Biosynthetic self-healing materials for soft machines

Abstract

Self-healing materials are indispensable for soft actuators and robots that operate in dynamic and real-world environments, as these machines are vulnerable to mechanical damage. However, current self-healing materials have shortcomings that limit their practical application, such as low healing strength (below a megapascal) and long healing times (hours). Here, we introduce high-strength synthetic proteins that self-heal micro- and macro-scale mechanical damage within a second by local heating. These materials are optimized systematically to improve their hydrogen-bonded nanostructure and network morphology, with programmable healing properties (2–23 MPa strength after 1 s of healing) that surpass by several orders of magnitude those of other natural and synthetic soft materials. Such healing performance creates new opportunities for bioinspired materials design, and addresses current limitations in self-healing materials for soft robotics and personal protective equipment.

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Fig. 1: Cephalopod-inspired biosynthetic proteins.
Fig. 2: Self-healing polypeptides.
Fig. 3: Self-healing of extreme mechanical damage.
Fig. 4: Self-healing, protein-based soft actuator.

Data availability

All relevant data that support the findings of this study are available in the article and its supplementary files. Source data for Figs. 1b,1c,4c are available in the Source Data files. Additional data can be obtained from the authors upon request.

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Acknowledgements

The authors thank H. Shahsavan and P. Cabanach for helpful discussions. M.C.D. and H.J. thank staff members of Penn State MRI and Huck user facilities. A.P.-F. and M.S. were supported by the Max Planck Society. A.P.-F. was also funded by the Alexander von Humboldt Foundation and the German Federal Ministry for Education and Research. M.S. was also funded by the European Research Council (ERC) Advanced Grant SoMMoR project with grant no: 834531. M.C.D. and H.J. were supported by the United States Army Research Office (grant no. W911NF-16-1-0019 and W911NF-18-1-026) and the Huck Endowment of The Pennsylvania State University.

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Authors

Contributions

A.P.-F., M.C.D., and M.S. conceived the project. A.P.-F. designed and performed the experiments, analysed the data, and wrote the manuscript. H.J. performed the protein expression and purification. All authors participated in manuscript revisions, discussions, and data interpretation.

Corresponding authors

Correspondence to Melik C. Demirel or Metin Sitti.

Ethics declarations

Competing interests

A.P.-F. and M.C.D. have issued patents (US patent 9,663,658 and US patent 10,253,144), and H.J. and M.C.D. have issued patents (US patent 9,765,121, US patent 10,047,127, and US patent 10,246,493) on technology related to processes described in this article. All other authors have no competing interests.

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Supplementary information

Supplementary Information

Supplementary Note 1, Supplementary Figs. 1–20, Supplementary Videos 1–5, and Supplementary References

Reporting Summary

Supplementary Video 1

Heat-assisted healing of TRn11 proteins

Supplementary Video 2

Protein-based pneumatic soft actuator

Supplementary Video 3

Protein-based soft gripper

Supplementary Video 4

Protein-based artificial muscle

Supplementary Video 5

Degradation of protein-based actuators

Supplementary Data 1

Self-healing performance benchmark

Supplementary Data 2

Actuator benchmark

Source data

Source Data Fig. 1b

Unprocessed SDS-PAGE gel from Fig. 1b

Source Data Fig. 1d

Cohesion and network parameter of polypeptides for Fig. 1d

Source Data Fig. 4c

Soft actuator displacement and force output for Fig. 4c

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Pena-Francesch, A., Jung, H., Demirel, M.C. et al. Biosynthetic self-healing materials for soft machines. Nat. Mater. (2020). https://doi.org/10.1038/s41563-020-0736-2

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