Mechanically programmable bend radius for fiber-reinforced soft actuators

TLDR

Soft actuator design guidelines enable diverse motions such as bending, contraction, extension, and twisting through multi‑step molding of composite materials and tailored geometry. The study presents a fiber‑reinforced soft bending actuator whose bend radius and axis are mechanically programmed via a selectively placed conformal covering. The authors fabricated multiple actuators, measured displacement and force, and designed a two‑digit end‑effector that uses the conformal covering to match a rectangular shape. The actuator achieved higher gripping force than a pure bending actuator, suggesting rapid customization for grasping tasks with known geometry.

Abstract

Established design and fabrication guidelines exist for achieving a variety of motions with soft actuators such as bending, contraction, extension, and twisting. These guidelines typically involve multi-step molding of composite materials (elastomers, paper, fiber, etc.) along with specially designed geometry. In this paper we present the design and fabrication of a robust, fiber-reinforced soft bending actuator where its bend radius and bending axis can be mechanically-programed with a flexible, selectively-placed conformal covering that acts to mechanically constrain motion. Several soft actuators were fabricated and their displacement and force capabilities were measured experimentally and compared to demonstrate the utility of this approach. Finally, a prototype two-digit end-effector was designed and programmed with the conformal covering to shape match a rectangular object. We demonstrated improved gripping force compared to a pure bending actuator. We envision this approach enabling rapid customization of soft actuator function for grasping applications where the geometry of the task is known a priori.