Issue 39, 2021

Ultrastable, stretchable, highly conductive and transparent hydrogels enabled by salt-percolation for high-performance temperature and strain sensing

Abstract

Ionic hydrogels are promising candidates for fabricating stretchable electronics, but the deficiency in drying and freezing tolerances severely limits their application. Here, we report a facile and versatile salt-percolated strategy to fabricate hydrogels with exceptional freezing and drying tolerances, high conductivity, and anti-swelling ability for sensitive temperature and strain detection within a broad temperature range. We discovered that lithium bromide (LiBr) was the most effective drying and freezing inhibitor for hydrogels among the various salts. The 50 wt% LiBr-percolated hydrogels retained ultrahigh stretchability (625% strain) and conductivity even at −78.5 °C or in ambient air for a year. The important role of LiBr in inhibiting the drying and freezing of hydrogels was understood using density functional theory (DFT) simulations on a molecular scale, revealing the formation of stable Li+–H2O and Br–H2O clusters. It was found that the introduction of LiBr enhanced the temperature and strain sensing performance, e.g., the stability and working temperature range. Multifunctional transparent sensors exhibited a high thermal sensitivity (2.54%/°C), broad temperature detection range (−78.5 to 97 °C), low detection limit (0.1% strain), and low hysteresis and baseline drift in cycling strain sensing. Attributed to the high tolerance of hydrogels to a wide range of temperatures, the strain sensing ability was maintained even at −20 °C. Various physiological signals, such as facial expressions, word pronunciation and knee bending, are real-time monitored using hydrogel-based epidermal sensors.

Graphical abstract: Ultrastable, stretchable, highly conductive and transparent hydrogels enabled by salt-percolation for high-performance temperature and strain sensing

Supplementary files

Article information

Article type
Paper
Submitted
31 may 2021
Accepted
04 iyl 2021
First published
05 iyl 2021

J. Mater. Chem. C, 2021,9, 13668-13679

Ultrastable, stretchable, highly conductive and transparent hydrogels enabled by salt-percolation for high-performance temperature and strain sensing

Z. Wu, W. Shi, H. Ding, B. Zhong, W. Huang, Y. Zhou, X. Gui, X. Xie and J. Wu, J. Mater. Chem. C, 2021, 9, 13668 DOI: 10.1039/D1TC02506F

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