Composition-Tuned Hydrogel Iontronic Patch With a Shared Electrode for Dual-Mode Pressure and Moisture-Electric Sensing in Wearable Health Monitoring.

Dual-mode wearable patches usually stack discrete sensing and energy modules made from dissimilar materials, which increases thickness and limits skin conformability. Here we report a hydrogel iontronic patch, 1.56 mm thick, in which both pressure sensing and moisture-electric signaling arise from a single H3PO4/ZnCl2/poly(vinyl alcohol) hydrogel by tuning the ZnCl2-to-H3PO4 ratio. The two functional layers share one Zn foil as a common internal electrode, merging two device stacks into a single compact unit while keeping the channels electrically independent. The pressure-sensing layer delivers a sensitivity of up to 0.60 nF kPa-1 with a measurement range extending to 2 MPa with stable response across 10,000 cycles. The moisture-electric layer generates about 0.8 V at 90% relative humidity and remains stable for over 100 h. The pressure channel captures arterial pulse, respiration, and joint motion, while the moisture channel tracks breathing- and perspiration-related humidity. Coupled with a one-dimensional convolutional neural network, the multichannel pressure output recognizes five representative tennis strokes, with cross-subject validation on five additional volunteers achieving 92.8% mean accuracy, offering a material-level route toward thinner, skin-conformable wearable healthcare.