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, most previous studies have relied on non-stretchable planar designs, requiring continuous water flow or ionic solutions. Here, we present a fully stretchable hydrovoltaic cell (FSHC) with a parallel double-helix configuration of neat and oxidized carbon nanotube (CNT) fibers wound around an elastomeric core. This winding-locked double-helix architecture ensures mechanical robustness and stable electrical properties under strain. When immersed in quiescent deionized water, the FSHC generates ~0.31 V and ~22.4 µA/cm², maintaining reliable performance up to 200% strain. To demonstrate its potential in wearable applications, the FSHC is integrated into a fabric glove. Moreover, multiple FSHCs connected in series or parallel provide sufficient power to drive a twisted CNT fiber actuator. This study introduces a deformable hydrovoltaic platform for fiber-based energy harvesters, broadening their applicability to wearable electronics and self-powered actuation.