Bioinspired dual-response actuators with Janus structure and good biodegradability

Smart materials that respond to external stimuli are the top choice as actuators. Herein, inspired by the natural plants, a smart dual-response actuator with Janus structure was fabricated from natural cellulose. Two cellulose derivatives with controllable chemical structure acted as the responsive elements, including ethanol-responsive cellulose 3,5-di-tert-butyl-4-hydroxybenzoate (CBH) and water-responsive carboxymethyl cellulose (CMC). Via changing the degree of substitution of 3,5-di-tert-butyl-4-hydroxybenzoate, the solubility, swellable property and swellable ratio of CBH in ethanol were precisely adjusted. After transforming the partial carboxylate group into the carboxylic acid, water-swellable CMC was obtained. Combining the ethanol-swellable CBH with water-swellable CMC by two-step blade-coating process, a Janus film was fabricated with dual-driven motility and complete biodegradability. This eco-friendly dual-responsive film can predict the concentration of ethanol/water mixture according to the different deformation angle. Moreover, it can be acted as a dual-responsive single-pole double-throw switch, indicating a huge potential in practical eco-friendly actuator. Graphical abstract