Direct microencapsulation of Ionic-Liquid-Based shear thickening fluid via rheological behavior transition for functional applications

In nature, various stimuli-responsive materials, such as bone, are self-adaptable to external loading by modulating their mechanical properties to prevent failure and self-healing after damage. Herein, for the first time, an oil-in-oil solvent-evaporation approach is proposed to directly microencapsulate a multifunctional self-adaptive material—ionic-liquid-based shear thickening fluid (ILSTF)—via rheological behavior transition. As the co-solvent completely changed the rheological responses of the dispersed phase, this approach proved ideal for encapsulating STFs with high viscosity and shear-thickening behavior. The resultant ILSTF microcapsules (MCs) exhibited high thermal stability (initial decomposition temperature of ∼380 °C) and controllable size at the micrometer level from 66 to 260 μm. The typical ILSTF MCs were incorporated into an elastomer matrix, achieving 33 % and 67 % enhancement of energy absorption ability compared with the pure polymer and IL MCs-embedded composites, respectively. Furthermore, the circuit comprised of ILSTF MCs-incorporated flexible conductor exhibited not only electrical stability upon impact, but also autonomic conductivity restoration after injury, demonstrating that the ILSTF MCs can serve as a multifunctional agent for emerging applications, such as deformable circuits and battery safety.