An ultra-large deformation bidirectional actuator based on a carbon nanotube/PDMS composite and a chitosan film

Actuating materials can convert external stimuli (humidity, light, electricity, etc.) into mechanical energy and realize multiple forms of movements. However, a majority of current actuating materials are driven by a single stimulus with a small degree of actuation and rough control which is unfavorable for practical applications. Here, a new type of bidirectional actuating material based on carbon nanotube/PDMS composites and chitosan films is proposed. Thanks to the robust mechanical support by PDMS, due to the ultra-large water capacity in between chitosan chains and strong near-infrared light absorption by carbon nanotube layers, the actuator can be driven by humidity and light for an ultra-large actuation curvature (3.91 cm^-1 in humidity actuation, 3.84 cm^-1 in light actuation). The well-established light power-curvature, relative humidity-curvature profiles and a fine mechanic modelling of the actuator show the possibility of controlling the actuator's bending. A lab application as a cargo-moving device preliminarily demonstrates a robust mechanical functionality of this actuator with a low body weight.