THE SCIENCE INSIDE
How sweat becomes data.
Tiny channels collect sweat, electrodes measure the local sample and models estimate losses across the body. Here is how those steps connect.
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PASSIVE MICROFLUIDICS
Let sweat lead the way.
Sweat enters a small inlet at the skin and follows a network of tiny channels. As liquid wets the channel walls, capillary forces can help draw it forward; pressure from newly arriving sweat also supports movement. A vent gives displaced air a way out, allowing the sample to advance without a powered pump.
Channel size, surface properties and pressure shape how liquid moves. The illustration explains fluid transport, rather than a specific cartridge design.
GENERAL FLUID-TRANSPORT PRINCIPLE
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ELECTROCHEMICAL SENSING
Turning sodium into a measurable signal.
A sodium-selective membrane responds preferentially to Na+ ions in the sample. Its electrical potential is measured against a stable reference electrode. The voltage follows sodium-ion activity, or effective concentration, on a logarithmic scale. Calibration turns this response into a local sodium concentration reading.
A tenfold change in ion activity produces a similar voltage step under the same conditions. This local reading does not directly measure total body sodium loss.
GENERAL ION-SELECTIVE PRINCIPLE · QUALITATIVE RESPONSE
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CAPACITIVE SENSING
Sensing sweat through electric fields.
Liquid and air respond differently to an electric field. When sweat enters a channel near two electrodes, it changes the dielectric properties, meaning how the material responds to the field. This reshapes the field distribution and changes how much charge the electrodes can store. The change in capacitance provides a signal of local liquid movement.
The response depends on the liquid, geometry and measurement conditions. Capacitive liquid sensing does not directly measure whole-body sweat rate.
GENERAL CAPACITIVE PRINCIPLE · QUALITATIVE RESPONSE
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WHOLE-BODY ESTIMATION
A small sample. A bigger picture.
Local measurements describe the sweat reaching the cartridge. To estimate losses across the body, a model combines those signals with athlete and exercise information. The app then adds up estimated fluid and elemental sodium losses over the session.
Whole-body values are model-derived estimates. This concept assumes successful model validation and does not present current validation evidence.
L/h · estimatedTotal fluid loss
L · estimatedTotal sodium loss
g · estimated
MEASURED LOCALLY. ESTIMATED FOR THE WHOLE BODY.
CLARITY IN EVERY NUMBER
Know what is measured.
Understand what is estimated.
Measured at the cartridge.
Local sweat sodium concentration is reported in mmol/L. Local channel movement and flow information describe the sample reaching the sensors.
Estimated for the whole body.
The model provides whole-body sweat rate in L/h, cumulative fluid loss in L, total elemental sodium loss in mg or g, and sodium loss rate in mg/h. A wrist cartridge does not measure whole-body losses directly.
EXPLORE NAESIA
Get to know your sweat.
See how the wearable concept could fit into your training.