Proximity Sensor Circuits for Non-Contact Hemodynamic Monitoring
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Solution Overview
Problem
Current proximity sensors face challenges in accurately monitoring hemodynamic changes, such as pulse-waveforms, due to limitations in sensitivity and interference from environmental noise, motion artifacts, and the need for direct skin contact.
Innovation Solution
A proximity sensor design featuring a free floating foil construction with dielectric and conductive layers, along with a foam layer for improved conformality, allows for non-invasive monitoring of capacitance changes near the skin, using a single electrode or array of electrodes with differential sensing to minimize noise and enhance signal fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct skin contact is used for sensing, then signal strength is improved, but comfort and hygiene are worsened
Solution Approach 1:
The patent introduces an intermediary capacitive sensing system that detects hemodynamic changes through the skin without direct contact. The sensor uses capacitive coupling to measure impedance changes caused by blood flow, allowing the sensing surface to remain non-contacting while still capturing physiological signals. This mediator approach enables signal detection through the skin barrier without breaking it.
2Measurement precision
If sensor sensitivity is increased to detect hemodynamic changes, then measurement precision is improved, but susceptibility to environmental noise and motion artifacts is worsened
Solution Approach 1:
The patent segments the sensing function into multiple independent capacitive sensors arranged in differential pairs. Each sensor measures local impedance changes, and the differential configuration subtracts common-mode noise signals. This segmentation allows the system to maintain high sensitivity to physiological changes while rejecting environmental interference and motion artifacts that affect all sensors equally.
Solution Approach 2:
The patent implements feedback mechanisms where the sensor system continuously monitors impedance changes and adjusts its measurement parameters to compensate for environmental conditions. The differential sensing configuration provides inherent feedback by comparing signals from adjacent sensors, allowing the system to distinguish between physiological changes and external disturbances.
3Measurement precision
If a complex multi-layer structure is used to improve sensing accuracy, then measurement precision is improved, but device complexity is worsened
Solution Approach 1:
The patent employs thin-film capacitor structures with flexible dielectric layers that can be deposited directly onto flexible substrates. This approach achieves the required sensing accuracy through controlled thin-film capacitance variations rather than complex bulk structures. The thin-film approach reduces material usage and structural complexity while maintaining the necessary electrical properties for accurate hemodynamic detection.
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
This design enables real-time, non-invasive monitoring of hemodynamic parameters like blood pressure and heart rate with reduced environmental interference and improved sensitivity, allowing for accurate pulse-waveform detection without direct skin contact.
Implementation Method 1
The sensor circuit is configured to monitor a capacitance signal between the at least one electrode and the skin of a user
Implementation Method 2
The first dielectric layer comprises an inner surface and an outer surface. The electrically conductive layer is positioned proximate to one of the inner surface or the outer surface of the first dielectric layer
Data Source
AI summary
Disclosed are one or more proximity sensors. At least one of the proximity sensors includes a first dielectric layer, an electrically conductive layer, and an electrode. The first dielectric layer includes an inner surface and an outer surface. The electrically conductive layer is positioned proximate to one of the inner surface or the outer surface of the first dielectric layer. The electrode includes an outer surface. The outer surface of the electrode is positioned proximate the inner surface of the first dielectric layer. The outer surface of the electrode and the electrically conductive layer define a gap.