Cellulose acetate for a humidity-responsive self-actuator bilayer composite

The use of stimuli-responsive polymers to produce environmentally responsive self-actuators continues to rise. Highly hygroscopic materials are attracting great interest for the design of humidity-responsive self-actuators. In this context, bilayer composites, formed by the coupling of a hygroscopic layer with a non-hygroscopic one, are relevant as they allow for the response to be tuned through the design of the composite layers. Therefore, the meticulous material characterization and the definition of descriptive models of their hygroscopic behavior are the primary steps towards the development of humidity-responsive self-actuators. This study is aimed at measuring and predicting the response of a bilayer composite made of a hygroscopic material layer and a layer of a non-hygroscopic material when subjected to changes in environmental humidity levels, to be used as a humidity-responsive self-actuator. A cellulose acetate was used as the hygroscopic material. Predictions for the induced hygroscopic deformation in the bilayer composite, based on two-physics finite element simulations, are compared to experimental measurements.