Device and method for combined microfluidic-micromagnetic separation of material in continuous flow

Abstract

A miniaturized, integrated, microfluidic device pulls materials bound to magnetic particles from one laminar flow path to another by applying a local magnetic field gradient. The device removes microbial and mammalian cells from flowing biological fluids without any wash steps. A microfabricated high-gradient magnetic field concentrator (HGMC) is integrated at one side of a microfluidic channel. When magnetic particles are introduced into one flow path, they remain limited to that flow path. When the HGMC is magnetized, the magnetic beads are pulled from the initial flow path into the collection stream, thereby cleansing the fluid. The microdevice allows large numbers of beads and materials to be sorted simultaneously, has no capacity limit, does not lose separation efficiency as particles are removed, and is useful for cell separations from blood and other biological fluids. This on-chip separator allows cell separations to be performed in the field outside of hospitals and laboratories.

What is claimed is: 
     
         1 . An integrated microfluidic separator device comprising:
 a microfluidic channel including:
 a source flow path including a source inlet and a source outlet, and 
 a collection stream flow path including a collection outlet,
 wherein a laminar streamline boundary separates the source flow path and the collection stream flow path; 
 
   a microfabricated high-gradient magnetic concentrator with a high curvature geometry integrated at a first side of the microfluidic channel; and   a magnetic source to magnetize the microfabricated high gradient magnetic field concentrator to move magnetically susceptible target material flowing in the source flow path to cross over the laminar streamline boundary and enter the collection stream flow path to separate the magnetically susceptible target material from a fluid flowing in the microfluidic channel.   
     
     
         2 . A method of separating target material from a fluid in continuous laminar flow, the method comprising:
 introducing the fluid containing a magnetically labeled target material through a source inlet into a source flow path of a microfluidic channel,
 wherein the microfluidic channel includes a source flow path with a source inlet and a source outlet and a collection stream flow path with a collection outlet, and wherein a laminar streamline boundary separates the source flow path and the collection stream flow path; and 
   magnetizing a microfabricated high-gradient magnetic field concentrator with a local magnetic field gradient to move the labeled target material from the source flow path into the collection stream flow path to a collection outlet to selectively remove the target material from the fluid in continuous laminar flow,
 wherein the microfabricated high-gradient magnetic field concentrator includes a high curvature geometry and the microfabricated high-gradient magnetic field concentrator is adjacent to a first side of the microfluidic channel. 
   
     
     
         3 . A microfluidic separator system comprising a plurality of integrated microfluidic separator devices included at a plurality of positions on a single chip to provide multiplexing separation of target material from a fluid, and wherein each microfluidic separator device includes:
 a microfluidic channel including:
 a source flow path including a source inlet and a source outlet, and 
 a collection stream flow path including a collection outlet,
 wherein a laminar streamline boundary separates the source flow path and the collection stream flow path; 
 
   a microfabricated high-gradient magnetic concentrator with a high curvature geometry integrated at a first side of the microfluidic channel; and   a magnetic source to magnetize the microfabricated high gradient magnetic field concentrator to move magnetically susceptible target material flowing in the source flow path to cross over the laminar streamline boundary and enter the collection stream flow path to separate the magnetically susceptible target material from a fluid flowing in the microfluidic channel.