Wearable EDA Sensor Using Infrared Light for Non-Intrusive Monitoring
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Solution Overview
Problem
Current methods for measuring electro-dermal activity are limited by their invasiveness, short duration, and interference from hair and noise, particularly when attempting long-term monitoring in natural environments.
Innovation Solution
A wearable device using infrared light in the 750-950 nm wavelength range, with a light source and sensor arranged 0.5-5 mm apart, to passively measure electro-dermal activity by evaluating changes in skin interaction with emitted light, reducing noise and interference from heart beats and hair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical current is injected into the skin to measure EDA, then measurement can be performed, but the method becomes intrusive and causes discomfort to the subject
Solution Approach 1:
The patent replaces the electrical measurement system with an optical system. Instead of injecting electrical current through electrodes to measure skin conductance, the invention uses a light source to emit light into the skin and a light sensor to detect changes in light properties caused by sweat secretion. This optical substitution eliminates the need for electrical contact, making the measurement non-intrusive and comfortable for long-term wear.
2Measurement precision
If measurements are performed in laboratory settings over short periods, then controlled conditions are maintained, but the duration and ecological validity are limited
Solution Approach 1:
The wearable device is designed to be self-sufficient for long-term monitoring. It includes integrated power supply (battery), processing unit, and communication capabilities that allow it to autonomously collect, process, and transmit EDA data over extended periods in natural environments, eliminating the need for continuous laboratory supervision or manual intervention.
3Object-affected harmful factors
If optical measurement is used to avoid intrusiveness, then comfort is improved, but interference from hair and noise reduces measurement accuracy
Solution Approach 1:
The patent optimizes specific parameters of the optical system to overcome interference. The light source wavelength is selected in the red to near-infrared range (650-950 nm) where tissue penetration is maximized and hemoglobin absorption is minimized. The distance between light source and sensor is carefully controlled (2-10 mm) to optimize the detection of light scattering changes caused by sweat while minimizing interference from hair and other noise sources.
4Adaptability or versatility
If wavelength range outside 750-950 nm is used, then other physiological information can be obtained, but heart beat interference and noise increase
Solution Approach 1:
The patent applies local quality by selectively evaluating only the infrared portion of the light spectrum (750-950 nm) detected by the broad-spectrum light sensor. The evaluation unit is configured to filter and analyze specifically the wavelength range where sweat-related optical changes occur, while ignoring other wavelength ranges that contain heart beat signals and other physiological noise, thus achieving high precision EDA measurement.
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
The solution provides a reliable and accurate long-term monitoring of electro-dermal activity, reducing noise and interference, and allowing for trend analysis over extended periods in natural environments, enhancing diagnostic capabilities in psychopathology, dermatology, and neurology.
Implementation Method 1
a light source for emitting light including infrared light in the wavelength range between 750 and 950 nm into tissue of the subject, a light sensor for receiving at least part of the emitted light after an interaction of the emitted light with the tissue
Implementation Method 2
emitting light including infrared light in the wavelength range between 750 and 950 nm
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a wearable device for determining electro- dermal activity of a subject (1). The device (10) comprises a light source (11) for emitting light including infrared light in the wavelength range between 750 and 950 nm into tissue of the subject, a light sensor (12) for receiving at least part of the emitted light after an interaction of the emitted light with the tissue, an evaluation unit (13) for determining the electro-dermal activity from the received light, and a support (14) for carrying the light source (11), the light sensor (12) and the evaluation unit (13), wherein the light source and the light sensor are arranged at a predetermined distance from each other.