Nano-Sieve-Enabled On-Chip Concentration and Multiplexed Detection of Raman-Dye-Labeled Nanocubes

To address persistent challenges in molecular detection-particularly signal variability, low analyte abundance, and poor spectral reproducibility-a portable bead-stacked nano-sieve 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 (SERS) efficiency. Time-resolved measurements revealed substantial increases in 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 four-hour 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. Collectively, these results establish the bead-stacked nano-sieve as a versatile, label-free, and scalable diagnostic architecture capable of achieving high sensitivity and spectral fidelity under continuous-flow conditions. Our technology holds significant promise for real-time, non-invasive molecular surveillance, point-of-care diagnostics, and early disease monitoring in resource-limited or field-deployable settings.