Architectural engineering of asymmetric phase connectivity in ionogels for tough, transparent, and highly conductive strain sensors

Achieving mechanical robustness and efficient ionic transport simultaneously remains a major challenge for ionogels, as mechanical reinforcement often restricts ion mobility. Here we report an architectural strategy that resolves this trade-off through composition-programmed asymmetric phase connectivity. By tuning the incompatibility among acrylic acid (AA), poly(ethylene glycol) methacrylate (PEGMA), and the ionic liquid [EMIM][TFSI], the polymer network spontaneously forms a microphase-separated structure in which a soft ion-conductive phase maintains network continuity while a rigid reinforcing phase remains confined to dispersed microdomains. This topology enables efficient energy dissipation without disrupting ionic transport or optical transparency. The resulting ionogels exhibit a balanced combination of high stretchability, enhanced toughness, high ionic conductivity, and optical clarity. In contrast, increasing connectivity of the rigid phase produces bicontinuous morphologies that lead to stiff and opaque gels. The optimized ionogel demonstrates excellent strain-sensing performance with high sensitivity, wide strain detection range, and outstanding durability under cyclic deformation. These results highlight phase connectivity as a key structural parameter governing ionogel performance and establish asymmetric phase architecture as a general design principle for multifunctional soft ionic conductors.