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Autonomous snapping and jumping polymer gels


Snap-through buckling is commonly used in nature for power-amplified movements. While natural examples such as Utricularia and Dionaea muscipula can autonomously reset their snapping structures, bio-inspired analogues require external mediation for sequential snap events. Here we report the design principles for self-repeating, snap-based polymer jumping devices. Transient shape changes during the drying of a polymer gel are exploited to generate mechanical constraint and an internal driving force for snap-through buckling. Snap-induced shape changes alter environmental interactions to realize multiple, self-repeating snap events. The underlying mechanisms are understood through controlled experiments and numerical modelling. Using these lessons, we create snap-induced jumping devices with power density outputs (specific power ≈ 312 W kg−1) that are similar to high-performing jumping organisms and engineered robots. These results provide the demonstration of an autonomous, self-repeating, high-speed movement, marking an important advance in the development of environmental energy harvesting, high-power motion that is important for microscale robots and actuated devices.

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Fig. 1: Repeating snap-through buckling transitions of a swollen PDMS strip.
Fig. 2: Autonomous snapping motion of externally buckled PDMS strips.
Fig. 3: Transient formation of a spherical shell from a flat disc.
Fig. 4: Details of the dynamic performance of a spherical shell jumping on a substrate.
Fig. 5: Dynamic performance metrics of the jumps of spherical shells (R0 = 5 mm, h0 = 0.6 mm) prepared under different initial de-swelling conditions.
Fig. 6: Application of the autonomous snapping mechanism for performing higher level tasks.

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Data availability

The authors declare that data supporting the findings of this study are available within the paper and its supplementary information files. Additional data used in constructing plots and figures are available from UMass ScholarWorks (


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This material is based upon work supported by, or in part by, the US Army Research Laboratory and the US Army Research Office under contract/grant number W911NF-15-1-0358.

Author information

Authors and Affiliations



Y.K. conceived and conducted the experiments, performed data analysis and contributed to the writing and editing of the manuscript. J.v.d.B. conducted experiments and performed data analysis. A.J.C. conceived experiments and contributed to the writing and editing of the manuscript.

Corresponding author

Correspondence to Alfred J. Crosby.

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The authors declare no competing interests.

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Supplementary information

Supplementary Information

Supplementary Video Legends 1–8, Sections 1–3, Note 1, Figs. 1–6 and refs. 1–7.

Supplementary Video 1

Multiple, sequential snap-through transitions of a swollen polymer gel strip with one fixed end.

Supplementary Video 2

Multiple, sequential snap-through transitions of a swollen polymer gel strip on a PTFE substrate.

Supplementary Video 3

Multiple, sequential snap transitions of an externally constrained PDMS strip (h0 = 0.5 mm, w0 = 5 mm, L = 50 mm, ΔL = 10 mm)

Supplementary Video 4

High-speed video of a snapping shell (R0 = 4 mm, h0 = 0.6 mm, tprep = 40 s).

Supplementary Video 5

High-speed video of a snapping shell (R0 = 3 mm, h0 = 0.3 mm, tprep = 30 s) jumping on the copper mesh.

Supplementary Video 6

A snapping shell climbing down a slope.

Supplementary Video 7

Snapping shells climbing a ladder with a height of 8 cm.

Supplementary Video 8

Movie of finite element simulation of buckling induced during evaporative de-swelling of an initially swollen elastomer beam.

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Kim, Y., van den Berg, J. & Crosby, A.J. Autonomous snapping and jumping polymer gels. Nat. Mater. 20, 1695–1701 (2021).

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