PPG Sensor Patch Structure for Motion-Tolerant Skin Contact
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Solution Overview
Problem
Existing photoplethysmography (PPG) sensing systems have large spatial profiles and high complexity, making them unsuitable for everyday use and motion-tolerant applications, particularly for subjects with varying skin conditions and physical dimensions.
Innovation Solution
A patch design incorporating a silicon-based adhesive layer, a rigid support structure, and an elastic spacer to maintain constant skin contact and minimize the effects of skin strain and anatomical variations, using a single PPG array to tolerate subject motion and low perfusion sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large sensing units with multiple arrays are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple PPG arrays into a single integrated sensing unit. The single array incorporates both light-emitting elements and light-detecting elements in a unified structure, eliminating the need for separate arrays while maintaining the capability to measure both reflected and transmitted light for accurate PPG signals.
Solution Approach 2:
The single PPG array is designed to perform multiple functions: it can detect both reflected and transmitted light, accommodate different skin types and conditions, and tolerate subject motion. This multi-functional design replaces the need for multiple specialized arrays while maintaining measurement precision across diverse conditions.
2Measurement precision
If large sensing footprints are used, then measurement precision is improved, but area of moving object increases
Solution Approach 1:
The patent concentrates sensing capability into a localized single array structure rather than distributing it across a large footprint. The light-emitting and light-detecting elements are positioned in optimal local configurations within the single array to maximize measurement precision while minimizing the overall area required.
Solution Approach 2:
By merging reflected and transmitted light detection into a single array, the patent achieves comprehensive PPG measurement capability in a compact form factor, reducing the sensing footprint while maintaining or improving measurement precision through integrated optical paths.
3Reliability
If multiple PPG arrays are used, then reliability is improved, but device complexity increases
Solution Approach 1:
The single PPG array is designed with dynamic adaptability to tolerate subject motion. The array can accommodate variations in skin surface geometry, contact pressure, and relative motion between the sensor and skin through its integrated design that captures both reflected and transmitted light, maintaining reliable measurements during movement.
Solution Approach 2:
The single array's multi-functional capability to detect multiple light types and adapt to various skin conditions provides inherent redundancy and reliability without requiring multiple separate arrays. This universal design ensures consistent performance across different physiological conditions and motion states.
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 patch provides low spatial profile, high motion tolerance, and accurate PPG signal capture on diverse skin types and conditions, enabling effective monitoring of biological signals like heart rate variability and oxygen levels.
Implementation Method 1
Photoplethysmography (PPG) generally refers to light-based techniques for detecting volumetric changes in blood. Typically, PPG is performed by directing an input light source at a subject's skin, measuring an amount of light reflected and/or transmitted by the skin
Implementation Method 2
an elastic spacer to maintain constant skin contact and minimize the effects of skin strain and anatomical variations
Data Source
AI summary
The present disclosure relates to devices and processes that produce superior photoplethysmography (PPG) signals. In various embodiments, the present devices and processes leverage load backing, conformal contact, and strain isolation mechanisms to produce higher quality and amplitude PPG signals, and provide more repeatable results than previous devices and processes. In at least one embodiment, the devices discussed herein include a rigid support structure and elastic spacer for supporting a PPG sensor and various adhesive layers.