Soft robotic grippers are advantageous for tasks in which a robot comes into close contact with a human, must handle a delicate object, or needs to conform to an object. Most soft robotic grippers, like their hard counterparts, require actuation to maintain a grip on an object. Here, we present a passive, soft robotic gripper that requires power to open and close but not to maintain a grip, which can be problematic in environments with limited energy availability (e.g. solar or battery power). Passive grip, by not requiring power to maintain grip on an object, provides a unique and safe alternative to energy-limited or energy-scarce environments. The Tufts Passive Gripper was inspired by the passive grip of the Manduca sexta and the simplicity of the Fin Ray ® Effect. The gripper can be three-dimensional printed as one part on a multimaterial three-dimensional printer and only requires four additional steps to install the motor/tendon actuation mechanism. The gripper was capable of picking up over 40 common household objects, including a tissue, a pen, silverware, a needle, a stapler, a cup, and so on. The maximum load a gripper could hold when oriented perpendicular and parallel to the ground was 530 g (1 lb) and 240 g (0.5 lb), respectively.

A soft climbing robot has the potential to access locations such as wiring ducts and tree canopies that are unreachable by humans and traditional rigid robots. In addition, a soft robot is robust and can fall without damaging itself or its environment. We present a soft, branch-crawling robot that is inspired by the passive gripping mechanisms used by caterpillars. The conformability of the robot’s soft body makes it uniquely suited to move in a complex 3D environment. A key innovation is that grip release is actively controlled and coordinated with propulsion generated by stored elastic energy. The robot is molded from silicone rubber and actuated using remote motor-tendons coupled to the structure through Bowden cables. Grip is achieved passively through an elastic flexure that pushes a compliant finger against the dowel. Experimental results show that the gripper is easily able to support the weight of the robot, and that the body structure allows the robot to crawl horizontally, vertically, and along branches. This robot demonstrates some key advantages of a soft robotic platform over traditional rigid robots.

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Modern legged robot morphologies assign most of their actuated degrees of freedom (DoF's) to the limbs and designs continue to converge to twelve DoF quadrupeds with three actuators per leg and a rigid torso often modeled as a Single Rigid Body (SRB). This is in contrast to the animal kingdom, which provides tantalizing hints that core actuation of a jointed torso confers substantial benefit for efficient agility. Unfortunately, the limited specific power of available actuators continues to hamper roboticists' efforts to capitalize on this bio-inspiration. This paper presents the initial steps in a comparative study of the costs and benefits associated with a traditionally neglected torso degree of freedom: a twisting spine. We use trajectory optimization to explore how a one-DoF, axially twisting spine might help or hinder a set of axially-active (twisting) behaviors: trots, sudden turns while bounding, and parkour-style wall jumps. By optimizing for minimum electrical energy or average power, intuitive cost functions for robots, we avoid hand-tuning the behaviors and explore the activation of the spine. Initial evidence suggests that for lower energy behaviors the spine increases the electrical energy required when compared to the rigid torso, but for higher energy runs the spine trends toward having no effect or reducing the electrical work. These results support future, more bio-inspired versions of the spine with inherent stiffness or dampening built into their mechanical design.