Programmable Etherified‐Starch Networks Enable Tunable Humidity‐Responsive Soft Actuators for Smart Textiles

Bio‐inspired, humidity‐responsive actuators hold great promises for flexible robotics, sensing, and intelligent energy systems. However, conventional fabrication methods often suffer from high cost, complex chemistry, and environmental concerns. Here, we report a sustainable molecular engineering strategy for starch‐derived films based on sequential acidification and etherification, which precisely modulates the intermolecular hydrogen‐bonding network to enhance flexibility, control moisture uptake, and enable reversible actuation. The optimized 0.1 mm‐thick films exhibit rapid bending (180° in 22 s under 70% relative humidity) and exceptional durability, maintaining structural integrity and actuation performance over 700 cycles. Atomic force microscopy confirms a significant reduction in surface roughness (∼8.6‐fold), minimizing stress concentrations and promoting uniform deformation. Importantly, these starch‐based actuators combine biodegradability with high‐performance actuation, demonstrating potential for next‐generation intelligent applications, including biomimetic inchworm‐like robots, reversible electronic switches, and self‐regulating ventilation systems for hazardous vapor detection. This work provides a rational, molecular‐level design strategy for sustainable, high‐performance soft actuators.