By Steve Bush 23rd September 2020
This is the smallest thermolectric cooler ever made, according to the scientists at UCLA that built it.
Total active volume is ~1μm3.
“We beat the record for the world’s smallest thermoelectric cooler by a factor of more than ten thousand,” according to UCLA physicist Xin Yi Ling
It consists of two 100nm thick single-crystal flakes, peeled from blocks of donor material – one of bismuth telluride (Bi2Te3) and one of antimony/bismuth telluride (Sb2-xBixTe3).
Indium nano-particles were deposited to measure temperatures using plasmon energy expansion thermometry (PEET) “a high-spatial-resolution, transmission electron microscopy-based technique,”according to the ACS Nano paper ‘Electron-transparent thermoelectric coolers demonstrated with nanoparticle and condensation thermometry’.
Temperature change was -21K (±4) from room temperature.
The team also found a way to measure temperature change by monitoring condensation (circle on lower image): “We establish proof-of-concept for condensation thermometry, a quantitative temperature-change mapping technique with a spatial precision of ≲300nm.”
For effective operation, thermoelectric coolers must combine high electrical conductivity and low thermal conductivity, and this research is an attempt to understand the interaction of these two characteristics at the atomic scale, then use this knowledge to design better bulk materials.
“Once we understand how thermoelectric coolers work at the atomic and near-atomic level, we can scale up to the macroscale, where the big payoff is,” said UCLA professor Chris Regan.
The indium particle indicate temperature by changing in size and therefore density – the particles are measured individually. “PEET has the spatial resolution to map thermal gradients at the few-nanometer scale,” said Regan.
THis was supplemented by inventing the condensation technique – watching the device through an optical microscope to see when dew appeared, indicating that it had reached the dew point temperature.
The abstract of the ACS Nano paper Electron-transparent thermoelectric coolers demonstrated with nanoparticle and condensation thermometry is available free here.
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