Magnetic beads separation characteristics of a microfluidic bioseparation chip based on magnetophoresis with lattice-distributed soft magnets

To continuously perform pretreatment operations of biological detection reagents, a kind of microfluidic bioseparation chip that integrates mixer, heater and soft magnets for detection of nucleic acid and extraction of molecular proteins with magnetic beads methods is presented in the paper. A specific magnetic field is formed in a desired chamber bonded with PDMS and PMMA sheets by embedding soft magnets of iron powders in the chip, and magnetized by an external magnetic field. Soft magnets distributed in different ways are designed respectively, and the characteristics of the magnetic field, as well as the magnetic trajectory of the magnetic beads are simulated by considering the magnetic-fluid coupling. An experimental platform to observe the capturing of magnetic beads is built and the capture phenomenon for magnetic beads with lattice-distributed soft magnets is also experimentally verified. Based on the experimental data, the capture efficiency of the magnetic beads is calculated with the image processing method. The results show that lattice-distributed soft magnets are more effective than the array-distributed soft magnets for separating the magnetic beads. Furthermore, the lattice-distributed soft magnets can improve the separation efficiency of the detected reagent maintained to be more than 80% when the inlet flow rate increases from 0.01 m/s to 0.05 m/s.