Environmental-Tolerant Ionic Colloidal Photonic Composites via Ion-Dipole Interactions for Synchronized Optical-Electrical Dual-Response Underwater Flexible Sensing

Inspired by dynamic structural colors in nature, ionic colloidal photonic composites (ICPCs) offer synchronized optical-electrical responses for advanced sensing applications. However, their practical deployment is hindered by environmental instability. Here, environmentally tolerant ICPCs with synchronized optical-electrical dual-response capabilities are developed. These ICPCs are fabricated by hot-pressing poly (2,2,3,4,4,4-hexafluorobutyl acrylate) (PHFBA)-grafted silica colloidal particles doped with 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl) imide ([EMIM]⁺[TFSI]⁻) ionic liquid (IL), synthesized through surface-initiated atom transfer radical polymerization. The resulting ICPCs exhibit well-balanced mechanical properties, high ionic conductivity (≈10⁻⁴ S m⁻¹), and vibrant structural color. They demonstrate remarkable dual optical-electrical response, with a mechanochromic sensitivity of 1.64 nm%⁻¹ (≈80 nm wavelength shift) and a gauge factor of 1.05. The inherent hydrophobic PHFBA matrix, negligible IL vapor pressure, and robust ion-dipole interactions between PHFBA's C─F bonds and [EMIM]⁺[TFSI]⁻'s imidazolium cations endow the ICPCs with exceptional environmental stability. These ICPCs maintain stable dual-response performance under extreme temperatures (−25 °C and 100 °C), humidity variations (20% and 99% RH), and immersion in various media, including water, acidic/basic solutions (pH 1/13), seawater, and hexane for 14 days. As a proof-of-concept, the ICPCs function as underwater flexible sensors, providing real-time optical-electrical feedback for joint motion monitoring and Morse code communication, offering a versatile platform for smart wearable electronics.