Printed NTC Temperature Sensor Using Segmented Micro-Particles
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Solution Overview
Problem
Current high reliability thermistors require high temperature processing, making them unsuitable for printing on common industrial and printed electronics substrates like plastics, rubbers, and composites, which affects their thermo-electrical properties.
Innovation Solution
A printable temperature sensor is developed by mixing semi-conducting micro-particles with negative temperature coefficient behavior in a dielectric matrix, allowing for low-temperature processing and retention of thermo-electric properties, enabling application on flexible substrates without the need for sintering or melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic NTC materials are used for high reliability thermistors, then thermo-electrical properties are improved, but processing temperature requirement increases to more than thousand degrees Celsius
Solution Approach 1:
The ceramic NTC material is divided into discrete micro-particles (1-50 micrometers in size) that are suspended in a dielectric matrix. This segmentation allows the material to be processed at low temperatures through printing techniques while maintaining the NTC properties of the individual ceramic particles.
Solution Approach 2:
The invention creates a composite material system combining ceramic NTC micro-particles with a polymeric dielectric matrix. This composite approach enables low-temperature processing compatible with flexible substrates while preserving the thermo-electrical properties through the NTC particle network.
2Reliability
If high temperature sintering is used for ceramic NTC materials, then material density and conductivity are improved, but substrate compatibility decreases for common industrial substrates
Solution Approach 1:
By segmenting the ceramic material into micro-particles, the invention eliminates the need for high-temperature sintering to achieve density. The particles can be densely packed in the dielectric matrix through printing, achieving good conductivity without substrate-damaging high temperatures.
Solution Approach 2:
The invention changes the processing parameters from high-temperature sintering (>1000°C) to low-temperature printing and curing (compatible with PEN, PET, FR4, polyimide substrates). This parameter change enables substrate compatibility while maintaining NTC functionality through proper particle concentration and network formation.
3Area of stationary object
If NTC material is printed as a continuous film, then coverage is improved, but particle merging requires high temperature processing
Solution Approach 1:
The sensor material is printed as a continuous film containing discrete NTC micro-particles. The particles remain individual rather than merging, forming conductive pathways through their network arrangement in the dielectric matrix without requiring high-temperature processing.
Solution Approach 2:
The dielectric matrix acts as an intermediary that binds the NTC micro-particles together in a continuous film structure. This matrix enables low-temperature processing while maintaining particle separation and network formation for conductivity.
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 solution provides a reliable printable temperature sensor with retained thermo-electric properties, suitable for conventional substrates, allowing for flexible and stretchable applications while maintaining conductivity and stability.
Implementation Method 1
The micro-particles comprise of a material with a strong NTC behavior
Implementation Method 2
The micro-particles are mixed in a dielectric matrix which is non-conducting
Implementation Method 3
The dielectric matrix is mixed with a solvent that is evaporated after application of the material at low temperatures
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3B
AI summary
A printed temperature sensor (10) comprising a substrate (1) with an electrical circuit (2) comprising a pair of electrodes (2a, 2b) separated by an electrode gap (G). A sensor material (3) is disposed between the electrodes (2a, 2b) to fill the electrode gap (G), wherein the sensor material (3) comprises semi-conducting micro-particles (3p) comprising an NTC material with a negative temperature coefficient (NTC), wherein the micro-particles(3p) are mixed in a dielectric matrix (3m) functioning as a binder for printing the sensor material (3); wherein the micro-particles (3p) contact each other to form an interconnected network through the dielectric matrix (3m), wherein the interconnected network of micro-particles (3p) acts as a conductive pathway with negative temperature coefficient between the electrodes (2a, 2b).