Correlations of the capture efficiency with the Dean number and its constituents in heterogeneous microfluidic immunosensors

Abstract

In heterogeneous microfluidic immunosensors, enhanced capture efficiencies of the antigens (Ag) in the carrier fluids by the surface-immobilized antibodies (Ab) facilitate lower detection limits and thus early detection of disease. Capture efficiency depends on the interplay of transport, reaction parameters and the geometry of the system. A detailed analysis on the enhanced capture efficiencies due to secondary flows in heterogeneous immunosensors has not received significant attention and is the theme of the present work. We conducted a systematic study to observe the significance of secondary forces on the capture efficiency, manifested as the average surface concentration (Cs,avg), in serpentine channels of different lengths (l) and radius of curvature (Rc) as a function of the Reynolds number (Re). Experimental observations were validated with numerical simulations. Micro-PIV studies at different planes and sections of the serpentine microchannels were conducted and matched with the simulated velocity profiles. Further investigation of the process and the geometrical parameters was conducted using numerical simulation and the behaviour of Cs,avg as a function of Re and Rc was plotted for different cases. A highlight of the present work are correlations of Cs,avg as a function of the Dean number (De), as well as its constituents (Re and α). The scientific studies of the geometrical and process parameters which affect the analyte capture advance the understanding of the phenomena and the proposed engineering correlations would be useful in the design of more efficient flow-based heterogeneous immunosensors.