External field—free magnetic biosensor

Patent metadata

Field	Value
Publication number	US-9927431-B2
Application number	US-201214343252-A
Country	US
Kind code	B2
Filing date	Sep 14, 2012
Priority date	Sep 14, 2011
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A biosensor includes a magnetic structure having grooved surface to biologically bond magnetic labels to a biological substance within the grooves. The grooves are positioned within the magnetic structure so that stray magnetic fields from the magnetic structure magnetize magnetic labels within the groove. The magnetic labels may be magnetic nanoparticles or magnetic microbeads. The techniques may reduce or eliminate the usage of any external magnetic field generator, e.g., electromagnets or current lines.

First claim

The invention claimed is:

1. A biosensor comprising:
a magnetic structure comprising a surface and a spin valve structure having a free layer and a pinned layer; and
a groove formed within the surface to biologically bond magnetic labels to a biological substance within or above the groove;
wherein the groove is positioned within the magnetic structure so that stray magnetic fields from both the free layer and the pinned layer pass through the groove for magnetization of the magnetic labels without the presence of an external applied magnetic field through the groove, and wherein the biosensor does not comprise a field-generating current line.

2. The biosensor of claim 1 , wherein the magnetic labels comprise magnetic nanoparticles (MNPs) having a diameter of less than approximately 100 nanometers.

3. The biosensor of claim 1 , wherein the magnetic labels comprise magnetic microbeads having a diameter of between approximately 1 and 2 microns.

4. The biosensor of claim 1 , wherein the groove is formed to extend through the free layer and at least a portion of the pinned layer.

5. The biosensor of claim 1 , wherein the free layer ranges from 1 to 10 nm in thickness and the pinned layer ranges from 10 to 50 nm in thickness.

6. The biosensor of claim 1 , wherein the groove is approximately 5 to 100 nanometers in depth.

7. The biosensor of claim 1 , wherein the biosensor comprises one of a giant magnetoresistance (GMR) sensing device having the spin valve structure, a magnetic tunnel junction (MTJ) sensing device having the spin valve structure, a giant magnetoimpedance (GMI) sensing device having the spin valve structure or a Hall sensing device having a soft magnetic layer underneath a Hall sensing layer, the soft magnetic layer responding to a sensing current and generating the magnetic field.

8. The biosensor of claim 1 , wherein the groove has a depth sufficient to contain the biological substance and biologically bond the magnetic label onto the biological substance within the groove.

9. The biosensor of claim 1 , wherein the groove is approximately 2 to 3 times a width of the magnetic labels.

10. The biosensor of claim 1 , further comprising at least one electrode to output an electrical signal representative of the bonding of the magnetic labels to the magnetic structure.

11. The biosensor of claim 1 , wherein the magnetic structure has a lateral dimension of at least one micrometer and the magnetic structure has a thickness of less than 500 nanometers.

12. The biosensor of claim 11 , wherein the magnetic structure has a thickness of less than 100 nanometers.

13. The biosensor of claim 1 , wherein the magnetic structure is less than approximately 3 μm long and is approximately 0.5 μm wide.

14. The biosensor of claim 1 , wherein the biosensor outputs a signal indicative of the detection of as few as ten magnetic labels bonded within the groove.

15. The biosensor of claim 1 , wherein the groove conforms to one of a linear, curved, sinusoidal, or sawtooth profile.

16. The biosensor of claim 1 , wherein the groove comprises one or more notches formed in the surface of the biosensor.

17. A method of manufacturing a magnetic biosensor chip, comprising:
forming a multi-layered magnetic structure on a substrate, the magnetic structure formed to have a grooved surface to biologically bond magnetic labels within a groove surface and a spin valve structure having a free layer and a pinned layer, wherein the magnetic structure is formed so that stray magnetic fields from both the free layer and the pinned layer pass through the groove for magnetization of the magnetic labels without the presence of an external applied magnetic field through the groove, and wherein the magnetic biosensor chip does not comprise a field-generating current line.

18. The method of claim 17 , wherein the magnetic labels comprise magnetic nanoparticles (MNPs) having a diameter of less than approximately 100 nanometers.

19. The method of claim 17 , wherein the magnetic labels comprise magnetic microbeads having a diameter of between approximately 1 and 2 microns.

20. The method of claim 17 , wherein the groove is formed to extend through the free layer and at least a portion of the pinned layer.

21. The method of claim 17 , wherein the free layer is formed to have thickness ranging from 1 to 10 nm in thickness and wherein the pinned layer is formed to have a thickness ranging from 10 to 50 nm in thickness.

22. The method of claim 17 , wherein the groove is formed to have a thickness approximately 10 to 100 nanometers in depth.

23. The method of claim 17 , wherein the biosensor comprises one of a giant magnetoresistance (GMR) sensing device having the spin valve structure, a magnetic tunnel junction (MTJ) sensing device having the spin valve structure, a giant magnetoimpedance (GMI) sensing device having the spin valve structure or a Hall sensing device having the spin valve structure.

24. The method of claim 17 , wherein the groove is formed to have a depth sufficient to contain a biological substance and biologically bond the magnetic label onto the biological substance and within the groove.

25. The method of claim 17 , wherein the groove is formed to have a width approximately 2 to 3 times a width of the magnetic labels.

26. The method of claim 17 , further comprising forming at least one electrode within the magnetic biosensor chip to include to output an electrical signal representative of the bonding of the magnetic labels to the magnetic structure.

27. The method of claim 17 , further comprising forming the magnetic structure to have a lateral dimension of at least one micrometer and a thickness of less than 500 nanometers.

28. The method of claim 17 , further comprising forming the magnetic structure to have a thickness of less than 100 nanometers.

29. The method of claim 17 , further comprising forming the magnetic structure to be less than approximately 3 μm long and approximately 0.5 μm wide.

30. A hand-held device comprising:
a sensing chip comprising a magnetic structure having a groove formed within a surface of the biosensor to biologically bond magnetic labels to a biological substance within the groove surface and a spin valve structure having a free layer and a pinned layer, wherein the groove is positioned within the magnetic structure so that stray magnetic fields from both the free layer and the pinned layer pass through the groove for magnetization of the magnetic without the presence of an external applied magnetic field through the groove, and wherein the hand-held device does not comprise a field-generating current line;
a controller to receive and process an electrical signal from the sensing chip, wherein the electrical signal provides an indication of the number of magnetic labels biologically bonded to the sensing chip; and
a display screen coupled to the controller to provide output indicative of the number of magnetic labels to a user.

31. The device of claim 30 , wherein the magnetic labels comprise magnetic nanoparticles (MNPs) having a diameter of less than approximately 100 nanometers.

32. The device of claim 30 , wherein the magnetic labels comprise magnetic microbeads having a diameter of between approximately 1 and 2 microns.

Assignees

• Wang Jian Ping
• Li Yuanpeng
• Yi Wang
• Univ Minnesota

Inventors

• Wang Jian-Ping
• Li Yuanpeng
• Yi Wang

Classifications

• G01R33/093

  using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00) · CPC title

• G01N27/745

  for detecting magnetic beads used in biochemical assays (concerning the assays G01N33/54326; sensors therefor G01R33/1269; automatic analysers therefor G01N35/0098) · CPC title

• G01R33/0052

  Manufacturing aspects; Manufacturing of single devices, i.e. of semiconductor magnetic sensor chips (devices based on galvano-magnetic effect or the like H10N50/85) · CPC title

• G01R33/09

  Magnetoresistive devices · CPC title

• Y10T29/4902

  Electromagnet, transformer or inductor · CPC title