Wearable PPG Sensor with Multi-Wavelength Light and Skin Prep
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Solution Overview
Problem
Wearable healthcare devices face challenges in accurately detecting pulse signals due to light scattering issues at the wrist, limiting their ability to provide high-quality biometric data, and existing solutions like fingertip oximeters are inconvenient for continuous or frequent use.
Innovation Solution
A wearable device with infra-red, green, and red light emitters and sensors on the side, capable of transmitting PPG signal data to a server for processing using machine-learned correlations, enabling the inference of biometric statistics such as health, mood, sleep quality, and stress without the need for invasive procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PPG sensors are positioned on the wrist for continuous monitoring, then ease of operation is improved, but measurement precision deteriorates due to light scattering from bones and inadequate skin-sensor seal
Solution Approach 1:
The patent introduces a skin prep solution as an intermediary substance applied between the sensor and skin to enhance the skin-sensor seal. This mediator improves light transmission quality and reduces scattering, allowing the sensor to achieve both wrist placement convenience and accurate PPG measurements.
Solution Approach 2:
The patent modifies the optical parameters of the sensing system by using multiple wavelengths (red, green, infrared LEDs) and adjusting LED intensity and pulse duration. These parameter changes enable the system to compensate for light scattering effects and maintain measurement precision at the wrist location.
2Measurement precision
If traditional fingertip oximeters are used for accurate PPG detection, then measurement precision is improved, but ease of operation deteriorates due to need for frequent re-attachment and restricted movement
Solution Approach 1:
The patent merges the accurate fingertip PPG sensing capability with a wearable watch format by positioning sensors on the wrist. This combination allows users to enjoy both measurement precision and continuous monitoring convenience without the need for frequent re-attachment or movement restrictions.
Solution Approach 2:
The patent transitions the sensing location from the fingertip (one-dimensional contact point) to the wrist surface (two-dimensional area with multiple sensor positions). This dimensional change enables continuous monitoring while maintaining accuracy through optimized sensor placement and skin preparation.
3Measurement precision
If high frequency wavelength light is used for pulse signal detection at the wrist, then measurement precision may be improved, but reliability deteriorates due to weak DC and AC signals and high signal-to-noise ratio
Solution Approach 1:
The patent employs a multi-wavelength LED system where red, green, and infrared LEDs work together to provide both high-frequency signal detection and robust signal quality assessment. This universal sensing approach enables accurate pulse detection while maintaining reliability through redundant optical measurements.
Solution Approach 2:
The patent implements feedback mechanisms where the system continuously monitors signal quality metrics and adjusts measurement parameters accordingly. When signal-to-noise ratio becomes too high or signals become weak, the system can re-configure LED intensity, pulse duration, or wavelength combinations to restore reliable measurements.
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 device provides continuous, high-quality biometric data, including heart rate, respiratory rate, and blood oxygen levels, while allowing for convenient, continuous monitoring without restricting user movement, enhancing personal health management.
Implementation Method 1
Light Emitting Diodes (LEDs) and Photodiodes (PDs) are typically positioned on the wrist where a relatively high presence of bones and low levels of capillaries and veins, and an inadequate skin-sensor seal, cause poor reflection of the various wavelengths of light used in pulse signal detection
Implementation Method 2
The reflected light is used to accurately detect the pulse wave, create the PPG signal from which the RR-interval (the interval between two successive heartbeats) and other important parameters can be deduced
Implementation Method 3
One of the challenges when using photoplethysmogram (PPG) technology in smartwatches and other wearable devices is pulse signal detection difficulty because of scattering of reflected light due to the device location
Data Source
AI summary
A wearable personal healthcare device for measuring personal health is provided that is configured to detect a photoplethysmograph (PPG) wave generated by infra-red, green, or red lights emitted from the device, the personal healthcare device. The device includes an outward facing face, a lateral side, and a bottom side, wherein the bottom side faces a user's skin, a plurality of electrical contact sensors, wherein a first of the plurality of sensors is located on one of the top face, lateral side, and bottom side, and a second of the plurality of sensors is located on one of the top face and lateral side of the personal health care device. The first and second sensors are configured to complete a circuit therebetween when a user contacts the first sensor with a first surface of the user's skin and contacts the second sensor with the first or a second surface of the user's skin. The device further includes a network communication module configured to transmit the detected PPG wave to a server, wherein the server processes the PPG wave and infers therefrom biometric data based on machine learned correlations generated from a training set of PPG waves and biometric data, a processor configured to generate the biometric data, and an interface screen comprising the biometric data.