Flexible Temperature Sensor Structure for Load-Isolated Sensing
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Solution Overview
Problem
Conventional temperature sensors with flexible substrates face challenges in achieving high load bearing capability and accurate temperature detection due to stress and deformation issues when a load is applied, leading to decreased detection accuracy.
Innovation Solution
A temperature sensor design featuring a flexible substrate with a first portion and a second portion of maximum thickness, where the sensor unit is located on the first portion and the detection surface is formed on the second portion, allowing the load to be applied to the second portion and reducing stress on the sensor unit, thereby enhancing load bearing capability and detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load is applied to the sensor unit to achieve sufficient contact with the object, then temperature detection accuracy is improved, but stress and deformation in the thermistor layer cause resistance change and deterioration, decreasing detection accuracy
Solution Approach 1:
The flexible substrate is divided into a sensor unit portion and a load-bearing portion, separating the functions of temperature sensing and load application. The sensor unit includes a thermistor layer on a first flexible substrate, while the load-bearing portion includes a second flexible substrate with different thickness, creating distinct functional zones that prevent stress transmission to the sensor unit.
Solution Approach 2:
The second flexible substrate is designed with different thickness in different regions, with the load-bearing portion having greater thickness than the sensor unit portion. This local variation in thickness creates a stiffness gradient that directs loads away from the sensitive thermistor layer while maintaining overall structural integrity and contact capability.
2Strength
If the flexible substrate thickness is increased to improve load bearing capability, then the sensor can withstand higher loads, but the flexibility and thinness of the sensor are compromised
Solution Approach 1:
The flexible substrate implements local quality variation through different thickness regions: the load-bearing portion has increased thickness for strength, while the sensor unit portion maintains original thickness for flexibility. This localized thickness modification resolves the contradiction by providing both load bearing capability and flexibility in appropriate locations.
Solution Approach 2:
The substrate is segmented into regions with different thickness characteristics, allowing the load-bearing portion to handle mechanical stresses while the sensor unit portion remains thin and flexible for accurate temperature detection, thus satisfying both requirements simultaneously.
3Strength
If the contact region area is increased to improve load bearing capability, then the sensor can distribute loads better, but heat is conducted away from the detection surface through the larger contact area, decreasing temperature detection accuracy
Solution Approach 1:
The contact region is segmented into a detection surface area for heat detection and a load-bearing area for force distribution. The load-bearing portion with increased thickness provides structural support and load distribution without interfering with the thermal detection function of the sensor unit, thus resolving the heat conduction issue.
Solution Approach 2:
Different regions of the substrate have different thermal and mechanical properties: the sensor unit portion maintains thinness for thermal sensitivity, while the load-bearing portion has increased thickness for mechanical strength. This local differentiation allows the contact region to both bear loads and preserve temperature detection accuracy.
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 design effectively eliminates stress in the sensor unit, improving load bearing capability and achieving high temperature detection accuracy while maintaining the flexibility and thinness of the sensor.
Implementation Method 1
a thermistor layer 1 having a negative temperature coefficient
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Provided is a temperature sensor that is excellent in load bearing capability and can obtain high temperature detection accuracy. Disclosed is a temperature sensor including a sensor unit formed on a flexible substrate, the flexible substrate including a first portion which is located at an end portion of the flexible substrate and in which the sensor unit is formed, and a second portion adjacent to the first portion in a distal direction from the end portion and having a maximum thickness between a first surface and a second surface facing each other, a surface of the first portion opposite to the sensor unit and the first surface of the second portion being on the same plane, at least the first surface of the second portion forming a detection surface in contact with an object whose temperature is to be detected, and a total thickness of the first portion and the sensor unit having a thickness smaller than the maximum thickness of the second portion.