Skin-Inspired 3D Printing Porous Ionogels with Microsphere-Interlocked Structures for Flexible Sensors

The demand for flexible sensors in wearable electronics, health monitoring, and other fields has driven the innovative development of ionogel materials. However, traditional ionogels face challenges such as ionic liquid leakage, insufficient mechanical properties, and difficulty in special structural design by facile methods. This study designs a photocurable ink containing the polymerizable ionic monomer [BVIM]Br, the multifunctional thiol pentaerythritol tetrakis(3-mercaptopropionate), and the cross-linking agent poly(ethylene glycol) diacrylate. By utilizing the fast and oxygen-inhibited thiol-ene click reaction, a strong and tough covalent cross-linked network is formed in 30 min by Digital Light Process (DLP) three-dimensional (3D) printing technology, in which the ionic groups are covalently anchored and can solve the problem of ionic liquid leakage. At the same time, polymerization-induced phase separation generates through-micropores in situ at the microscopic scale, forming a dual-scale cooperative enhancement mechanism. Additionally, a microsphere interlocking array mimicking the dermal-epidermal interface of skin is precisely designed on a macroscopic scale. This structure not only significantly enhances the interfacial adhesion and mechanical stability of the material but also provides efficient three-dimensional channels for ion migration. The resulting porous ionogel exhibits high flexibility, high sensitivity (-0.819 kPa^-1), fast response time (64.2 ms), and durability of 1000 cycles, demonstrating excellent performance in human motion monitoring and Morse code communication. This study gives some ideas for the development of high-performance flexible sensors based on ionogels with bioinspired structures.