Osmosis-driven actuation offers a promising strategy for developing untethered, environmentally responsive soft and shape shifting mechanisms and robots. In this work, we explore the use of superabsorbent polymer (SAP) pellets as large-scale, shape-morphing actuators. Upon exposure to water, these approximately 2mm diameter spherical pellets undergo a dramatic volumetric expansion, up to 300 times their initial volume, generating actuation forces of approximately 10 N under constrained conditions. We further demonstrate reversible cyclic actuation via controlled swelling-deswelling using ethanol-water solutions. Finally, we integrate these systems into a shape-morphing wheel design to enable adaptive locomotion that passively transitions between terrestrial and aquatic environments. Our findings demonstrate SAP-based osmotic actuators as an environmentally-driven solution for soft robotics, and shape-shifting soft hybrid mechanisms.

Gecko-inspired adhesives have the advantage of being able to grasp and release flat surfaces in a vacuum using their microwedge structures. This makes them an especially attractive solution for perching on and grasping flat objects in space for free-flying robots. To grasp and anchor onto these flat surfaces, the gripper must ensure contact between the gecko adhesives and the surface before applying the appropriate forces to activate their adhesion. However, in the case of a free-flying robot in microgravity, physical contact with the surface induces reaction forces, causing the robot to quickly bounce away from the surface. To solve this issue, we propose a simple passive mechanism and a control method of a robotic arm on a free-flying robot with a gecko adhesive gripper. The gripper utilizes a single-motor controlled tendon-driven mechanism mounted at the end of a robotic arm equipped with controllable stiffness joints and a linear spring-damper system. A free-flying robot on an air-bearing platform can successfully perch on a flat surface with a velocity of up to 72.5mm/s and with an approach angle misalignment of up to 33.0 degrees.

ReachBot is a robot that uses extendable and retractable booms as limbs to move around unpredictable environments such as martian caves. Each boom is capped by a microspine gripper designed for grasping rocky surfaces. Motion planning for ReachBot must be versatile to accommo-date variable terrain features and robust to mitigate risks from the stochastic nature of grasping with spines. In this paper, we introduce a graph traversal algorithm to select a discrete sequence of grasps based on available terrain features suitable for grasping. This discrete plan is complemented by a decoupled motion planner that considers the alternating phases of body movement and end-effector movement, using a combination of sampling-based planning and sequential convex programming to optimize individual phases. We use our motion planner to plan a trajectory across a simulated 2D cave environment with at least 90% probability of success and demonstrate improved robustness over a baseline trajectory. Finally, we use a simplified prototype to verify a body movement trajectory generated by our motion planning algorithm.

ReachBot is a new concept for planetary exploration, consisting of a small body and long, lightweight extending arms loaded primarily in tension. The arms are equipped with spined grippers for anchoring on rock surfaces. The design and testing of a planar prototype is presented here. Experiments with rock grasping and coordinated locomotion illustrate the advantages of low inertia passive grippers, triggered by impact and using stored mechanical energy for the internal force. Gripper design involves a trade-off among the range of possible grasp angles, maximum grasp force, required triggering force, and required reset force. The current prototype can pull with up to 8N when gripping volcanic rock, limited only by the strength of the 3D printed components. Calculations predict a maximum pull of 26N for the same spines and stronger materials.

Gecko-inspired adhesives have several desirable characteristics in robotic grasping: controllable activation and deactivation of adhesion, ability to grasp and release with minimal disturbance, and grasping without the need of form closure. Previously proposed grippers with this technology either require a complex activation mechanism or multiple activation steps. In this paper, we present an underactuated gecko-inspired adhesive gripper that can grasp a wide range of curved surfaces using a single actuator through a simple tendon-driven mechanism that attaches and adheres in one step. We derive a theoretical model of the adhesive contact area and resulting gripper grasp force, which is verified experimentally. The actual performance of the proposed mechanism is demonstrated by successfully grasping several surfaces with different curvature diameters.