Dual‐Scale Hydration‐Induced Electrical and Mechanical Torsional Energy Harvesting in Heterophilically Designed CNT Yarns

Abstract Water holds vast potential for a useful energy source, yet traditional approaches capture only a fraction of it. This study introduces a heterophilically designed carbon nanotube (CNT) yarn with an asymmetric configuration. This yarn is capable of both electrical and mechanical torsional energy harvesting through dual‐scale hydration. Fabricated via half‐electrochemical oxidation, the yarn contains a hydrophilic region enriched with oxygen‐containing functional groups and a hydrophobic pristine CNT region. Molecular‐scale hydration triggers proton release in the hydrophilic region. Consequently, a concentration gradient is established that generates a peak open‐circuit voltage of 106.0 mV and a short‐circuit current of 20.6 mA cm ⁻² . Simultaneously, microscale hydration induces water absorption into inter‐bundle microchannels, resulting in considerable yarn volume expansion. This process leads to hydro‐driven actuation with a torsional stroke of 78.8° mm ⁻¹ and a maximum rotational speed of 1012 RPM. The presented simultaneous harvesting results in electrical and mechanical power densities of 3.5 mW m ⁻² and 34.3 W kg ⁻¹ , respectively, during a hydration cycle. By integrating molecular and microscale hydrations, the proposed heterophilic CNT yarns establish an unprecedented platform for simultaneous electrical and mechanical energy harvesting from water, representing a groundbreaking development for sustainable applications.