One-pot in situ preparation of alginate/gelatin-based hydrogel sensor loading menthol

Hydrogel sensors are superior materials for human motion detection. However, the facile "one-pot" in situ preparation of natural-based hydrogels loading hydrophobic drugs remains particularly challenging. Here, OSA and GelMA-NBNAGA, derived from alginate and gelatin, were dissolved in "one-pot" with a little CaCl₂ and photoinitiator. OSA referred to oxidized sodium alginate, whereas GelMA-NBNAGA denoted gelatin modified using maleic anhydride (MA) and N'-(2-nitrobenzyl)-N-acryloyl glycinamide (NBNAGA). Upon UV irradiation within several seconds, the O_x-(G_y-N_z)-Ca_r hydrogel in situ formed with quadruple crosslinked networks, including Schiff base bonds, metal coordination, covalent bonds, and dual hydrogen bonds. The effects of substitution degree and concentration were investigated to achieve optimal mechanical performance, exhibiting tensile strain of 410% and stress of 324 kPa. Meanwhile, the healing efficiency of 85.5%, adhesion strength of 120 kPa to porcine skin, and conductivity of 0.51 S/m were achieved. As a hydrogel sensor, it demonstrated satisfactory strain sensitivity (gauge factor, GF, 1.1) and rapid response time (∼0.2 s). More importantly, menthol can be loaded on the hydrophobic NB groups, enabling a sustained release of 28 h, with antibacterial efficacy >99.99%. Therefore, apart from the advantages of convenient preparation, in situ application, and excellent comprehensive performance, which endow it with significant application potential in wearable sensors, its sustained antibacterial properties are especially suitable for scenarios that require a cool wearing experience and long-term monitoring.