Thermometric Hydrogel Flexible Thermal Sensors
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Solution Overview
Problem
Conventional temperature sensors, such as thermocouples and resistance thermometers, are typically made of rigid electronic materials, which limit their flexibility, sensitivity, and fabrication cost, posing challenges for applications requiring flexible and cost-effective thermal sensing solutions.
Innovation Solution
Development of thermometric hydrogel compositions comprising polyquaternium (PQ) with quaternary ammonium groups, an ion source, and a solvent, such as water, to create flexible ionic hydrogels that exhibit high thermopower and ease of fabrication, enabling the creation of flexible thermal sensors with improved sensitivity and reduced production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional rigid electronic materials (metals and semiconductors) are used to make temperature sensors, then the sensors have good stability and reliability, but they exhibit poor flexibility and high fabrication cost
Solution Approach 1:
The patent changes the fundamental material parameter from rigid electronic materials to flexible ionic hydrogel materials. The hydrogel composition includes polyquaternium, ion source, and solvent, creating a material that inherently possesses flexibility while maintaining sensing functionality through ionic conduction mechanisms rather than electronic conduction.
Solution Approach 2:
The patent creates a composite hydrogel system combining polyquaternium polymer matrix with ion sources (such as metal salts or ionic liquids) and solvents. This composite structure provides both the flexibility needed for conformal sensing and the ionic conductivity required for temperature sensing, eliminating the need for complicated packaging processes.
2Adaptability or versatility
If liquid-state ionic materials are used for thermal sensing, then high sensitivity and flexibility are achieved, but potential leakage issues require careful and complicated encapsulating process
Solution Approach 1:
The patent changes the physical state parameter from liquid to semi-solid gel form. The hydrogel's crosslinked polymer network structure provides mechanical stability and containment of the ionic components, eliminating leakage issues while maintaining the flexibility and high sensitivity characteristics of liquid ionic materials. No complicated encapsulation is needed as the gel structure itself prevents leakage.
Solution Approach 2:
The polyquaternium polymer matrix acts as an intermediary structure that contains the ion sources and solvents within a stable gel network. This intermediary gel structure provides both mechanical integrity to prevent leakage and ionic pathways to maintain high sensitivity, replacing the need for external encapsulation layers.
3Reliability
If solid-state ionic conductors are used for thermal sensing, then better stability is achieved without complicated packaging, but poor contact with electrodes poses a great challenge for sensor fabrication
Solution Approach 1:
The patent changes the mechanical property parameter from rigid to soft and conformable. The hydrogel's soft nature allows it to conform to electrode surfaces and fill gaps, ensuring excellent contact without requiring complicated fabrication processes. The gel can be directly cast or deposited onto flexible substrates with pre-patterned electrodes, simplifying manufacturing.
Solution Approach 2:
The hydrogel exhibits dynamic mechanical properties, being soft and conformable during fabrication to ensure good electrode contact, yet stable during operation. The gel's viscoelastic nature allows it to adapt to the electrode geometry during the casting process, ensuring intimate contact across the entire interface without requiring precise alignment or complex assembly steps.
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 flexible thermal sensors based on these hydrogels demonstrate high thermopower, excellent formability, and good electrode contact, offering high sensitivity and low fabrication costs, suitable for detecting spatial temperature signals on deformable surfaces.
Implementation Method 1
The sensitivity of ionic conductors can be described by thermopower (mV/K), which represents the generated potential difference per unit temperature difference.
Implementation Method 2
charge carriers are ions rather than electrons
Data Source
AI summary
In some embodiments, provided is a thermometric hydrogel composition for thermal sensor and methods of making thereof, wherein the composition including at least one polyquaternium (PQ), at least one ion source and a solvent. In other aspect, provided is a device comprising the thermometric hydrogel composition and methods of making thereof. Other example embodiments are described herein. In certain embodiments, the flexible thermal sensor comprising such thermometric hydrogel composition has high flexibility, high thermal sensitivity and low fabrication cost.