Microgel-Reinforced Multifunctional Hydrogel Strain Sensors for Wearable Human Motion Monitoring

With the rapid development of wearable materials, the research of hydrogel-based sensors has attracted extensive attention due to their flexible properties and adjustable functionalities. However, integrating multiple functions involving excellent mechanical properties, high ionic conductivity, antifreezing properties, long-term stability, strong adhesion, and transparency into a single hydrogel remains a critical challenge. Here, we report a strategy for achieving a combination of all of these excellent properties in one ionic hydrogel sensor by introducing ionic microspheres (MS) into a continuous hydrogel matrix constructed from a xanthan gum/agarose (XG/AG) network. The ionic microspheres containing ionic liquid act as dynamic cross-linkers and sacrificial units via reversible physical cross-linking, redistributing stress concentrations and dissipating energy. The MS-induced multiple hydrogen bonds and electrostatic interactions endowed the hydrogel with ultrahigh stretchability (failure strain: 2389%), toughness, and interfacial adhesion (19.35 kPa). Simultaneously, the hydrogel achieved high transparency (∼90%), low-temperature flexibility, and ionic conductivity of 7.87 S·m–1. As a strain sensor, it exhibited superior sensitivity (gauge factor = 7.68 in the strain of 100–600%), detection limit (0.2%), and durability, enabling stable such as pulse waves and laryngeal vibrations. This work provides valuable insights for the development of multifunctional flexible sensors.