Epidermal Devices for Analysis of Temperature and Thermal Transport Characteristics

• US 20180014734A1
• Filed: 08/11/2015
• Published: 01/18/2018
• Est. Priority Date: 08/11/2014
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: ROGERS, John A., GAO, Li, MALYARCHUK, Viktor, WEBB, Richard Chad
• Granted Patent: US 11,160,458 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/04 Constructional details of apparatus
• CPC Class Codes: A61B 2562/0271 Thermal or temperature sensors
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 2562/0285 Nanoscale sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 2562/12 Manufacturing methods specially adapted for producing sensors for in-vivo measurements
• CPC Class Codes: A61B 2562/164 the sensor is mounted in or on a conformable substrate or carrier
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/0048 Detecting, measuring or recording by applying mechanical forces or stimuli A61B5/021, A61B5/4884 and A61B9/00 take precedence
• CPC Class Codes: A61B 5/015 By temperature mapping of body part
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/028 by thermo-dilution
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/6802 Sensor mounted on worn items
• CPC Class Codes: A61B 5/6824 : Arm or wrist
• CPC Class Codes: A61B 5/683 : Means for maintaining contact with the body A61B5/6802 takes precedence
• CPC Class Codes: A61B 5/6832 : using adhesives A61B5/259 takes precedence

Abstract

Tissue-mounted devices and methods for monitoring a thermal transport property (e.g., thermal conductivity, thermal diffusivity, heat capacity) of tissue, such as skin, are disclosed. The devices conformally mount to the tissue and comprise one or more thermal actuators and a plurality of sensors. The actuator applies heat to the tissue and the sensors detect a spatio temporal distribution of a physiological tissue parameter or physical property resulting from the heating. This spatio temporal information may be correlated with a rate, velocity and/or direction of blood flow, the presence of a vascular occlusion, circulation changes due to in flammation, hydration level and other physiological parameters.

Claims

1. A device for interfacing with a tissue in a biological environment, the device comprising:

a flexible or stretchable substrate; and

one or more thermal actuators and a plurality of thermal sensors supported by said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors for characterizing a thermal transport property of said tissue;

wherein said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors provide a net bending stiffness such that the device is capable of establishing conformal contact with a surface of the tissue.

2. The device of claim 1, wherein said one or more thermal actuators and said plurality of thermal sensors spatially and/or temporally characterize said thermal transport property of said tissue.

4. The device of claim 1, wherein said thermal sensors are for characterizing a spatio temporal distribution of temperature resulting from heating provided by said one or more thermal actuators.

5. The device of claim 1, wherein said thermal transport property is thermal conductivity, thermal diffusivity or heat capacity.

6. The device of claim 1, wherein said thermal transport property correlates with a tissue property selected from the group consisting of hydration state, inflammation state, occlusion state and any combination of these.

7. The device of claim 1, wherein said thermal transport property correlates with a physiological parameter selected from the group consisting of macrovascular blood flow direction, macrovascular blood flow rate, microvascular blood flow direction, microvascular blood flow rate, presence of an occlusion, macrovascular perfusion, microvascular perfusion, circulation changes due to inflammation, and any combination of these.

8. The device of claim 1, wherein said device does not substantially impact the natural temperature of said tissue upon establishing conformal contact.

13. The device of claim 1, wherein said thermal actuators and thermal sensors comprise stretchable or flexible structures, thin film structures and/or filamentary metal structures.

16. The device of claim 1, wherein said thermal sensors provide a spatial resolution greater than or equal to 10 μ

m and/or a temporal resolution greater than or equal to 1 μ

s.

18. The device of claim 1, wherein at least one of said thermal sensors is a temperature sensor for measuring background temperature to compensate for drift.

19. The device of claim 1, wherein said thermal actuators provide a power input to said tissue selected over the range of 0.1 mW mm⁻

2 to 50 mW mm<sup>−

2</sup>.

20. The device of claim 1, wherein said thermal actuators provide a constant heating of said tissue or a pulsed heating of said tissue.

22. The device of claim 1, wherein said thermal sensors are symmetrically arranged with respect to said one or more thermal actuators, and two of said thermal sensors form matched pairs on opposite sides of said thermal actuator for obtaining comparative data as an indication of an anisotropic thermal transport property, wherein said anisotropic thermal transport property indicates a direction of blood flow.

25. The device of claim 22, wherein said thermal sensors are arranged as one or more concentric rings having one of said thermal actuators at a center of the one or more concentric rings.

26. The device of claim 1, wherein each thermal sensor and thermal actuator provides an individual pixel independently corresponding to an individual position of a pixelated array, wherein said individual pixels have average lateral dimensions selected from the range of 10 μ

m to 1 cm.

30. The device of claim 26, wherein said pixelated array comprises 10 to 100,000 pixels and has a footprint selected from the range of 10 mm² to 2000 cm².

32. The device of claim 26, wherein at least a portion of said pixels comprise micro-encapsulated structures or nano-encapsulated structures.

33. The device of claim 1, wherein the device further comprises:

one or more electrodes, transistors, inducers, resistors, LEDs, capacitors, oscillators, photodiodes, diodes or any combinations of these;

one or more amplifiers, strain gauges, temperature sensors, wireless power coils, solar cells, inductive coils, high frequency inductors, high frequency capacitors, high frequency oscillators, high frequency antennae, multiplex circuits, electrocardiography sensors, electromyography sensors, electroencephalography sensors, electrophysiological sensors, thermistors, transistors, diodes, resistors, capacitive sensors, light emitting diodes, or any combinations of these; and

/or

one or more wireless communication antenna structures or near-field communication coils supported by said flexible or stretchable substrate.

36. The device of claim 1, wherein said one or more actuators and/or said plurality of sensors are connected by an electronic circuit, wherein the electronic circuit is flexible or stretchable and comprises one or more electronic devices or device components having a curved, serpentine, bent, wavy or buckled geometry.

39. The device of claim 36, wherein the electronic circuit comprises a plurality of electrodes selected from the group consisting of meander electrodes, interdigitated electrodes, circular electrodes and annular electrodes.

40. The device of claim 36, wherein the flexible or stretchable substrate and the electronic circuit provide a net bending stiffness of the device less than or equal to 1 mN m.

41. The device of claim 1, wherein the flexible or stretchable substrate has an average modulus less than or equal to 100 MPa.

48. The device of claim 1, comprising a multilayer device wherein said sensors and actuators are at least partial partially encapsulated by a barrier layer.

57. The device of claim 1, wherein the device has an areal mass density less than or equal to 100 mg cm⁻

2.

61. The device of claim 1, further comprising a barrier layer at least partially encapsulating at least a portion of said thermal actuator and said thermal sensors.

3. (canceled)

9-12. -12. (canceled)

14-15. -15. (canceled)

17. (canceled)

21. (canceled)

23-24. -24. (canceled)

27-29. -29. (canceled)

31. (canceled)

34-35. -35. (canceled)

37-38. -38. (canceled)

42-47. -47. (canceled)

49-56. -56. (canceled)

58-60. -60. (canceled)

62-65. -65. (canceled)

66. A method of sensing a tissue of a biological environment, the method comprising:

providing a device comprising;

a flexible or stretchable substrate; and

one or more thermal actuators and a plurality of thermal sensors supported by said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors for characterizing a thermal transport property of said tissue;

wherein said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors provide a net bending stiffness such that the device is capable of establishing conformal contact with a surface of the tissue;

contacting the device to a receiving surface of the tissue, wherein contact results in said conformal contact with said surface of the tissue;

thermally actuating said tissue with said one or more thermal actuators; and

measuring one more temperatures of said tissue with at least a portion said thermal sensors.

67-79. -79. (canceled)

80. A method for characterizing vasculature of tissue, the method comprising:

providing a device comprising;

a flexible or stretchable substrate; and

one or more thermal actuators and a plurality of thermal sensors supported by said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors for characterizing a thermal transport property of said tissue;

wherein said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors provide a net bending stiffness such that the device is capable of establishing conformal contact with a surface of the tissue;

contacting the device to a receiving surface of the tissue, wherein contact results in said conformal contact with said surface of the tissue;

sequentially measuring a steady-state temperature at the location of each thermal sensor;

thermally actuating said tissue with said one or more thermal actuators while simultaneously recording a non-equilibrium temperature of the thermal actuator and said plurality of thermal sensors; and

identifying pairs of symmetrically disposed thermal sensors on opposing sides of the thermal actuator.

81. The method of claim 80 further comprising comparing a normalized change in the non-equilibrium temperatures of the pairs of symmetrically disposed thermal sensors versus time to model results to determine vessel depth.

82. The method of claim 80 further comprising normalizing the steady-state temperature difference between the pairs of symmetrically disposed thermal sensors by the non-equilibrium temperature at the actuator to determine blood flow velocity.

83-85. -85. (canceled)

86. A method for determining a hydration level of tissue, the method comprising:

providing a device comprising;

a flexible or stretchable substrate; and

one or more thermal actuators and a plurality of thermal sensors supported by said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors for characterizing a thermal transport property of said tissue;

wherein said flexible or stretchable substrate, said one or more thermal actuators and said plurality of thermal sensors provide a net bending stiffness such that the device is capable of establishing conformal contact with a surface of the tissue;

contacting the device to a receiving surface of the tissue, wherein contact results in said conformal contact with said surface of the tissue;

sequentially supplying a current to each thermal sensor and measuring a voltage from each thermal sensor;

calculating resistance change over time to determine thermal conductivity; and

comparing said thermal conductivity with a corresponding hydration level of said tissue.