LASER-SCRIBED FERROGEL SENSOR WITH MAGNETIC PARTICLES

• US 20150087945A1
• Filed: 12/01/2014
• Published: 03/26/2015
• 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: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Ziaie, Babak, Siegel, Ronald A.
• Granted Patent: US 9,999,369 B2
• Time in Patent Office: Days
• US Class Current: 600/365
• 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 method of making a sensor, the method comprising:

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;

sacrificing the hydrogel 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; and

enclosing the islands of the hydrogel in an enclosure at least partly permeable to a selected fluid.

2. The method according to claim 1, wherein the sacrificing includes removing hydrogel from the selected region(s) by laser patterning.

3. The method according to claim 2, wherein the laser patterning includes irradiating the hydrogel with a laser having a substantially Gaussian spot.

4. The method according to claim 1, wherein the selected region(s) are shaped so that each island of the hydrogel is substantially quadrilateral, substantially triangular, or substantially circular.

5. The method according to claim 4, wherein the selected region(s) are arranged so the islands of the hydrogel form a checkerboard pattern.

6. The method according to claim 1, further including operatively arranging a device coil with respect to the hydrogel so that changes in the magnetic property modulate an electrical property of the sensor, wherein the selected region(s) at least partly overlay electrode(s) of the device coil.

7. The method according to claim 1, further including arranging the substrate in a substantially cylindrical form.

8. The method according to claim 7, wherein the arranging includes inserting the substrate into a substantially cylindrical tube.

9. A sensor for detecting a condition, the sensor comprising:

a substrate;

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

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

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

10. The sensor according to claim 9, wherein the magnetic property is effective permeability and the electrical property is resonant frequency.

11. The sensor according to claim 9, wherein the substrate is formed in a cylindrical shape.

12. The sensor according to claim 9, further including a tube configured to retain the substrate in a substantially cylindrical shape.

13. The sensor according to claim 9, wherein the islands of hydrogel are configured as geometrical units.

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

15. The sensor according to claim 9, wherein the islands of hydrogel are arranged in a layer and the device coil is a planar coil arranged substantially parallel to the layer.

16. The sensor according to claim 9, further including a substrate and a membrane arranged to form a cavity in which the hydrogel is located and can swell or shrink, wherein the membrane is configured to allow passage of a fluid across the membrane and block passage of particles of a predetermined size that are suspended in the fluid.

17. The sensor according to claim 16, wherein the hydrogel, the substrate, and the membrane are configured so that the hydrogel does not completely fill the cavity.

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

19. A system for detecting a condition, the sensor comprising:

a substrate;

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

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

a magnetic-field detector operatively arranged to measure the magnetic field of the hydrogel.

20. The system according to claim 19, wherein the substrate is formed in a cylindrical shape.

21. The system according to claim 19, wherein the islands of hydrogel are configured as geometrical units.

22. The sensor according to claim 21, wherein the geometrical units include tetrahedral, cubic, octahedral, dodecahedral, icosahedral, or pyramidal shapes.

23. The system according to claim 19, further including a tube configured to retain the substrate in a substantially cylindrical shape.

24. The system according to claim 19, further including a membrane arranged to form a cavity in which the 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.

25. The system according to claim 19, wherein the magnetic-field detector includes a Hall-effect sensor.