Printable NTC Thermistor Sensor for Rapid Body Temperature Tracking
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Solution Overview
Problem
Traditional temperature sensing technologies for wearable devices face challenges in achieving accurate and rapid body temperature measurement due to limited thermal contact area and slow thermal equilibrium establishment, leading to prolonged measurement times and difficulty in continuous monitoring of physiological signals.
Innovation Solution
A temperature sensor utilizing a printable NTC thermistor with a substrate, Si—C film, and electrodes, integrated with a control circuitry and power source, and featuring a thermally insulated frame for rapid thermal equilibrium, along with a constant current driving circuit to maintain optimal operation temperature and prevent moisture penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional electronic temperature sensors (NTC ceramic, PT-100, infrared) are used for wearable body temperature tracking, then the sensor structure is simple and manufacturing is easy, but the thermal contact area is limited and thermal equilibrium takes 10-15 minutes or longer
Solution Approach 1:
The patent transitions from traditional point-contact temperature sensors to a planar flexible film sensor that contacts the skin surface over a two-dimensional area. This dimensional change from point to surface contact dramatically increases the thermal contact area, enabling rapid thermal equilibrium within 1-2 seconds while maintaining wearable form factor.
Solution Approach 2:
The temperature sensor employs a composite structure consisting of a flexible substrate, temperature-sensitive material layer, and protective coating layer. This composite design combines the flexibility needed for wearable application with the thermal sensitivity required for accurate measurement, achieving both rapid response and comfort.
2Speed
If flexible thin films of platinum sensors are used to increase thermal contact area, then the thermal equilibrium speed improves, but the cost increases significantly due to limited area (1 mm-2 mm) and expensive Pt material
Solution Approach 1:
The patent replaces expensive platinum materials with cost-effective alternatives such as NTC ceramic particles or other temperature-sensitive materials embedded in a flexible polymer matrix. This substitution dramatically reduces material cost while maintaining the flexible wearable form factor and rapid thermal response capability.
Solution Approach 2:
The patent changes the material composition parameter from precious metals to affordable ceramic particles or composite materials, while adjusting the film thickness and particle distribution to optimize thermal conductivity and maintain rapid response characteristics without relying on expensive platinum.
3Measurement precision
If the NTC thermistor operates at high current to improve signal strength, then the measurement sensitivity improves, but the operation temperature increases causing degradation of polymer binder crosslinking and film quality
Solution Approach 1:
The patent implements a constant current driving circuit that actively monitors and maintains the operating current within an optimal range. This feedback control prevents excessive current that would raise the operating temperature and degrade the polymer binder, while ensuring sufficient signal strength for accurate temperature measurement.
Solution Approach 2:
The patent optimizes the electrical parameters by using a constant current driving mode instead of constant voltage, carefully selecting the current magnitude to balance signal strength and thermal stability. This parameter optimization ensures the operating temperature remains below the degradation threshold of the polymer binder while maintaining measurement precision.
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
Enables fast and accurate tracking of body temperature, achieving thermal equilibrium in as little as 1-2 seconds with improved moisture resistance and extended operational stability.
Implementation Method 1
an negative temperature coefficient (NTC) thermistor for temperature sensing
Implementation Method 2
the frame element is at least partially thermally insulated to establish thermal equilibrium within the temperature sensor
Implementation Method 3
a Si—C film printed on the substrate
Data Source
AI summary
Provided are wireless temperature sensors. A temperature sensor with a flexible, large-area printed thermistor can include an negative temperature coefficient (NTC) thermistor for temperature sensing, a control circuitry for electrically connecting with the NTC thermistor and obtaining the temperature sensed by the NTC thermistor, a power source for providing power supply to the NTC thermistor and the control circuitry, and a frame element for supporting the NTC thermistor, the control circuitry and the power source, where the frame element is at least partially thermally insulated to establish thermal equilibrium within the temperature sensor. The temperature sensor can sense the temperature in a fast and accurate way due to fast thermal equilibrium established within the sensor.