Fabrication of micromixers for efficient antigen-antibody binding

Abstract

Microfluidic systems are microscale systems that allow the manipulation of fluids inside their channel. They are increasingly gaining interest in many scientific fields owing to their favorable advantages as they can be utilized for many applications. Microfluidic immunosensors are a fast-growing research field, due to the economic nature of microfluidic systems in price, sample volumes, and consumption of time. The fluid flow inside these microsystems can be described as laminar, where the fluid sheets move in parallel to each other. This poses a challenge in microfluidic immunosensing as it hinders the interaction between species in the fluid. In this study, micromixers were designed and fabricated to enhance the interaction between the immunological species. Several micromixers were designed and simulated using COMSOL Multiphysics software and the three geometries that showed the best mixing were then fabricated. The microfluidic designs were etched on a 3-inch silicon wafer using the photolithography technique and PDMS was subsequently patterned using replica molding techniques and bonded on a glass substrate using the Oxygen plasma bonding method. Interdigitated screen-printed electrodes were purchased and used to carry out electrochemical measurements to assess the binding between the infused species. Streptavidin magnetic beads and biotinylated peptide were suspended in PBS and infused through the two inlets of the microfluidic channel at multiple flow rates. The two species were allowed to mix inside the microfluidic micromixer before being collected from the outlet. A constant concentration of streptavidin magnetic beads was chosen to mix with different concentrations of the biotinylated peptide at a time. The bound magnetic beads were then immobilized on the surface of the screen-printed electrode using a magnet and impedance measurements were taken. Preliminary results indicate that the fabricated micromixers were able to induce turbulence in the laminar flow and enhance mixing.