Cellulose-based shape change smart material responding to moisture and light

Over the past few years, researchers have focused on smart materials that respond to multiple stimuli. Using these materials, they can create soft robots that can replace more complex robots. Multi-response properties, very easy manufacturing with the cheapest materials, controllable smart deformation, and applicability in various industries are all very important for the development of intelligent soft robots. Since light and humidity are two available stimuli, here we report a type of cellulose-based smart sensor responsive to humidity and light, which can be used in the construction of cheap and soft robots. This sensor is easily made by heating thermal paper. As humidity increases, this sensor absorbs water molecules and changes shape. When light is illuminated on it, it desorbs the water molecules and returns to its original state. When the sensor is exposed to 100 % humidity, it can rotate about 552° with the speed of 6 °/s and return to its original position at a speed of 3 °/s when illuminated with infrared light. Due to its high response rate to both humidity and infrared light, various applications for the fabricated sensor are presented.