Stretchable Microneedle Adhesive Patches for Stable EP Signals
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Solution Overview
Problem
Existing wearable electrophysiological (EP) signal sensors face challenges in maintaining high-quality signal acquisition over long periods due to skin condition variations, moisture evaporation, and mechanical mismatch with skin tissue, leading to signal degradation and discomfort.
Innovation Solution
A stretchable microneedle adhesive patch (SNAP) with a conductive adhesive layer and serpentine interconnects that penetrate the stratum corneum, providing direct epidermal contact, low impedance, and adhesion, while accommodating skin deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a thin-film epidermal electronics electrode is used to maintain conformal contact along skin curves, then long-term wearability is greatly improved, but signal quality becomes significantly different depending on skin condition and van der Waals force attachment makes signal acquisition difficult during intense exercise or sweating
Solution Approach 1:
The patent introduces a microneedle array as an intermediary element that penetrates the stratum corneum to directly contact the epidermal layer, bridging the gap between the electrode substrate and skin tissue. This intermediary penetration mechanism ensures stable electrical contact regardless of skin conditions, sweat, or movement, resolving the reliability issue while maintaining long-term wearability
Solution Approach 2:
The patent changes the attachment mechanism from surface-level van der Waals force to deep-tissue penetration through microneedles. By altering the interaction depth and mechanism, the system achieves consistent signal quality across different skin conditions, exercise intensities, and environmental factors while preserving conformal contact for long-term wear
2Measurement precision
If a flexible microneedle electrode is developed to improve signal quality by penetrating the stratum corneum, then signal quality is improved, but due to large difference in modulus between electrode substrate and skin tissue and lack of appropriate elasticity and adhesiveness, it is not suitable for comfortable long-term wearing
Solution Approach 1:
The patent applies parameter changes by adjusting the elastic modulus of the electrode substrate to match skin tissue properties. The substrate is designed with an elastic modulus of 1-100 kPa, closely matching skin tissue characteristics, which enables comfortable long-term wearing while maintaining the microneedle penetration capability for high-quality signal acquisition
Solution Approach 2:
The patent employs composite materials combining a soft elastic substrate (1-100 kPa) with conductive microneedle arrays. This composite structure integrates the mechanical compliance needed for comfortable wear with the electrical conductivity required for high-quality EP signal measurement, resolving the contradiction between signal quality and wearability
3Measurement precision
If wet electrodes are used to obtain appropriate signal quality, then signal quality is maintained, but due to evaporation of moisture in gel during long-term use, signal quality degrades
Solution Approach 1:
The patent extracts and eliminates the gel moisture component from the electrode system entirely. By using a dry electrode architecture with microneedle penetration, the system removes the source of evaporation-related degradation, enabling long-term signal stability without relying on moisture-retaining gels
Solution Approach 2:
The patent replaces the moisture-based electrical interface (wet electrode with gel) with a mechanical penetration-based interface (microneedle array). This substitution eliminates the evaporation problem by transitioning from a fluid-based to a solid-contact electrical interface, maintaining signal quality over extended periods
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
Enables high-quality EP signal measurement without skin preparation, maintaining stability and comfort during prolonged use, reducing skin contact impedance, and minimizing motion artifacts.
Implementation Method 1
a microneedle sensor including a microneedle array configured to penetrate the stratum corneum by passing through the ECA layer and to directly contact the skin epidermis of the user
Implementation Method 2
The ECA layer may be configured to enhance an electrical interface between the microneedle sensor and the user skin by providing an additional electrical conductive path to the user's skin around the microneedle sensor and by lowering skin contact impedance between the microneedle sensor and the user's skin
Implementation Method 3
conductive wire-based stretchable interconnects having a serpentine structure that is electrically and mechanically connected to the microneedle sensor to dynamically adapt to skin deformation of the user
Data Source
AI summary
Disclosed are a stretchable microneedle adhesive patch (SNAP) capable of performing high-quality electrophysiological (EP) signal measurement without skin preparation, such as exfoliating the skin or removing sweat, a SNAP system, and an operating method thereof. The disclosed SNAP capable of performing skin preparation-free high-quality EP signal measurement includes an electrically conductive adhesive (ECA) layer configured to attach to a user's skin to obtain an EP signal regardless of the user's skin condition; a microneedle sensor including a microneedle array configured to penetrate the stratum corneum by passing through the ECA layer and to directly contact the skin epidermis of the user; and conductive wire-based stretchable interconnects having a serpentine structure that is electrically and mechanically connected to the microneedle sensor to dynamically adapt to skin deformation of the user.