Xiong et al. reported in Nature Communication on wearable sensors based on sliding hydrogels . Acrylated β-cyclodextrin with bile acid is self-assembled into a polymerizable pseudorotaxane via precise host-guest recognition, which is photopolymerized with acrylamide to obtain conductive polymerizable rotaxane hydrogels (PR-Gel). The topological networks of PR-Gel enable all desirable properties in this system due to the large conformational freedom of the mobile junctions, including the excellent stretchability along with superior fatigue resistance. PR-Gel based strain sensor can sensitively detect and distinguish large body motions and subtle muscle movements. The three-dimensional printing fabricated sensors of PR-Gel exhibit high resolution and altitude complexity, and real-time human electrocardiogram signals are detected with high repeating stability. PR-Gel can self-heal in air, and has highly repeatable adhesion to human skin, demonstrating its great potential in wearable sensors.A.
Fig. 1a Illustration of the topological networks constructed by the polyrotaxane of PEG with α-CD in SR hydrogels; b illustration of the topological networks of PR-Gel constructed by the polymerizable pseudorotaxane crosslinkers of BA with β-CD derivatives; c design and assembly of polymerizable pseudorotaxane crosslinker and further applications of superior fatigue-resistant hydrogels and 3D printing fabrication of wearable flexible sensors. DLP 3D printer and PAm refer to the digital light processing (DLP) based 3D printer and polyacrylamide (PAm), respectively. It should be noted that CD-AC is a mixture of acrylate modified β-CD and the acrylate units on each CD-AC were averaged to be ca. 1.9.
A similar sytem has already been reported on CDN blog: https://cyclodextrinnews.com/2022/04/06/stretchable-slide-ring-supramolecular-hydrogel-for-flexible-electronic-devices/
 Xiong, X., Chen, Y., Wang, Z. et al. Polymerizable rotaxane hydrogels for three-dimensional printing fabrication of wearable sensors. Nat Commun 14, 1331 (2023). https://doi.org/10.1038/s41467-023-36920-3
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