Self-actuating origamis realized by independently printable and controllable stimuli-responsive creases

Abstract

Flexible origami structures can mimic the complicated motions of small creatures that are otherwise difficult to be achieved by rigid robots with limited degree of motion freedom. However, actuating origami structures in a compact and self-contained way has been a critical challenge. Here, we demonstrate a versatile approach of actuating origami micro-robots by printed self-folding creases made of a type of stimuli-responsive transition metal hydroxides/oxides that can undergo large actuation under electrochemical or light stimulations. Two enabling technologies are pivotal: (i) a microfluidic electrochemical writing method to selectively print the stimuli-responsive material (SRM) at the actuating creases to enable them to self-fold independently “on demand”, and (ii) a micro-scale riveting method to provide strong adhesion of the SRM on the origami body. Such strategies allow the successful construction of actuating creases made from different stimuli-responsive transition metal hydroxides/oxides that can self-fold into curvature exceeding 1 mm−1 under low-intensity visible-light stimulation in ambient conditions, or low-potential electrochemical stimulation in electrolytic environments, with response time as fast as in seconds. Based on the high performance of such active creases, complex miniaturized origami designs powered by hinges activated in an independently controllable way are demonstrated, including self-folding Miura and a full micro-robotic hand with independently programmable finger joints. These results prove a new, versatile paradigm for robotics, where a transferrable approach is applicable to design and fabricate a wide variety of customizable micro-robots with compact construction and complex motions using different stimuli-responsive ceramic-based materials.