Orientation-Independent Temperature Indicator Using Phase-Change Absorption

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Solution Overview

Problem

Existing temperature indicators, particularly RFID tags, are orientation-dependent and may malfunction when accidentally turned upside down or knocked over during shipping, leading to improper functioning and unreliable temperature exposure detection.

Innovation Solution

A temperature exposure indicator/RFID tag design that includes a first and second electrode with a temperature responsive material composed of an insulating material and conductive particles between them, coupled with an absorbent, where the insulating material changes state to liquid or semi-liquid above a threshold temperature, allowing diffusion into the absorbent and creating a conductive path between electrodes, independent of orientation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing temperature indicators (RFID tags) are used, then temperature detection function is provided, but the device becomes orientation-dependent and may malfunction when turned upside down or knocked over

Engineering Contradiction:

Improvetemperature detection reliabilityVSAvoidorientation independence

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the physical state parameter of the insulating material from solid to liquid/semi-liquid through phase transition at a specific temperature threshold. This parameter change enables the material to flow and be absorbed by the absorbent material, creating a conductive path that triggers the temperature indicator regardless of device orientation, thus resolving the orientation-dependency issue while maintaining reliable temperature detection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes phase transition of the insulating material as the core mechanism. When the temperature exceeds the threshold, the insulating material transitions from solid to liquid or semi-liquid state, allowing it to diffuse into the absorbent material. This phase transition creates an irreversible conductive path between electrodes, providing reliable temperature exposure indication independent of device orientation

Inventive Principle:

Principle #36Phase transitions

2Adaptability or versatility

If the insulating material changes state to liquid or semi-liquid above threshold temperature, then orientation-independent temperature detection is achieved, but the structural integrity of the temperature responsive material changes

Engineering Contradiction:

Improveorientation independenceVSAvoidmaterial state stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent segments the temperature responsive material into two distinct functional components: insulating material that undergoes phase transition and conductive particles that form conductive paths. This segmentation allows the insulating material to change state and be absorbed without compromising the overall structural function, as the conductive particles remain to establish the conductive path when needed, thus achieving orientation independence while managing compositional stability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The absorbent material serves as an intermediary that receives the insulating material after phase transition. This intermediary component facilitates the transformation process by absorbing the liquid/semi-liquid insulating material, thereby managing the compositional change and enabling the conductive particles to form the necessary conductive path for temperature indication regardless of orientation

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

Ensures reliable temperature exposure detection regardless of orientation by changing electrical properties, such as resistance or capacitance, providing irreversible indicators of historical temperature exposure.

Implementation Method 1

the insulating material is configured, in response to exposure to a temperature above a predetermined threshold temperature, to change a state from solid or semi-solid to liquid or semi-liquid

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

at least a portion of the insulating material of the temperature responsive material is absorbed into the absorbent coupled to the temperature responsive material

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 3

allowing diffusion into the absorbent and creating a conductive path between electrodes

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12455198B2Orientation-independent temperature sensor

Publication Date: 2025.10.28 ZEBRA TECHNOLOGIES CORP

AI summary

A temperature exposure indicator includes a substrate, a first electrode and a second electrode on the substrate, the second electrode spaced apart from the first electrode, a temperature responsive material disposed between the first electrode and the second electrode, wherein the temperature responsive material comprises an insulating material and conductive particles, and an absorbent coupled to the temperature responsive material. In response to exposure to a temperature above a predetermined threshold temperature, at least a portion of the insulating material of the temperature responsive material is absorbed into the absorbent coupled to the temperature responsive material, changing an electrical property of the temperature responsive material.