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Published May 29, 2018 | Published + Supplemental Material
Journal Article Open

Harnessing bistability for directional propulsion of soft, untethered robots


In most macroscale robotic systems, propulsion and controls are enabled through a physical tether or complex onboard electronics and batteries. A tether simplifies the design process but limits the range of motion of the robot, while onboard controls and power supplies are heavy and complicate the design process. Here, we present a simple design principle for an untethered, soft swimming robot with preprogrammed, directional propulsion without a battery or onboard electronics. Locomotion is achieved by using actuators that harness the large displacements of bistable elements triggered by surrounding temperature changes. Powered by shape memory polymer (SMP) muscles, the bistable elements in turn actuate the robot's fins. Our robots are fabricated using a commercially available 3D printer in a single print. As a proof of concept, we show the ability to program a vessel, which can autonomously deliver a cargo and navigate back to the deployment point.

Additional Information

© 2018 National Academy of Sciences. Published under the PNAS license. Edited by John A. Rogers, Northwestern University, Evanston, IL, and approved April 23, 2018 (received for review January 9, 2018). Published ahead of print May 15, 2018. We thank Jung-Chew Tse for fabrication support and Connor McMahan and Ethan Pickering for support in experiments. This work was supported by Army Research Office Grant W911NF-17-1-0147 and Eidgenössische Technische Hochschule (ETH) Postdoctoral Fellowship FEL-26 15-2 (to O.R.B.). Author contributions: O.R.B. and C.D. designed research; T.C. and O.R.B. performed research; T.C., O.R.B., K.S., and C.D. analyzed data; and T.C., O.R.B., K.S., and C.D. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1800386115/-/DCSupplemental.

Attached Files

Published - 5698.full.pdf

Supplemental Material - pnas.1800386115.sapp.pdf

Supplemental Material - pnas.1800386115.sm01.mp4

Supplemental Material - pnas.1800386115.sm02.mp4

Supplemental Material - pnas.1800386115.sm03.mp4

Supplemental Material - pnas.1800386115.sm04.mp4

Supplemental Material - pnas.1800386115.sm05.mp4

Supplemental Material - pnas.1800386115.sm06.mp4

Supplemental Material - pnas.1800386115.sm07.mp4

Supplemental Material - pnas.1800386115.sm08.mp4


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August 21, 2023
October 18, 2023