Dual Modality Sensor for Motion Artefact Correction
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Solution Overview
Problem
Biomedical electrodes, especially dry electrodes, suffer from significant signal quality degradation due to mechanical motion artefacts when in contact with human or animal tissue, which is problematic for long-term monitoring and applications requiring user convenience.
Innovation Solution
A dual modality sensor is introduced, comprising a tissue-contact electrode and a mechanical sensor that senses mechanical displacement, allowing for the attenuation or removal of motion artefacts from bioelectrical signals through combined electrical and mechanical signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dry electrodes are used for long-term monitoring, then ease of operation and user convenience are improved, but signal quality deteriorates due to motion artefacts
Solution Approach 1:
The patent combines a dry electrode with a mechanical sensor (accelerometer or displacement sensor) into an integrated assembly. The mechanical sensor detects motion artefacts generated during electrode-skin relative motion, and this information is used to correct the electrical signal, thereby maintaining high signal quality while preserving the ease of use and long-term monitoring capabilities of dry electrodes.
Solution Approach 2:
The mechanical sensor acts as an intermediary that measures the motion artefact between the electrode and skin. By introducing this intermediate measurement, the system can identify and correct the artefact's contribution to the electrical signal, thus preserving signal quality without compromising the dry electrode's operational simplicity.
2Measurement precision
If wet gel electrodes are used for extended monitoring, then signal quality is improved, but reliability deteriorates as the gel dries out
Solution Approach 1:
The patent merges a dry electrode with a mechanical sensor into a single assembly. This combination allows the use of dry electrodes (which do not suffer from gel drying issues) while compensating for their lower signal quality through real-time motion artefact correction using the mechanical sensor's output.
Solution Approach 2:
The integrated dry electrode with mechanical sensor can be designed as a disposable or replaceable unit. Since dry electrodes do not degrade over time like gel electrodes, the entire assembly can be used for extended periods or replaced easily, ensuring continuous reliable monitoring without the gel drying problem.
3Measurement precision
If mechanical sensors are added to reduce motion artefact, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent segments the electrode assembly into distinct functional components: the electrical sensing element (electrode), the mechanical sensing element (accelerometer or displacement sensor), and the signal processing unit. This segmentation allows each component to be optimized independently and simplifies the integration process, making the overall system manageable despite its multi-functional nature.
Solution Approach 2:
The mechanical sensor serves multiple functions: it detects motion artefacts, provides information for signal correction, and can potentially monitor other mechanical parameters. This multi-functionality justifies the added complexity by providing multiple benefits from a single additional component.
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 dual modality sensor effectively reduces noise in bioelectrical signals, enabling high-quality continuous recordings in natural environments and improving signal accuracy by correlating mechanical sensor outputs with electrical signals to de-noise and derive physiological parameters like heart rate variability and breathing rate.
Implementation Method 1
a mechanical sensor overlying the cutaneous electrode and configured to sense a mechanical displacement of the first surface through the electrode
Implementation Method 2
The mechanical sensor may comprise a vibration sensor, a microphone or a piezoelectric transducer
Data Source
AI summary
A dual modality sensor comprises a tissue-contact electrode having a first surface configured for receiving an electrical signal from a user's tissue when attached thereto; and a mechanical sensor overlying the cutaneous electrode and configured to sense a mechanical displacement of the first surface through the electrode. The electrode and the mechanical sensor thereby provide electrical and mechanical signals which originate from precisely the same tissue location.