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 H 3 PO 4 /ZnCl 2 /poly(vinyl alcohol) hydrogel by tuning the ZnCl 2 ‐to‐H 3 PO 4 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.