Elastic instability-mediated actuation by a supra-molecular polymer


In nature, fast, high-power-density actuation can be achieved through the release of stored elastic energy by exploiting mechanical instabilities in systems including the closure of the Venus flytrap1 and the dispersal of plant or fungal spores2. Here, we use droplet microfluidics to tailor the geometry of a nanoscale self-assembling supra-molecular polymer to create a mechanical instability. We show that this strategy allows the build-up of elastic energy as a result of peptide self-assembly, and its release within milliseconds when the buckled geometry of the nanotube confined within microdroplets becomes unstable with respect to the straight form. These results overcome the inherent limitations of self-assembly for generating large-scale actuation on the sub-second timescale and illuminate the possibilities and performance limits of irreversible actuation by supra-molecular polymers.

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Figure 1: FF tubes are able to pierce through water-in-oil double layer interfaces.
Figure 2: Tailoring the geometry of FF self-assembly to create a mechanical instability.
Figure 3: Control of FF nanotube unbuckling by external stimuli and generation of external work.
Figure 4: Comparison of energy and power generation by biological and synthetic systems.


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This work was supported by a short-term fellowship from EMBO and from FEBS (A.L.), the Newman Foundation (A.L., T.O.M., T.P.J.K.), the Tel Aviv University Center for Nanoscience and Nanotechnology (A.L.), St John’s College Cambridge (T.C.T.M.), the Israeli National Nanotechnology Initiative and Helmsley Charitable Trust (E.G.), Elan Pharmaceuticals (T.O.M.), the UK BBSRC (T.P.J.K.) and the ERC (T.P.J.K., T.C.T.M.). We thank P. Marcu and Z. Arnon for their assistance with the high-resolution scanning electron microscopy imaging, and members of the Gazit and Knowles groups for helpful discussion.

Author information

A.L., T.C.T.M., L.M., E.G. and T.P.J.K. conceived and designed the experiments. A.L., T.O.M., B.Z. and T.C.T.M. planned and performed the experiments. T.C.T.M., L.M. and T.P.J.K. developed the theory and analysed the experimental data. T.M. provided the fast camera set-up. A.L., T.C.T.M., L.A.-A., T.O.M., T.M., L.M., E.G. and T.P.J.K. wrote the manuscript. All authors discussed the results, provided intellectual input and critical feedback and commented on the manuscript.

Correspondence to Ehud Gazit or Tuomas P. J. Knowles.

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Levin, A., Michaels, T., Adler-Abramovich, L. et al. Elastic instability-mediated actuation by a supra-molecular polymer. Nature Phys 12, 926–930 (2016). https://doi.org/10.1038/nphys3808

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