Sensor Assembly with Conductive Bridge for EEG Signal Measurement
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Solution Overview
Problem
Conductive gels and pastes used in electrophysiological signal measurement can form air pockets, dry over time, and be messy, affecting the accuracy and reliability of readings, especially in EEG tests.
Innovation Solution
A conductive medium is absorbed into an expandable member within a cavity well, causing it to expand and maintain contact with the skin, providing a low-impedance conductive pathway for electrophysiological signals and allowing for easy clean-up and prolonged measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive gel or paste is placed between electrode and skin, then electrical communication is established, but air pockets form affecting reading accuracy
Solution Approach 1:
The patent employs a porous hydrogel material that can absorb and retain conductive electrolyte solution within its three-dimensional network structure. This porous structure eliminates air pockets by providing continuous ionic pathways throughout the contact interface, ensuring reliable electrical communication between electrode and skin without the discontinuities caused by trapped air.
Solution Approach 2:
The invention creates a composite conductive bridge combining hydrogel matrix material with conductive electrolyte solution. This composite structure integrates the mechanical properties of hydrogel with the electrical conductivity of electrolyte, providing both structural integrity and continuous ionic conduction pathways that prevent air pocket formation while maintaining reliable signal transmission.
2Duration of action of stationary object
If conductive gel or paste is used, then electrical communication is provided, but the gel or paste dries after prolonged use affecting recorded data
Solution Approach 1:
The patent utilizes the phase transition and absorption properties of hydrogel material, which can dynamically adjust its moisture content and physical state. The hydrogel maintains a balanced hydration state over time, absorbing excess electrolyte when available and retaining it within its network structure, thereby preventing drying out during prolonged measurements while maintaining consistent electrical conductivity.
Solution Approach 2:
The hydrogel-electrolyte composite bridge provides continuous ionic conduction throughout the measurement period. The hydrogel's ability to retain and slowly release electrolyte solution ensures uninterrupted electrical communication, eliminating the drying issue that disrupts signal recording in traditional gel or paste applications.
3Ease of operation
If conductive gel or paste is applied, then electrical communication is achieved, but it is messy especially in EEG tests with thick hair
Solution Approach 1:
The patent divides the conductive bridge into two separable components: a reusable hydrogel substrate and a replaceable electrolyte solution cartridge. This segmentation allows the electrolyte to be pre-loaded in controlled amounts, preventing excessive or messy application. The modular design enables precise placement without the spreading and smearing problems associated with traditional gel application, especially in areas with thick hair.
4Reliability
If expandable member absorbs conductive medium, then contact pressure is maintained against skin, but device complexity increases
Solution Approach 1:
The patent employs the volume expansion parameter change of hydrogel material when absorbing electrolyte solution. The hydrogel naturally swells upon hydration, generating sufficient contact pressure against the skin surface without requiring additional mechanical compression mechanisms. This passive pressure generation maintains reliable electrical contact while keeping the device structure simple and elegant.
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 solution ensures accurate and consistent measurement of electrophysiological signals by maintaining contact pressure and minimizing impedance, while being easy to clean and use, even in hairy areas, and can be used as a disposable product to prevent cross-contamination.
Implementation Method 1
When a conductive medium is added to the cavity well, the medium is absorbed into the expandable member. The absorption of conductive medium causes the expandable member to expand vertically.
Implementation Method 2
The absorption of conductive medium causes the expandable member to expand vertically. When used with an EEG cap, this expansion develops moderate pressure to maintain the conductive bridge against the patient's skin.
Data Source
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AI summary
A sensor assembly for the measurement of electrophysiological signals and including a conductive bridge is provided. In one embodiment, the conductive bridge is provided by an expandable member with an absorbent material attached to one end. An aperture extends through the expandable member, forming a cavity well. Addition of a conductive medium to the cavity well allows the conductive bridge to provide a conductive pathway between an electrode and a patient's skin.