Microminiature refrigeration - small is better

Microminiature Joule-Thomson refrigerators have been fabricated using a novel photolithographic process. We discuss the scaling laws which allow one to design these refrigerators of arbitrarily small size and the fabrication process which makes it possible to mass produce them at low cost. Commercial systems are now available for operation with N2 gas from ambient to 80 K with a refrigerator capacity of 250 mW. Lower temperature operation using H2 and He is presently under development. The use of these devices for microcalorimetry, material research and other applications is reported.