Rapid Moisture-Responsive Biopolymer Film Actuators

Moisture-responsive actuators are promising for advanced applications, including biosensors and soft robotics. However, the fabrication process and actuating performance need improvement. Here, we report a rapid moisture-responsive thin film fabricated from tempo-oxidized cellulose nanofibers (TOCNFs) by direct ink writing (DIW). The thin film is lightweight and flexible, and the resulting actuator exhibits a subsecond response upon moisture exposure. This rapid actuation is owing to the water molecules' stress differential throughout the thickness of the thin film and their interaction with the polar groups in the thin film to form hydrogen bonds. This thin film-based actuator has demonstrated a good weight-lifting capability and can be utilized in intelligent lifts, textile layers, and wearable electronics.