On-Body Sensor Unit Integrating ECG and PPG via Light-Absorbing Electrode
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Solution Overview
Problem
Existing on-body sensor devices that combine ECG and PPG modalities are large and cumbersome, leading to discomfort and reduced device lifetime due to increased skin contact area, which affects sensor accuracy and adherence.
Innovation Solution
A body-mountable sensor unit with a skin-contact surface that integrates a PPG sensor and an ECG sensor, where a light-absorbing surface element between the light source and optical detector prevents direct light penetration, allowing the ECG electrode to be absorptive of the spectral composition, thereby reducing the total skin-contact surface area without compromising accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the device combines ECG and PPG modalities in a single on-body unit, then functional versatility is improved, but device size and surface area increase making it large and cumbersome
Solution Approach 1:
The patent merges the ECG electrode and PPG light-blocking structure into a single integrated surface element. The electrode serves dual purposes: as an electrical contact for ECG sensing and as a light-absorbing element for PPG optical isolation. This combining of functions reduces the overall device surface area while maintaining both ECG and PPG modalities.
Solution Approach 2:
The surface element is designed with multi-functionality, serving simultaneously as an ECG electrode for electrical signal acquisition and as a light-blocking structure for PPG optical isolation. This universal design allows a single component to fulfill multiple roles, thereby reducing the total number of components and device surface area.
2Measurement precision
If the device increases skin contact area to improve sensor accuracy, then measurement precision is improved, but device comfort and adherence deteriorate
Solution Approach 1:
By merging the ECG electrode and PPG light-blocking function into a single surface element, the patent reduces the total skin contact area required while maintaining both sensing modalities. This integration allows the device to achieve adequate measurement precision with a smaller surface area, thereby improving comfort and adherence.
3Ease of operation
If the device reduces skin contact area to improve comfort and adherence, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The integration of ECG electrode and PPG light-blocking function into a single surface element allows the device to maintain both sensing modalities with reduced skin contact area. This merging enables the device to improve comfort and adherence while preserving measurement precision through efficient space utilization.
Solution Approach 2:
The patent utilizes the vertical dimension by positioning the PPG light source, detector, and light-blocking electrode in a layered configuration. This three-dimensional arrangement allows multiple functions to be packed into a smaller footprint, maintaining sensing accuracy while reducing the lateral skin contact area.
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 enables a more comfortable and less cumbersome device with improved sensor accuracy and adherence, maintaining reliability for physiological parameter monitoring by efficiently sharing surface regions for multiple functions.
Implementation Method 1
a light-absorbing surface element between the light source and optical detector prevents direct light penetration
Implementation Method 2
Photoplethysmography (PPG) is an optical measurement technique that evaluates a time-variant change of light reflectance or transmission of an area or volume of interest. PPG is based on the principle that blood absorbs light more than surrounding tissue
Implementation Method 3
The electrodes detect small electrical changes in underlying conductive tissue of the skin which arise due to the heart muscle's electrophysiological pattern of depolarizing and repolarizing during each heartbeat
Data Source
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Figure 3~4
AI summary
An on-body sensor unit (12) comprises a PPG sensor and an ECG sensor, each having sensor parts exposed at a skin-contacting surface (16) of the unit. The PPG includes an optical detector (22) and at least one light source (20a, 20b). Disposed between the at least one light source and the optical detector is a light-intercepting surface element (28), adapted to be absorptive of light of at least a majority of a spectral composition which is generated by the at least one PPG light source (20a, 20b). Located within, or forming, this surface element is an electrode (32a, 32b) comprised by the ECG sensor, said electrode having at least an exposed skin-interfacing surface which is absorptive of a majority of the spectral composition of said light generated by the at least one light source.