Exploring the potential of magnetorheology in robotic grippers

Soft robotics is an emerging domain focusing on integrating soft, flexible materials and structures, often derived from biological organisms, in robotics. Unfortunately, soft manipulators and grippers can only excite low forces with low precision relative to conventional hard grippers. On the other hand, they offer the major advantage of infinitely many degrees of freedom and high compliance. Future research should therefore focus on combining the best of these two worlds: hard and soft grippers. Herein, magnetorheological (MR) fluids show great potential and can play an important role. These fluids become a viscoelastic solid due to particle alignment under the influence of an external magnetic field. By simply varying the field strength, the stiffness of the gripper can be changed within the continuous spectrum between non-rigid and rigid. This paper will look at the properties of magnetorheology and the accomplished designs in literature, such as car suspensions, seismological dampers, liquid body armours and robotics. Based on these designs, the potential benefits and challenges of magnetorheology in robotics will be discussed, with a focus on robotic grippers and manipulators. In general, the current MR based robotic grippers lack three imperative requirements for acceptance by industry: high grasping forces, high grasping speeds and compactness. These will be addressed and required future work will be pointed out to benefit from MR materials in robotics.