%0 journal article
%@ 1530-6984
%A Cheng, C.,Luehrs, L.,Krekeler, T.,Ritter, M.,Weissmueller, J.

%D 2017
%J Nano Letters
%N 8
%P 4774-4780 
%R doi:10.1021/acs.nanolett.7b01526
%T Semiordered Hierarchical Metallic Network for Fast and Large Charge-Induced Strain
%U https://doi.org/10.1021/acs.nanolett.7b01526
8 
%X Nanoporous metallic actuators for artificial muscle applications are distinguished by combining the low operating voltage, which is otherwise reserved for polymer-based actuators with interesting values of strain amplitude, strength, and stiffness that are comparable of those of piezoceramics. We report a nanoporous metal actuator with enhanced strain amplitude and accelerated switching. Our 3D macroscopic metallic muscle has semiordered and hierarchical nanoporous structure, in which μm-sized tubes align perpendicular with the sample surface, while nm-sized ligaments consist of the tube walls. This nanoarchitecture combines channels for fast ion transportation with large surface area for charge storage and strain generation. The result is a record reversible strain amplitude of 1.59% with a strain rate of 8.83 × 10–6 s–1 in the field of metallic based actuators. A passive hydroxide layer is self-grown on the metal surface, which not only contributes a supercapacitive layer, but also stabilizes the nanoporous structure against coarsening, which guarantees sustainable actuation beyond ten-thousand cycles.