Programmable Hydration Pathways Enable Reconfigurable Ionic Thermoelectrics for Energy Harvesting and Thermal‐Tactile Interaction

ABSTRACT Ionic thermoelectric (iTE) materials deliver large thermovoltages but face a trade‐off among thermopower, speed, and stability. Here we realize reconfigurable iTE performance in polyquaternium hydrogels by programming hydration pathways across scales, coupling microscopic solvation and polymer‐ion interactions to mesoscopic water channels and macroscopic boundary conditions. This hydration‐gated protonics framework decouples ion transport barriers from water activity and thermal gradient, enabling two distinct operating states. An open, breathable state amplifies asymmetric water activity and yields ultrahigh thermopower of 44.8 mV K ^{− 1} in PAETC/PSS hydrogels. A sealed state suppresses hydration exchange, yields subsecond dynamics, and supports long‐term stability. Guided by thermo‐hydration co‐design that treats the hydration boundary as a tunable parameter, we translate the mechanism into two platforms. A wearable energy‐harvesting module with a stable vertical bias ΔT = 3.0 K delivers a thermovoltage of ∼0.6 V, while a high‐sensitivity, fast‐response (0.5 s), long‐term‐stable (> 90 days) iTE sensor array with sealed‐mode reliability is integrated with a robotic hand for thermal–tactile interaction.