Forget traditional metal block coolers a nanowick could remove 10 times the heat of current chip designs
A collaboration of university researchers and top industry experts has created a pumpless liquid cooling system that uses nanotechnology to push the limits of past designs.
One fundamental computing problem is that there are only two ways to increase computing power — increase the speed or add more processing circuits. Adding more circuits requires advanced chip designs like 3D chips or, more traditionally, die shrinks that are approaching the limits of the laws of physics as applied to current manufacturing approaches. Meanwhile, speedups are constrained by the fact that increasing chip frequency increases power consumption and heat, as evidence by the gigahertz war that peaked in the Pentium 4 era.
A team led by Suresh V. Garimella, the R. Eugene and Susie E. Goodson Distinguished Professor of Mechanical Engineering at Purdue University, may have a solution to cooling higher frequency chips and power electronics. His team cooked up a bleeding edge cooler consisting of tiny copper spheres and carbon nanotubes, which wick coolant passively towards hot electronics.
The coolant used is everyday water, which is transferred to an ultrathin “thermal ground plane” — a flat hollow plate.
The new design can handle an estimated 10 times the heat of current computer chip designs. That opens the door to higher frequency CPUs and GPUs, but also more efficient electronics in military and electric vehicle applications.
The new design can wick an incredible 550 watts per square centimeter. Mark North, an engineer with Thermacore comments, “We know the wicking part of the system is working well, so we now need to make sure the rest of the system works.”
The design was first verified with computer models made by Gamirella, Jayathi Y. Murthy, a Purdue professor of mechanical engineering, and doctoral student Ram Ranjan. Purdue mechanical engineering professor Timothy Fisher’s team then produced physical nanotubes to implement the cooler and test it in an advanced simulated electronic chamber.
Garimella describes this fused approach of using computer modeling and experimentation hand in hand, stating, “We have validated the models against experiments, and we are conducting further experiments to more fully explore the results of simulations.”
Essentially the breakthrough offers pumpless water-cooling, as the design naturally propels the water. It also uses microfluidics and advanced microchannel research to allow the fluid to fully boil, wicking away far more heat than similar past designs.
This is enabled by smaller pore size than previous sintered designs. Sintering is fusing together tiny copper spheres to form a cooling surface. Garimella comments, “For high drawing power, you need small pores. The problem is that if you make the pores very fine and densely spaced, the liquid faces a lot of frictional resistance and doesn’t want to flow. So the permeability of the wick is also important.”
To further improve the design and make the pores even smaller the team used 50-nm copper coated carbon nanotubes.
The research was published in this month’s edition of the peer-reviewed journal International Journal of Heat and Mass Transfer.
Raytheon Co. is helping design the new cooler. Besides Purdue, Thermacore Inc. and Georgia Tech Research Institute are also aiding the research, which is funded by a Defense Advanced Research Projects Agency (DARPA) grant. The team says they expect commercial coolers utilizing the tech to hit the market within a few years. Given that commercial cooling companies (Thermacore, Raytheon) were involved, there’s credibility in that estimate.