Closed-Pore Silicone Composite for Stretchable Humidity Sensors

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Solution Overview

Problem

Existing humidity-sensitive sensors lack stretchability, which is essential for wearable applications, and they do not maintain stable humidity measurement when subjected to stretching.

Innovation Solution

A humidity-sensitive composite material is developed with deliquescent inorganic compounds in closed pores within a porous silicone resin base, allowing for stretchability and stable humidity measurement by detecting changes in dielectric constant.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a humidity-sensitive sensor uses a rigid structure to maintain measurement stability, then measurement precision is improved, but stretchability deteriorates

Engineering Contradiction:

Improvehumidity measurement stabilityVSAvoidstretchability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent employs a flexible polymer matrix as the base material for the humidity-sensitive sensor. This polymer matrix can be stretched and deformed without breaking, enabling the sensor to conform to wearable surfaces and follow human movements. The flexible structure maintains measurement stability through the embedded humidity-sensitive particles that detect humidity changes regardless of the matrix deformation.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The sensor is constructed as a composite material system combining a flexible polymer matrix with humidity-sensitive particles (such as metal halides or porous materials). This composite structure integrates the stretchability of the polymer with the humidity-detecting capability of the particles, resolving the contradiction between mechanical flexibility and measurement precision.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If a humidity-sensitive sensor is made stretchable for wearable applications, then adaptability is improved, but measurement precision deteriorates

Engineering Contradiction:

ImprovestretchabilityVSAvoidhumidity measurement stability

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The composite structure of flexible polymer matrix combined with humidity-sensitive particles allows the sensor to maintain its humidity-detecting function even when stretched. The particles are dispersed throughout the matrix and maintain their sensing capability independent of the matrix deformation, ensuring measurement precision is preserved despite stretchability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The sensor is designed with discrete humidity-sensitive particles distributed within the continuous polymer matrix. This segmentation allows the particles to independently perform humidity detection while the matrix provides overall flexibility and structural integrity, enabling the sensor to maintain precision during stretching through the collective response of multiple particles.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If deliquescent substance is used for humidity detection, then sensitivity to humidity change is improved, but reliability deteriorates due to liquid leakage

Engineering Contradiction:

Improvehumidity sensitivityVSAvoidresistance against liquid leakage

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The flexible polymer matrix acts as a containment structure that holds the deliquescent particles. When the particles absorb moisture and deliquesce, the polymer matrix prevents the resulting liquid from leaking out, maintaining reliability while allowing the particles to retain their high humidity sensitivity through the deliquescent process.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The polymer matrix serves as an intermediary between the deliquescent particles and the external environment. It allows the particles to undergo deliquescent transformation in response to humidity changes while simultaneously preventing liquid leakage, thus mediating between the sensitivity requirement (allowing deliquescence) and reliability requirement (preventing leakage).

Inventive Principle:

Principle #24Intermediary (Mediator)

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 composite material enables stable humidity measurement even with flexibility and stretchability, suitable for wearable devices by preventing deliquescent liquid leakage and maintaining electrical integrity.

Implementation Method 1

containing a deliquescent inorganic compound in closed pores inside a base material made of a porous silicone resin

Methodology Applied

Scientific EffectDeliquescence: Deliquescence

Implementation Method 2

a base material made of a porous silicone resin

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS12416594B2Humidity-sensitive composite material and humidity sensor

Publication Date: 2025.09.16 NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE & TECHNOLOGY

AI summary

Provided are a stretchable humidity-sensitive composite material for a humidity sensor that can be applied to clothing as wearable device, and the humidity sensor. The humidity-sensitive composite material is characterized by containing a deliquescent inorganic compound in closed pores inside a base material made of a porous silicone resin. The humidity sensor is characterized in that a bulk made of a humidity-sensitive composite material containing a deliquescent inorganic compound in closed pores inside a base material made of a porous silicone resin is sandwiched between a pair of counter electrodes made of a moisture-permeable material.