Microfluidic Biosensing Method Using the Motion of Magnetic Microparticles

In this paper a microfluidic biosensing method for detecting a bioanalyte using the motion of magnetic microparticles (MPs) is presented. The system consists of a microfluidic channel, in which the MPs are suspended and current carrying microconductors positioned underneath the channel. These microconductors are used in order to move the MPs from the inlet to the outlet of the channel. The MPs are functionalized by modifying their surface, thus enabling them to chemically bind to a specific (non-magnetic) bioanalyte. Once the MPs binds to the bioanalyte new compounds are formed (LMPs). These compounds have a bigger overall volume than the bare MPs but still the same magnetic volume. The MPs and LMPs are manipulated inside the microfluidic channel by exposing them to magnetic field generated by the microconductors. When both, MPs and LMPs, are accelerated by the same magnetic field density, the LMPs are going to be slower than the MPs due to their increased (non-magnetic) volume. This difference in velocity is used to discriminate between MPs and LMPs. Calculations concerning the velocity change of MPs and the magnetic field generated by the current carrying microconductors were carried out. Simulations of various geometries for the conductors and various MPs were performed using finite element analysis software. Several chips were fabricated and experiments with different MPs and LMPs were conducted as a proof of concept.