CD-ELISA uses the microfluidic ranking method and centrifugal force to control the testing solution as it flows into the reaction region. The most challenging part of CD-ELISA is controlling the flow process for different biological testing solutions, i.e. the controlling sequence for the microfluidic channel valves. The microfluidic channel valve is therefore the most important fluid channel structure for CD-ELISA. In this study, we propose a valve design suitable for a wide range rotational speeds which can be applied for mass production (molding). Together with supporting experiments, simulation based on two-phase flow theory is used in this study, and the feasibility of this novel valve design is confirmed. Influencing design factors for the microfluidic channel valves in CD-ELISA are investigated, including various shapes of the arc, distance d, radius r, the location of the center of the circle, and the contact angle. From both the experimental results and the simulated results, it is evident that the narrowest channel width and the contact angle are the primary factors influencing valve burst frequency. These can be used as the main controlling factors during the design.
A compact disk-based enzyme linked immunosorbent assay (CD-ELISA) is used in a wide range of applications including cancer and human immunodeficiency virus testing, drug screening, and micro-organism identification. Bifurcation design is the most important structure for microfluidic channels in CD-ELISA. In this study, a bifurcation design feasible for mass production and suitable for applications over a wide range of rotational speeds is proposed. Simulations based on two-phase flow theories along with incompressible flow theories were used in this study to confirm the feasibility of the novel design. The factors that influenced the bifurcation ratio for microfluidic channels in CD-ELISA were also investigated. The geometric length for bifurcation, opening angles, and the bifurcation shape in the middle section were varied to investigate the effects of each factor on the bifurcation ratio. From the experimental results, the factors with the greatest influence on the bifurcation ratio were the geometry of the end face of the partitioning plate and the distance from the opening end. These factors can be used as controlling factors for the design of microfluidic channels.
Enzyme-linked immunosorbent assay (ELISA) is the most widely used immunoassay for the detection and quantification of biological agents (mainly proteins and polypeptides). One challenge in developing microfluidic devices for immunogenic and enzymatic assays is to split the fluid evenly into microchannels. To prevent uneven splitting, we propose a buffer-structure design, which holds the stream lines in the radial direction before they enter into bifurcation channels. To study the feasibility of this design, a three-dimensional numerical model, based on the Navier-Stoke equation, was constructed. Upon verification, it was successfully demonstrated that the proposed halfcircle design can split flow evenly under the existence of Coriolis forces during operation.
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