Microparticles Focusing Inside Rigid Zigzag Microchannels and Application to Bacteria Enrichment

Abstract

Sample preparation is vital for biomedical diagnostics, environmental monitoring, and food safety, with enrichment of microparticles and microorganisms essential for reliable detection. Label-free microfluidic enrichment offers a portable alternative to centrifugation and filtration, which require bulky equipment or external forces. Passive inertial microfluidics, particularly zigzag microchannels, enable efficient, high-throughput particle manipulation through Dean flow. However, knowledge gaps remain in understanding micrometer-sized behavior in rigid zigzag channels, evaluating design parameters, and predicting Dean drag velocity and force. This thesis systematically investigates rigid zigzag microchannels for focusing and enrichment. Objective 1 compared rigid (PMMA) and soft (PDMS) devices using microparticles (1-3.9 µm) and E. coli bacteria, showing superior focusing in rigid channels. Objective 2 employed COMSOL Multiphysics and Taguchi DOE to optimize geometry, achieving > 80% focusing efficiency. Objective 3 demonstrated enrichment of GFP-labeled E. coli with factors of 2.6 and 8 after one and two passes while preserving ~84% viability. This work establishes a robust, biocompatible platform with strong potential for portable diagnostics.