Covalent-supramolecular hybrid polymers as muscle-inspired anisotropic actuators

• Published in: Nature communications Vol. 9; no. 1; pp. 2395 - 11
• Main Authors: Chin, Stacey M., Synatschke, Christopher V., Liu, Shuangping, Nap, Rikkert J., Sather, Nicholas A., Wang, Qifeng, Álvarez, Zaida, Edelbrock, Alexandra N., Fyrner, Timmy, Palmer, Liam C., Szleifer, Igal, Olvera de la Cruz, Monica, Stupp, Samuel I.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.06.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/923/1028; 639/301/923/966; Actuation; Algorithms; Alignment; Anisotropy; BASIC BIOLOGICAL SCIENCES; Biocompatible Materials - chemistry; Biomechanical Phenomena; Chains (polymeric); Coding; Composite materials; Contraction; Finite element method; GENERAL AND MISCELLANEOUS; High temperature; Humanities and Social Sciences; Humans; Hydrogels; Hydrogels - chemistry; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; Mathematical analysis; Molecular chains; multidisciplinary; Muscle, Skeletal - physiology; Muscles; Musculoskeletal system; Nanofibers; Nanofibers - chemistry; Nanofibers - ultrastructure; NMR; Nuclear magnetic resonance; Peptides; Polymerization; Polymers; Polymers - chemistry; Science; Science (multidisciplinary); Self-assembly; Skeletal muscle; Task complexity; Temperature; Thermodynamics; Tubes
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-04800-w

Skeletal muscle provides inspiration on how to achieve reversible, macroscopic, anisotropic motion in soft materials. Here we report on the bottom-up design of macroscopic tubes that exhibit anisotropic actuation driven by a thermal stimulus. The tube is built from a hydrogel in which extremely long supramolecular nanofibers are aligned using weak shear forces, followed by radial growth of thermoresponsive polymers from their surfaces. The hierarchically ordered tube exhibits reversible anisotropic actuation with changes in temperature, with much greater contraction perpendicular to the direction of nanofiber alignment. We identify two critical factors for the anisotropic actuation, macroscopic alignment of the supramolecular scaffold and its covalent bonding to polymer chains. Using finite element analysis and molecular calculations, we conclude polymer chain confinement and mechanical reinforcement by rigid supramolecular nanofibers are responsible for the anisotropic actuation. The work reported suggests strategies to create soft active matter with molecularly encoded capacity to perform complex tasks. Skeletal muscles are impressive as they can achieve reversible, macroscopic, anisotropic motion in soft materials. Here the authors show a bottom-up design of macroscopic hydrogel tubes containing supramolecular nanofibers that can undergo anisotropic actuation by thermal stimuli.