Printable Piezoresistive Hybrid Hydrogels Based on 2D MoS₂ for Flexible Pulse Sensing

The incorporation of two-dimensional (2D) nanomaterials such as molybdenum disulfide (MoS₂) nanoflakes/nanosheets into hydrogel matrices offers significant potential for the development of flexible and biocompatible piezoresistive sensors. Scalable synthesis methods, including liquid-phase exfoliation and hydrothermal processes, enable the efficient production of 2D MoS₂while reducing cost and environmental impact. Owing to the high surface area, anisotropy, and tunable electronic properties, these materials enhance sensitivity, mechanical strength, and electrical performance in hybrid systems. In this work, 1T- MoS₂-based hybrid hydrogels were fabricated via UV curing by forming cross-linked networks with polyethylene glycol diacrylate (PEGDA) and chitosan (CH). Electrical conductivity was further improved through in situ interfacial polymerization of aniline. The equivalent 3D-printed hydrogels exhibited enhanced mechanical strength, few-cycles structural stability, swelling, and controlled deformation compared to simply UV-cured systems, enabling more reproducible electromechanical responses. Both fabrication approaches showed linear and reversible piezoresistive behavior within the physiological blood pressure range. Furthermore, the optimized hydrogel demonstrated to be reliable in pulse monitoring (ca. 85 bpm) with good temporal correlation to the electrocardiogram signal and biocompatibility with human fibroblast cells, underscoring its potential for soft, flexible, and bio-integrated sensing applications.