Stretchable temperature sensing material, stretchable temperature sensor, and method of making the same

Abstract

This invention discloses a stretchable temperature sensing material, a stretchable temperature sensor, and a method for preparing the same. The stretchable temperature sensing material includes a temperature-sensitive ink and an electrode paste. Both the temperature-sensitive ink and the electrode paste comprise an elastic resin matrix, a carbon-based temperature-sensitive filler, a dispersant, a rheology modifier, and a solvent. The temperature-sensitive ink and electrode paste are highly compatible, requiring no high-temperature sintering, and can be integrally printed on a flexible substrate, simplifying the process. The entire sensing material maintains stable temperature response characteristics under mechanical deformation such as stretching and bending, solving the problems of traditional rigid sensors being unable to adapt to deformation and prone to breakage. It is particularly suitable for fields with high requirements for flexibility and comfort, such as wearable health monitoring, electronic skin, and soft robots, and has good industrialization prospects.

Description

Technical Field

[0001] This invention relates to the field of temperature sensor technology, and more specifically, to stretchable temperature sensing materials, stretchable temperature sensors, and methods for their fabrication. Background Technology

[0002] With the rapid development of flexible electronics technology, emerging applications such as wearable devices and electronic skin are placing higher demands on the mechanical performance of sensors. Traditional temperature sensors are typically made of rigid or semi-rigid materials, such as silicon-based semiconductors, metal thin films, or ceramic materials. While these materials possess stable thermoelectric properties, they lack elastic deformation capabilities. In fields such as medical health monitoring, exercise physiology research, and intelligent robotics, sensors need to conformally fit with human skin or flexible surfaces, requiring them to possess stretchability to adapt to complex deformations such as bending and torsion. However, the structural design and material selection of existing temperature sensors limit their normal operation under tension. When subjected to external stretching forces, their conductive pathways are prone to breakage, and the thermoelectric sensitive materials may experience performance degradation or complete failure.

[0003] Research has employed a composite system of polyethylene oxide (PEO) and silver nanowires to construct a temperature-sensitive functional layer. This system utilizes the semi-crystalline properties of PEO to achieve a temperature-resistance response mechanism through its crystalline-amorphous phase transition. Specifically, PEO, as the temperature-sensitive matrix material, exhibits a temperature dependence on its resistance due to the change in the ratio of crystalline to amorphous regions with temperature. Meanwhile, the silver nanowires dispersed within the matrix act as conductive fillers, significantly enhancing the conductivity of the composite material and effectively amplifying the rate of resistance change. In terms of fabrication, this material is formed through melt blending combined with slot coating technology, ultimately integrated into a multilayer film structure.

[0004] However, while PEO, as a thermoplastic crystalline polymer, possesses soft and tough mechanical properties, it is not inherently an elastomer and is prone to plastic deformation or fracture failure under cyclic tensile loads. Furthermore, the introduction of silver nanowires, as rigid metallic nanomaterials, further degrades the tensile properties of the composite system. Due to these material limitations, this composite system struggles to meet the mechanical performance requirements of wearable devices or curved surface-fit sensors, which demand repeated stretching and bending deformation.

[0005] Meanwhile, in existing technologies, the temperature-sensitive layer and the electrode layer of temperature sensors are often designed with different systems. The two have differences in mechanical properties and coefficients of thermal expansion, which makes it easy for interface peeling or poor contact to occur during stretching deformation, affecting the long-term stability of the sensor.

[0006] In view of this, the present invention is proposed to solve the above-mentioned technical defects existing in the prior art. Summary of the Invention

[0007] The purpose of this invention is to provide a stretchable temperature sensing material, a stretchable temperature sensor and a method for preparing the same, overcoming the problems of poor stretchability, mismatch between the mechanical properties of the temperature-sensitive layer and the electrode layer, and difficulty in adapting to dynamic deformation scenarios in existing temperature sensing materials.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a stretchable temperature sensing material, comprising a temperature-sensitive ink and / or an electrode paste, wherein the temperature-sensitive ink comprises, by weight: 20-55 parts by weight of elastic resin matrix; 3-30 parts by weight of carbon-based temperature-sensitive filler; Dispersant 0.5-5 parts by weight; Rheology modifier 1-8 parts by weight; The temperature-sensitive ink has a viscosity of 2000-15000 cP, and a solvent. The electrode paste comprises, by weight, the following: 40-70 parts by weight of elastic resin matrix; 15-40 parts by weight of carbon-based temperature-sensitive filler; Dispersant 1 part by weight - 5 parts by weight; Rheology modifier 1-8 parts by weight; The electrode slurry contains a solvent and has a viscosity of 2000-15000 cP.

[0009] In an optional embodiment, the temperature-sensitive ink comprises, by weight percentage: Elastic resin matrix 20%-55%; Carbon-based temperature-sensitive fillers: 3%-30%; Dispersant 0.5%-5%; Rheology modifiers 1%-8%; And the remaining solvent; And / or, the electrode paste comprises, by weight percentage: Elastic resin matrix 40%-70%; Carbon-based temperature-sensitive fillers: 15%-40%; Dispersant 1%-5%; Rheology modifiers 1%-8%; And the remaining solvent.

[0010] In an optional embodiment, the elastic resin matrix is ​​selected from at least one of polyurethane resin, silicone resin, SEBS thermoplastic elastomer, natural rubber, styrene-butadiene rubber, acrylate elastomer, and fluororubber. And / or, the carbon-based temperature-sensitive filler includes at least two of graphene materials, carbon nanotubes, and conductive carbon black.

[0011] In an optional embodiment, the mass fraction of graphene material in the temperature-sensitive ink is 2%-10%; And / or, the mass fraction of carbon nanotubes in the temperature-sensitive ink is 1%-8%; And / or, the mass fraction of conductive carbon black in the temperature-sensitive ink is 1%-5%; And / or, the mass fraction of graphene material in the electrode slurry is 5%-20%; And / or, the mass fraction of carbon nanotubes in the electrode slurry is 5%-15%; And / or, the mass fraction of conductive carbon black in the electrode slurry is 5%-10%; And / or, the carbon-based thermosensitive filler further includes at least one of vanadium oxide nanoparticles, barium titanate particles, and conductive polymer particles.

[0012] In an optional embodiment, the graphene material includes at least one of monolayer graphene, multilayer graphene, graphene microsheets, and graphene oxide.

[0013] In an optional embodiment, the dispersant is selected from at least one of polyvinylpyrrolidone (PVP) and BYK series dispersants (such as BYK-154, BYK-190 and DISPERBYK-161, etc.); And / or, the rheology modifier includes at least one of a thickener, a leveling agent, and a defoamer; And / or, the solvent is selected from at least one of water, N-methylpyrrolidone, cyclohexanone, butanone, isophorone, propylene glycol methyl ether acetate, ethyl paraben, terpineol, toluene, xylene, and ethyl acetate.

[0014] In an optional embodiment, the thickener is selected from at least one of carboxymethyl cellulose, fumed silica, and polyamide wax; And / or, the leveling agent is selected from at least one of BYK-333, BYK-354, and BNK-4021; And / or, the defoamer is selected from at least one of BYK-088, BYK-019, BYK-024, and BYK-028; And / or, the temperature-sensitive ink includes 0.5%-3% thickener; And / or, the temperature-sensitive ink includes 0.1%-2% leveling agent; And / or, the temperature-sensitive ink includes 0.1%-1% defoamer; And / or, the electrode slurry includes 0.5%-3% thickener; And / or, the electrode slurry includes 0.1%-2% leveling agent; And / or, the electrode slurry includes 0.1%-1% defoamer.

[0015] Secondly, the present invention provides a method for manufacturing a stretchable temperature sensor, comprising: A patterned electrode is formed on a stretchable substrate using the electrode paste described in any of the foregoing embodiments, followed by pre-curing and curing to obtain a stretchable patterned electrode substrate. A temperature-sensitive layer in contact with the patterned electrode is formed on a stretchable substrate using the temperature-sensitive ink described in any of the foregoing embodiments, thereby obtaining the structure to be cured; The structure to be cured is sequentially pre-cured, cured, and encapsulated to obtain a stretchable temperature sensor.

[0016] In an optional embodiment, the patterned electrode is formed by screen printing, inkjet printing, flexographic printing, transfer printing or extrusion 3D printing. And / or, the thermosensitive layer is formed by a method selected from screen printing, gravure printing, spraying, flexographic printing, transfer printing or extrusion 3D printing; And / or, the pre-curing temperature is 60-80℃ and the time is 50-70min; And / or, the curing method is selected from at least one of hot air curing, infrared curing, ultraviolet curing or moisture curing.

[0017] In an optional embodiment, the curing is carried out at a high temperature of 100-140°C and a curing time of 20-90 minutes. And / or, the material of the stretchable substrate is a thermoplastic polyurethane film, a polydimethylsiloxane film, a silicone rubber film, or a fabric; And / or, the encapsulation film is a thermoplastic polyurethane film, a polydimethylsiloxane film, a silicone rubber film, or a fabric; And / or, the encapsulation film is a stretchable transparent film.

[0018] Thirdly, the present invention provides a stretchable temperature sensor, which is prepared by the stretchable temperature sensor preparation method described in the foregoing embodiments.

[0019] The present invention has the following beneficial effects: The stretchable temperature sensing material described in this invention possesses high sensitivity, excellent flexibility, and reliable durability. The temperature-sensitive ink, serving as the temperature-sensing functional layer, has a moderate viscosity of 2000–15000 cP and good rheological properties, facilitating the formation of a uniform thin film through printing. Its carbon-based temperature-sensitive filler generates a reversible resistance response under temperature changes, enabling accurate temperature measurement. The elastic resin matrix endows the coating with excellent tensile resilience, adapting to dynamic deformation environments. The electrode paste also uses an elastomer as its matrix, containing a higher proportion of conductive filler to ensure low-resistance, high-stability electrical signal extraction. It also exhibits good interfacial compatibility with the temperature-sensitive layer, resulting in a strong bond and preventing delamination or contact failure. Both material systems are highly compatible, requiring no high-temperature sintering, and can be integrally printed on a flexible substrate, significantly simplifying the process. The entire sensing material maintains stable temperature response characteristics under mechanical deformation such as stretching and bending, solving the problems of traditional rigid sensors' inability to adapt to deformation and their susceptibility to breakage. It is particularly suitable for fields with high requirements for flexibility and comfort, such as wearable health monitoring, electronic skin, and soft robots, and has promising industrialization prospects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the overall structure of the stretchable temperature sensor provided by the present invention; Figure 2 This is a schematic diagram of the layered cross-sectional structure of the stretchable temperature sensor provided by the present invention. Figure: 1-Stretchable temperature-sensitive layer; 2-Stretchable electrode; 3-Stretchable substrate layer; 4-Stretchable encapsulation layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] This invention provides a stretchable temperature sensing material, comprising a temperature-sensitive ink and / or an electrode paste, wherein the temperature-sensitive ink comprises, by weight: The elastic resin matrix is ​​20 parts by weight to 55 parts by weight, for example, 20 parts by weight, 24 parts by weight, 28 parts by weight, 32 parts by weight, 36 parts by weight, 40 parts by weight, 44 parts by weight, 48 parts by weight, 52 parts by weight, and 55 parts by weight. Carbon-based temperature-sensitive fillers are available in quantities of 3 to 30 parts by weight, such as 3 parts by weight, 5 parts by weight, 8 parts by weight, 11 parts by weight, 14 parts by weight, 17 parts by weight, 20 parts by weight, 23 parts by weight, 26 parts by weight, 29 parts by weight, and 30 parts by weight. The dispersant is used in amounts of 0.5 parts by weight to 5 parts by weight, such as 0.5 parts by weight, 1.0 parts by weight, 1.5 parts by weight, 2.0 parts by weight, 2.5 parts by weight, 3.0 parts by weight, 3.5 parts by weight, 4.0 parts by weight, 4.5 parts by weight, and 5 parts by weight. Rheology modifiers ranging from 1 part by weight to 8 parts by weight, for example, 1 part by weight, 1.8 parts by weight, 2.6 parts by weight, 3.3 parts by weight, 4.1 parts by weight, 4.9 parts by weight, 5.6 parts by weight, 6.4 parts by weight, 7.1 parts by weight, and 8 parts by weight; The temperature-sensitive ink has a viscosity of 2000-15000 cP, for example, 2000 cP, 3444 cP, 4889 cP, 6333 cP, 7778 cP, 9222 cP, 10667 cP, 12111 cP, 13556 cP, 15000 cP; and a solvent, wherein the viscosity of the temperature-sensitive ink is 2000-15000 cP, for example, 2000 cP, 3444 cP, 4889 cP, 6333 cP, 7778 cP, 9222 cP, 10667 cP, 12111 cP, 13556 cP, 15000 cP; The electrode paste comprises, by weight, the following: The elastic resin matrix is ​​40 parts by weight to 70 parts by weight, for example, 40 parts by weight, 43 parts by weight, 46 parts by weight, 49 parts by weight, 52 parts by weight, 55 parts by weight, 58 parts by weight, 61 parts by weight, 64 parts by weight, 67 parts by weight, and 70 parts by weight. Carbon-based temperature-sensitive filler in quantities of 15-40 parts by weight, such as 15 parts by weight, 18 parts by weight, 21 parts by weight, 24 parts by weight, 27 parts by weight, 30 parts by weight, 33 parts by weight, 36 parts by weight, 39 parts by weight, and 40 parts by weight. The dispersant is 1 part by weight to 5 parts by weight, for example, 1 part by weight, 1.4 parts by weight, 1.9 parts by weight, 2.3 parts by weight, 2.8 parts by weight, 3.2 parts by weight, 3.7 parts by weight, 4.1 parts by weight, 4.6 parts by weight, and 5 parts by weight; Rheology modifiers ranging from 1 part by weight to 8 parts by weight, for example, 1 part by weight, 1.8 parts by weight, 2.6 parts by weight, 3.3 parts by weight, 4.1 parts by weight, 4.9 parts by weight, 5.6 parts by weight, 6.4 parts by weight, 7.1 parts by weight, and 8 parts by weight; The electrode slurry has a viscosity of 2000-15000 cP, for example, 2000 cP, 3444 cP, 4889 cP, 6333 cP, 7778 cP, 9222 cP, 10667 cP, 12111 cP, 13556 cP, and 15000 cP.

[0024] This invention provides a temperature-sensitive ink with excellent temperature responsiveness and processing applicability. The elastic resin matrix imparts superior flexibility and adhesion to the ink, ensuring stable conductivity even after repeated bending on a flexible substrate. The carbon-based temperature-sensitive filler generates a reversible resistance response to temperature changes, achieving sensitive temperature sensing. The dispersant effectively prevents filler agglomeration and improves the system's storage stability. Rheology modifiers, combined with viscosity control, give the ink both good flowability and anti-sagging properties, making it suitable for printing processes such as screen printing, resulting in uniform film formation without clogging intricate patterns. This invention helps solve problems such as cracking, uneven dispersion, and narrow process windows in traditional temperature-sensitive materials, making it particularly suitable for low-cost, high-reliability manufacturing of flexible sensors.

[0025] The electrode paste described in this invention possesses excellent conductivity, flexibility, and printability. The elastic resin matrix, as the continuous phase, endows the paste with good mechanical elasticity and substrate adhesion, allowing it to maintain the integrity of the electrode structure even after repeated deformation in flexible or stretchable devices. The carbon-based temperature-sensitive filler not only provides a stable conductive network but also imparts intrinsic temperature response characteristics to the electrode, enabling integrated sensing functionality. The dispersant effectively improves the uniformity of filler dispersion in the resin system, preventing sedimentation and agglomeration, and ensuring the long-term storage stability of the paste. The rheology modifier synergistically controls the paste viscosity, giving it suitable rheological properties, making it suitable for printing processes such as screen printing. It forms a smooth film and can precisely fill microstructures, such as the gaps between image electrodes. The solvent system can be water-based or organic, depending on processing requirements, and is compatible with various substrates. This electrode paste can form a high-performance conductive layer without high-temperature sintering. The preparation process is simple and low-cost, making it particularly suitable for mass production in fields such as flexible temperature sensors and wearable electronics, solving the problems of high brittleness, poor flexibility, and complex processes associated with traditional metal electrodes.

[0026] The stretchable temperature sensing material of this invention comprises the aforementioned thermosensitive ink and electrode paste. Their synergistic effect achieves a balance of high sensitivity, excellent flexibility, and reliable durability. The thermosensitive ink, as the temperature-sensing functional layer, possesses a moderate viscosity of 2000–15000 cP and good rheological properties, facilitating the formation of a uniform thin film through printing. Its carbon-based thermosensitive filler generates a reversible resistance response under temperature changes, enabling accurate temperature measurement. The elastic resin matrix endows the coating with excellent tensile resilience, adapting to dynamic deformation environments. The electrode paste, also based on an elastomer, contains a higher proportion of conductive filler, ensuring low-resistance, high-stability electrical signal extraction. It also exhibits good interfacial compatibility with the thermosensitive layer, resulting in a strong bond and preventing delamination or contact failure. Both material systems are highly compatible, requiring no high-temperature sintering, and can be integrally printed on a flexible substrate, significantly simplifying the process. The entire sensing material maintains stable temperature response characteristics under mechanical deformation such as stretching and bending, solving the problem that traditional rigid sensors cannot adapt to deformation and are prone to breakage. It is particularly suitable for fields with high requirements for flexibility and comfort, such as wearable health monitoring, electronic skin and soft robots, and has good industrialization prospects.

[0027] In an optional embodiment, the temperature-sensitive ink comprises, by weight percentage: Elastic resin matrix 20%-55%, for example 20%, 24%, 28%, 32%, 36%, 40%, 44%, 48%, 52%, 55%; Carbon-based temperature-sensitive fillers, 3%-30%, for example, 3%, 5%, 8%, 11%, 14%, 17%, 20%, 23%, 26%, 29%, 30%; Dispersant 0.5%-5%, for example 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5%; Rheology modifiers 1%-8%, for example 1%, 1.8%, 2.6%, 3.3%, 4.1%, 4.9%, 5.6%, 6.4%, 7.1%, 8%; And the remaining solvent.

[0028] In an optional embodiment, the electrode paste comprises, by weight percentage: Elastic resin matrix 40%-70%, for example 40%, 43%, 46%, 49%, 52%, 55%, 58%, 61%, 64%, 67%, 70%; Carbon-based temperature-sensitive fillers range from 15% to 40%, for example, 15%, 18%, 21%, 24%, 27%, 30%, 33%, 36%, 39%, and 40%. Dispersant 1%-5%, for example 1%, 1.4%, 1.9%, 2.3%, 2.8%, 3.2%, 3.7%, 4.1%, 4.6%, 5%; Rheology modifiers 1%-8%, for example 1%, 1.8%, 2.6%, 3.3%, 4.1%, 4.9%, 5.6%, 6.4%, 7.1%, 8%; And the remaining solvent.

[0029] This group of proportions synergistically optimizes the functionality and processability of the temperature-sensitive ink and electrode paste, taking into account conductivity, temperature response, flexibility, and printability. Through the reasonable matching of elastic matrix and filler, it ensures that both layers of materials maintain stable electrical properties under tensile deformation, thus realizing the integrated fabrication of a high-performance stretchable temperature sensor.

[0030] In an optional embodiment, the elastic resin matrix is ​​selected from at least one of polyurethane resin, silicone resin, SEBS (hydrogenated styrene-butadiene block copolymer) thermoplastic elastomer, natural rubber, styrene-butadiene rubber, acrylate elastomer, and fluororubber; the elastic resin may be provided in the form of solution, emulsion, prepolymer, or photocurable prepolymer, and the elastic matrix is ​​formed by casting, coating, or printing.

[0031] Polyurethane offers strong abrasion resistance and adhesion, silicone exhibits excellent high and low temperature resistance, SEBS boasts good processability and high transparency, and acrylate demonstrates strong weather resistance. Each of the selected elastic resin matrices has its own advantages. This range of choices allows the ink system to be flexibly formulated according to specific application scenarios, taking into account mechanical extensibility, thermal stability, and substrate compatibility. It effectively buffers stress concentration in carbon-based fillers under temperature or deformation, prevents crack propagation, and ensures long-term stable operation of sensors. It is particularly suitable for fields with high reliability requirements, such as flexible electronics and wearable devices.

[0032] In an optional embodiment, the carbon-based thermosensitive filler includes at least two of graphene, carbon nanotubes, and conductive carbon black, constructing a three-dimensional conductive network through the synergistic construction of multi-scale carbon materials. Graphene provides high conductivity pathways and a large specific surface area, carbon nanotubes act as "conductive bridges" to enhance interfacial connectivity, and conductive carbon blacks such as acetylene black and Super P can fill micropores and reduce costs. The synergy of any two of these materials not only improves overall conductivity and thermosensitive response sensitivity but also enhances filler dispersion stability and mechanical coupling performance, generating repeatable resistance changes with temperature variations. This composite system effectively reduces the percolation threshold, enhances thermo-electric response linearity and cycle durability, and is suitable for the fabrication of high-performance flexible temperature sensors.

[0033] In an optional embodiment, the mass fraction of graphene material in the temperature-sensitive ink is 2%-10%, for example 2%, 2.9%, 3.8%, 4.7%, 5.6%, 6.4%, 7.3%, 8.2%, 9.1%, or 10%.

[0034] In an optional embodiment, the mass fraction of carbon nanotubes in the temperature-sensitive ink is 1%-8%, for example, 1%, 1.8%, 2.6%, 3.3%, 4.1%, 4.9%, 5.6%, 6.4%, 7.1%, or 8%.

[0035] In an optional embodiment, the mass fraction of conductive carbon black in the temperature-sensitive ink is 1%-5%, for example, 1%, 1.4%, 1.9%, 2.3%, 2.8%, 3.2%, 3.7%, 4.1%, 4.6%, or 5%.

[0036] This invention constructs a three-dimensional conductive permeation network by uniformly dispersing carbon nanomaterials (such as graphene and carbon nanotubes) with a negative temperature coefficient (NTC) effect within an elastic resin matrix, thereby achieving a highly sensitive response between temperature and resistance. As temperature increases, the resistance of the carbon material itself decreases, while the thermal expansion of the resin matrix causes an increase in the spacing between the fillers and a rise in contact resistance. By controlling the type, content, and dispersion state of the fillers, these two opposing temperature-sensitive mechanisms work synergistically to achieve an adjustable and significant change in net resistance, thus realizing excellent thermosensitive performance. Simultaneously, the elastic resin, as a continuous phase, endows the material with intrinsic stretchability, and its polymer chains can undergo reversible deformation during stretching. The nanoscale carbon fillers, in a well-dispersed state, have minimal mechanical interference with the matrix, effectively maintaining the material's flexibility and structural stability.

[0037] Limiting the amount of carbon-based thermosensitive filler in thermosensitive ink within the above-mentioned range can ensure the connectivity of the conductive network while avoiding excessive aggregation, significantly improving the sensitivity and linearity of thermosensitive response; the components work together to reduce the percolation threshold, enhancing the repeatability and stability of thermal resistance changes; taking into account dispersibility, film quality and process adaptability, it is suitable for flexible printed electronics applications that require both temperature sensing accuracy and mechanical durability.

[0038] In an optional embodiment, the mass fraction of graphene material in the electrode slurry is 5%-20%, for example 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 20%; the graphene material provides two-dimensional conductive planes and surface contacts, reducing contact resistance.

[0039] In an optional embodiment, the mass fraction of carbon nanotubes in the electrode slurry is 5%-15%, for example 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%; the carbon nanotubes provide a one-dimensional conductive bridge, connecting the graphene material and carbon black particles, enhancing network integrity and mechanical strength.

[0040] In an optional embodiment, the mass fraction of conductive carbon black in the electrode slurry is 5%-10%, for example, 5%, 5.6%, 6.1%, 6.7%, 7.2%, 7.8%, 8.3%, 8.9%, 9.4%, or 10%; the highly conductive carbon black fills the gaps between the nanosheets and nanotubes, reducing costs and facilitating dispersion.

[0041] This invention utilizes the large-area conductivity of graphene, the long-range bridging effect of carbon nanotubes, and the interstitial filling of conductive carbon black to form a highly efficient three-dimensional conductive network with a relatively low total filler content. The sheet resistance can reach the order of 10-100 Ω / sq, meeting the requirements of temperature sensor electrodes. Simultaneously, since both the filler and the matrix are carbon / organic materials, the interfacial bonding is excellent. The elastic resin provides the main stretchability, while the one-dimensional carbon nanotubes and two-dimensional graphene materials themselves possess a certain degree of flexibility, bending with the deformation of the matrix rather than breaking. Therefore, the elongation of the cured film can be greater than 50%, and the rate of change in resistance is small. Furthermore, the cost of carbon materials is significantly lower than that of silver nanowires, and they are homologous to carbon-based temperature-sensitive layer materials, exhibiting excellent compatibility. The same or similar solvent and resin systems can be used, facilitating integrated printing and co-curing.

[0042] Within the specified range, carbon-based thermosensitive fillers in the electrode paste can construct a high-density, multi-scale synergistic conductive network. Graphene provides highly conductive in-plane pathways, carbon nanotubes bridge the interlayer gaps to enhance three-dimensional connectivity, and conductive carbon black fills micropores and improves paste density, significantly reducing electrode sheet resistance and improving current distribution uniformity. This formulation maintains good flexibility while ensuring excellent conductivity, allowing the electrode to maintain stable contact under repeated stretching. It is suitable for the printing and fabrication of high-performance, stretchable sensor devices, balancing conductivity, processability, and long-term reliability.

[0043] In an optional embodiment, the carbon-based thermosensitive filler further includes at least one of vanadium oxide (VO2) nanoparticles, barium titanate (BaTiO3) particles, and conductive polymer particles, which is beneficial for adjusting the linearity or sensitivity of the temperature sensor's thermosensitive curve. The conductive polymer may be PEDOT:PSS.

[0044] In an optional embodiment, the graphene material includes at least one of monolayer graphene, multilayer graphene, graphene microsheets, and graphene oxide.

[0045] In an optional embodiment, the dispersant is selected from at least one of polyvinylpyrrolidone (PVP) and BYK (BYK Chemicals) series dispersants (such as BYK-154, BYK-190 and DISPERBYK-161).

[0046] In an optional embodiment, the rheology modifier includes at least one of a thickener, a leveling agent, and a defoamer; the thickener can prevent the sedimentation of carbon-based temperature-sensitive fillers, the leveling agent promotes uniform spreading, and the defoamer eliminates bubble defects. The synergistic effect of the three is conducive to comprehensively improving printing accuracy and film quality.

[0047] In an optional embodiment, the solvent is selected from at least one of water, N-methylpyrrolidone (NMP), cyclohexanone, butanone, isophorone, propylene glycol methyl ether acetate (PMA), ethyl terephthalate, terpineol, toluene, xylene, and ethyl acetate, and may be specifically selected according to the solubility of the resin.

[0048] In an optional embodiment, the thickener is selected from at least one of carboxymethyl cellulose, fumed silica, and polyamide wax to impart suitable thixotropic properties to the ink and meet the requirements of screen printing.

[0049] In an optional embodiment, the leveling agent is selected from at least one of BYK-333, BYK-354, and BNK-4021, which can improve the surface smoothness of the printed film.

[0050] In an optional embodiment, the defoamer is selected from at least one of BYK-088, BYK-019, BYK-024, and BYK-028, and is capable of preventing bubbles from being generated during the printing process.

[0051] In an optional embodiment, the temperature-sensitive ink includes 0.5%-3% thickener, for example 0.5%, 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3%, 2.6%, 2.9%, or 3%.

[0052] In an optional embodiment, the temperature-sensitive ink includes 0.1%-2% leveling agent, for example, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, or 2%.

[0053] In an optional embodiment, the temperature-sensitive ink includes 0.1%-1% of an antifoaming agent, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0054] In an optional embodiment, the electrode slurry includes 0.5%-3% thickener, for example 0.5%, 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, 2.3%, 2.6%, 2.9%, or 3%.

[0055] In an optional embodiment, the electrode slurry includes 0.1%-2% leveling agent, for example, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, or 2%.

[0056] In an optional embodiment, the electrode slurry includes 0.1%-1% of a defoamer, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0057] Adjusting the type and amount of rheology modifiers facilitates the regulation of the rheological properties of the two-component system, improving the thixotropy, anti-settling properties, and coating uniformity of the slurry, preventing printing screen blockage, edge jaggedness, and bubble defects; at the same time, it ensures the dispersion stability under high filler loading, so that both the temperature-sensitive layer and the electrode layer have excellent film-forming quality and interface integrity, making it suitable for high-precision, mass production of flexible sensors, and significantly improving device consistency and reliability.

[0058] This invention also provides a method for fabricating a stretchable temperature sensor, comprising: A patterned electrode is formed on a stretchable substrate using the electrode paste described in any of the foregoing embodiments, followed by pre-curing and curing to obtain a stretchable patterned electrode substrate. A temperature-sensitive layer in contact with the patterned electrode is formed on a stretchable substrate using the temperature-sensitive ink described in any of the foregoing embodiments, thereby obtaining the structure to be cured; The structure to be cured is sequentially pre-cured, cured, and encapsulated to obtain a stretchable temperature sensor.

[0059] The method for fabricating a stretchable temperature sensor provided by this invention first involves printing patterned electrodes onto a stretchable substrate using electrode paste, ensuring low resistance and excellent flexibility. Then, temperature-sensitive ink is used to pattern and cover the electrode area on the substrate, forming a temperature-sensitive functional layer with effective contact, achieving efficient temperature-to-resistance signal conversion. In this method, the temperature-sensitive ink and electrode paste system are highly compatible, with a strong interface bond, avoiding delamination or contact failure. By sequentially performing pre-curing to remove solvent, complete curing to establish a cross-linked network, and encapsulation, the environmental stability and mechanical durability of the device can be improved. The entire process does not require high-temperature sintering, is suitable for roll-to-roll continuous production, and has good scalability and industrialization prospects. The fabricated sensor maintains stable temperature response characteristics under stretching, bending, and other deformation conditions, exhibiting high sensitivity and good repeatability, making it particularly suitable for dynamic applications such as wearable health monitoring, electronic skin, and flexible robots.

[0060] In an optional embodiment, the patterned electrode is formed by screen printing, inkjet printing, flexographic printing, transfer printing, or extrusion 3D printing.

[0061] In an optional embodiment, the thermosensitive layer is formed by screen printing, gravure printing, spraying, flexographic printing, transfer printing, or extrusion 3D printing.

[0062] In an optional embodiment, the pre-curing temperature is 60-80℃, for example 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃; the time is 50-70min, for example 50min, 52min, 54min, 56min, 58min, 60min, 62min, 64min, 66min, 68min, 70min; this can remove most of the solvent in the temperature-sensitive ink and electrode paste, avoiding the generation of bubbles or blistering during subsequent high-temperature curing; at the same time, it maintains moderate movement of the elastic matrix chain segments, promotes the initial stabilization of the filler network, and improves the film density and interlayer bonding force.

[0063] In an optional embodiment, the curing method is selected from at least one of hot air curing, infrared curing, ultraviolet curing, or moisture curing.

[0064] In an optional embodiment, the curing is carried out at a high temperature of 100-140℃, such as 100℃, 104℃, 108℃, 112℃, 116℃, 120℃, 124℃, 128℃, 132℃, 136℃, and 140℃; the curing time is 20-90 min, such as 20 min, 28 min, 36 min, 44 min, 52 min, 60 min, 68 min, 76 min, 84 min, and 90 min. This promotes the cross-linking reaction of the elastic resin matrix, improves mechanical strength and thermal stability, enhances the filler-matrix interface bonding, reduces contact resistance, improves the repeatability of conductivity and temperature-sensitive response, and ensures long-term stable operation of the sensor under stretchable conditions.

[0065] In an optional embodiment, the stretchable substrate is made of thermoplastic polyurethane (TPU) film, polydimethylsiloxane (PDMS) film, silicone rubber film, or fabric.

[0066] In an optional embodiment, the encapsulation film is a thermoplastic polyurethane (TPU) film, a polydimethylsiloxane (PDMS) film, a silicone rubber film, or a fabric.

[0067] In an optional embodiment, the encapsulation film is a stretchable transparent film.

[0068] The present invention also provides a stretchable temperature sensor, the structure of which is as follows: Figure 1 and Figure 2 As shown, the stretchable temperature sensor is prepared by the method described in the foregoing embodiments, specifically including a stretchable temperature-sensitive layer 1, a stretchable electrode 2, a stretchable substrate layer 3, and a stretchable encapsulation layer 4.

[0069] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0070] Example 1 This embodiment provides a method for fabricating a stretchable temperature sensor, specifically including the following steps: 1. Prepare electrode paste and temperature-sensitive ink according to Table 1; 2. Using a TPU film (100μm thick) as a stretchable substrate, a serpentine electrode is formed on the stretchable substrate by screen printing (300 mesh, squeegee pressure 0.3MPa) using electrode paste. After pre-curing at 70℃ for 30min (to remove most of the solvent) and curing at 100℃ for 30min (hot air curing), a stretchable patterned electrode substrate is obtained. 3. Using temperature-sensitive ink, a temperature-sensitive layer (50μm thick) is formed on a stretchable substrate by screen printing (300 mesh, squeegee pressure 0.25MPa) to contact the patterned electrode, covering the effective area of ​​the electrode, to obtain the structure to be cured; 4. The structure to be cured is placed in a series of conditions: pre-curing at 70°C for 60 min (to remove most of the solvent) and high-temperature curing at 100°C for 60 min (hot air curing), and then encapsulated. The encapsulation film is a TPU film (thickness 80 μm). The encapsulation is completed by hot pressing (temperature 100°C, pressure 0.2 MPa, time 10 min) to obtain a stretchable temperature sensor.

[0071] Table 1

[0072] Note: In Table 1, the elastic resin matrix is ​​PU resin, polyethylene oxide (PEO) resin, or silicone resin; the dispersant is BYK-190; the thickener is fumed silica; the leveling agent is BYK-333; the defoamer is BYK-088; and the solvent is a compound system of cyclohexanone and NMP (mass ratio of cyclohexanone:NMP = 8:2). In each example / comparative example, the amount of solvent used in the temperature-sensitive ink and electrode paste is the balance, that is, the sum of the proportions of each group is 100%.

[0073] 2. Using a 100 μm thick TPU film as a stretchable substrate, serpentine electrodes are formed on the stretchable substrate using electrode paste and screen printing (300 mesh, 0.3 MPa squeegee pressure, 50 mm / s printing speed). After pre-curing at 70℃ for 30 min (to remove most of the solvent) and high-temperature curing at 100℃ for 30 min (hot air curing), a stretchable patterned electrode substrate is obtained. 3. Using temperature-sensitive ink, a temperature-sensitive layer in contact with the patterned electrode is formed on a stretchable substrate by screen printing (300 mesh, squeegee pressure 0.2MPa, printing speed 40mm / s), and the thickness of the temperature-sensitive layer is controlled to be 25μm to obtain the structure to be cured. 4. The structure to be cured is placed in a series of conditions: pre-curing at 70°C for 40 min and high-temperature curing at 100°C for 30 min, and then encapsulated. The encapsulation film is a TPU film, thus obtaining a stretchable temperature sensor.

[0074] Example 2 This embodiment is basically the same as Embodiment 1, except that the slurry formulation uses the lower limit of the scope of the claims. The specific formulation is shown in Table 1. The pre-curing conditions are adjusted to 60℃ for 70 min, and the curing conditions are 100℃ for 30 min.

[0075] Example 3 This embodiment is basically the same as Embodiment 1, except that the slurry formulation adopts the upper limit of the scope of the claims. The specific formulation is shown in Table 1. The pre-curing conditions are adjusted to 70℃ for 30 min, and the curing conditions are 100℃ for 30 min.

[0076] Comparative Example 1 (Comparison of Non-elastic Resins) This comparative example is basically the same as Example 1, except that the polyurethane (PU) elastic resin in the temperature-sensitive ink and electrode paste is replaced with the thermoplastic polymer polyethylene oxide (PEO). The specific formulation is shown in Table 1. The remaining components and preparation process are the same as in Example 1.

[0077] Comparative Example 2 (Comparison of Single Carbon Filler) This comparative example is basically the same as Example 1, except that the carbon-based thermosensitive filler in the thermosensitive ink and electrode paste is replaced with a composite system of "graphene + carbon nanotubes + conductive carbon black" with only graphene material (the total mass fraction is the same as in Example 1). The specific formula is shown in Table 1. The remaining components and preparation process are the same as in Example 1.

[0078] Comparative Example 3 (Comparison of interlayer material mismatch) This comparative example is basically the same as Example 1, except that the elastic resin matrix in the electrode paste is replaced with an organosilicon resin, which has poor compatibility with polyurethane, while the temperature-sensitive ink still uses a polyurethane matrix. The specific formulation is shown in Table 1. The remaining components and preparation process are the same as in Example 1.

[0079] Performance testing The performance of the stretchable temperature sensors prepared in the above embodiments and comparative examples was tested using the following methods: 1. Initial resistance test: The initial resistance value of the sensor at 25℃ is measured using a digital multimeter.

[0080] 2. Temperature Coefficient of Resistance (TCR) Test: Place the sensor on a heating platform and record the resistance value every 10°C within the range of 30-80°C, and calculate the temperature coefficient of resistance (TCR).

[0081] 3. Maximum tensile strength test: Use a universal tensile testing machine to stretch the sensor at a rate of 10 mm / min and record the maximum tensile strength when the resistance change rate does not exceed 10%.

[0082] 4. Tensile stability test: Perform 500 cycles of tensile testing under 20% strain conditions and record the rate of change in resistance before and after tensile testing.

[0083] 5. Interface bonding test: After 100 cycles of cyclic stretching under 20% strain conditions, observe the interface between the temperature-sensitive layer and the electrode layer using an optical microscope to see if peeling or cracks occur.

[0084] The test results are shown in Table 2.

[0085] Table 2 Performance test results of each embodiment and comparative example

[0086] This invention achieves a balance between high tensile strength (maximum tensile rate 30-70%), high sensitivity (TCR 0.2-0.9% / ℃ at 30-80℃), and excellent durability in a stretchable temperature sensor. A comparison of Comparative Example 1 and Example 1 shows that using an elastic resin matrix (such as polyurethane or silicone) instead of a thermoplastic polymer (such as PEO) allows the sensor to maintain structural integrity and stable response after 500 cycles of 20% strain, while the non-elastic matrix fails within 50 cycles. This fully demonstrates that an intrinsically elastic matrix is ​​key to achieving stretchability. The material is intrinsically flexible; after 500 cycles of 20% strain, the resistance change rate of Example 1 is less than 4%, and that of Example 3 is less than 3%, exhibiting minimal temperature response drift and good mechanical-electrical stability. The ink system's viscosity and rheological properties are optimized to the range of 2000–15000 cP, making it suitable for screen printing processes and enabling patterned, continuous, and low-cost mass production on flexible roll materials.

[0087] A comparison of Comparative Example 2 and Example 1 shows that, compared with a single filler system, the multi-scale carbon-based filler compound (graphene + carbon nanotubes + conductive carbon black) increases the TCR by about 60% (from 0.5% / ℃ to 0.8% / ℃) and the maximum elongation by 20% (from 50% to 60%), demonstrating that the synergistic effect of the multi-scale filler significantly enhances the temperature sensitivity and tensile stability.

[0088] The electrodes and temperature-sensitive layer utilize a compatible resin system (e.g., Examples 1-3 all use the same or compatible polyurethane matrix), forming a strong interfacial bond and even interpenetrating molecular chains after curing. A comparison of Comparative Example 3 and Example 1 shows that when the electrode layer and temperature-sensitive layer use mismatched resin systems (e.g., the electrode layer is silicone and the temperature-sensitive layer is polyurethane), interfacial microcracks and drastic fluctuations in contact resistance appear after 100 cycles of stretching. In contrast, the compatible system shows no delamination after 500 cycles, effectively preventing delamination failure during stretching and ensuring stable and reliable signal output under dynamic operating conditions. The overall solution combines high performance, high reliability, and industrialization potential, making it particularly suitable for applications requiring both flexibility and long-term stability, such as wearable health monitoring and soft robot sensing.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A stretchable temperature sensing material comprising a temperature sensitive ink and / or an electrode paste, characterized in that, The temperature-sensitive ink comprises, by weight, the following: 20-55 parts by weight of elastic resin matrix; 3-30 parts by weight of carbon-based temperature-sensitive filler; Dispersant 0.5-5 parts by weight; Rheology modifier 1-8 parts by weight; The temperature-sensitive ink has a viscosity of 2000-15000 cP, and a solvent. The electrode paste comprises, by weight, the following: 40-70 parts by weight of elastic resin matrix; 15-40 parts by weight of carbon-based temperature-sensitive filler; Dispersant 1 part by weight - 5 parts by weight; Rheology modifier 1-8 parts by weight; The electrode slurry contains a solvent and has a viscosity of 2000-15000 cP.

2. The stretchable temperature sensing material of claim 1, wherein, The temperature-sensitive ink comprises, by weight percentage: Elastic resin matrix 20%-55%; Carbon-based temperature-sensitive fillers: 3%-30%; Dispersant 0.5%-5%; Rheology modifiers 1%-8%; And the remaining solvent; And / or, the electrode paste comprises, by weight percentage: Elastic resin matrix 40%-70%; Carbon-based temperature-sensitive fillers: 15%-40%; Dispersant 1%-5%; Rheology modifiers 1%-8%; And the remaining solvent.

3. The stretchable temperature sensing material according to claim 1, characterized in that, The elastic resin matrix is ​​selected from at least one of polyurethane resin, silicone resin, SEBS thermoplastic elastomer, natural rubber, styrene-butadiene rubber, acrylate elastomer and fluororubber; And / or, the carbon-based temperature-sensitive filler includes at least two of graphene materials, carbon nanotubes, and conductive carbon black.

4. The stretchable temperature sensing material according to claim 1, characterized in that, The mass fraction of graphene material in the temperature-sensitive ink is 2%-10%; And / or, the mass fraction of carbon nanotubes in the temperature-sensitive ink is 1%-8%; And / or, the mass fraction of conductive carbon black in the temperature-sensitive ink is 1%-5%; And / or, the mass fraction of graphene material in the electrode slurry is 5%-20%; And / or, the mass fraction of carbon nanotubes in the electrode slurry is 5%-15%; And / or, the mass fraction of conductive carbon black in the electrode slurry is 5%-10%; And / or, the carbon-based thermosensitive filler further includes at least one of vanadium oxide nanoparticles, barium titanate particles, and conductive polymer particles; And / or, the graphene material includes at least one of monolayer graphene, multilayer graphene, graphene microsheets, and graphene oxide.

5. The stretchable temperature sensing material according to claim 1, characterized in that, The dispersant is selected from at least one of polyvinylpyrrolidone and BYK series dispersants; And / or, the rheology modifier includes at least one of a thickener, a leveling agent, and a defoamer; And / or, the solvent is selected from at least one of water, N-methylpyrrolidone, cyclohexanone, butanone, isophorone, propylene glycol methyl ether acetate, ethyl paraben, terpineol, toluene, xylene, and ethyl acetate.

6. The stretchable temperature sensing material according to claim 5, characterized in that, The thickener is selected from at least one of carboxymethyl cellulose, fumed silica, and polyamide wax; And / or, the leveling agent is selected from at least one of BYK-333, BYK-354, and BNK-4021; And / or, the defoamer is selected from at least one of BYK-088, BYK-019, BYK-024, and BYK-028; And / or, the temperature-sensitive ink includes 0.5%-3% thickener; And / or, the temperature-sensitive ink includes 0.1%-2% leveling agent; And / or, the temperature-sensitive ink includes 0.1%-1% defoamer; And / or, the electrode slurry includes 0.5%-3% thickener; And / or, the electrode slurry includes 0.1%-2% leveling agent; And / or, the electrode slurry includes 0.1%-1% defoamer.

7. A method for fabricating a stretchable temperature sensor, characterized in that, include: A patterned electrode is formed on a stretchable substrate using the electrode paste described in any one of claims 1-6, followed by pre-curing and curing to obtain a stretchable patterned electrode substrate. A temperature-sensitive layer in contact with the patterned electrode is formed on a stretchable substrate using the temperature-sensitive ink described in any one of claims 1-6, thereby obtaining the structure to be cured; The structure to be cured is sequentially pre-cured, cured, and encapsulated to obtain a stretchable temperature sensor.

8. The method for fabricating the stretchable temperature sensor according to claim 7, characterized in that, The patterned electrode is formed by screen printing, inkjet printing, flexographic printing, transfer printing or extrusion 3D printing. And / or, the thermosensitive layer is formed by a method selected from screen printing, gravure printing, spraying, flexographic printing, transfer printing or extrusion 3D printing; And / or, the pre-curing temperature is 60-80℃ and the time is 50-70min; And / or, the curing method is selected from at least one of hot air curing, infrared curing, ultraviolet curing or moisture curing.

9. The method for preparing the stretchable temperature sensor according to claim 7, characterized in that, The curing process employs high-temperature curing, with a curing temperature of 100-140℃ and a curing time of 20-90 minutes. And / or, the material of the stretchable substrate is a thermoplastic polyurethane film, a polydimethylsiloxane film, a silicone rubber film, or a fabric; And / or, the encapsulation film is a thermoplastic polyurethane film, a polydimethylsiloxane film, a silicone rubber film, or a fabric; And / or, the encapsulation film is a stretchable transparent film.

10. A stretchable temperature sensor, characterized in that, It is prepared by the method for preparing the stretchable temperature sensor as described in claim 8 or 9.

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