Fully Stretchable Hydrovoltaic Cells Based on Winding-Locked Double-Helical Carbon Nanotube Fibers

Hydrovoltaic power generators that convert water-nanomaterial interactions into electricity represent a promising route for sustainable energy harvesting. However, many previous studies have relied upon conventional two-dimensional planar designs with rigid, non-stretchable materials, typically operating in environments that require continuous water flow or specially designed ionic solutions. These stringent conditions restrict their practical applications, particularly in flexible and wearable systems. Hence, the present study introduces a fully stretchable hydrovoltaic cell (FSHC) that features a parallel double-helix configuration in which neat and oxidized carbon nanotube (CNT) fibers are spirally wound around an elastomeric core. This winding-locked double-helix architecture ensures robust mechanical integrity and stable electrical performance under large deformations. When immersed in quiescent deionized water, the FSHC generates an open-circuit voltage of ~ 0.31 V and a short-circuit current of ~ 2.24 µA/cm ² . Notably, the FSHC maintains consistent performance under 200% tensile strain. To demonstrate its potential in wearable applications, the FSHC is integrated into a fabric glove. Moreover, multiple FSHCs connected in series or parallel generate sufficient power to drive a twisted CNT fiber-based torsional actuator, suggesting a pathway toward self-powered actuation systems. This study offers a deformable hydrovoltaic platform for fiber-based energy harvesters, broadening their applicability in wearable electronics and autonomous actuation.