Freeform Liquid 3D Printing of Soft Functional Components for Soft Robotics

Freeform liquid three-dimensional printing (FL-3DP) is a promising new additive manufacturing process that uses a yield stress gel as a temporary support, enabling the processing of a broader class of inks into complex geometries, including those with low viscosities or long solidification kinetics that were previously not processable. However, the full exploitation of these advantages for the fabrication of complex multilateral structures has been hindered by difficulties in controlling the interfaces between inks and supports. In this work, an in-depth study of the rheological properties and interfacial stabilities between a nanoclay-modified support and silicone-based inks enabled a better understanding of the impact printing parameters have on the extruded filament morphology, and thus on printing resolutions. With these improvements, the fabrication of functional multimaterial pneumatic components applied to soft robotics could be demonstrated, exhibiting superior capabilities compared to casting or traditional extrusion-based additive manufacturing in terms of geometric freedom (overhanging and multimaterial structures), tunability of the component's functionality, and robustness between different phases. Overall, the full exploitation of FL-3DP advantages enables a broader design space for features and functionalities in soft robotic components that require complex and robust combinations of materials.