Organic-inorganic composite reversible temperature change material and preparation method thereof
By preparing a reversible thermochromic thin film based on the PEDOT:COOH–CuCl2·2H2O composite system, the problems of expensive equipment, limited accuracy and poor stability of HIFU focal zone temperature monitoring were solved. Visualized temperature response and flexible monitoring in the range of 40℃~90℃ were achieved, which is suitable for temperature sensors and anti-counterfeiting labels.
Patent Information
- Application Number
- CN202511671704.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-02-06
AI Technical Summary
Existing HIFU (High-Intensity Focused Ultrasonic Fusion) coke oven temperature monitoring methods and equipment are expensive, have limited accuracy, narrow temperature measurement range, poor stability, and insufficient mechanical strength, making it impossible to achieve real-time visualization and flexible monitoring.
A reversible thermochromic thin film based on the PEDOT:COOH–CuCl2·2H2O composite system was used. By combining conductive polymer and transition metal salt, a thin film with reversible coordination rearrangement properties was prepared on the substrate through methods such as screen printing, and a visible temperature response in the range of 40℃ to 90℃ was achieved.
It achieves wide temperature range response, high reversibility, and visualized color changes, facilitating real-time monitoring. Its flexible structure is not easily broken, making it suitable for complex curved surfaces. Furthermore, it is easy to prepare, low in cost, and suitable for large-area thin film production.
Smart Images
Figure CN121471667A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultrasound therapy technology, and more specifically to a reversible thermochromic thin film material based on organic polymers and transition metal salts and its preparation method. Background Technology
[0002] Thermochromic materials are a class of functional materials that undergo reversible color changes with temperature variations, and are widely used in smart windows, temperature sensors, decorative coatings, anti-counterfeiting labels, and other fields. In recent years, inorganic salt materials have attracted widespread attention due to their excellent thermal stability and reversibility. Among them, transition metal salts such as CuCl2·2H2O, NiCl2·6H2O, and CoCl2·6H2O possess reversible coordination rearrangement properties, and their color change mechanisms are clear and their response speed is fast, making them ideal candidate materials for thermochromic materials.
[0003] HIFU (High-Intensity Focused Ultrasound) is a non-invasive ultrasound therapy technique with broad application prospects. It utilizes the penetrability and focusability of ultrasound waves in tissues to concentrate the emitted ultrasound waves from a transducer onto the treatment target area. The acoustic-thermal effect of the tissue generates temperatures exceeding 65°C, causing protein tissue to shrink, denature, and eventually coagulative necrosis within a short time, thus achieving the therapeutic goal. During HIFU treatment, accurate temperature control is crucial to ensure the treatment targets the tissue without damaging surrounding normal tissues. Real-time temperature and efficacy monitoring are of great significance for the clinical application of HIFU.
[0004] Currently, focal zone temperature monitoring in HIFU systems mainly relies on thermocouples, ultrasound echo analysis, and MRI imaging. Thermocouples are susceptible to distortion due to acoustic field disturbances; ultrasound methods are highly indirect and have limited real-time accuracy; while MRI can achieve visualized temperature measurement, the equipment is expensive and has low clinical applicability.
[0005] Thermocouples heat up when irradiated by an ultrasound beam and require good contact with the area being measured, which can disturb the sound field and lead to inaccurate temperature measurements. Ultrasound is an indirect method of temperature measurement and may be affected by various factors, so its real-time performance and accuracy cannot be guaranteed. MRI equipment is expensive, which limits its widespread clinical application.
[0006] Traditional thermosensitive membranes have a sensitive temperature range of 50℃-70℃, which cannot cover the entire tissue treatment temperature field; they require microscopic observation and cannot quickly provide feedback on the focal temperature; the dye membrane is uneven, which can affect the sound field; organic color-changing materials are easily degraded in the air, making long-term preservation difficult; and their mechanical strength is insufficient, which can easily cause the membrane to rupture.
[0007] For example, Chinese patent CNU101513554A describes a thermosensitive membrane proposed as a visual temperature measurement method, but its color change range is narrow (mostly concentrated in 50~70℃), and it has problems such as unstable organic dyes, poor film uniformity, and slow response.
[0008] Therefore, there is an urgent need for a thermochromic material that has a wide temperature range, is stable and reversible, is mechanically flexible, and can be mass-produced, in order to achieve real-time visual monitoring of ultrasonic focal zone temperature. Summary of the Invention
[0009] This invention aims to solve the problems of existing HIFU focal zone temperature measurement methods and equipment being expensive, having limited accuracy, narrow temperature measurement range, poor stability, and insufficient mechanical strength. It provides a reversible thermochromic film based on the PEDOT:COOH–CuCl2·2H2O composite system, which realizes a visualized temperature response in the range of 40℃~90℃, for low-cost and flexible focal zone temperature monitoring.
[0010] This invention provides an organic-inorganic composite reversible thermochromic material, comprising a conductive polymer and a transition metal salt with reversible coordination rearrangement properties; By combining the good film-forming properties and flexibility of conductive polymers, and incorporating transition metal salts, reversible color changes are induced by reversible coordination rearrangement structural changes. Polymer films containing different concentrations of copper salts are prepared on a substrate to obtain thermosensitive color-changing materials.
[0011] According to a further preferred embodiment of the above-described scheme of the present invention, the transition metal salt is one or more combinations of CuCl2·2H2O, NiCl2·6H2O, and CoCl2·6H2O.
[0012] According to a further preferred embodiment of the above-described scheme of the present invention, the conductive polymer is PEDOT:COOH or its derivative, or a material with good charge transfer properties such as polyaniline (PANI) or polypyrrole (PPy).
[0013] According to a further preferred embodiment of the above-described scheme of the present invention, the conductive polymer is PEDOT:COOH or its derivative, or a material with good charge transfer properties such as polyaniline (PANI) or polypyrrole (PPy).
[0014] A further preferred embodiment of the above-described scheme according to the present invention further includes a polymer adhesive; The polymer binder includes one or more of polyvinyl alcohol (PVA), polyacrylic acid (PAA), or polyurethane (PU).
[0015] In a further preferred embodiment of the above-described scheme of the present invention, the substrate is glass, plastic, or metal.
[0016] A further preferred embodiment of the present invention includes a thermally conductive filler, wherein the thermally conductive filler comprises one or more of Al2O3, SiO2, or BN nanoparticles.
[0017] This invention also provides a method for preparing an adjustable color-changing thin film based on the aforementioned organic-inorganic composite reversible thermochromic material, comprising the following steps: The transition metal salt was dissolved in deionized water to prepare a solution; The solution is coated onto the substrate surface using screen printing, spraying, drop coating, or spin coating to form a uniform thin film, thereby achieving control over different thicknesses and response rates; The coated film is subjected to heat annealing and curing to form a film with adjustable color-changing properties.
[0018] According to a further preferred embodiment of the above-described scheme of the present invention, the color-changing temperature of the thin film can be controlled by adjusting the type, concentration, number of printing layers, or annealing temperature of the metal salt.
[0019] According to a further preferred embodiment of the above-described scheme of the present invention, the thin film is suitable for temperature sensors or anti-counterfeiting labels.
[0020] According to the present invention, the following outstanding technical effects and advantages are achieved: 1. Wide temperature range response: By adjusting the type and concentration of metal salt, the number of printing layers or the annealing temperature, the color change temperature range of 40–90℃ can be achieved, which fully covers the HIFU focal zone temperature. 2. High reversibility and repeatability: The color can be restored multiple times; 3. High visibility: Color changes are visible to the naked eye, facilitating real-time monitoring; 4. Flexible structure: The substrate is not easily broken, making it suitable for complex curved surfaces and improving the thermal response speed and repeatability of the thin film; 5. Simple preparation and low cost: The screen printing process is mature, supports the preparation of large-area films, and is suitable for large-scale production; 6. Excellent environmental stability: The PEDOT:COOH system can be sealed to prevent moisture and improve service life.
[0021] Overall, the solution of this invention effectively solves the problems of the prior art, such as the inability to adjust the color-changing temperature, poor film uniformity, slow response speed, difficulty in achieving large-area film preparation, and limited color change. Attached Figure Description
[0022] Figure 1This is a schematic diagram illustrating the process of preparing a PEDOT:COOH thin film layer on a substrate according to an embodiment of the present invention. Figure 2 Optical diagrams showing the effects of material composition variations and the number of printed layers on the film morphology in embodiments of the present invention. Detailed Implementation
[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Those skilled in the art will understand that this description is exemplary and that the present invention is not limited to these specific embodiments.
[0024] Figure 1 This is a schematic diagram illustrating the process of preparing a PEDOT:COOH thin film layer on a substrate according to an embodiment of the present invention. Figure 2 Optical diagram showing the effect of changes in material composition and the number of printed layers on the morphology of the thin film.
[0025] like Figure 1 As shown, the process for preparing the PEDOT:COOH thin film layer of the present invention is as follows: ① providing one or more screens; ② coating photosensitive emulsion on the screens after plasma treatment; ③ exposing the mask to ultraviolet light; ④ developing to form a pattern; ⑤ coating the pattern with color-changing ink; ⑥ printing under constant temperature; ⑦ photocuring for shaping.
[0026] like Figure 2 As shown, (a) is the morphology of the original PEDOT:COOH film sample, (b) is the micro-grains that begin to form in the film of sample II-2.0-0.2, (c) as the number of printed layers doubles to sample II`-2.0-0.2, the grain size increases significantly and particle agglomeration occurs, (d) when the amount of CS added is further increased (sample III-2.0-0.4), the copper crystal concentration increases and dendritic structures are formed in the film, and (e) when the double electric layer printing process is used, the dendritic structure formed by particle agglomeration in sample III`-2.0-0.4 is very obvious, and the formed dendritic structure is coarser.
[0027] The reversible thermochromic material, the preparation method for forming an adjustable color-changing film, and the film preparation process of the present invention will be described in detail below through examples.
[0028] Example 1:
[0029] Example 1 of the present invention provides an organic-inorganic composite reversible thermochromic material, comprising a conductive polymer and a transition metal salt having reversible coordination rearrangement characteristics.
[0030] This embodiment 1 utilizes the excellent film-forming properties and flexibility of conductive polymers, incorporating transition metal salts (such as CuCl2·2H2O). The reversible coordination rearrangement of these salts induces reversible color changes. Polymer films containing different concentrations of copper salts are prepared by screen printing onto a PET substrate, achieving low-cost, scalable manufacturing of temperature-sensitive color-changing materials. Temperature is determined by observing the color change of the film.
[0031] In Embodiment 1 of the present invention, the transition metal salt is preferably CuCl2·2H2O, but metal salts with reversible coordination rearrangement characteristics such as NiCl2·6H2O and CoCl2·6H2O can also be used; the conductive polymer is PEDOT:COOH or its derivatives, and materials with good charge transfer characteristics such as polyaniline (PANI) and polypyrrole (PPy) can also be used to form different optical response systems.
[0032] Example 2:
[0033] This invention also provides a method for preparing an adjustable color-changing film based on an organic-inorganic composite reversible thermochromic material. First, a metal salt is dissolved in deionized water to prepare a solution. Second, the solution is coated onto the substrate surface using screen printing, spraying, drop coating, or spin coating to form a uniform film, thereby achieving control over different thicknesses and response rates. Finally, the coated film is subjected to thermal annealing and curing to form a film with adjustable color-changing properties.
[0034] In the preparation method of this embodiment, a uniform film is formed by screen printing, spraying or spin coating and then cured by thermal annealing; the color-changing temperature can be adjusted by adjusting the metal salt concentration, the number of printing layers or the annealing temperature; the finally formed adjustable color-changing film is used for ultrasonic focal zone temperature monitoring and other occasions that require visual temperature control.
[0035] Example 3:
[0036] In Embodiment 3 of the present invention, a process for preparing an adjustable color-changing film is also provided, comprising: S1: A 0.1M aqueous solution of copper chloride dihydrate prepared using DI water (deionized water) is called CS; S2: A PEDOT:COOH film layer is prepared on a 160-mesh PET substrate using a screen printing process. The specific process steps are as follows: Figure 1 As shown: ① Screen stretched on a frame; ② Screen coated with emulsion; ③ Selective exposure to ultraviolet light using a mask alignment; ④ Patterned screen after development and rinsing off the unexposed emulsion; ⑤ Applying ink to the pattern; ⑥ Screen printing using extrusion; ⑦ Substrate for screen printing.
[0037] S3: The prepared film underwent a two-stage heat treatment: the first stage involved slow drying at 40–70°C (5–60 min) to control the distribution of the coordination precursor; the second stage involved coordination reconstruction / short-path annealing at 90–120°C (0.5–10 min), followed by immersion in a prepared CS solution (1.2 g / mL) for 2–3 hours. The film was then rinsed with water and dried with nitrogen. Finally, the color difference of the film as a function of temperature was observed for detection.
[0038] S4: Different volumes (0.2 ml and 0.4 ml) of CS solution were mixed with different concentrations (0, 1.2 g / L and 2.0 g / L in DI water) in PEDOT:COOH (1 g) and printed onto PET sheets. The distance between the screen and the substrate was set to 3 mm. Double-layer printing was performed for samples with high concentrations. The experimental design is shown in Table 1.
[0039] Table 1 Experimental Design
[0040] To observe the thermochromic phenomenon, the film was placed on a hot plate, and the temperature was gradually increased from 40°C to 90°C in 5°C increments, with each temperature point held for 2 minutes. All experiments were conducted in the same humidity environment to maintain consistency.
[0041] Process and structural description: To investigate the effects of changes in material composition and the number of printed layers on the film morphology, optical images were observed in this embodiment. For example... Figure 2 As shown, the original PEDOT:COOH film sample has a relatively smooth morphology (a). When copper salt is introduced, micro-grains begin to form in the film of sample II-2.0-0.2 (b). As the number of printed layers doubles to sample II'-2.0-0.2, the grain size increases significantly and particle agglomeration occurs (c). When the amount of CS added is further increased (as shown in III-2.0-0.4), the copper crystal concentration increases, leading to the formation of dendritic structures in the film (d). When using the double-layer printing process, particle agglomeration is obvious, and the dendritic structure formed as shown in (e) is even coarser.
[0042] Thermochromic image analysis: Samples were photographed during the heating process, and the relationship between color change and changes in CS concentration, CS volume, and number of printing layers was analyzed.
[0043] a) For samples with low CS concentrations (I-1.2-0.2), the color does not change significantly with increasing temperature; b) As the volume of the CS solution increases (I-1.2-0.4), the color slightly turns yellow at 65℃; c) Increasing the concentration of CS solution introduced into PEDOT:COOH (II-2.0-0.2) resulted in a lighter color in the liquid crystals, and a significant yellow change was observed at the transition temperature of 60°C. d) When the same ingredients are printed in a double layer, the original color becomes darker and the transition temperature shifts to 70°C; e) As the volume of this concentrated CS solution (III-2.0-0.4) increases, the color of the resulting film becomes lighter and turns yellow at 65°C; f) When the same composition is printed in a double layer (III`-2.0-0.4), the color becomes darker, and the color change can be clearly observed at a temperature of 65°C.
[0044] Explanation of the principle: The chemical principle behind thermochromic phenomena is that heating causes the loss of water of crystallization, transforming the copper(II) hexahydrate complex in the film into a tetrachlorocopper(II) complex. Furthermore, the reversibility of this reaction allows the complex to revert to the copper(II) hexahydrate complex upon cooling, thus restoring the film's original color. When CS is introduced into the PEDOT:COOH system, Cu²⁺ undergoes reversible coordination reconstruction with the -COOH group in the PEDOT derivative. As the temperature increases, the coordination number between Cu²⁺ and –COOH decreases, and the change in coordination field strength leads to a reversible shift in electronic transition energy levels, causing a reversible drift in the film's absorption spectrum, manifested as a macroscopic color change.
[0045] Based on the above principles, various transformations can be made to the constituent materials, such as: (I) Preparation of single metal salt thin films Material selection: CuCl2·2H2O was selected as the thermochromic material.
[0046] Solution preparation: Dissolve CuCl2·2H2O in deionized water to prepare a 0.5 mol / L solution.
[0047] Thin film preparation: A thin film was prepared on a glass substrate by screen printing, with two printing layers.
[0048] Heat annealing: Anneal in an 80℃ oven for 30 minutes.
[0049] Performance test: The film changes from blue to light green at 65°C and returns to its original color after cooling, with a response time of less than 10 seconds.
[0050] (II) Mixed metal salt system Material selection: Mix CuCl2·2H2O and NiCl2·6H2O in a mass ratio of 3:1.
[0051] Solution preparation: Dissolve the mixed salts in deionized water to prepare a 0.6 mol / L solution.
[0052] Thin film preparation: A thin film was prepared on a plastic substrate by spraying, with three sprayings.
[0053] Heat annealing: Anneal at 90℃ for 20 minutes.
[0054] Performance testing: The film exhibits a blue-green color at 60°C and turns brownish-red at 80°C, achieving a two-stage color change.
[0055] (III) Introducing adhesives to improve adhesion Material selection: CuCl2·2H2O + 5wt% PVA binder.
[0056] Solution preparation: Dissolve PVA in deionized water, add CuCl2·2H2O and stir until homogeneous.
[0057] Thin film preparation: A film was formed on a metal substrate by spin coating.
[0058] Heat annealing: Anneal at 70℃ for 40 minutes.
[0059] Performance testing: The film adhesion is significantly enhanced, the color change stability is improved, and there is no significant performance degradation after 100 cycles of use.
[0060] (IV) Introducing thermally conductive fillers to improve response speed Material selection: CuCl2·2H2O + 10wt% Al2O3 nanoparticles.
[0061] Solution preparation: Add Al2O3 nanoparticles to CuCl2·2H2O solution and disperse evenly by ultrasonication.
[0062] Thin film preparation: A film is formed on a glass substrate by spraying.
[0063] Heat annealing: Anneal at 100℃ for 15 minutes.
[0064] Performance testing: Response time reduced to less than 5 seconds, thermal conductivity improved, and color change more rapid.
[0065] (V) Large-area thin film preparation Material selection: CuCl2·2H2O Solution preparation: 0.4 mol / L Film preparation: Films are continuously formed on a flexible PET substrate using roll-to-roll screen printing.
[0066] Hot annealing: online annealing at 100℃.
[0067] Performance testing: Successfully achieved continuous production of 1m×1m film with uniform color change, suitable for packaging anti-counterfeiting.
[0068] The present invention has been described in detail above with reference to the embodiments. Those skilled in the art will understand that the present invention can be modified in various ways. As long as these modifications do not depart from the spirit and purpose of the present invention, they should all fall within the scope of this application. The scope of protection of the present invention is defined by the appended claims.
Claims
1. An organic-inorganic composite reversible thermochromic material, characterized in that, Including conductive polymers and transition metal salts with reversible coordination rearrangement properties; By combining the good film-forming properties and flexibility of conductive polymers, and incorporating transition metal salts, reversible color changes are induced by reversible coordination rearrangement structural changes. Polymer films containing different concentrations of copper salts are prepared on a substrate to obtain thermosensitive color-changing materials.
2. The organic-inorganic composite reversible thermochromic material as described in claim 1, characterized in that, The transition metal salt includes one or more combinations of CuCl2·2H2O, NiCl2·6H2O, and CoCl2·6H2O.
3. The organic-inorganic composite reversible thermochromic material as described in claim 1 or 2, characterized in that, The conductive polymer is a PEDOT derivative with a coordinating group, which is one of -COOH, -SO3 or -SH, or a complex of the coordinating group with PSS, or a material with good charge transfer properties such as polyaniline (PANI) or polypyrrole (PPy).
4. The organic-inorganic composite reversible thermochromic material as described in claim 1, characterized in that, It also includes polymer adhesives; The polymer binder includes one or more of polyvinyl alcohol (PVA), polyacrylic acid (PAA), or polyurethane (PU).
5. The organic-inorganic composite reversible thermochromic material as described in claim 1, characterized in that, It also includes thermally conductive fillers, which include one or more of Al2O3, SiO2, or BN nanoparticles.
6. The organic-inorganic composite reversible thermochromic material as described in claim 1, characterized in that, The substrate is made of glass, plastic, or metal.
7. The organic-inorganic composite reversible thermochromic material as described in claim 3, characterized in that, in, The molar ratio of the derivatives is 1:(0.2–8).
8. A method for preparing an adjustable color-changing thin film based on the organic-inorganic composite reversible thermochromic material according to any one of claims 1 to 7, characterized in that, Includes the following steps: The transition metal salt was dissolved in deionized water to prepare a solution; The solution is coated onto the substrate surface using screen printing, spraying, drop coating, or spin coating to form a uniform thin film, thereby achieving control over different thicknesses and response rates; The coated film is subjected to heat annealing and curing to form a film with adjustable color-changing properties.
9. The preparation method according to claim 8, characterized in that, The color-changing temperature can be adjusted by regulating the concentration of metal salts, the number of printing layers, or the annealing temperature.
10. The preparation method according to claim 8 or 9, characterized in that, The film is suitable for temperature sensors or anti-counterfeiting labels.