Coconut pollen paper soft actuator: tunable shape morphism driven by vapor

This study presents a bio-derived, multi-vapor-responsive paper actuator fabricated from monocolpate pollen grains of Cocos nucifera (coconut). The pollen paper demonstrates reversible and tunable shape morphing under water and alcohol vapor stimuli, bending in opposite directions depending on vapor type (“smiley-faced” vs. “sad-faced” deformation). Through surface patterning and geometry control, the team achieved directional control of bending axes and optimized humidity-driven actuation speed. The actuator exhibited robust mechanical performance and recovery over extended vapor exposure, supporting its potential for sustainable and adaptive energy-harvesting or sensing applications. Finite element analysis correlated structural corrugation patterns with anisotropic bending response, providing insight into soft actuator design principles.