Issue 6, 2023

A sweat-pH-enabled strongly adhesive hydrogel for self-powered e-skin applications

Abstract

On-skin hydrogel electrodes are poorly conformable in sweaty scenarios due to low electrode–skin adhesion resulting from the sweat film formed on the skin surface, which seriously hinders practical applications. In this study, we fabricated a tough adhesive cellulose-nanofibril/poly(acrylic acid) (CNF/PAA) hydrogel with tight hydrogen-bond (H-bond) networks based on a common monomer and a biomass resource. Furthermore, inherent H-bonded network structures can be disrupted through judicious engineering using excess hydronium ions produced through sweating, which facilitate the transition to protonation and modulate the release of active groups (i.e., hydroxyl and carboxyl groups) accompanied by a pH drop. The lower pH enhances adhesive performance, especially on skin, with a 9.7-fold higher interfacial toughness (453.47 vs. 46.74 J m−2), an 8.6-fold higher shear strength (600.14 vs. 69.71 kPa), and a 10.4-fold higher tensile strength (556.44 vs. 53.67 kPa) observed at pH 4.5 compared to the corresponding values at pH 7.5. Our prepared hydrogel electrode remains conformable on sweaty skin when assembled as a self-powered electronic skin (e-skin) and enables electrophysiological signals to be reliably collected with high signal-to-noise ratios when exercising. The strategy presented here promotes the design of high-performance adhesive hydrogels that may serve to record continuous electrophysiological signals under real-life conditions (beyond sweating) for various intelligent monitoring systems.

Graphical abstract: A sweat-pH-enabled strongly adhesive hydrogel for self-powered e-skin applications

Supplementary files

Article information

Article type
Communication
Submitted
06 2 2023
Accepted
21 3 2023
First published
27 3 2023

Mater. Horiz., 2023,10, 2271-2280

A sweat-pH-enabled strongly adhesive hydrogel for self-powered e-skin applications

L. Zhang, S. Wang, Z. Wang, Z. Huang, P. Sun, F. Dong, H. Liu, D. Wang and X. Xu, Mater. Horiz., 2023, 10, 2271 DOI: 10.1039/D3MH00174A

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