Apparatus and method for magnetic-based manipulation of microscopic particles

Abstract

Apparatus and method for manipulating particles on a micro- or nano-scale. An embodiment of the present invention includes a magnetic micro-manipulation technique that utilizes micro-coils and soft magnetic microscopic wires for localized manipulation of particles. Another embodiment of the present invention uses magneto-static interaction between two magnetic microscopic wires to mechanically manipulate particles. Yet another embodiment of the present invention combines a magnetic particle with a magnetic manipulator or other device for generating magnetic fields to operate as a micro-fluidic micro-motor. Other embodiments of the present invention employ a magnetic separation system employing porous membranes partially filled with magnetic wires.

What is claimed is:  
     
         1 . An apparatus for magnetically manipulating at least one microscopic particle, the apparatus comprising: 
 a soft magnetic wire, said magnetic wire having a magnetic probe tip;    a wire coil wound around at least a portion of said soft magnetic wire and electrically isolated from said soft magnetic wire.    
     
     
         2 . The apparatus of  claim 1  further comprising: 
 a current source for supplying current to said coil.  
 
     
     
         3 . The apparatus of  claim 1  wherein said soft magnetic wire has a microscopic diameter.  
     
     
         4 . The apparatus of  claim 1  wherein the probe tip is formed by electrochemically etching an end of said soft magnetic wire.  
     
     
         5 . The apparatus of  claim 1  wherein said coil comprises a microscopic diameter insulated, conducting, non-magnetic wire wound around said soft magnetic wire.  
     
     
         6 . The apparatus of  claim 1  wherein the probe tip is positioned sufficiently near said coil to increase magnetization of the probe tip from magnetic fields produced by said coil when current is applied to said coil.  
     
     
         7 . The apparatus of  claim 1  wherein said soft magnetic wire and said coil occupy a combined volume of less than 1 mm 3 .  
     
     
         8 . A method of manipulating at least one microscopic particle, the method comprising: 
 positioning a magnetic manipulator near the particle, the magnetic manipulator comprising a coil disposed around a soft magnetic wire and electrically isolated therefrom, the magnetic wire having a probe tip;    supplying current to the magnetic manipulator.    
     
     
         9 . The method of  claim 8  wherein said step of positioning includes positioning the tip of the magnetic manipulator within a sufficient range of the particle to allow force manipulation of the particle.  
     
     
         10 . The method of  claim 8  wherein the micro-coil comprises a microscopic diameter conductive non-magnetic wire wound around said soft magnetic wire.  
     
     
         11 . The method of  claim 8  wherein said step of supplying comprises supplying current from at least one of a programmable constant current source and a programmable pulsed current source.  
     
     
         12 . The method of  claim 8  wherein the probe tip is formed by electrochemically etching an end of said soft magnetic wire.  
     
     
         13 . A system for mechanical manipulation of microscopic particles, the system comprising: 
 a plurality of magnetic microscopic wires, each having first and second ends;    a magnetic actuator for affecting a magnetization of at least a portion of at least one of said microscopic wires to cause the first ends of said microscopic wires or the second ends of said microscopic wires to attract or repel one another, whereby said magnetic microscopic wires form a clamp that can be selectively opened and closed by said magnetic actuator.    
     
     
         14 . The system of  claim 13  wherein each of said microscopic wires comprises a single domain magnetic wire.  
     
     
         15 . The system of  claim 13  wherein each of said microscopic wires are fixed at one end.  
     
     
         16 . The system of  claim 13  wherein said magnetic actuator is configured for selectively causing magnetization vectors of said microscopic wires to be parallel or antiparallel to one another.  
     
     
         17 . The system of  claim 13  wherein said microscopic wires comprise at least one magnetic material and at least one non-magnetic material.  
     
     
         18 . The system of  claim 13  wherein said magnetic actuator comprises a soft magnetic wire having a probe tip and a coil wound around said soft magnetic wire.  
     
     
         19 . The system of  claim 18  wherein the probe tip is positioned near one or more of the microscopic wires.  
     
     
         20 . The system of  claim 18  wherein said magnetic actuator is configured for creating an attractive force between one of said microscopic wires and the probe tip based on relative magnetizations of said microscopic wires.  
     
     
         21 . A method for mechanically manipulating a micro- or nano-scale particle, the method comprising: 
 positioning a pair of microscopic wires to partially surround the particle;    magnetically bringing ends of the pair of microscopic wires toward one another to close the pair of microscopic wires and clamp the particle.    
     
     
         22 . The method of  claim 21  further comprising: 
 moving the pair of microscopic wires to move said particle.  
 
     
     
         23 . The method of  claim 21  wherein said step of magnetically bringing comprises applying an external magnetic field to create an attractive force between the ends of the microscopic wires.  
     
     
         24 . The method of  claim 21  further comprising: 
 causing the end of each of the microscopic wires to separate from one another, thus releasing the particle.  
 
     
     
         25 . A method of examining a molecule in accordance with the method of  claim 21 , further comprising steps of: 
 bringing a pair of metal microscopic wires each having at least one non-magnetic component within close proximity of one another so that the non-magnetic components surround the molecule to increase electromagnetic field enhancement between the microscopic wires;    using Raman spectroscopy to examine the molecule.    
     
     
         26 . The method of  claim 25  wherein said bringing comprises applying a magnetic field to magnetic components of the microscopic wires to cause the microscopic wires to be attracted to one another.  
     
     
         27 . An apparatus for separation of microscopic particles, the apparatus comprising: 
 a nano-porous membrane comprising a plurality of pores, one or more of said pores containing a magnetic wire;    a device for applying a magnetic field to the magnetic wire, the magnetic field being perpendicular to a long axis of the wire.    
     
     
         28 . The apparatus of  claim 27  further comprising: 
 at least one magnetic bead, said magnetic bead being configured to selectively bind with at least one of the particles.  
 
     
     
         29 . The apparatus of  claim 27  wherein the particles are of a particular system among a plurality of systems, and wherein said at least one magnetic bead is configured to bind to the particular system.  
     
     
         30 . The apparatus of  claim 27  wherein the pores have a diameter on the order of nanometers.  
     
     
         31 . A micro- or nano-scale electromotor comprising: 
 a rotor, the rotor comprising a microscopic magnetic particle;    a stator, the stator comprising a plurality of microscopic magnetic manipulators arranged substantially symmetrically to surround the rotor along a plane;    a device for supplying current to the stator, said device being coupled to the stator.    
     
     
         32 . The electromotor of  claim 31  wherein each of the magnetic manipulators comprises a micro-coil wound around a soft magnetic wire, the magnetic wire having a probe tip.  
     
     
         33 . The electromotor of  claim 31  wherein said stator comprises three of the magnetic manipulators disposed in an equilateral triangle arrangement about said rotor.  
     
     
         34 . The electromotor of  claim 31  wherein said device for supplying current to the stator is configured for selectively supplying current to each of the magnetic manipulators.  
     
     
         35 . The electromotor of  claim 31  wherein each of said magnetic manipulators has a volume of less than 1 mm 3 .  
     
     
         36 . The electromotor of  claim 31  wherein the magnetic particle comprises a single domain magnetic particle.  
     
     
         37 . The electromotor of  claim 36  wherein the magnetic particle of said rotor comprises a cylindrical particle fabricated by electro-deposition into a porous nano-channel membrane.  
     
     
         38 . A microfluidic system comprising: 
 at least one inlet port;    at least one outlet port;    a plurality of channels disposed between said inlet port and outlet port;    an electromotor disposed within at least one of said inlet port, outlet port and said plurality of channels, said electromotor comprising a rotor and a stator, the rotor comprising a microscopic magnetic particle, the stator comprising a plurality of microscopic magnetic manipulators arranged substantially symmetrically to surround the rotor along a plane, the electromotor further including a device for supplying current to the stator, the device being coupled to the stator.