A mechanically robust, highly sensitive, resilient, and degradable dual physically cross-linked hydrogel for heart rate health detection

Abstract

Hydrogel sensors with excellent stability have received wide attention in various fields. However, unsatisfactory mechanical properties, poor sensitivity and non-degradability severely limit the range of sensing applications. Inspired by the unique structure of human skin, a novel dual-physically cross-linked hydrogel has been fabricated by micellar copolymerization as a soft ‘elastin matrix’ to form a hydrophobically conjugated network. Phytic acid (PA) has been introduced as an ‘enhancement factor’, which effectively enhances the comprehensive performance of the material. The dynamic mechanical response behavior and network structure evolution are characterized using rheology and multi-quantum (MQ) nuclear magnetic resonance (NMR) spectroscopy. The hydrogel exhibits outstanding comprehensive properties, including superior mechanical performance (strength of 437 kPa, fracture strain of 990%, and resilience of 93.8%), excellent frost resistance (−36.7 °C), and notable electrical conductivity (1.7 ± 0.28 S m⁻¹, GF = 1.16). Moreover, it is capable of not only differentiating between large-scale body movements and subtle physiological signals but also functioning as a highly sensitive flexible touch sensor. The sensor can also be employed as an electrode for detecting human electrocardiogram (ECG) signals. Furthermore, the sensor possesses biodegradable properties, ensuring that it does not generate electronic waste or contribute to environmental pollution upon disposal. Consequently, the new fabrication strategies for PA-based conductive hydrogels are promising to display great promise for bioelectronics applications.