Flexoionic effect on ionic liquid based polymer composites for bending and pressure sensing applications

Abstract

Due to their ionic composition, adaptability, and responsiveness to different stimuli, ionic liquids (ILs) are among the most suitable systems to develop smart stimuli-responsive materials, to be applied as sensors and actuators, in particular when incorporated into a polymer matrix, with improved processability and integration into devices. In the present work, films based on the IL 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim][FeCl4]) incorporated into a poly(vinylidene fluoride) (PVDF) matrix with different concentrations (5, 10, and 20 wt.%) are prepared by solvent casting. Samples are used for the fabrication by doctor blade and screen printing of a fully printed flexoelectric device suitable for bending and pressure monitoring. The highest sensing response is observed for the composites incorporating 20 wt.% IL content, leading to a bending angle and pressure sensitivity of 7.29 µV/° and 0.7 µV kPa−1, respectively. The technological potential of the developed materials and their flexoionic response, combined with their processability by printing techniques, has been demonstrated in a finger movement monitoring system, opening the possibility of application in areas including wearables and robotics.