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Making bioinspired 3D-printed autonomic perspiring hydrogel actuators

Nature Protocols volume 16, pages 2068–2087 (2021)Cite this article

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Abstract

To mitigate the adverse effects of elevated temperatures, conventional rigid devices use bulky radiators, heat sinks and fans to dissipate heat from sensitive components. Unfortunately, these thermoregulation strategies are incompatible with soft robots, a growing field of technology that, like biology, builds compliant and highly deformable bodies from soft materials to enable functional adaptability. Here, we design fluidic elastomer actuators that autonomically perspire at elevated temperatures. This strategy incurs operational penalties (i.e., decreased actuation efficiency and loss of hydraulic fluid) but provides for thermoregulation in soft systems. In this bioinspired approach, we 3D-print finger-like actuators from smart gels with embedded micropores that autonomically dilate and contract in response to temperature. During high-temperature operation, the internal hydraulic fluid flows through the dilated pores, absorbs heat and vaporizes. Upon cooling, the pores contract to restrict fluid loss and restore operation. To assess the thermoregulatory performance, this protocol uses non-invasive thermography to measure the local temperatures of the robot under varied conditions. A mathematical model based on Newton’s law of cooling quantifies the cooling performance and enables comparison between competing designs. Fabrication of the sweating actuator usually takes 3–6 h, depending on size, and can provide >100 W/kg of additional cooling capacity.

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Fig. 1: Bioinspired 3D-printed hydrogel actuator.
Fig. 2: Characterization of smart pores.
Fig. 3: Robotic systems for performance testing.
Fig. 4
Fig. 5: Dynamic response of hydrogel pores.
Fig. 6: Performance of sweating actuators.
Fig. 7: Thermo-manipulation of grasped objects.

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Data availability

The data used in this protocol are available in the supporting primary research article, and the design files are accessible at https://doi.org/10.6084/m9.figshare.12964811.

Software availability

The MATLAB code used in this protocol can be found in the Supplementary Information.

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Acknowledgements

This research was supported in part by the Office of Naval Research Young Investigator Program (N00014-17-1-2837). This work made use of the Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC program (DMR-1719875).

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Authors and Affiliations

  1. Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA

    Anand Kumar Mishra & Robert F. Shepherd

  2. Facebook Reality Labs, Redmond, WA, USA

    Wenyang Pan & Thomas J. Wallin

  3. Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA

    Wenyang Pan, Emmanuel P. Giannelis & Thomas J. Wallin

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  1. Anand Kumar Mishra
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Contributions

A.K.M., W.P., and T.J.W. developed the protocol. E.P.G. and R.F.S. obtained resources to support this research effort. A.K.M. and T.J.W. generated figures and took the lead in writing the manuscript with support from W.P., E.P.G. and R.F.S.

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Correspondence to Thomas J. Wallin.

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Peer review information Nature Protocols thanks Dacheng Wei and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Key reference using this protocol

Mishra, A. et al. Sci. Robot. 5, eaaz3918 (2020): https://doi.org/10.1126/scirobotics.aaz3918

Supplementary information

Supplementary Information

MATLAB code and Supplementary Figs. 1–12.

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Mishra, A.K., Pan, W., Giannelis, E.P. et al. Making bioinspired 3D-printed autonomic perspiring hydrogel actuators. Nat Protoc 16, 2068–2087 (2021). https://doi.org/10.1038/s41596-020-00484-z

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