Semiordered Hierarchical Metallic Network for Fast and Large Charge-Induced Strain

• Published in: Nano letters Vol. 17; no. 8; pp. 4774 - 4780
• Main Authors: Cheng, Chuan, Lührs, Lukas, Krekeler, Tobias, Ritter, Martin, Weissmüller, Jörg
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.08.2017
• Subjects: Artificial muscle; electrochemical actuation; charge-induced strain; nanoporous metal; hierarchical nanoporous structure
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.7b01526

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.