The goal of this project is the design, fabrication, control and testing of novel, lightweight actuators that will be able to apply large forces and achieve large displacements using compact mechanisms. The proposed concept for novel actuation devices is based on a hybrid combination of Electro-Rheological Fluids (ERF) and electromagnetic actuation concepts. The proposed new class of actuation devices is called ECFS (Electrically Controlled Force and Stiffness) actuators. Design, fabricate and control compact prismatic joints mobilized by ECFS actuators will be studied. Extensive tests will be performed to demonstrate the effectiveness of the ECFS actuators. Furthermore, the possibility of using the ECFS actuators to power the joints of force-feedback devices and haptic interfaces will be investigated. The broader impact and outreach activities of this project are: a) the initiation of undergraduate students in research; b) the establishment of collaborative projects on engineering design and robotic systems with the science and technology high schools of New Jersey with the objective to attract new students in this field; c) the organization of a special session at the annual ASME International Mechanical Engineering Congress and Exposition (IMECE) and of a focused section in one issue of the journal IEEE / ASME Transactions on Mechatronics on the design, modeling and control of advanced actuators; d) the development and maintenance of a webpage on ERF based devices; and e) the establishment of international collaborative activities in the area of advanced actuators.