Aligned Single‐Walled Carbon Nanotubes Film Chiral Metasurfaces for Terahertz Polarization Sensing

Abstract Single‐wall carbon nanotube (SWCNT)‐based metasurface biosensors have demonstrated great potential for ultra‐sensitive, rapid‐response, and trace‐level biomarker detection. However, challenges such as complex functionalization procedures and the inability to precisely distinguish chiral enantiomers remain. Meanwhile, existing chiral metasurface sensors also suffer from high costs, complex fabrication processes, and long production cycles due to the introduction of asymmetric structures. Here, a novel chiral metasurface is proposed based on aligned SWCNT films, constructed on wafer‐scale, highly oriented films prepared via a groove‐assisted vacuum filtration method. In contrast to conventional chiral metasurfaces that rely on asymmetric geometries to achieve chirality, this new metasurface design exploits the intrinsic anisotropic response of aligned SWCNT films in combination with a simple symmetric resonant structure to generate a pronounced chiral effect without the need for deliberately chiral patterns. This metasurface enables both qualitative and quantitative polarization‐based sensing of lactic acid (LA) enantiomers, achieving an excellent sensitivity of 20.7° mL g −1 . Compared with conventional reflection/absorption spectroscopy‐based sensing methods, this approach enables a more intuitive and comprehensive observation of the intrinsic chiral properties of the analyte. The results provide a new and promising strategy for optical field manipulation and enantiomer sensing based on chiral metasurfaces.