Octopus-Inspired Adaptable Soft Grippers Based on 4D Printing: Numerical Modeling, Inverse Design, and Experimental Validation

Soft grippers based on stimuli-responsive materials show great promise to perform safe interaction and adaptive functions in unstructured environments. Hence, improving flexibility and designability of the stimuli-responsive soft grippers for better grasping ability are highly desired. Inspired by the biological structure of octopuses, a class of temperature-driven polylactic acid grippers is fabricated by 4D printing in this work, which consists of two types of bilayer structures, separately imitating the web and tentacles of an octopus. Compared with the traditional pure-bending soft grippers, the integrated structure results in a 1.5 times wider reachable area and enhanced flexibility. The complex grasping behaviors are predicted with the 4D printing parameters (i.e., printing paths and printing speeds) using the reduced bilayer plate theory. Moreover, a method for determining the printing parameters of the gripper is provided to realize the desired grasping behavior depending on different objects. The feasibility of the design method is experimentally verified by gasping three distinctive objects, including an egg, a weight, and a Metatron's cube, which is in good agreement with the simulation results. Herein, a promising strategy is provided to achieve the easy-fabricated, low-cost, and versatile soft graspers using smart materials.