spherical shape.  The spherical shape is governed by Young-LaPlace's equation.  Adding glycerin makes the bubbles stronger by changing the surface tension at the soaps water interface making this layer more robust. 

The equilibrium relationship between transmural pressure difference (dP), wall tension (T), and radius of curvature (R) in a concave surface; for a sphere: dP = 2T/R; for a cylinder: dP = T/R.

Thus pressure difference between the inside and outside of a bubble depends upon the surface tension and the radius of the bubble. The relationship can be obtained by visualizing the bubble as two hemispheres and noting that the internal pressure which tends to push the hemispheres apart is counteracted by the surface tension acting around the cirumference of the circle.

These Guys Understood the Surface Tension of Soap

Who made these relationships and the equation?  In Physics and other natural sciences they name the discovery after you.  In biology in particular you are allowed to give the latin name to animals and chemistry name an element like Curium.  Being a dead scientist has its merits.  At least the following two guys probably thought so.

For a 17th century polymath ThomasYoung was a rockstar.  He studied everything from medicine, physics to Egyptian hieroglypics.  Some of many achievements include partly deciphering the Rosetta Stone, understanding wave theory of light, analyzing language grammer from 400 different languages and of course the theory of capillary phenomena on the principle of surface tension which was later put into theYoung-Laplace equation.  

Pierre Laplace a mathematician and astronomer also had great achievements on the other side of the English Channel in France.  Not quite a rockstar but cool enough to  make Napoleon laugh.  He was even close to discovering black holes 100 years in advance of Hubble.  He also understood probabilities and confused amused Napoleon on the religion.  After looking into Young's a year after he understood the math behind it to make the Young-Laplace equation.  This work was later unified and derived 25 years later by Carl Gauss to make a formula that describes the capillary pressure difference sustained across the interface between two static fluids e.g. water and soap.

So the next time you are in your back yard making soap bubbles think about surface tension and the people that derived the formula to understand your past time.