Sustainable soft actuators based on chitosan and choline containing ionic liquids with high bending response

The implementation of smart and multifunctional materials for sensor and actuator applications in the framework of the Internet of Things represents an increasing trend. Thus, it is relevant that those materials, together with increased functional response, comply with sustainability standards, being the use of natural polymers for their development and excellent opportunity. So, this work reports the development of sustainable bending actuators based on chitosan blended with different ionic liquids (ILs) sharing the same cation [Choline]. The samples were prepared with 2 wt% of chitosan in 0.5 % acetic acid solution and 20 wt% of the different ionic liquids [Choline][Acetate] ([Ch][Ac]), [Choline][Dihydrogen Phosphate] ([Ch][DHP]) and [Choline][Serinate] ([Ch][Ser]), in order to properly tune actuation response. The influence of the ILs on the morphological, physicochemical, structural, thermal, mechanical and ionic conductivity characteristics was investigated. The introduction of these ILs into the chitosan matrix induced a mechanical plasticizing effect on the polymer and enhanced the ionic conductivity. The bending actuation response was the largest for the sample with [Ch][Ac] IL, with a maximum displacement of 3.74 and 7.47 mm for applied voltages of 5 V and 20 V, respectively. Thus, the present work represents a step forward in the development of sustainable soft actuators for robotics, microfluidics, and related applications.