  We demonstrate here a controllable variation in the Casimir force. Changes in
the force of up to 20% at separations of ~100 nm between Au and AgInSbTe (AIST)
surfaces were achieved upon crystallization of an amorphous sample of AIST.
This material is well known for its structural transformation, which produces a
significant change in the optical properties and is exploited in optical data
storage systems. The finding paves the way to the control of forces in
nanosystems, such as micro- or nanoswitches by stimulating the phase change
transition via localized heat sources.
