Sweat conductivity, volumetric sweat rate, and galvanic skin response devices and applications
Inventors
Begtrup, Gavi • Bertrand, Jacob A. • Heikenfeld, Jason • Morgan, Austin • Weinle, Nathan
Assignees
Publication Number
US-10405794-B2
Publication Date
2019-09-10
Expiration Date
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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.
Core Innovation
The disclosure provides 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.
Sweat sensing technologies have enormous potential for applications ranging from athletics, to neonatology, to pharmacological monitoring, to personal digital health, to name a few applications, and a primary goal of the disclosed invention is to provide decision support to a sweat sensor system user that is informative at the level of the individual patient. Algorithms and techniques are required to adjust sweat analyte signatures to account for variabilities unrelated to differences in concentrations, for example where sweat concentrations vary depending on sweat rate, the body location from which a sample is taken, kidney or liver disease or function, external temperatures, and other factors.
These three capabilities can be combined in a single device, which can use a volumetric sweat rate sensor to calibrate the individual's sweat conductivity and GSR measurements, and thereby provide useful information about the individual's physiological state, including sweat rate, sweat content, water loss, and dehydration state; and 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 Coverage
Two independent claims are identified. The following inventive features are extracted from the independent claims (seven main inventive features).
Sweat collector with concave surface and circular seal
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;
Microfluidic channel with known volume
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;
GSR electrodes located outside the collector seal
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;
Conductivity electrodes proximate to the channel inlet
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;
Volumetric sweat rate sensor with electrodes at known intervals
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.
Serpentine microfluidic channel with hydrophobic coating
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;
Detection circuit with electrodes separated by increasing intervals
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.
The independent claims disclose wearable sweat sensing devices comprising (1) a sweat collector with a concave surface and seal and a fluid port, (2) a microfluidic channel with a known volume (including serpentine layout and hydrophobic coating in one independent claim), (3) GSR electrodes located outside the collector seal, (4) conductivity electrodes proximate to the channel inlet, and (5) a volumetric sweat rate detection circuit using multiple electrodes that intersect the channel at known intervals with progressively larger spacing toward the channel's second end.
Stated Advantages
Provide decision support to a sweat sensor system user that is informative at the level of the individual patient.
Use volumetric sweat rate to calibrate and inform sweat conductivity and galvanic skin response measurements to improve and extend sweat rate estimates.
Inform composite estimates of sweat onset, sweat cessation, sweat ion concentration, and sweat rate.
Use 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.
Provide useful information about the individual's physiological state, including sweat rate, sweat content, water loss, and dehydration state.
Documented Applications
Athletics.
Neonatology.
Pharmacological monitoring.
Personal digital health.
Workplace safety, athletic, military, and clinical diagnostic settings.
Determining the existence of a physiological condition and performing measurements of concentrations, ratios, and trends of sweat analytes.
Detecting dehydration, determining fitness level, and characterizing the degree of heat acclimation.
Identifying wearers in need of additional monitoring or instruction, such as the need to drink additional water or to adhere to a drug regimen.
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