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2011-12-22 11:29:46
Self-repairing electronic chips are one step closer, according to a team of US
researchers.
The group has created a circuit that heals itself when cracked thanks to the
release of liquid metal which restores conductivity.
The process takes less than an eye blink to bring the circuit back to use.
The researchers said that their work could eventually lead to longer-lasting
gadgets as well as solving one of the big problems of interplanetary travel.
The work was carried out by a team of scientists and engineers at the
University of Illinois at Urbana-Champaign and is published in the journal
Advanced Materials.
The process works by exploiting the stress that causes the initial damage in
the chips to break open tiny reservoirs of a healing material that fills in the
resulting gaps, restoring electrical flow.
Cracked circuits
To test their theory the team patterned lines of gold onto glass to form a
circuit.
They then either placed microcapsules 0.01mm wide directly onto the lines or
added a thin laminate into which they embedded larger 0.2mm microcapsules.
In both cases the microcapsules contained eutectic gallium-indium - a metallic
material chosen for its high conductivity and low melting point.
This device was then sandwiched between another layer of glass and acrylic and
connected to electricity.
The researchers then bent the circuit until it cracked causing the monitored
voltage to fall to zero.
They said the ruptured microcapsules then healed most of the test circuits
within one millisecond and restored nearly all of the measured voltage.
The smaller capsules healed the device every time but were a little less
conductive than the larger ones which had a slightly lower success rate. The
team suggested that a mix of differently sized capsules would therefore give
the best result.
The devices were then monitored for four months during which time the
researchers said there was no loss of conductivity.
Safe space travel
The leader of the group said the theory could prove a boon to the space
industry.
"The only avenue one has right now is to simply remove that circuitry when it
fails and replace it- there is no way to manually go in and fix something like
this," aerospace engineering professor Scott White told the BBC.
Graphic showing how the self-healing process works The research team hope to
adapt the process to create longer lasting rechargeable batteries
"I think the real application area that you'll see for something like this is
in electronics which are incredibly difficult to repair or replace - think
about satellites or interplanetary travel where it's physically impossible to
swap out something."
The research is an offshoot of the university's research into extending the
lifetime of rechargeable batteries.
The reason current systems fail after repeated use is often because microdamage
inside the devices has disrupted the conductive flow of electrons from one end
of the batteries to the other.
The team said that if they could solve the problem electric car batteries might
last years longer than they do at present, making the vehicles much cheaper to
maintain.
Greener gadgets
The group also claimed that the technique had the potential to offer more
sustainable consumer electronic devices.
Professor White gave the example of mobile phone buttons that stopped working
if repeated use had caused cracks in the circuitry below. He said self-healing
systems would extend handsets' lifespans.
When asked whether profit-driven electronics makers would want this he replied:
"I believe any company would want to provide their customer with the best
performing product and if they don't, then other companies will step into the
market to provide it.
"Basically what you see is that electronics are cycled now to give you added
functionality.
"Maybe the way to do this is not to physically build new circuits and packages
every time, but let's have longer lasting ones.
"Then the redesigns can be more software based or functionality driven, saving
us from using up our precious resources by building millions of cellphones
every year."