Thursday, 17 January 2013

Sweat Powered Nanoelectronics from Capillary Action

Acrobatics of a Polymer Film is not Cirque de Soleil

Can your ipod shuffle with water vapor or your own sweat? 

Previously, I wrote about capillary action and perpetual motion machines.  Since Boyle's original intent was to use capillary action (a force that does not require energy and goes against gravity) to run the perpetual motion machine.  However, as stated the capillary action within the tube would also keep the liquid from running out which would hinder your production of energy.

Boyle maybe did not think about two different types of materials that counter each other.  MIT researchers at the David H. Koch Institute for Inegrative Cancer Research has developed polymer films that generates their power from water vapor.  Basically you have two films of polymers opposing each other on a 20 micrometer thick film.  One film is hyrodrophilic (water loving) whereas the other is hydrophobic (water hating).  When you place the water vapor on the hydrophilic surface the bottom layer curls away generating some force and electricity.  The water evaporates the bottom layer becomes dry and the cycle repeats when more water is placed. 

But just how much force?

As written by David Szondy in Gizmag:

“By incorporating the two different kinds of polymers, you can generate a much bigger displacement, as well as a stronger force,” postdoctoral student Liang Guo said.

The film exploits the water gradient between dry and moist environments. When it lies on a surface with even a small amount of moisture present, the bottom layer curls away. This exposes the polymer to the air where the water evaporates from its surface. The bit of film does a somersault and the cycle starts over.
This isn’t just a laboratory curiosity. The polymer film exerts a surprising amount of force as it curls. A 25-milligram film can lift 380 times its own weight or carry along a load of silver wires ten times its weight. According to the researchers, that’s enough force to replace electric actuators in small robotic limbs. What’s more, it can do so without manipulating the environment. If water is available, the film will work.
This property gives it an advantage not only as a mini-motor, but as a power source. The film could use piezoelectric materials to generate electricity. Currently, the film can produce 5.6 nanowatts, which is enough to run ultra-low power microelectronic devices.

 So you can literally just put this film in your bathtub, walk away and get some energy?

The researchers also envision the film creating power by being placed over a body of water or incorporated into clothing where sweat could power wearable electronics. For the immediate future, the team is working to improve the film’s efficiency to allow smaller films to power larger devices.'

Yep!  Although it seems as perpetual as the drinking bird.  Not so much power but with enough of these you might be able to charge your ipod shuffle. 

Where can I find more?

Check out the this video:

In the January 11th Issue of Science you can find the original article.