  The thermal Casimir-Lifshitz force among two bodies held at different
temperatures displays striking features that are absent in systems in thermal
equilibrium. The manifestation of this force has been observed so far only in
Bose-Einstein condensates close to a heated substrate, but never between two
macroscopic bodies. Observation of the thermal Casimir-Lifhitz force out of
thermal equilibrium with conventional Casimir setups is very difficult, because
for experimentally accessible separations the thermal force is small compared
to the zero-temperature quantum Casimir force, unless prohibitively large
temperature differences among the plates are considered. We describe an
apparatus that allows for a direct observation of the thermal force out of
equilibrium for submicron separations and for moderate temperature differences
between the plates.
