A micromachined Joule–Thomson cryogenic cooler with parallel two-stage expansion

There is an increasing need for localized cooling in integrated circuit/microfluidic chips, where cooling is currently achieved by relatively large and bulky cooling systems. Joule–Thomson (JT) cryocoolers are suitable to address these size limitations because they have no cold moving parts and, therefore, can be easily miniaturized. We present a JT microcooler with parallel two-stage expansion that cools down to a no-load temperature of 83 K with an ambient temperature of 295 K, whereas a single-stage microcooler typically cools to about 100 K. In addition, this microcooler has the attractive feature of providing cooling powers at two temperature levels without additional manufacturing or processing steps. In changing the temperature at the first expansion position, the cooling power can be exchanged between the two expansion stages. A dynamic model was developed to predict the actual performance of the microcooler. The accuracy of this model was verified through the comparison between experimental and simulation results.