By a whisker

Soft-metal whiskers, tiny metallic protrusions that grow like hair from soft metals, are a problem that can cause electronic short circuits leading, in some cases, to the failure of devices such as heart pacemakers, avionic relays and satellites.

What to do with the unwanted whiskers - and understanding how they form - is a problem that's been around for 50 years.

Now, researchers at Drexel University have arrived at what they think is an explanation and a potential method for alleviating them.

Basically, the whiskers form because of reactions between oxygen and the soft metal such as tin or indium. The reaction results in a volume increase that pushes the whiskers out.

The whiskers that form do not have to break off to be troublesome; sometimes they cause mischief by bridging two neighbouring electronic pathways that are supposed to be insulated from each other.

The scientists believe that an oxygen-barrier coating on pertinent surfaces should prevent whiskers from developing.