Microtube sensor for physiological monitoring

Patent metadata

Field	Value
Publication number	US-11525796-B2
Application number	US-201816487983-A
Country	US
Kind code	B2
Filing date	Feb 19, 2018
Priority date	Feb 28, 2017
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

A soft, flexible microtube sensor and associated method of sensing force are described. A liquid metallic alloy is sealed within a microtube as thin as a strand of human hair to form the physical force sensing mechanism. The sensor is hardly distinguishable with the naked eye, and can be used for the continuous biomonitoring of physiological signals, such as unobtrusive pulse monitoring. Also described is a method of fabricating the microtube sensor and wearable devices incorporating one or more microtube sensors.

First claim

What is claimed is:

1. A microtube sensor, comprising:
a flexible microtube comprising a polymer and defining a lumen, the flexible microtube having (i) an inner diameter of about 10 μm to about 200 μm and an outer diameter, and (ii) a wall having a uniform thickness surrounding the lumen, the wall having a uniform thickness of about 10 μm to about 40 μm; and
a liquid-state conductive element within the lumen of the flexible microtube, the flexible microtube having closed ends to retain the liquid-state conductive element in the lumen,
wherein the microtube sensor has a property that a change in electrical resistance of the liquid-state conductive element is indicative of a force-induced deformation of the flexible microtube,
wherein the force sensitivity of the sensor is about 2.8 N −1 to about 68 N −1 for static force loads from about 5 mN to about 900 mN.

2. The microtube sensor of claim 1 , wherein the polymer is a silicone elastomer, an ultraviolet sensitive polymer, polyurethane, a conductive polymer, conductive rubber, polyimide, a thermoset polymer or a thermoplastic polymer.

3. The microtube sensor of claim 2 , wherein the silicone elastomer is polydimethylsiloxane, phenyl-vinyl silicone, methyl-siloxane, fluoro-siloxane or platinum cured silicone rubber.

4. The microtube sensor of claim 2 , wherein the ultraviolet sensitive polymer is a fluorinated resin with acrylate/methacrylate groups, styrene-acrylate-containing polymer, polyacrylate polyalkoxy silane, a positive photoresist, a negative photoresist, diazonaphthoquinone-based positive photoresist or epoxy-based negative photoresist.

5. The microtube sensor of claim 1 , wherein the liquid-state conductive element is a liquid metallic alloy.

6. The microtube sensor of claim 5 , wherein the liquid metallic alloy is eutectic gallium-indium-tin or eutectic gallium-indium (eGaIn).

7. The microtube sensor of claim 1 , wherein a ratio of the outer diameter to the inner diameter is about 1.05 to about 111.

8. The microtube sensor of claim 1 , wherein the length of the microtube is about 1 m or less.

9. The microtube sensor of claim 1 , wherein the microtube has a circular, elliptical, rectangular, square, triangular, star, non-circular, or irregular cross-sectional shape.

10. The microtube sensor of claim 1 , further comprising connectors at the ends of the microtube and in electrical contact with the liquid-state conductive element, to measure the electrical resistance of the liquid-state conductive element.

11. A method of sensing force, comprising:
exposing the microtube sensor of claim 1 to a mechanical force; and
measuring the change in the electrical resistance of the liquid-state conductive element within the lumen of the flexible microtube in response to the mechanical force,
wherein the change in the electrical resistance of the liquid-state conductive element is indicative of the force-induced deformation of the flexible microtube.

12. The method of claim 11 , further comprising using the measured change in the electrical resistance to monitor a physiological parameter.

13. The method of claim 12 , wherein the physiological parameter is at least one of pulse pressure, blood pressure, heart rate, foot pressure, tactile force and tremor.

14. The microtube sensor of claim 1 , wherein the microtube sensor is woven into a fabric substrate.

15. A wearable electronic device, comprising:
a fabric substrate configured to be worn on a body; and
a microfiber woven into the fabric substrate, the microfiber comprising the microtube sensor of claim 1 .

16. The microtube sensor of claim 1 , wherein the outer diameter is less than 120 μm.

17. The microtube sensor of claim 1 , wherein the outer diameter is from about 100 μm to about 200 μm.

18. The microtube sensor of claim 1 , wherein the sensor can measure strain, pressure or a combination of these.

19. A method of making a microtube sensor, comprising:
providing a flexible microtube comprising a polymer and defining a lumen, the flexible microtube having (i) an inner diameter of about 10 μm to about 200 μm and an outer diameter, and (ii) a wall having a uniform thickness surrounding the lumen, the wall having a uniform thickness of about 10 μm to about 40 μm;
injecting a liquid-state conductive element into the lumen of the flexible microtube; and
closing ends of the flexible microtube to retain the liquid-state conductive element in the lumen, to thereby make the microtube sensor that has a property that a change in electrical resistance of the liquid-state conductive element is indicative of a force-induced deformation of the flexible microtube,
wherein the force sensitivity of the sensor is about 2.8 N −1 to about 68 N −1 for static force loads from about 5 mN to about 900 mN.

20. The method of claim 19 , further comprising:
placing connectors at the ends of the microtube and in electrical contact with the liquid-state conductive element, to measure the electrical resistance of the liquid-state conductive element.

Assignees

• Nat Univ Singapore

Inventors

• Yeo Joo Chuan
• Xi Wang
• Yu Longteng
• Lim Chwee Teck

Classifications

• A61B5/1038

  Measuring plantar pressure during gait · CPC title

• A61B5/02444

  Details of sensor (A61B5/02427 takes precedence) · CPC title

• A61B5/6807

  Footwear · CPC title

• G01N27/06 Primary

  of a liquid (involving electrolysis G01N27/26) · CPC title

• A61B2562/028

  Microscale sensors, e.g. electromechanical sensors [MEMS] · CPC title