Stretchable slide-ring supramolecular hydrogel for flexible electronic devices

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Researchers at Nankai University developed flexible hydrogel to be used in electronic devices for human-computer interactions [1].

Slide-ring materials with movable cross-links have received attention due to their excellent mechanical properties. However, due to the poor solubility of polyrotaxane and low synthesis efficiency, their applications are hindered. Here, we use hydroxypropyl-modified α-cyclodextrin (Hy-α-CD) and Acrylamide-PEG20000-Acrylamide (ACA-PEG20000-ACA) to construct a polypseudorotaxane with good water solubility. Through photo-initiated polymerization of polypseudorotaxane with acrylamide in-situ, the capped polyrotaxane was easily obtained and further cross-linked by 1,4-butanediol diglycidyl ether in sodium hydroxide solution to form a slide-ring supramolecular hydrogel. The hydrogel can be stretched to 25.4 times its original length, which recovers rapidly on unloading, and the addition of Ca2+ ions during crosslinking enhances ionic conductivity. The Ca2+-doped hydrogels are used to prepare wearable strain sensors for monitoring human motion.

Fig. 6
a Hydrogel could adhere to the skin. (Hy-α-CD-ACA-PEG20000-ACA/Ca hydrogel; ACA-PEG20000-ACA: Hy-α-CD = 1:5). b The hydrogel exhibited universal adhesiveness on material surfaces of glass and rubber. c Optical photo of a transparent hydrogel covering the Nankai University 100th Anniversary emblem. d Hydrogel could conduct electricity to brighten the bulb, and the bulb would become darker when the hydrogel was stretched.

[1] Wang, S., Chen, Y., Sun, Y. et al. Stretchable slide-ring supramolecular hydrogel for flexible electronic devices. Commun Mater 3, 2 (2022). https://doi.org/10.1038/s43246-022-00225-7

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