Design and performance of an electromechanical sensor using sulfonated PEEK-based IPMC with ionic liquid integration

Abstract Ionomeric polymer–metal composites (IPMCs) are electroactive materials extensively studied for sensing and actuation applications. While Nafion ® is the most used ionomer in IPMCs, its high cost and environmental impact have motivated research into alternative materials. This work introduces a novel composite membrane formed by integrating the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) into a highly sulfonated poly(ether ether ketone) (SPEEK) matrix (90.7% degree of sulfonation). The performance of this novel composite membrane as an electromechanical sensor was systematically evaluated. The fabricated IPMCs demonstrated the electrochemical stability to operate under voltages up to 5 V without evidence of water hydrolysis, addressing a common limitation of conventional H + -based IPMCs. Additionally, electromechanical sensing tests showed that BMIM-based IPMCs effectively detected motion trajectories (linear, cubic, and quadratic) and frequencies from 0.08 to 2 Hz. The BMIM-BMIM + system exhibited an exceptionally high sensing response, reaching potential amplitudes 100 times greater than conventional Nafion ® -H + IPMCs. These findings highlight the potential of SPEEK-IL as a promising alternative for high-performance electroactive devices.