Role of hierarchy structure on the mechanical adaptation of self-healing hydrogels under cyclic stretching

Xueyu Li; Kunpeng Cui; Yong Zheng; Ya Nan Ye; Chengtao Yu; Wenqi Yang; Tasuku Nakajima; Jian Ping Gong

doi:10.1126/sciadv.adj6856

Role of hierarchy structure on the mechanical adaptation of self-healing hydrogels under cyclic stretching

Sci Adv. 2023 Dec 22;9(51):eadj6856. doi: 10.1126/sciadv.adj6856. Epub 2023 Dec 20.

Authors

Xueyu Li¹, Kunpeng Cui^{2

3}, Yong Zheng², Ya Nan Ye^{1

4}, Chengtao Yu^{5

6}, Wenqi Yang⁵, Tasuku Nakajima^{1

2}, Jian Ping Gong^{1

2}

Affiliations

¹ Laboratory of Soft and Wet Matter, Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
² Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 001-0021, Japan.
³ Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
⁴ College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
⁵ Laboratory of Soft and Wet Matter, Division of Soft Matter, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
⁶ Institute of Zhejiang University-Quzhou, Quzhou 324000, China.

Abstract

Soft materials with mechanical adaptability have substantial potential for various applications in tissue engineering. Gaining a deep understanding of the structural evolution and adaptation dynamics of soft materials subjected to cyclic stretching gives insight into developing mechanically adaptive materials. Here, we investigate the effect of hierarchy structure on the mechanical adaptation of self-healing hydrogels under cyclic stretching training. A polyampholyte hydrogel, composed of hierarchical structures including ionic bonds, transient and permanent polymer networks, and bicontinuous hard/soft-phase networks, is adopted as a model. Conditions for effective training, mild overtraining, and fatal overtraining are demonstrated in soft materials. We further reveal that mesoscale hard/soft-phase networks dominate the long-term memory effect of training and play a crucial role in the asymmetric dynamics of compliance changes and the symmetric dynamics of hydrogel shape evolution. Our findings provide insights into the design of hierarchical structures for adaptive soft materials.