Negative Poisson's ratio materials for ear plugs and mouth guards

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Solution Overview

Problem

Existing materials for ear plugs, ear muffs, and mouth guards do not effectively attenuate sound or absorb impact energy while maintaining a lightweight design, and there is a need for materials with improved energy absorption and attenuation capabilities.

Innovation Solution

Utilization of negative Poisson's ratio (NPR) materials, such as NPR polymer foams, in conjunction with positive Poisson's ratio (PPR) materials, to create composite structures that absorb and attenuate energy, providing enhanced sound reduction and impact protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional positive Poisson's ratio (PPR) materials are used for ear plugs, ear muffs, and mouth guards, then the objects provide basic protection and durability, but they do not effectively attenuate sound or absorb impact energy and are heavier in weight

Engineering Contradiction:

Improveenergy absorption and attenuation capabilityVSAvoidweight of ear plugs, ear muffs, and mouth guards

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent applies parameter changes by transforming the Poisson's ratio parameter from positive (traditional materials) to negative (NPR materials). This fundamental parameter change enables the material to exhibit auxetic behavior, where compression in one direction causes expansion in perpendicular directions, creating voids that enhance energy absorption and sound attenuation while reducing density and weight.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by combining NPR materials with PPR materials in various configurations. This composite approach allows the object to leverage the superior energy absorption and attenuation properties of NPR materials while incorporating the durability and structural stability of PPR materials, achieving a balance between performance and weight.

Inventive Principle:

Principle #40Composite materials

2Reliability

If NPR materials are used to improve energy absorption and attenuation, then sound and impact protection is enhanced, but the material structure becomes more complex

Engineering Contradiction:

Improvesound attenuation and impact protectionVSAvoidmaterial structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent utilizes porous materials by incorporating NPR materials with cellular or porous structures. These porous structures create voids and air pockets that enhance sound attenuation through acoustic absorption and improve impact energy absorption through cell collapse mechanisms. The porous nature also reduces material density, contributing to weight reduction while maintaining protective functionality.

Inventive Principle:

Principle #31Porous materials

3Reliability

If NPR materials are used for ear plugs and ear muffs, then sound attenuation is improved, but the coefficient of friction with the ear canal increases

Engineering Contradiction:

Improvesound attenuationVSAvoidease of insertion and removal

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies local quality by using different materials for different parts of the ear plug or ear muff. The portion that contacts the ear canal is made of PPR material with lower coefficient of friction to ensure ease of insertion and removal, while the bulk or outer portions use NPR materials to provide superior sound attenuation and impact protection. This spatial differentiation of material properties resolves the contradiction between attenuation performance and ease of operation.

Inventive Principle:

Principle #3Local quality

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

NPR materials offer improved energy absorption and attenuation, resulting in lighter and more effective ear plugs, ear muffs, and mouth guards that reduce sound and impact forces, while maintaining durability and comfort.

Implementation Method 1

NPR materials in ear plugs or ear muffs attenuate sound waves, thereby reducing the magnitude of the sound that reaches the wearer's eardrum

Methodology Applied

Scientific EffectSound wave attenuation: Acoustic Absorption

Implementation Method 2

NPR materials in mouth guards absorb energy from impacts, e.g., from tooth grinding or from impact by an external object, such as a sports ball, thereby helping to protect the wearer's teeth and jaw

Methodology Applied

Scientific EffectImpact energy absorption: Absorption (physical)

Implementation Method 3

NPR materials are durable and capable of attenuating or absorbing energy... NPR materials in ear plugs or ear muffs attenuate sound waves... NPR materials in mouth guards absorb energy from impacts

Methodology Applied

Scientific EffectNegative Poisson's ratio effect: Poisson's Effect

Data Source

PatentUS12533264B2Negative Poisson's ratio materials for ear plugs and mouth guards

Publication Date: 2026.01.27 PARK JOON BU

AI summary

An ear plug includes an elongated body sized and shaped to be partially inserted into an ear canal of a wearer, in which the body includes a negative Poisson's ratio (NPR) polymer foam material having a Poisson's ratio of between 0 and −1. A mouth guard includes an arc-shaped element sized to be received into a mouth of a wearer. The arc-shaped element has an outer wall, an inner wall, and a biting wall connecting the outer wall and the inner wall. The outer wall, the inner wall, and the biting wall define a channel that is sized to receive upper teeth of the wearer or lower teeth of the wearer. The outer wall, the biting wall, or both includes a negative Poisson's ratio (NPR) material having a Poisson's ratio between 0 and −1.