Stretchable Photonic Crystal-Enhanced ECL for Sweat Neurotransmitter Detection

Depression is linked to dysregulated neurotransmitter levels, making efficient and facile monitoring crucial for early diagnosis and improved treatment outcomes. However, rigid electrodes or unstable luminescence on flexible substrates have limited the adoption of electrochemiluminescence (ECL) in flexible health-monitoring platforms. Herein, we introduce a stretchable conductive photonic-crystal hydrogel (PCH) as an ECL electrode for sweat-based neurotransmitter detection. By the integration of a PAM-PVA-(O-β-CD)-Gel porous hydrogel with a poly(St-MMA-AA) latex-sphere nanomatrix, the photonic crystal (PC) structure effectively loads the [Ru(bpy)₃]²⁺, enhances ion diffusion, and accelerates electron transfer to amplify the initial ECL signal. Its mechanochromic structural color properties enable a continuously tunable band gap that matches the luminophore's emission wavelength, further boosting the ECL intensity and providing a clear optical discrimination. This PCH platform achieves qualitative and quantitative analyses of 11 neurotransmitters with 100% accuracy and a 7.5 μM limit of detection in PBS buffer and artificial sweat. These findings establish the mechanistic basis for the future integration of PCH-ECL sensors into dynamic, skin-contact, and point-of-care applications.