Sweat conductivity, volumetric sweat rate, and galvanic skin response devices and applications

• US 10,405,794 B2
• Filed: 07/18/2017
• Issued: 09/10/2019
• Est. Priority Date: 07/19/2016
• Status: Active Grant

• Current Assignee: Epicore Biosystems, Inc.
• Original Assignee: Eccrine Systems Inc.
• Inventors: Begtrup, Gavi, Bertrand, Jacob A., Heikenfeld, Jason, Morgan, Austin, Weinle, Nathan
• Primary Examiner(s): Jackson, Gary
• Assistant Examiner(s): Kuo, Jonathan
• Application Number:
  US15/653,494
• Publication Number:
  US 20180020966A1
• Time in Patent Office: 784 Days
• Field of Search: 600300-301, 600307, 600345-346
• CPC Class Codes: A61B 2503/04 Babies, e.g. for SIDS detection
• CPC Class Codes: A61B 2503/10 Athletes
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/14 Coupling media or elements to improve sensor contact with skin or tissue
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/0533 Measuring galvanic skin response
• CPC Class Codes: A61B 5/14517 for sweat
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/4266 sweat secretion
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor

Abstract

The disclosed invention includes sweat sensing devices configured to periodically measure sweat conductivity and galvanic skin response, devices to measure volumetric sweat flow rate, and devices that combine the three functions. The disclosure further includes methods for using a device configured to perform periodic sweat conductivity measurements, galvanic skin response measurements, and volumetric sweat rate measurements so that each sensor modality informs composite estimates of sweat onset, sweat cessation, sweat ion concentration, and sweat rate. The method uses those measurements to inform other sweat sensing device functions, such as determining the existence of a physiological condition, or performing measurements of concentrations, ratios, and trends of sweat analytes.

Claims

1. A sweat sensing device configured to be worn on an individual'"'"'s skin, comprising:

a sweat collector, comprising a concave surface facing the skin, a substantially circular seal, and a fluid port, wherein the concave surface creates a clearance from the skin to promote natural flow of sweat, wherein the seal interacts with the skin to create a coverage area within the collector that is determined, and wherein the seal is configured to substantially prevent sweat from exiting the coverage area from skin located inside the coverage area, and to substantially prevent sweat and surface contaminants from entering the coverage area from skin located outside the coverage area, and wherein the fluid port is in fluidic communication with the microfluidic channel inlet;

a microfluidic channel for receiving and transporting a sweat sample, wherein the channel has an inlet at a first end, an outlet at a second end, and has a known volume;

a plurality of GSR electrodes for measuring galvanic skin response (“

GSR”

), wherein said GSR electrodes are configured to contact the individual'"'"'s skin when the device is being worn, and wherein the GSR electrodes are located outside the seal of the sweat collector;

a plurality of conductivity electrodes for measuring sweat conductivity, wherein said conductivity electrodes are in fluid communication with said channel, and wherein the conductivity electrodes are located proximate to the first end of the channel; and

a volumetric sweat rate sensor, wherein the volumetric sensor includes a detection circuit that includes a plurality of sweat rate electrodes, wherein said sweat rate electrodes intersect said channel at known intervals, where said sweat rate electrodes are in fluid communication with the channel, wherein said sweat rate electrodes divide the channel into a plurality of channel sections, and wherein a plurality of primary sweat rate electrodes located proximate to the channel'"'"'s first end are separated by a first interval, and a plurality of secondary sweat rate electrodes located proximate to the channel'"'"'s second end are separated by a second interval, and wherein the second interval is greater than the first interval.

2. The device of claim 1, further including at least one of the following:

an electrochemical aptamer-based sensor;

a micro-thermal flow rate sensor; and

a pressure-based flow rate sensor.

3. The device of claim 1, wherein the microfluidic channel includes at least one of the following to reduce air bubble interference with at least one electrode:

an air bubble vent; and

an air trap.

4. A wearable sweat sensing device configured to volumetrically determine sweat rate, and configured to be placed on an individual'"'"'s skin, comprising:

a sweat collector, comprising a concave surface facing the skin, a substantially circular seal, and a fluid port, wherein the concave surface creates a clearance from the skin to promote natural flow of sweat, wherein the seal interacts with the skin to create a coverage area within the collector that is determined, and wherein the seal is configured to substantially prevent sweat from exiting the coverage area from skin located inside the coverage area, and to substantially prevent sweat and surface contaminants from entering the coverage area from skin located outside the coverage area, and wherein the fluid port is in fluidic communication with the microfluidic channel inlet;

a microfluidic channel for receiving and transporting a sweat sample, wherein the channel has an inlet at a first end, an outlet at a second end, has a known volume, has a serpentine layout, and at least one surface with a hydrophobic coating; and

a detection circuit that includes a plurality of electrodes, wherein said electrodes intersect said channel at known intervals, wherein said electrodes are in fluid communication with the channel, and wherein said electrodes divide the channel into a plurality of channel sections, and wherein a plurality of primary electrodes located proximate to the channel'"'"'s first end are separated by a first interval, a plurality of secondary electrodes located between the primary electrodes and the channel'"'"'s second end are separated by a second interval, a plurality of tertiary electrodes located between the secondary electrodes and the channel'"'"'s second end are separated by a third interval, and wherein the third interval is greater than the second interval, and the second interval is greater than the first interval.

5. The device of claim 4, wherein the electrodes are configured as a plurality of interdigitated electrode switches that reroute current upon contact with the sweat sample.

6. The device of claim 4, wherein the channel has one of the following arrangements:

constant cross section; and

variable cross section.

7. The device of claim 4, further including at least one of the following:

a micro-thermal flow rate sensor;

a capacitive skin proximity sensor; and

an accelerometer.

8. The device of claim 4, wherein said sweat rate is developed using aggregated sweat sensor data that is correlated to relevant external information, wherein the external information includes at least one of the following:

air temperature, humidity, the individual'"'"'s age, the individual'"'"'s heartrate, the individual'"'"'s initial hydration state, the individual'"'"'s fluid intake, the individual'"'"'s body mass index, the individual'"'"'s kidney health, the individual'"'"'s fitness level, and the individual'"'"'s recent physical activity.