Sweat electrolyte loss monitoring devices
Inventors
Begtrup, Gavi • Morgan, Austin • Larson, Mikel • Bertrand, Jacob A. • Bailey, Nicholas • Newland, Cory • Beech, Robert • Hanley, Brian
Assignees
Publication Number
US-10736565-B2
Publication Date
2020-08-11
Expiration Date
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Abstract
Embodiments of the disclosed invention provide devices and methods to incorporate suspension-based, i.e., hydrogel-based and thixotropic compound-based, ion-selective electrodes and reference electrodes into a wearable sweat sensing device. Embodiments of this device are configured to monitor sweat electrolyte concentrations, trends, and ratios under demanding use conditions. The accompanying method includes use of the disclosed device to track fluid and electrolyte gain and loss in order to produce an electrolyte estimate, such as a sweat electrolyte concentration, a sweat electrolyte concentration trend, a sweat rate, or a concentration ratio between a plurality of electrolytes.
Core Innovation
Embodiments of the disclosed invention provide devices and methods to incorporate suspension-based, i.e., hydrogel-based and thixotropic compound-based, ion-selective electrodes and reference electrodes into a wearable sweat sensing device. Embodiments of this device are configured to monitor sweat electrolyte concentrations, trends, and ratios under demanding use conditions. The accompanying method includes use of the disclosed device to track fluid and electrolyte gain and loss in order to produce an electrolyte estimate, such as a sweat electrolyte concentration, a sweat electrolyte concentration trend, a sweat rate, or a concentration ratio between a plurality of electrolytes.
What is needed are simple, yet robust methods to incorporate ISEs and reference electrodes into wearable configurations that are free from drift, delamination, and abrasion over the use period of a sweat sensing device. Bench-top ion selective electrodes and their accompanying reference electrodes achieve required sensitivity and specificity in stable laboratory environments, but when moved to wearable, semi-disposable devices they must be greatly reduced in size, are often deposited on a flexible substrate, exposed to skin, and become prone to drift, interference from the body, delamination, or abrasion. Sweat has an unpredictable sampling rate in the absence of technological solutions, which further motivates wearable configurations that provide chronological assurance and reliable sampling.
The disclosure addresses these problems by employing suspension-based electrodes in cassette-style microfluidic housings in wearable devices, wherein suspensions such as hydrogels or thixotropic compounds serve as a structure for suspending salts that allow exchange of ions between the electrode and the sweat sample. Example embodiments include a cassette housing with a plurality of wells arranged along a microfluidic channel, wells containing suspension-based ISEs and a suspension-based reference electrode with a salt bridge, and protective non-vapor transmissible layers to interface with the sweat sample while maintaining electrode stability and operational lifespan.
Claims Coverage
The asserted claim set includes two independent claims, each presenting a distinct inventive feature: a layered wearable sweat sensing device with a suspension-containing reference electrode arrangement, and a method for monitoring an individual's electrolyte levels using ISE measurements combined with user inputs.
Layered sweat sensing device comprising ion selective electrode sensors and a reference electrode
A device with a first layer comprising one or more ion selective electrode (ISE) sensors located in a sensor channel having an inlet and an outlet, the inlet being in fluidic communication with the skin surface and the ISE sensors located between the inlet and the outlet; and a second layer comprising a water impermeable substrate and a reference electrode that includes a reference chamber containing a mixture that includes a fumed silica matrix and a reference salt and a fill port at a first end, a salt bridge chamber at a second end containing a mixture that includes a fumed silica matrix and a bridge salt and including an exchange port configured to fluidically connect the reference electrode to the one or more ISE sensors (wherein the exchange port connects to the sensor channel at a location between the inlet and the one or more ISE sensors), and a wire electrode extending into the reference chamber from the fill port.
Method of monitoring an individual's electrolyte levels using ISE measurements and user inputs
Receiving one or more measurements of a concentration of an ion in a sweat sample with an ion selective electrode (ISE) sensor; receiving input relevant to one or more of the following: a hydration status for the individual; an electrolyte status for the individual; a fluid intake for the individual; a fluid output for the individual; an electrolyte intake for the individual; and an electrolyte output for the individual; using said measurements and said input to develop one or more electrolyte values including a sweat electrolyte concentration, a sweat electrolyte concentration trend, a sweat rate, and a concentration ratio between a plurality of electrolytes; and outputting information derived from the one or more electrolyte values.
The independent claims cover (1) a multilayer wearable sweat sensing device combining on-channel ISE sensors with a fumed-silica-matrix-containing reference electrode having a salt bridge and an exchange port positioned between the inlet and ISEs, and (2) a method that integrates ISE-derived ion concentration measurements with user-provided hydration/electrolyte/fluids inputs to compute and output electrolyte-related values such as concentration, trend, rate, and inter-electrolyte ratios.
Stated Advantages
Configured to monitor sweat electrolyte concentrations, trends, and ratios under demanding use conditions.
Enables tracking of fluid and electrolyte gain and loss to produce electrolyte estimates such as sweat electrolyte concentration, concentration trends, sweat rate, or concentration ratios between electrolytes.
Improves a device wearer's safety or physical performance by monitoring electrolyte loss amounts, trends and ratios.
Fosters redundancy and feedback loops among device sensors (ISEs, GSR, sweat conductivity, volumetric sweat rate, temperature) to improve the quality of information derived from a device wearer's sweat.
Provides chronologically assured sampling and composite sweat rate estimation by combining contemporaneous measurements from multiple sensor modalities.
Documented Applications
Workplace safety, athletic, and military settings as applications for a robust, wearable sweat electrolyte loss monitor.
Monitoring electrolyte concentrations, trends, ratios and sweat rate to improve wearer safety or physical performance.
Using the device and method to monitor an individual's electrolyte levels and output information or recommendations, including recommendations to consume an amount of fluid or an amount of electrolyte.
Wearable form factors including patches, bands, straps, portions of clothing or equipment to bring sweat collecting and/or sweat sensing technology into intimate proximity with sweat as it is generated.
An example use scenario of securing the electrolyte loss monitor to an endurance runner's bicep to initialize the device with a smartphone, measure sweat electrolytes, compute electrolyte loss estimates, and communicate results to the wearer.
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