Porous Triple Network Hydrogel Humidity Sensor with Ultrafast Response for Wearable Health Monitoring

Vollständiger Abstract

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Abstract The rapid advancement of flexible and wearable electronics calls for humidity sensors that combine mechanical compliance with high sensitivity and fast response. However, conventional rigid-substrate sensors cannot conformally attach to soft surfaces and often suffer from signal instability under deformation. Here, we report a porous conductive triple network hydrogel humidity sensor designed through synergistic structural, electrical, and mechanical engineering. An interconnected microporous structure created by in situ CO 2 foaming accelerates water vapor transport. Carboxylated carbon nanotubes construct a uniform conductive network that enables efficient electrical signal transmission, whereas the triple-network matrix, integrated with covalent polyacrylamide crosslinks, sodium alginate–Ca 2+ ionic coordination, and tannic acid–Fe 3+ metal–phenolic interactions, effectively restrains volumetric swelling and imparts outstanding mechanical stability. The sensor achieves a wide RH sensing range (11.3%–97.3% RH), an ultrafast response/recovery time of ≤0.144 s, and stable operation over 300 cycles. It successfully distinguishes different breathing patterns and pathways in real time and enables non-contact finger proximity detection at millimeter distances. This work provides a rational design strategy for high speed wearable humidity sensors and intelligent non contact interfaces.