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  • Protocol
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Design and build of small-scale magnetic soft-bodied robots with multimodal locomotion

Abstract

Small-scale magnetic soft-bodied robots can be designed to operate based on different locomotion modes to navigate and function inside unstructured, confined and varying environments. These soft millirobots may be useful for medical applications where the robots are tasked with moving inside the human body. Here we cover the entire process of developing small-scale magnetic soft-bodied millirobots with multimodal locomotion capability, including robot design, material preparation, robot fabrication, locomotion control and locomotion optimization. We describe in detail the design, fabrication and control of a sheet-shaped soft millirobot with 12 different locomotion modes for traversing different terrains, an ephyra jellyfish-inspired soft millirobot that can manipulate objects in liquids through various swimming modes, a larval zebrafish-inspired soft millirobot that can adjust its body stiffness for efficient propulsion in different swimming speeds and a dual stimuli-responsive sheet-shaped soft millirobot that can switch its locomotion modes automatically by responding to changes in the environmental temperature. The procedure is aimed at users with basic expertise in soft robot development. The procedure requires from a few days to several weeks to complete, depending on the degree of characterization required.

Key points

  • The protocol describes a sheet-shaped millirobot with 12 locomotion modes for traversing different terrains, a jellyfish-inspired millirobot for manipulating objects in liquids, a zebrafish-inspired millirobot for efficient swimming and a dual stimuli-responsive millirobot that can switch locomotion modes automatically by responding to the environmental temperature.

  • Rigid-bodied robots lack deformation capabilities, limiting them to specific functions, whereas soft-bodied millibots display sophisticated locomotion strategies similar to those adopted by small-scale organisms.

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Fig. 1: Magnetic soft-bodied miniature robots with multimodal locomotion capability.
Fig. 2: Example results of characterization of magnetic materials.
Fig. 3: Design of the magnetic soft-bodied miniature robots with multimodal locomotion.
Fig. 4: The distributions of magnetic microparticles in polymer matrixes.
Fig. 5: Fabrication process of the magnetic soft composite films.
Fig. 6: Fabrication process of the magnetic soft composite thin films with microstructures.
Fig. 7: Fabrication process of the magnetic soft composite films that can also respond to other nonmagnetic stimuli.
Fig. 8: Producing 3D shapes for the magnetic soft composite materials.
Fig. 9: Magnetizing and assembly of the soft robot components.
Fig. 10: Measuring the B–H curve using VSM.
Fig. 11: Magnetic actuation setups for controlling the locomotion of small-scale magnetic soft robots.
Fig. 12: Realization of different locomotion modes of the sheet-shaped robot on solid surfaces.
Fig. 13: Realization of locomotion modes of the sheet-shaped robot on water–air interfaces, within water, and in tubular structures with internal liquid flows.
Fig. 14: Realization of transition modes of the sheet-shaped robot.
Fig. 15: Realization of five swimming modes of the ephyra jellyfish-inspired robot.
Fig. 16: Realization of multimodal locomotion of the larval zebrafish-inspired robot and the dual stimuli-responsive sheet-shaped robot.
Fig. 17: Medical imaging setup for ex vivo experiments.
Fig. 18: Particle image velocimetry (PIV) fluid flow visualization experiments.

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Data availability

All data required for robot fabrication are included in the main text. Other data on robot locomotion characterization and optimization have been published in our previous papers14,15,16,17,18,19 and are available from the corresponding author upon reasonable request.

Code availability

The codes used for locomotion performance evaluation and optimization has been published in our previous papers and are available from the corresponding author on reasonable request.

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Acknowledgements

We thank the Max Planck Society, European Research Council Advanced Grant SoMMoR project (grant no. 834531) and the German Research Foundation Soft Material Robotic Systems (SPP 2100) Program (grant no. 497562474) for funding this project.

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Z.R. planned and prepared the manuscript. M.S. planned, supervised and edited the manuscript.

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Correspondence to Metin Sitti.

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Key references

Hu, W. et al. Nature 554, 81–85 (2018): https://doi.org/10.1038/nature25443

Ren, Z. et al. Sci. Adv. 7, eabh2022 (2021): https://doi.org/10.1126/sciadv.abh2022

Ren, Z. et al. Nat. Commun. 10, 2703 (2019): https://doi.org/10.1038/s41467-019-10549-7

Wang, T. et al. Sci. Adv. 7, eabf7364 (2021): https://doi.org/10.1126/sciadv.abf7364

Zhang, J. et al. (2021). Adv. Mater. 33, 2006191 (2021): https://doi.org/10.1002/adma.202006191

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Ren, Z., Sitti, M. Design and build of small-scale magnetic soft-bodied robots with multimodal locomotion. Nat Protoc 19, 441–486 (2024). https://doi.org/10.1038/s41596-023-00916-6

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