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Surface-chemistry-driven actuation in nanoporous gold


Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first1. Here, we demonstrate that surface-chemistry-driven actuation can be realized in high-surface-area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes of the order of a few tenths of a per cent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress2, and can be used to convert chemical energy directly into a mechanical response, thus opening the door to surface-chemistry-driven actuator and sensor technologies.

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Figure 1: Illustration of surface-chemistry-driven actuation in nanoporous gold.
Figure 2: Performance of a surface-chemistry-driven nanoporous Au actuator.
Figure 3: Surface-stress-induced relaxation of Au nanostructures studied by fully atomistic molecular dynamics simulations.


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Part of this work was carried out under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The authors want to express special thanks to F. F. Abraham (LLNL) and M. Duchaineau (LLNL) for generating the nanoporous Au samples for the molecular dynamics simulations.

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Biener, J., Wittstock, A., Zepeda-Ruiz, L. et al. Surface-chemistry-driven actuation in nanoporous gold. Nature Mater 8, 47–51 (2009).

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