Microfluidic Sweat Analysis With Dual-Electrode Flow Measurement
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Solution Overview
Problem
Existing sweat analysis devices face issues with inaccurate measurements due to small collection zones leading to increased friction and sweat loss, complex dimensioning for varying sweat rates, and imprecise flow rate determination, especially during intense efforts.
Innovation Solution
A device with a large collection zone and optimized microfluidic channel design that ensures a continuous sweat flow, using a rim to prevent sweat loss and employing two pairs of electrodes for real-time conductance measurements to calculate flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small collection zone is used to reduce microfluidic channel filling speed, then the channel can be filled more slowly, but friction increases and measurement accuracy is significantly lost
Solution Approach 1:
The patent transitions from a two-dimensional surface collection to a three-dimensional cavity collection zone. The cavity has depth and volume, allowing it to collect sweat from a larger effective area while maintaining a controlled outlet to the microfluidic channel. This dimensional change enables the collection zone to accumulate sufficient sweat volume without requiring a long microfluidic channel, thus maintaining measurement accuracy while extending measurement duration.
2Productivity
If the collection zone is reduced to several millimeters in diameter, then the microfluidic channel filling speed is reduced, but friction from channel walls increases and accuracy is significantly lost
Solution Approach 1:
The cavity collection zone performs preliminary accumulation of sweat before it enters the microfluidic channel. By collecting sweat in the cavity first, the system ensures that the microfluidic channel receives a sufficient volume of sweat, reducing the relative impact of wall friction during the measurement process. This preliminary action in the cavity allows the channel to be shorter while still maintaining adequate measurement conditions.
3Duration of action of moving object
If a long microfluidic channel is used to extend measurement, then measurement duration is extended, but the collection zone must be very small which increases inference error
Solution Approach 1:
The patent uses a three-dimensional cavity collection zone to replace the need for a long microfluidic channel. The cavity's volume and depth provide the necessary measurement extension in a compact space, eliminating the need for a long horizontal channel that would require a tiny collection zone. This dimensional change maintains measurement duration while significantly reducing inference error.
4Productivity
If the collection zone is made small, then sweat storage measurement is enabled, but infiltration from other zones causes exponential increase in inference error
Solution Approach 1:
The cavity collection zone performs preliminary collection and isolation of sweat from a controlled area. The cavity's physical structure with its defined walls and outlet creates a barrier that prevents infiltration from surrounding skin zones. This preliminary isolation in the cavity ensures that the sweat entering the microfluidic channel comes only from the intended collection area, maintaining measurement precision while enabling continuous measurement capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately measures sweat flow rate and concentration continuously, providing precise and reliable data without storage, suitable for various sweat rates and physical activities.
Implementation Method 1
a collection means (100) arranged into a sweat collector capable of recovering a sweating to form a continuous flow of sweat
Implementation Method 2
measurement of a first conductance of the continuous flow of sweat; measurement of a second conductance of the continuous flow of sweat
Data Source
AI summary
Disclosed is a method for analyzing sweat produced by the skin of a user including a first step of collecting sweat released by the skin by a collector of a housing to form a continuous flow of sweat of a second face of the housing, which is provided with a microfluidic channel. The method includes a third step of measuring a first conductance of the continuous flow of sweat by a first pair of electrodes housed inside the microfluidic channel and a fourth step of measuring a second conductance of the continuous flow of sweat by a second pair of electrodes located at an electrode distance from the first pair of electrodes. The method includes a fifth step of determining a period of time taken for the second conductance to become equal to the first conductance and a sixth step of calculating a flow rate of the sweat.