Terahertz microfluidic sensor with a <i>β</i> -cyclodextrin functionalized chiral metasurface for identification and detection of amino acid enantiomers

Chiral recognition of amino acids, particularly biologically prevalent L-enantiomers, is crucial yet challenging for sensitive methods. We present a terahertz microfluidic biosensor based on a β -cyclodextrin ( β -CD)-functionalized dual-layer chiral metasurface for highly selective and sensitive amino acid enantiomer identification. The metasurface generates a strong superchiral near-field (84-fold enhancement) to significantly strengthen light–matter interactions. An integrated microfluidic channel improves the coupling between terahertz waves and analytes in liquid environments. Additionally, the β -CD functionalization provides the key selectivity, enabling preferential capture of L-amino acids through host–guest interactions. Experimental results demonstrate both qualitative recognition and quantitative detection, with sensing frequency shifts for L-phenylalanine reaching about 5 times those of their D-counterparts at the maximum concentration. A detection limit as low as 0.05 mg/mL for L-type amino acids is achieved. This approach, combining engineered near-field confinement, enhanced terahertz wave–matter interactions, and selective host-guest chemistry, provides an effective strategy for highly sensitive quantitative detection and chirality identification in the analysis of biochemical materials.