Tuesday, October 13, 2009

Diodes, Diodes Everywhere

This is the week of the diode. Not the standard electrical diode that only lets current flow in one direction. Those exist everywhere - your computer is loaded with them and you can't recharge your cell phone without one. Instead, this is about rectifying other actions that are much more difficult to control.

Take heat for instance. In standard conduction patterns, it flows from hot to cold. But now if can be made to flow in one direction based on geometry, not temperature. By using two components, one with good conductivity at high temperatures but not low, and the other component with the opposite properties, the magic occurs.

A similar result (at a gross level) was found with a photonic crystal that directs microwaves in only one direction.

Since this is a rheology blog, proposing a flow rectifier would be appropriate. Check valves already exist (first in cardiac organs, then in human creations). A way to control reptation would be neat, and could certainly lead to some unusual rheology - it would take much longer for a given stress to relax. I'm sure the "much" longer could be quickly quantified, but I'm not the greatest at reptation theory and way to busy in the lab to hash through it today.

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