Integrated Acoustofluidic Manipulation and Oscillation-Stabilized Magnetic Relaxation Biosensing for Salmonella Detection.

Reliable pathogen detection in complex suspensions requires both effective sample handling and stable signal generation. Here, we report an acoustofluidic-magnetic relaxation biosensing (MRB) platform for Salmonella detection that combines acoustofluidic particle manipulation with oscillation-stabilized magnetic readout. A cylindrical-array region enhances encounters between Salmonella and immunomagnetic nanobeads (IMNBs) through convective mixing, while a butterfly-shaped acoustic streaming vortex (BSAV) region preferentially retains micron-scale Salmonella-IMNB complexes and generates a nanoscale-dominant outlet suspension. This outlet suspension is subsequently analyzed by an oscillation-assisted MRB system, in which axial micro-oscillation suppresses bead sedimentation and aggregation and stabilizes the ΔT2 response. Under optimized conditions, the biosensor showed a linear response from 4.8 × 101 to 4.8 × 105 CFU/mL, with a limit of detection of 29 CFU/mL and a total assay time of approximately 40 min. The platform also exhibited good specificity and satisfactory recoveries of 92.68-103.95% in spiked chicken samples. The results demonstrate that acoustofluidic restructuring of suspension composition can support stable and quantitative magnetic relaxation detection in the Salmonella-spiked chicken model system.