Surface reaction between immobilized magnetic microbead-tagged antibodies and electroosmotic flow-driven antigens in a microfluidic device for a realistic higher Damkohler number – a numerical approach

Abstract Microfluidic devices integrate and allow the transport of nanoliter samples with reacting species such as antibodies (Ab), enabling the isolation and capture of target antigens (Ag) in immunoassay applications. The objective of this research is to investigate surface reaction between immobilized magnetic microbeads tagged antibodies and Ag for: 1) realistic Ag concentrations ranging from 1 × 10 −1 M–1 × 10 −6 M and, 2) varying reaction rate constant for a physiological range (1 × 10 3 –1 × 10 9 L mol −1 · s −1 ) in the presence of a fixed electric field of 150 V cm −1 . This research investigated realistic high Damkohler number regimes (6.8 × 10°–6.8 × 10 7 ), indicating transport-limited behavior in which surface reaction rates dominate over Ag transport. The results show that the depletion time of mMB: Ab increases as Ag concentration decreases. Also, the surface reaction kinetics remain nearly unchanged as the rate constant increases. The approach adopted in this study offers a scalable and adaptable platform for evaluating Ag capture dynamics in a next-generation diagnostic device.