Laser-scribed ferrogel sensor with magnetic particles

• US 9,999,369 B2
• Filed: 12/01/2014
• Issued: 06/19/2018
• Est. Priority Date: 03/13/2012
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University)), Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University)), Regents of The University of Minnesota (University of Minnesota)
• Inventors: Ziaie, Babak, Siegel, Ronald A.
• Primary Examiner(s): Winakur, Eric
• Assistant Examiner(s): Fardanesh, Marjan
• Application Number:
  US14/557,247
• Publication Number:
  US 20150087945A1
• Time in Patent Office: 1,296 Days
• Field of Search: None
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/14503 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61K 47/32 Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. carbomers , poly(meth)acrylates, or polyvinyl pyrrolidone
• CPC Class Codes: A61K 9/0009 involving or responsive to electricity, magnetism or acoustic waves; Galenical aspects of sonophoresis, iontophoresis, electroporation or electroosmosis microelectromechanical systems A61K9/0097
• CPC Class Codes: A61K 9/06 Ointments; Bases therefor; Other semi-solid forms, e.g. creams, sticks, gels composition of ointments, creams or gels A61K47/00
• CPC Class Codes: G01R 3/00 Apparatus or processes specially adapted for the manufacture or maintenance of measuring instruments , e.g. of probe tips
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A method of making a sensor includes depositing a layer of hydrogel over a substrate, the hydrogel configured to change thickness or volume in response to a selected condition and including a plurality of magnetic particles disposed in the hydrogel so that a magnetic property of the hydrogel changes with changes of thickness or volume of the hydrogel. The hydrogel is sacrificed in selected region(s) of the layer so that the hydrogel outside the selected region(s) forms a plurality of spaced-apart islands of the hydrogel. The islands of the hydrogel are enclosed in an enclosure at least partly permeable to a selected fluid. A sensor for detecting a condition includes the substrate, islands, and a device coil arranged with respect to the hydrogel so that changes in the magnetic property modulate an electrical property of the sensor. A system includes the substrate, islands, and a magnetic-field detector.

Claims

1. A sensor comprising:

a substrate;

a plurality of spaced-apart islands of hydrogel arranged over the substrate, the plurality of spaced-apart islands of hydrogel configured to change respective thicknesses or volumes in response to a condition;

a plurality of magnetic particles arranged in the islands of hydrogel so that respective magnetic properties of the islands of hydrogel change with changes of respective thicknesses or volumes of the islands of hydrogel;

a device coil arranged with respect to the islands of hydrogel so that changes in the respective magnetic properties of the islands of hydrogel cause changes in an electrical property of the sensor; and

a tube retaining at least a portion of the substrate disposed at least partly within the tube in a substantially cylindrical shape, the tube having a first end, a second end opposite the first end, and a substantially cylindrical outer shell extending from the first end to the second end.

2. The sensor according to claim 1, wherein the respective magnetic properties are respective effective permeabilities and the electrical property is resonant frequency.

3. The sensor according to claim 1, wherein the substrate is formed in a cylindrical shape.

4. The sensor according to claim 1, wherein each island of the plurality of islands of hydrogel is configured as a geometrical unit.

5. The sensor according to claim 4, wherein the geometrical units include tetrahedral, cubic, octahedral, dodecahedral, icosahedral, or pyramidal shapes.

6. The sensor according to claim 1, further comprising a hydrogel layer, wherein each island of the plurality of islands of hydrogel is arranged in the hydrogel layer, and the device coil is a planar coil arranged substantially parallel to the hydrogel layer.

7. The sensor according to claim 1, wherein:

the sensor further includes a membrane forming a cavity in which each island of the plurality of islands of hydrogel is located;

each island of the plurality of islands of hydrogel can swell or shrink in the cavity; and

the membrane is configured to allow passage of a fluid across the membrane and to block passage of particles of a predetermined size that are suspended in the fluid.

8. The sensor according to claim 7, wherein the islands of hydrogel, the substrate, and the membrane are configured so that the islands of hydrogel do not completely fill the cavity.

9. The sensor according to claim 1, wherein the condition is moisture, temperature, pH, concentration of glucose, or concentration of a selected metal ion.

10. The sensor according to claim 1, wherein the sensor is 2 mm-3 mm in diameter.

11. A system comprising:

a sensor comprising;

a substrate;

a plurality of spaced-apart islands of hydrogel arranged over the substrate, each island of the islands of hydrogel configured to change a respective thickness or a respective volume in response to a condition;

a plurality of magnetic particles arranged in at least some of the islands of hydrogel so that respective magnetic fields of the at least some of the islands of hydrogel change with changes of the respective thicknesses or the respective volumes of the at least some of the islands of hydrogel; and

a tube retaining at least a portion of the substrate disposed at least partly within the tube in a substantially cylindrical shape, the tube having a first end, a second end opposite the first end, and a substantially cylindrical outer shell extending from the first end to the second end; and

a magnetic-field detector configured to measure the magnetic field of the hydrogel.

12. The system according to claim 11, wherein the substrate is formed in a cylindrical shape.

13. The system according to claim 11, wherein each of the at least some of the islands of hydrogel is configured as a geometrical unit.

14. The sensor according to claim 13, wherein the geometrical units include tetrahedral, cubic, octahedral, dodecahedral, icosahedral, or pyramidal shapes.

15. The system according to claim 11, the sensor further including a membrane arranged to form a cavity in which each of the islands of hydrogel is located and can swell or shrink, wherein the membrane is configured to allow passage of fluid across the membrane and block passage of particles of a predetermined size that are suspended in the fluid.

16. The system according to claim 11, wherein the magnetic-field detector includes a Hall-effect sensor.

17. The system according to claim 11, wherein the sensor is 2 mm-3 mm in diameter.

18. A sensor comprising:

a shell having a substantially cylindrical shape, wherein the shell has a plurality of holes therethrough;

a hydrogel arranged within the shell and configured to change thickness or volume in response to a condition;

a plurality of magnetic particles arranged in the hydrogel so that a magnetic property of the hydrogel changes with changes of the thickness or volume of the hydrogel; and

a device coil arranged within the shell,

wherein the device coil is arranged with respect to the hydrogel so that changes in the magnetic property of the hydrogel modulate an electrical property of the sensor.

19. The sensor according to claim 18, wherein:

the sensor further comprises a substrate arranged within the shell; and

the hydrogel comprises an island of the hydrogel arranged over the substrate.

20. The sensor according to claim 19, wherein the shell retains at least a portion of the substrate in a substantially cylindrical shape.

21. The sensor according to claim 18, wherein:

the sensor further comprises a membrane configured to allow passage of fluid across the membrane and block passage of particles of a predetermined size that are suspended in the fluid; and

the membrane is arranged at least partly between the holes and the hydrogel.

22. The sensor according to claim 18, wherein the magnetic property is effective permeability and the electrical property is resonant frequency.

23. The sensor according to claim 18, wherein:

the shell forms a cavity containing the hydrogel; and

the hydrogel does not completely fill the cavity.

24. The sensor according to claim 18, wherein hydrogel comprises a plurality of islands configured as respective geometrical units.

25. The sensor according to claim 18, wherein the geometrical units include tetrahedral, cubic, octahedral, dodecahedral, icosahedral, or pyramidal shapes.