The effect of microchamber geometry on the efficiency of magnetic microbead mixing

The necessity for low-cost and user-friendly medical diagnostics has an impact on the development of innovative Lab-On-Chip technologies for in-vitro point-of-care diagnostic testing. The Philips Minicare I-20 platform for the diagnosis of myocardial infarction is such a system that provides precise, quantitative and fast results. The system is based on controlled movement of magnetic nanoparticles where the Troponin analyte is captured on the antibody coated particle and the detection is optical. In this way, the scheme supports quantitative results of Troponin in the patient’s drop of blood. Nevertheless, the efficiency of analyte biochemical binding is strongly dependent on the homogeneity of the reagents within the matrix, which, due to the low Reynolds numbers inside the microfluidic chip, is inefficient.

The aim of our research is to solve this mixing problem by developing novel approaches to reach homogeneity of reagents to achieve high precision handheld diagnostics, in which we make use of the “magnetic infrastructure” of the system. In this report, we focus on the effect of the chip geometry of the microfluidic processing and detection chamber, in combination with optimized magnetic actuation protocols, on the overall mixing efficiency of the reagents. To investigate this, we carry our dedicated experiments with a unique magnetic actuation set-up, and we perform microscopic fluid flow characterization. It is expected that smart geometrical chip designs can positively affect active mixing and achieve homogeneity.