LEGO® Block Structures as a Sub-Kelvin Thermal Insulator

We report measurements of the thermal conductance of a structure made from commercial Acrylonitrile Butadiene Styrene (ABS) modules, known as LEGO (R) blocks, in the temperature range from 70 mK to 1.8 K. A power law for the sample's thermal conductivity kappa = (8.7 +/- 0.3) x 10(-5) (TWK-1)-W-1.75 +/- 0.02 m(-1) was determined. We conclude that this ABS/void compound material provides better thermal isolation than well-known bulk insulator materials in the explored temperature range, whilst maintaining solid support. LEGO blocks represent a cheap and superlative alternative to materials such as Macor or Vespel. In our setup, <400 nW of power can heat an experimental area of 5 cm(2) to over 1 K, without any significant change to the base temperature of the dilution refrigerator. This work suggests that custom-built modular materials with even better thermal performance could be readily and cheaply produced by 3D printing.