A team of researchers at the University of Illinois developed a technology for switching heat flows on or off

By Warren Miller,
contributing writer

A team of researchers at the University of Illinois at
Urbana-Champaign have devised a new kind of heat switch, a mechanism by which the
flow of heat into an electronic system can be shut off or turned back on with
the push of a button. The flow of heat can significantly affect the long-term
performance and reliability of mechanical and electrical components, including
everything ranging from laptops to cell phones to automobile engines. If the
new UI heat switch can be reproduced in commercial electronic products, it
could become a ubiquitous part of modern technology.

At this point, you may be asking yourself, “What’s the big
deal? I’ve got a thermostat in my house/apartment, isn’t that a just a switch
that turns the heat on and off?” Well, yes and no. The thermostat tells your
home’s internal heating system when to operate and for how long, but it doesn’t
cut off the flow of heat so much as it stops producing it. The UI heat switch
can instantaneously stop the flow of heat from one place to another, a key factor
in protecting electronic systems from overheating. In order to do this, the
researchers used a small droplet of liquid metal as a heat conductor.

“The technology is based on the motion of a liquid
metal droplet,” said Nenad Miljkovic, the project co-leader and Assistant
Professor in the Department of Mechanical Science and Engineering at UI
Urbana-Champaign. “The metal droplet can be positioned to connect a heat
flow path, or moved away from the heat flow path in order to limit the
heat flow.” 


Image source: Illinois

The UI team created a model for the technology based on
common electronics systems, placing a power source to generate heat on one side
of the switch and a liquid cooling element on the other side to extract the
heat being generated. When the metal droplet was placed in between the two
elements, the researchers were able to capture heat at a rate of 10W/cm2. When
the metal droplet was removed, the flow heat decreased by a factor of almost

Perhaps the most interesting application of this technology
could be for directing heat to different ‘destinations.’ The switch could cut
off heat transport from one destination and send it to another. This could
improve and optimize cooling by sending heat ‘pulses’ to different heat sinks,
thus allowing them time to dissipate the heat via convection. Pulses could be
directed and timed to optimize the flow of the conductive medium to insure heat
generating electronic components stay as cool as possible. Heat flow could also
be directed based on which components are generating heat, making the system
much more adaptive and responsive to heat generation variations, as different
parts of the system are active.

Not surprisingly, William King, another project co-leader
and the Andersen Chair Professor in the Department of Mechanical Science and
Engineering, plans on developing a prototype by incorporating the heat switch
into a circuit board. If successful, this technology could fundamentally change
the way electronic systems manage heat.