Supervised folding of origami soft actuators enabled by magnetic e-skins

Reconfigurable[1], soft[2], and lightweight[3] actuators are expected to be implemented in robotic systems biomimicking the multifunctional and adaptive capabilities of living organisms. The integration of sensing elements in soft actuators enables smart motion events increasing reliability, efficiency, and safe integration in diverse environments[4]. Specifically, for origami-based systems[5], the tracking of the orientation and the readiness of the folding is important to achieve reliable assembly of the structures.
Integration of sensing elements with soft actuators is typically addressed with stimuli-responsive materials[6] and commercial sensors[7] that lack feedback capabilities and high compliancy, respectively. Recent approaches measuring strain[8], curvature[9], and optical[10] signals have been demonstrated for localized single folding in soft actuators. Until recently, there were no reports of an onboard sensing platform that enables the folding of multiple flaps as needed for origami.
Here, we will show the integration of flexible e-skins on magnetic actuators for supervision of the sequence and folding assembly of hinges defined on the fly. Highly compliant magnetic sensors (GMR and Hall effect) were laminated into ultrathin magnetic origami actuators enabling the detection of the readiness for actuation, the orientation, and the hinge folding process. The actuator, a magnetic composite based on a shape memory polymer with embedded NdFeB microparticles, actuates during a light softening and magnetic stimuli sequence[11]. We optimized the thickness (60 µm) and composition (NdFeB - 40 wt%) of the composite to achieve the 180 deg basic fold for origami structures. The capabilities of the system with laminated sensing e-skin were demonstrated after self-guided assembly of the origami platform with multiple hinges into box- and boat-like layouts[12]. We envision that further development of alike self-supervised systems will bring closer the realization of adaptive mechatronic soft systems for different environments and even remote applications.

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