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BIT team has made important progress in the field of self-growing hydrogels

News Source: School of Aerospace Engineering

Photographer: School of Aerospace Engineering

Editor: Zhao Yakang

Reviewer: Long Teng

Recently, Professor Zhang Kai and his team of the Beijing Institute of Technology has made important progress in self-growing hydrogels. Relevant research results were published in the top international journal Advanced Materials under the title of “Bioinspired Self-Growing Hydrogels by Harnessing the Interfacial Polymerization”, and was selected as the cover paper of the current issue. Professor Zhang Kai from the School of Aerospace Engineering of BIT and Professor Liu Ji from the Department of Mechanical and Energy Engineering of Southern University of Science and Technology are the co-corresponding authors of this paper, and 2019 PhD student Jian Nannan from the School of Aerospace Engineering is the first author.

Natural organisms are able to adapt to different external environments through spontaneous growth. In contrast to such fully dynamic and open self-growing systems, synthetic materials are usually in static and closed systems. At present, biomimetic synthetic materials can be endowed with smart properties (such as stimuli responsiveness, self-healing performance, etc.) similar to natural materials, and are widely used in emerging fields such as sensors, soft robotics, biomedical engineering and wearable electronic devices. However, designing and fabricating synthetic materials with self-growing properties remains challenging.

In response to this problem, inspired by the self-growing behaviors of keratin proteins, the team proposed a continuous free radical polymerization strategy at the interface between liquid metal (EGaIn) and aqueous monomer acrylamide (AAm) solution, endowing synthetic polyacrylamide (PAAm) hydrogel material with unprecedented self-growing characters (Figure 1a-c). When the self-growing hydrogels were further added to the monomer solution, it was found that the hydrogels showed the characteristics of continuous self-growing (Figure 1d-f).

Figure 1. Design principle and implementation method of self-growing hydrogel

The self-growing behaviors of hydrogels successfully mimic the phenomena of natural vine climbing (Figure 2a-d), exhibiting great promise in soft wall-climbing robots, with distinct advantages in small curved pipes. In addition, inspired by the "breaking through the soil" of natural plants, the research team converted the self-growing "power" into a "actuation force" by designing an actuator based on self-growing hydrogels (Figure 2e-f), which successfully opened a specific container. Unlike most hydrogel actuators, which require external energy such as light, heat or electricity to trigger, self-growing hydrogel actuators do not require any extra energy input, and their power density is significantly higher than that of other hydrogel actuators, demonstrating spontaneous, efficient and controllable actuation function.

Figure 2. Self-growing hydrogels mimiking the climbing behaviors of natural vines and as soft actuators.

The research was supported by The National Natural Science Foundation of China, Natural Science Foundation of Guangdong Province, and some other fundings.

Details of the paper: Nannan Jian, Rui Guo, Lei Zuo, Yibo Sun, Yu Xue, Ji Liu*, Kai Zhang*, Bioinspired Self-Growing Hydrogels by Harnessing Interfacial Polymerization. Advanced Materials, 2022: 2210609.

Full text link:https://onlinelibrary.wiley.com/doi/10.1002/adma.202210609

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