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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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 (https://scholarworks.umass.edu/data/116).
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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.
The authors declare no competing interests.
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Supplementary Video Legends 1–8, Sections 1–3, Note 1, Figs. 1–6 and refs. 1–7.
Multiple, sequential snap-through transitions of a swollen polymer gel strip with one fixed end.
Multiple, sequential snap-through transitions of a swollen polymer gel strip on a PTFE substrate.
Multiple, sequential snap transitions of an externally constrained PDMS strip (h0 = 0.5 mm, w0 = 5 mm, L = 50 mm, ΔL = 10 mm)
High-speed video of a snapping shell (R0 = 4 mm, h0 = 0.6 mm, tprep = 40 s).
High-speed video of a snapping shell (R0 = 3 mm, h0 = 0.3 mm, tprep = 30 s) jumping on the copper mesh.
A snapping shell climbing down a slope.
Snapping shells climbing a ladder with a height of 8 cm.
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). https://doi.org/10.1038/s41563-020-00909-w