Conductive Pressure-Sensitive Adhesive for Skin Sensors

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Solution Overview

Problem

There is a need for electrically conductive pressure-sensitive adhesives that provide long-term adhesion on both uneven, low-energy surfaces like skin and flat, high-energy surfaces such as metals, without leaving residue and causing skin irritation, while also ensuring flexibility and breathability.

Innovation Solution

A pressure-sensitive adhesive with a polymer network comprising a copolymer containing 70-98.5% non-polar monomers and 1.5-30% polar monomers, incorporating electrically conductive particles, particularly carbon-based microplatelets, which optimizes breathability and adhesion without using ionic liquids, ensuring biocompatibility and sufficient electrical conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ionic liquids are added to ensure electrical conductivity, then electrical conductivity is improved, but long-term adhesion and skin compatibility deteriorate

Engineering Contradiction:

Improveelectrical conductivityVSAvoidskin irritation and adhesion loss

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes ionic liquids from the adhesive formulation entirely and replaces them with electrically conductive particles (silver, aluminum, or carbon particles) dispersed in a biocompatible polymer matrix. This extraction of the harmful substance while maintaining the desired electrical conductivity function resolves the contradiction between conductivity and skin compatibility.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses inert, biocompatible polymer matrices (such as polyurethane, acrylic, or silicone-based adhesives) that provide a stable, non-irritating base. These polymers serve as a safe carrier for conductive particles, ensuring long-term skin compatibility while maintaining adhesive performance without the harmful effects of ionic liquids.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Object-affected harmful factors

If the adhesive is made highly breathable, then moisture vapor transmission is improved, but moisture accumulates in the adhesive reducing long-term adhesion

Engineering Contradiction:

Improvemoisture accumulationVSAvoidlong-term adhesion

Core Design Contradiction:

Object-affected harmful factorsVSDuration of action of stationary object

Solution Approach 1:

The patent optimizes the breathability parameter of the adhesive to achieve a balanced state. By carefully selecting polymer composition and controlling adhesive formulation, the adhesive provides sufficient moisture vapor transmission to prevent skin irritation while limiting moisture accumulation that would compromise long-term adhesion. This parameter optimization resolves the contradiction between breathability and adhesion durability.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the adhesive provides strong adhesion to skin, then skin adhesion is improved, but removal may leave residue or cause irritation

Engineering Contradiction:

Improveskin adhesionVSAvoidresidue and skin irritation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent carefully adjusts the adhesive strength parameters by selecting appropriate polymer types and formulations. The adhesive is designed to provide sufficient bond strength for sensor attachment while maintaining ease of removal without residue or irritation. This parameter optimization within the adhesive composition resolves the contradiction between adhesion strength and safe removal.

Inventive Principle:

Principle #35Parameter changes

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 solution provides improved long-term adhesion and flexibility, ensuring the adhesive can be removed without residue and does not cause skin irritation, while maintaining sufficient electrical conductivity for various applications, including skin and metal surfaces.

Implementation Method 1

Carefully adjusting the polarity of the copolymer can advantageously optimize the breathability of the pressure-sensitive adhesive. Insufficient breathability leads to an accumulation of moisture between the pressure-sensitive adhesive and a surface to which the pressure-sensitive adhesive is applied

Methodology Applied

Scientific EffectBreathability: Permeation

Implementation Method 2

The pressure-sensitive adhesive contains at least one type of electrically conductive particles... the pressure-sensitive adhesive preferably has an impedance of no more than 50 Ω at 10 Hz at 25°C

Methodology Applied

Scientific EffectElectrical conductivity: Conduction (electrical)

Data Source

PatentEP4428185A1Pressure-sensitive adhesive, pressure-sensitive adhesive layer and pressure-sensitive tape

Publication Date: 2024.09.11 LOHMANN GMBH & CO KG

Figure 1

AI summary

The invention relates to an adhesive, particularly for skin applications, comprising a polymer network containing at least one copolymer and at least one type of electrically conductive particles. To improve long-term adhesion and efficiency, it is proposed that the copolymer contain 70 to 98.5 wt.% of nonpolar monomers and 1.5 to 30 wt.% of polar monomers.