SOFT ROBOTICS

3D printing of soft robotic systems

Abstract

Soft robots are capable of mimicking the complex motion of animals. Soft robotic systems are defined by their compliance, which allows for continuous and often responsive localized deformation. These features make soft robots especially interesting for integration with human tissues, for example, the implementation of biomedical devices, and for robotic performance in harsh or uncertain environments, for example, exploration in confined spaces or locomotion on uneven terrain. Advances in soft materials and additive manufacturing technologies have enabled the design of soft robots with sophisticated capabilities, such as jumping, complex 3D movements, gripping and releasing. In this Review, we examine the essential soft material properties for different elements of soft robots, highlighting the most relevant polymer systems. Advantages and limitations of different additive manufacturing processes, including 3D printing, fused deposition modelling, direct ink writing, selective laser sintering, inkjet printing and stereolithography, are discussed, and the different techniques are investigated for their application in soft robotic fabrication. Finally, we explore integrated robotic systems and give an outlook for the future of the field and remaining challenges.

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Fig. 1: Soft robots created by replica moulding.
Fig. 2: Mechanical properties and crosslinking of polymeric materials.
Fig. 3: Extrusion-based and powder-based 3D printing of soft actuators.
Fig. 4: Photocurable ink-based 3D printing of soft materials.
Fig. 5: 3D-printed soft sensors.
Fig. 6: Integrated soft robotic systems.

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Acknowledgements

The authors thank the Air Force Office of Scientific Research (Young Investigator Award under Award Number FA9550-15-1-0160), the Office of Naval Research (Young Investigator Award under Award Number N00014-17-1-2837) and the National Science Foundation (under Award Number CMMI-1537413) for their support.

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Correspondence to R. F. Shepherd.

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This Review appropriately references an article “Click chemistry stereolithography for soft robots that self-heal.” J. Mat. Chem. B (2017). Portions of this referenced work have been disclosed to the United States Patent and Trademark Office as Provisional Patent 62/369,327: Polymer Compositions for 3D printing and 3D. Two of the authors, R.S. and T.W., are inventors on this patent.

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Wallin, T.J., Pikul, J. & Shepherd, R.F. 3D printing of soft robotic systems. Nat Rev Mater 3, 84–100 (2018). https://doi.org/10.1038/s41578-018-0002-2

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