By Jesse Emspak: Subscribe to Jesse's RSS feed
October 22, 2010 7:31 PM EDT
Often when something goes awry with technology the first thing to check is the connection. Connectors for USB ports have to stand up to repeated plugging and unplugging, and deal with corrosion as well.
Most connectors are coated with a thin layer of gold. Gold is one of the better electrical conductors out there, and it doesn't corrode. But it is soft and has a tendency to get scraped off, causing a failure. That has prompted a search for alternatives.
"Nine out of ten times when a flash drive fails it's because of the connector," said Mark Aindow, professor of materials science at the University of Connecticut. He decided to see if there was a way to make metals that would retain the electrical conductivity of gold but be better able to stand up to repeated use.
Aindow said the reason most manufacturers use gold is simple: it doesn't oxidize. Silver and copper are much better conductors than gold, but they both tend to oxidize, which results in electrical contacts covered in a substance that doesn't conduct well at all. But if a metal oxidized and still conducted electricity, there might be a way to make a connector that wouldn't run into that problem.
To make his new materials, Aindow used three different techniques. One is doping, borrowed from the makers of silicon chips. The second is to mix two metals, each of which forms a different kind of oxide. The result is either rod-like structures that stick out of the base metal, or metals that form different regions, one of which can still conduct. Aindow used three different mixtures of metals: copper and lathanum, iron and vanadium, and nickel and ruthenium.
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The reason these oxides can carry current, where other types do not, is because of the way the electrons on the individual atoms are configured. Aindow noted that doping the copper with lanthanum creates a configuration of atoms with spaces in the outer electron shells, allowing for current to move. In pure copper oxide those spaces aren't there.
With the iron-vanadium mix the atoms allow for polaron hopping, which is the movement not only of electrons but the positively-charged "holes" they leave behind. The electrons hop from one atom to the next, driving other electrons to the next atom in the line. The improvement in conductivity was large and the components, Aindow said, are also relatively cheap compared to gold.
These are not the only ones that are possible. One of the things Aindow's team discovered was the kinds of metals that would be best for future research. "We've taken these binary systems and proven the principles," he said.
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