A striking feature of living systems is their ability to produce motility by amplification of collective molecular motion from the nanoscale up to macroscopic dimensions. Some of nature's protein motors, such as myosin in muscle tissue, consist of a hierarchical supramolecular assembly of very large proteins, in which mechanical stress induces a coordinated movement. However, artificial molecular muscles have often relied on covalent polymer-based actuators. Here, we describe the macroscopic contractile muscle-like motion of a supramolecular system (comprising 95% water) formed by the hierarchical self-assembly of a photoresponsive amphiphilic molecular motor. The molecular motor first assembles into nanofibres, which further assemble into aligned bundles that make up centimetre-long strings. Irradiation induces rotary motion of the molecular motors, and propagation and accumulation of this motion lead to contraction of the fibres towards the light source. This system supports large-amplitude motion, fast response, precise control over shape, as well as weight-lifting experiments in water and air.
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This work was supported financially by the Netherlands Organization for Scientific Research (NWO-CW), the European Research Council (ERC, advanced grant no. 694345 to B.L.F.), the Ministry of Education, Culture and Science (Gravitation Program no. 024.001.035) and a Grant-in-Aid for Scientific Research on Innovative Areas ‘π-Figuration’ (nos. 26102008 and 15K21721) of The Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The synchrotron XRD experiments were performed at BL45XU in SPring-8 with the approval of the RIKEN SPring-8 Center (proposal no. 20160027).
The authors declare no competing financial interests.
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Chen, J., Leung, FC., Stuart, M. et al. Artificial muscle-like function from hierarchical supramolecular assembly of photoresponsive molecular motors. Nature Chem 10, 132–138 (2018). https://doi.org/10.1038/nchem.2887
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