Self-Prepping Biopotential Sensor with Rigid Tine Array
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Solution Overview
Problem
Existing biopotential electrodes face challenges in achieving low impedance at the skin-electrode interface due to the stratum corneum barrier, leading to noise artifacts and requiring complex skin preparation processes, which are not cost-effective for disposable devices.
Innovation Solution
A self-prepping device with an array of short, rigid, non-conductive tines integrated into the electrodes, which penetrate the stratum corneum to create micro-conduits for conductive gel to reach low impedance layers, reducing skin impedance and improving signal quality, and can be mass-produced using injection molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional skin preparation methods (abrasion, cleaning) are used, then skin impedance is reduced, but the process becomes complex and time-consuming
Solution Approach 1:
The electrode incorporates a textured component with protrusions that pre-penetrate or pre-abrade the stratum corneum layer before the electrode is fully applied. This preliminary action removes the high-impedance barrier in advance, allowing the conductive gel to directly contact low-impedance skin layers, thereby reducing overall skin impedance without requiring separate preparation steps
Solution Approach 2:
The skin preparation function is merged with the electrode structure itself. The textured component with protrusions is integrated into the electrode, combining the preparation mechanism and the sensing element into a single unified device, eliminating the need for separate preparation tools and procedures
2Reliability
If macro-sized tines are used to penetrate stratum corneum, then impedance is reduced, but electrode size cannot be minimized
Solution Approach 1:
The invention changes the scale parameter of the penetrating structures from macro-sized tines to micro-sized protrusions. These micro-protrusions are sufficiently small to allow high-density packing on the electrode surface, enabling the electrode to maintain a compact size while still achieving effective stratum corneum penetration and low impedance through the collective action of numerous micro-structures
Solution Approach 2:
The single penetrating function is segmented into multiple micro-protrusions distributed across the electrode surface. Instead of relying on a few large tines, the electrode employs numerous small protrusions that collectively penetrate the stratum corneum, allowing the electrode to reduce its overall size while maintaining or improving impedance characteristics through increased contact density
3Ease of operation
If long flexile tines are used, then skin is parted, but orientation and insertion angle vary causing non-repeatable signals
Solution Approach 1:
The protrusions are designed with rounded or spherical tips rather than sharp angular points. This curvature allows the micro-protrusions to naturally self-align and penetrate the skin at consistent angles when pressure is applied, reducing variation in insertion orientation and improving the repeatability of the electrical contact and signal acquisition across different users and applications
Solution Approach 2:
The invention changes the flexibility parameter from flexible to rigid for the protrusions. Rigid micro-protrusions maintain their structural integrity and predetermined geometry during application, ensuring consistent penetration depth and angle, which leads to more repeatable impedance values and signal quality compared to flexible tines that can bend and deform
4Measurement precision
If rigid tines are used, then orientation control is improved, but manufacturing complexity increases
Solution Approach 1:
The invention changes the size parameter of the rigid structures from macro to micro scale. Micro-protrusions can be manufactured using standard injection molding techniques with molds that define their rigid geometry. The small scale allows these rigid structures to be integrated into disposable electrodes without requiring complex assembly processes, as they can be formed as a single molded piece with the electrode substrate
Solution Approach 2:
The rigid textured component is designed as a disposable element integrated into single-use electrodes. This approach eliminates the need for complex cleaning, sterilization, or reconfiguration processes that would be required for reusable rigid tine structures. The rigid micro-protrusions are molded directly into the disposable electrode, simplifying manufacturing while maintaining precise orientation control
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 device achieves repeatable bioelectrical signals with impedance less than 20 kΩ, enhancing signal quality and allowing for cost-effective, disposable biopotential sensors with simplified skin preparation and reduced manufacturing complexity.
Implementation Method 1
an array of short, rigid, non-conductive tines integrated into the electrodes, which penetrate the stratum corneum to create micro-conduits
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
The skin preparation device and sensor of the present invention include an array of rigid tines. The tines serve to "self-prepare" the skin at each electrode site. These tines, when pressed against the skin, penetrate the stratum corneum, thereby reducing skin impedance and improving signal quality. A self-prepping device of the present invention is an optimized array of short non-conductive rigid tines in which the individual tines are created in a geometry that allows for a sharp point at the tip when molding, machining or etching is used as a method of fabrication. This non- conductive array with rigid penetrating structures may, therefore, be used in combination with a conductive medium, preferably an ionic conductive gel. In penetrating the stratum corneum, micro-conduits are created in the layers of the skin enabling the conductive medium to reach the low impedance layers and to transmit bioelectrical signals from the skin to the electrode surface. Such a self-prepping device can be readily mass produced using molding methods or possibly other manufacturing methods, thereby providing for a low cost means of achieving improved performance of the biopotential sensor. Additionally this invention includes the integration of this self-prepping device into a biopotential sensor comprising an array of one or more electrodes.