Photo-driven Molecular Wankel Engine B$_{13}^+$
  We report a molecular Wankel motor, the dual-ring structure B13+, driven by circularly-polarized infrared electromagnetic radiation, under which a guided uni-directional rotation of the outer ring is achieved with rotational frequency of the order of 300 MHz. 
Jin Zhang, Alina P. Sergeeva, Manuel Sparta, Anastassia N. Alexandrova
physics.chem-ph cond-mat.mtrl-sci