Enhancing computer cooling with ionic technology

As more devices are added to computer chips to increase processing power capacity, heat generation becomes increasingly concentrated. This heat must be removed to maintain chip performance. This is currently achieved by circulating water through millimetre-scale channels to cool nanosized hotspots. This scale mismatch reduces the cooling efficiency by consuming more water than necessary, thereby raising environmental concerns.

Now, researchers at the University of Osaka have developed a strategy to enhance cooling by driving the flow of ions through nanoscale channels. This ionothermoelectric strategy is analogous to the Peltier technique, in which passing an electric current through a material results in heating or cooling. The researchers have published their findings in ACS Nano.

“We fabricated a nanosized pore in a semiconductor membrane and surrounded the nanopore with a ‘gate’, in the form of a nanowire. Applying a voltage to the gate induced the flow of ions through the nanopore,” said lead author Makusu Tsutsui. “Varying the voltage modulated the surface charge of the nanopore.”

A negative applied voltage resulted in a negatively charged nanopore that was only permeable to positively charged ions, or cations. Consequently, each ion drags a certain quantity of heat along with its charge. The team created a concentration gradient in saltwater around the nanopore to drive cation transport in one direction, effectively pumping heat out of the nanopore. Reversing the applied voltage made the nanopore surface positive and permeable only to negative ions, or anions, therefore switching the system from cooling to heating.

“We placed a nanoscale thermocouple next to the holes within the materials — or nanopores — to map temperature changes driven by the voltage-induced ion transport,” said senior author Tomoji Kawai. “Switching from heating to cooling resulted in temperature drops of over 2 K. We found that the ionic heat transfer depended on the input power as well as the ion species used.”

Solid-state nanopores are fully compatible with semiconductor fabrication technologies. Thus, implementing the ionic refrigeration strategy developed at the University of Osaka could increase the capability of next-generation semiconductor chips. These advances in thermal control could also ease environmental concerns.

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