A fully integrated micromachined magnetic particle manipulator and separator

A micromachined magnetic particle manipulator which can be used to influence magnetic particles suspended in liquid solutions has been realized on a silicon wafer. One important application for these devices is the separation of magnetic particles from dilute fluid suspensions. Previously, macro-scale versions of such devices have been realized using permanent magnets. In the device presented here, integrated inductive components have been used in place of permanent magnets, which yields several advantages in design flexibility, compactness, electrical control, and integration feasibility (thus enabling mass production). To show the feasibility of the device, magnetic fluid containing superparamagnetic particles of 0.8-1.3 /spl mu/m in diameter suspended in a buffer solution is flowed through a 100 /spl mu/m wide channel arranged between the poles of an integrated electromagnet quadrupole. An initial movement of magnetic particles is observed when the DC current in the coils reaches 100 mA. At 500 mA of DC current, approximately 0.03 Tesla of magnetic flux density is achieved at the gap between the quadrupoles, and the particles rapidly move toward the quadrupoles, separate from the buffer solution, and clump on the poles. The magnetic particles clumped on the poles are also easily released when the DC current is removed, achieving the primary purpose of a separator. This prototype device illustrates the high potential of integrated micromagnetics in chemical and biological applications where the manipulation of small amounts of reagent are important.