Actively entangling filaments for passive adaption in soft robotic grippers*

Human hands are remarkably adept at navigating complex and uncertain environments, gently grasping objects that we cannot fully see, and adapting to topologically complex and compliant structures. These remain particularly challenging tasks for the traditional robotic grippers that we rely on in scenarios that are impractical or dangerous for human hands. The compliance of soft robots makes them particularly well suited for grasping applications where target objects are fragile, compliant, or topologically complex, as well as scenarios where target objects have an uncertain size or location. That same compliance also makes deterministic control of soft robots complex and computationally expensive. Instead of pursuing precise control, a stochastic strategy of robotic grasping employing arrays of actively entangling filaments can passively adapt to the needs of challenging grasping tasks, by embracing material compliance and amplifying structural compliance. The collective entanglement of highly compliant soft robotic filaments can provide randomly distributed points that are individually gentle but collectively strong. We demonstrate a soft robotic gripper made of an array of slender, hollow, elastomeric filaments that are reversibly and pneumatically actuated to take a highly curved state, enabling entanglement on demand for grasping. The filament fabrication leverages passive forces of surface tensions and gravity for a simple, repeatable, and inexpensive manufacturing method that is compatible with commercially available elastomers. Soft robotic filaments enable a platform for a passively adatiptive nondeterministic grasping strategy to minimize perception, planning, and feedback requirements. Furthermore, soft robotic filaments may be used as a platform to more broadly study systems of active entanglement.