Fecha de publicación: -- Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE This work presents an asymmetric composite film that exhibits continuous bidirectional deformation under constant solvent stimulation without external environmental switching. The asymmetric architecture induces differential swelling between the components, creating an internal stress mismatch that drives the bidirectional motion. This unique mechanism offers a new design strategy for continuous soft actuators and intelligent responsive devices.

ABSTRACT
The frequent leakage of organic solvents necessitates the development of intelligent monitoring systems and solvent-responsive actuators. Conventional actuators, however, often rely on “on/off” switching of external stimuli, typically resulting in passive and unidirectional deformation, which is insufficient for continuous actuation applications. This study introduces graphitic carbon nitride (g-C3N4), a two-dimensional layered material, into a polylactic acid (PLA)-poly(propylene carbonate) (PPC) system, successfully constructing an asymmetrically structured g-C3N4/PLA-PPC composite film. The film exhibited continuous and autonomous bidirectional deformation in a constant organic solvent environment, overcoming the limitation of unidirectional response typical of conventional materials. The bidirectional actuation performance was systematically investigated with respect to g-C3N4 content, polymer blending ratio, film geometry, and type of layered inorganic materials. The mechanism underlying the continuous bidirectional deformation of the film in a constant organic solvent environment was elucidated through systematic adsorption and structural analyses. Finally, utilizing this characteristic, biomimetic butterflies, artificial octopuses, intelligent protective devices, and smart alarms were designed, demonstrating potential application scenarios for bidirectional intelligent actuators.