One-Shot 3D Printed Soft Device Actuated Using Metal-Filled Channels and Sensed with Embedded Strain Gauge

In this article, the multimaterial extrusion (M-MEX) technology is used to fabricate, in a single step, a threedimensional printed soft electromagnetic (EM) actuator, based on internal channels, filled with soft liquid metal (Galinstan) and equipped with an embedded strain gauge, for the first time. At the state of the art, M-MEX techniques result underexploited for the manufacture of soft EM actuators: only traditional manufacturing approaches are used, resulting in many assembly steps. The main features of this work are as follows: (1) one shot fabrication, (2) smart structure equipped with sensor unit, and (3) scalability. The actuator was tested in conjunction with a commercial magnet, showing a bending angle of 22.4 degrees (when activated at 4A), a relative error of 0.7%, and a very high sensor sensitivity of 49.7 omega/degrees degree. Two more examples, showing all the potentialities of the proposed approach, are presented: a jumping frog-inspired soft robot and a dual independent two-finger actuator. This article aims to push the role of extrusion-based additive manufacturing for the fabrication of EM soft robots: several advantages such as portability, no cooling systems, fast responses, and noise reduction can be achieved by exploiting the proposed actuation system compared to the traditional and widespread actuation mechanisms (shape memory polymers, shape memory alloys, pneumatic actuation, and cable-driven actuation).