Nanosieve-enabled on-chip concentration and multiplexed detection of Raman-reporter-labeled nanocubes

To address persistent challenges in molecular detection—particularly signal variability, low analyte abundance, and poor spectral reproducibility—a portable bead-stacked nanosieve platform was engineered to enable robust on-chip Raman signal amplification using silver nanocubes (AgNCs) functionalized with Raman-active thiolated ligands. The microdevice integrates deformable elastomeric channels with magnetic bead stacking to immobilize and concentrate AgNCs within confined nanoscopic junctions, thereby generating densely packed plasmonic hot spot architectures that markedly enhance surface-enhanced Raman scattering efficiency. Time-resolved measurements revealed substantial increases in the Raman intensity for both 4-mercaptobenzoic acid (4-MBA) and 4-aminothiophenol (4-ATP), outperforming corresponding off-chip assays and maintaining stable enhancement factors over a 4 h operational window. Furthermore, the platform successfully demonstrated multiplexed sensing capability: mixed-analyte experiments containing 4-MBA, 4-ATP, and cysteamine produced clearly distinguishable spectral fingerprints, even under serial dilution and dynamically pulsed sample delivery. These results establish the bead-stacked nanosieve as a versatile and scalable diagnostic architecture capable of achieving high sensitivity and spectral fidelity under continuous-flow conditions.