Flexible films assembled from polyimide microparticles loaded with ionic liquids for iontronic sensors

Abstract

Iontronic sensors for wearable electronics and health monitoring, which exploit the electric double layer at ionic–electronic interfaces, offer exceptionally high unit-area capacitance, thereby improving sensitivity, resolution, and robustness against environmental interference. However, persistent challenges include ion leakage in liquid-based conductors, compromised capacitance in solid-state polyelectrolytes, and complex manufacturing processes required for high-precision microstructures. Herein, we present an innovative nonsolvent shear-induced phase separation strategy that integrates hydrodynamic shear fields with solvent–nonsolvent exchange to fabricate ionic conductors. Microparticles laden with abundant free ions—while displaying tunable sizes and morphologies—precipitate from the ionic liquid and subsequently assemble into free-standing films. Controlled cold-pressing eliminates excess ionic liquid while preserving the microparticle aggregate network, thus enhancing stability and supporting wide-range pressure detection (up to 500 kPa). Furthermore, the strain-sensitive slit-interconnected architectures formed by intertwined high-aspect-ratio microparticles enable the iontronic micro-strain sensor to achieve a limit of detection (∼10με) approximately one order of magnitude lower than that of conventional configurations. This straightforward and effective method harmonizes morphological tunability, ion retention, and functional performance, pointing the way toward next-generation flexible iontronic sensors.