The addition of components to computer chips to increase processing power capacity in turn increases heat generation. Removal of this heat is necessary to maintain desired chip performance and is currently achieved by circulating water through millimeter-scale channels to cool hotspots. As heat generation becomes more concentrated at the nanoscale, this scale mismatch reduces cooling efficiency by consuming more water than necessary.
A solution devised by researchers from University of Osaka (Japan), University of Tokyo (Japan), Italian Institute of Technology and the National Institute of Advanced Industrial Science and Technology (Japan) enhances cooling by driving the flow of ions through nanoscale channels. The ionothermoelectric strategy described in ACS Nano is analogous to the Peltier technique, in which passing an electric current through a material results in heating or cooling.
“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,” explained the developers. “Varying the voltage modulated the surface charge of the nanopore.”
A negatively charged nanopore that is only permeable to positively charged ions, or cations, results from a negative applied voltage, causing each ion to transmit a certain quantity of heat along with its charge. The technology was tested with 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. Switching from heating to cooling resulted in temperature drops of over 2 K.
This ionic refrigeration strategy is expected to increase the capability of next-generation semiconductor chips.
