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

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.