Capacitive Motion-Gated Biophysical Sensing for Artifact-Free Wearables
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Solution Overview
Problem
Conventional biophysical sensors, such as those measuring arterial pressure waveforms, are adversely affected by subject movement, leading to motion artifacts and reduced fidelity due to the need for signal filtering to remove these artifacts.
Innovation Solution
Implementing a biophysical sensor system that includes both a feature sensor and a capacitive sensor, where the capacitive sensor detects movement and switches the biophysical sensor between a sense mode for stable readings and a sleep mode when movement is detected, thereby avoiding motion artifacts and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal filtering is applied to remove motion artifacts, then measurement reliability is improved, but measurement precision deteriorates due to loss of important morphology
Solution Approach 1:
The system performs preliminary motion detection using capacitance sensors before acquiring biophysical measurements. By detecting motion in advance and preventing measurement acquisition during motion periods, the system avoids capturing motion artifacts altogether, eliminating the need for post-acquisition filtering that would compromise signal morphology.
2Measurement precision
If continuous sensing is performed to capture all measurements, then measurement completeness is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous sensing, the system implements periodic measurement acquisition gated by motion detection events. The biophysical sensor operates in discrete sensing intervals only when the capacitance sensors confirm the subject is motionless, creating a periodic sampling pattern that ensures measurement completeness while dramatically reducing energy consumption during extended wear.
3Ease of operation
If motion artifacts are allowed in measurements, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The system employs self-service motion monitoring where capacitance sensors continuously monitor subject motion and automatically control the gating of biophysical measurement acquisition. This self-regulating mechanism allows the device to maintain high measurement precision without requiring active user intervention to remain still, as the system autonomously adapts to the subject's natural movement patterns.
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 approach provides more accurate biophysical readings by eliminating motion artifacts and conserving power, allowing the sensor to operate effectively even when the subject is moving, and enabling wearable devices with extended battery life.
Implementation Method 1
senses motion of the body with a capacitance sensor
Data Source
AI summary
A method can include attaching a sensor device contained in a sensor structure to a body; sensing motion of the body with at least one motion capacitive sensor of the sensor device that senses a capacitance change resulting from a difference in orientation of the motion capacitive sensor and a surface of the body. If motion of the body is not sensed with the motion capacitive sensor, sensor readings can be acquired with a biophysical sensor that emits signals into a portion of the body below the sensor structure, and generate data for a feature of the body with the sensor readings. If motion of the body is not sensed with the motion capacitive sensor, data for the feature of the body is not generated. Related devices and systems are also disclosed.