US micro heat pump firm Nextreme has technology to cut heat leakage through its devices.
Based on research on nanomaterials acquired from North Carolina's RTI International in 2004, Nextreme has been awarded a patent: 'Phonon-blocking, electron-transmitting low-dimensional structures'.
An ideal heat pump material to separate hot and cold parts of a heat pump would be a superconductor that blocked all heat flow.
"The nano-approach uses a commonly available thermoelectric material called bismuth telluride, constructed on a nanoscale to create an assembly that researchers believe blocks the transmission of phonons, which carry heat, and enhances the transmission of electrons, which carry electrical energy," said Nextreme. "The result is a radical boost in material efficiency with reports of 40 to 140 per cent improvement."
Nextreme, also of North Caroline, specialises in tiny heat pumps and recently released OptoCooler (pictured), claimed to be the world's smallest thermoelectric cooler "and the industry's first device to offer a heat pumping density in excess of 70 W/cm2", it said.
It integrates thin-film thermoelectrics into on-chip copper pillar bumps to create a thermal bump. "This approach has provided a scalable and inexpensive pathway for integrating thermal management functionality directly into electronic packaging."
OptoCooler can pump heat at up to 78W/cm2 - based on 90mW from a 300x200µ laser diode, a density of 150W/cm2. "Even if that power is spread by a factor of 30 [5W/cm2), it still falls outside the operating regime of a typical bulk thermoelectric cooler, especially within the constraints of the package size," said Nextreme.
It can remove a maximum of 420mW at 25°C ambient through an active footprint of 0.55mm2 - the 78W/cm2, or cool up to 45°C.
"At 85°C, these values increase to 610mW, 112W/cm2 and 60degC, respectively," said Nextreme.