  Casimir interactions play an important role in the dynamics of nanoscale
objects. Here, we investigate the noncontact transfer of angular momentum at
the nanoscale through the analysis of the Casimir torque acting on a chain of
rotating nanoparticles. We show that this interaction, which arises from the
vacuum and thermal fluctuations of the electromagnetic field, enables an
efficient transfer of angular momentum between the elements of the chain.
Working within the framework of fluctuational electrodynamics, we derive
analytical expressions for the Casimir torque acting on each nanoparticle in
the chain, which we use to study the synchronization of chains with different
geometries and to predict unexpected dynamics, including a rattleback-like
behavior. Our results provide new insights into the Casimir torque and how it
can be exploited to achieve efficient noncontact transfer of angular momentum
at the nanoscale, and therefore have important implications for the control and
manipulation of nanomechanical devices.
