Articulating minimally invasive ultrasonic tool for robotics-assisted surgery In this paper, a robotics-assisted articulating ultrasonic surgical scalpel for minimally invasive soft tissue cutting and coagulation is designed and developed. For this purpose, the optimal design of a Langevin transducer with stepped horn profile is presented for internal-body applications. The modeling, optimization and design of the ultrasonic scalpel are performed through equivalent circuit theory and verified by finite element analysis. Moreover, a novel two degrees-of-freedom (DOFs) surgical end effector (1-DOF pitch, 1-DOF grip) with decoupled motions is developed that is compatible with the da Vinci® surgical system. The developed instrument is then driven using the dVRK (da Vinci® research kit) and the Classic da Vinci® surgical system.