Gradient temperature control flexible electronic heating device and preparation method thereof

Abstract

The invention discloses a gradient temperature control flexible electronic heating device and a preparation method thereof. The preparation method comprises the following steps: selecting a three-layer composite insulating material as a base material, wherein the three-layer composite insulating material consists of an upper layer of aramid paper, a lower layer of aramid paper and a polyimide film positioned between the two layers of aramid paper; performing line scanning laser direct writing processing on the aramid paper on one surface of the base material by adopting a pulse laser, and inducing to generate a three-dimensional porous graphene network layer; and preparing an electrode on the three-dimensional porous graphene network layer to obtain the gradient temperature control flexible electronic heating device. After bias voltage is applied to the gradient temperature control flexible electronic heating device, a temperature gradient which is gradually reduced from the center area to the edge area is formed. The thermal characteristics and the structure of the material are utilized, center heat and edge temperature gradient thermal field distribution meeting the human body physiotherapy requirement is achieved under single voltage driving, and meanwhile the device has the advantages of being low in cost, high in flexibility and fast in response.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic heating devices and their fabrication, and particularly to a gradient temperature-controlled flexible electronic heating device and its fabrication method. Background Technology

[0002] Flexible devices, with their excellent stretchability, adaptability, and wide range of applications, have become a focus of attention in many disciplines. Combining flexible materials with functional materials, such as semiconductor materials, can create multifunctional flexible composite materials, which in turn can be used to develop flexible photodetectors, flexible heaters, and other similar products.

[0003] However, most existing flexible heaters prioritize uniform temperature. In practical biomedical applications, such as joint heating or acupuncture point therapy, a non-uniform "gradient thermal field" is often required—that is, achieving high-temperature thermal stimulation (e.g., 45-50°C) at the center of the acupoint, while maintaining a lower temperature (e.g., 37-40°C) in the surrounding area to prevent burns and provide thermal buffering. Traditional screen printing or coating processes struggle to achieve this complex resistance distribution on a single substrate in one step, typically requiring the splicing of different materials, leading to complex processes and unstable interfaces. Summary of the Invention

[0004] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide a gradient temperature-controlled flexible electronic heating device and its preparation method. By using a composite material with a three-layer structure of aramid paper-polyimide film-aramid paper as the substrate, a porous graphene structure is induced on one side of the aramid paper using a laser as the heating substrate. Utilizing the thermal properties and structure of the material itself, a gradient thermal field distribution of "center heat and edge temperature" that meets the needs of human physiotherapy can be achieved under a single voltage drive. At the same time, it has the advantages of low cost, high flexibility, and fast response.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for fabricating a gradient temperature-controlled flexible electronic heating device, comprising the following steps:

[0007] (1) A three-layer composite insulating material is selected as the substrate, wherein the three-layer composite insulating material consists of two layers of aramid paper and a polyimide film located between the two layers of aramid paper;

[0008] (2) A pulsed laser is used to perform line scanning laser direct writing on one surface of the substrate to induce the generation of a three-dimensional porous graphene network layer.

[0009] (3) An electrode is prepared on a three-dimensional porous graphene network layer to obtain a gradient temperature-controlled flexible electronic heating device; after a bias voltage is applied, the gradient temperature-controlled flexible electronic heating device forms a temperature gradient that gradually decreases from the central region to the edge region.

[0010] In some embodiments of the present invention, the specific process parameters for the line scanning laser direct writing process described in step (2) are as follows:

[0011] The laser power is 1.8~2.0 W, the scanning speed is 140~150 mm / s, and the scanning interval is 35~45 µm.

[0012] In some embodiments of the present invention, the pulsed laser is a pulsed laser with a wavelength of 10.64µm.

[0013] In some embodiments of the present invention, during the line scan laser direct writing process, the polyimide film blocks laser penetration, and laser induction is limited to the aramid paper on one of the surfaces.

[0014] In some embodiments of the present invention, in the three-layer composite insulating material, the thickness of the aramid paper is 30~60µm, and the thickness of the polyimide film is 120~150µm.

[0015] In some embodiments of the present invention, the preparation of electrodes on the three-dimensional porous graphene network layer specifically involves: the three-dimensional porous graphene network layer being square, with conductive silver paste applied to the edge regions of two opposite sides and copper foil adhered thereon as electrodes.

[0016] The present invention also provides a gradient temperature-controlled flexible electronic heating device, comprising, in sequence, a three-dimensional porous graphene network layer, a polyimide film, and a lower aramid paper layer; the three-dimensional porous graphene network layer is generated by laser induction from aramid paper.

[0017] The present invention also provides the application of the gradient temperature-controlled flexible electronic heating device in the preparation of mirror defogging patches, flexible medical physiotherapy skin patches, and light source detectors.

[0018] In some embodiments of the present invention, the flexible medical therapeutic skin patch is subjected to a bias voltage of 2 to 2.5V during use.

[0019] In some embodiments of the present invention, when the flexible medical physiotherapy skin patch is used, the temperature of the central area is 45~55°C and the temperature of the peripheral area is 37~40°C.

[0020] The mechanism of this invention is as follows:

[0021] In the online scanning laser direct writing process, the intermediate PI film plays a crucial "energy cutoff" role, blocking laser penetration, preventing substrate burn-through, and widening the process window. At the same time, utilizing the unique disordered three-dimensional fiber structure of aramid paper, laser energy is scattered and absorbed between the fibers, inducing the generation of a continuous three-dimensional porous graphene network without obvious periodic scanning traces. This eliminates microscopic hot spots and achieves an isotropic and uniform conductive layer. The three-layer structure of "three-dimensional porous graphene-polyimide film-aramid paper" brings unique thermal properties, thereby achieving a gradient thermal field distribution of "center heat and edge temperature" that meets the needs of human physiotherapy under a single voltage drive.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The temperature-controlled flexible electronic heating device of the present invention utilizes the thermal properties of the material and device structure to generate a gradient temperature distribution of "high in the center and low at the edge" under single voltage drive. This thermal field distribution perfectly matches the needs of traditional Chinese medicine moxibustion and joint physiotherapy - it can provide sufficient heat dose at the center of the affected area, and form a thermal buffer transition through the low temperature zone at the edge, solving the problem of discomfort to the surrounding skin caused by traditional uniform heaters, and providing an "adaptive gradient thermal field" that meets clinical needs.

[0024] (2) The method for fabricating the temperature-controlled flexible electronic heating device of the present invention uses a three-layer composite material of "aramid paper-polyimide (PI)-aramid paper" as the substrate, which exhibits unique advantages, providing a wide process window and high yield. The dense PI layer in the middle acts as a key "laser energy cutoff layer", which effectively blocks excess energy from penetrating when performing high-density (small-pitch) laser scanning on high-temperature areas, preventing the substrate from burning through or carbonizing. This structure, combined with the efficient laser direct writing process, ensures an extremely high success rate when manufacturing complex gradient patterns, and only requires coating with silver paste and copper strips for subsequent use, greatly reducing the fabrication difficulty and production cost.

[0025] (3) When the preferred laser scanning speed (e.g., 140 mm / s) is used in this invention, the formed paper-based LIG surface does not show obvious periodic laser scanning trajectory, which ensures a dense porous structure and a relatively uniform temperature distribution.

[0026] (4) The heater of the present invention has a three-layer structure of "three-dimensional porous graphene-polyimide film-aramid paper". The middle polyimide film also provides flexible support, and the lower aramid paper can also provide breathability when in direct contact with human skin. The lower aramid paper has a loose and porous structure, which naturally forms an "air thermal resistance layer". When the heater is attached to human skin, the bottom aramid paper acts as a thermal damper. It makes the temperature rise on the side in contact with the skin delayed and more gentle, preventing the heater from causing thermal shock or low-temperature burns to the skin in a very short time, and providing better thermal insulation buffer than a simple PI film.

[0027] (5) The heater of the present invention has excellent mechanical flexibility and portability, excellent bending resistance and is extremely lightweight, and is easy to fit closely to human joints or skin. At the same time, the gradient heating design avoids the need for complex external control circuits to achieve multiple temperature zones, which greatly improves the integration and portability of the device.

[0028] (6) The heater of the present invention has negative feedback thermal regulation characteristics when it is bent. When it is attached to the human joint and performs large-scale activities, the device can sense the deformation and automatically adjust to reduce the output heat, preventing heat accumulation and burns caused by the folding and squeezing of the skin inside the joint. It provides a passive safety protection mechanism that does not require additional sensors.

[0029] (7) The heater of the present invention has extremely fast thermal response and long-term working stability. Under the drive of a low safety voltage, the time to reach the peak temperature is less than 30 seconds (even faster in some high power density areas). At the same time, thanks to the excellent temperature resistance and chemical stability of the aramid substrate, the device can maintain stable operation at a high temperature for a long time and maintain performance without degradation in a variety of complex scenarios such as mirror defogging and medical hot compress. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a gradient temperature-controlled flexible electronic heating device prepared according to an embodiment of the present invention.

[0031] Figure 2 SEM images of the three-dimensional porous graphene network layer (a) and the monolayer PI after laser induction (b) of the gradient temperature-controlled flexible electronic heating device prepared for embodiments of the present invention.

[0032] Figure 3 The images shown are SEM images of three-dimensional porous graphene network layers prepared using different scanning speeds according to embodiments of the present invention; wherein, (a)-(c): corresponding to a scanning speed of 150 mm / s, (b) is a magnified view of (a), and (c) is a magnified view of (b); (d)-(f): corresponding to a scanning speed of 140 mm / s, (e) is a magnified view of (d), and (f) is a magnified view of (e).

[0033] Figure 4 for Figure 3 EDS analysis results corresponding to the SEM image in (b); where (a) is the distribution map of C element; (b) is the distribution map of N element; and (c) is the distribution map of O element.

[0034] Figure 5 SEM images of the cross-section of the gradient temperature-controlled flexible electronic heating device prepared according to an embodiment of the present invention; wherein (b) is a partial magnified view of the unprocessed aramid paper in (a), (c) is a partial magnified view of the three-dimensional porous graphene network layer in (a); (d) is the C element distribution map corresponding to (a); (e) is the N element distribution map corresponding to (a); and (f) is the O element distribution map corresponding to (a).

[0035] Figure 6 Raman spectra (a) and IV curves (b) of the gradient temperature-controlled flexible electronic heating device prepared for embodiments of the present invention; wherein, sample 1 corresponds to the device with a scanning speed of 150 mm / s; and sample 2 corresponds to the device with a scanning speed of 140 mm / s.

[0036] Figure 7 The peak temperature comparison results of the gradient temperature-controlled flexible electronic heating device prepared according to the embodiments of the present invention are shown below; (a) is the peak temperature of the heater prepared with a scanning speed of 150 mm / s under different applied voltages; (b) is the peak temperature of the heater prepared with a scanning speed of 140 mm / s under different applied voltages; (c) is the peak temperature of the heater prepared with different parameters under an applied voltage of 6V. Sample 1 corresponds to the device with a scanning speed of 150 mm / s; Sample 2 corresponds to the device with a scanning speed of 140 mm / s.

[0037] Figure 8 The results of long-term heating test and bending resistance test of the gradient temperature-controlled flexible electronic heating device prepared for the embodiments of the present invention are shown, wherein (a) cyclic test; (b) 10 heating-to-room temperature test; (c) resistance change test after 800 bending-to-recovery cycles.

[0038] Figure 9 To observe the real-time temperature distribution of the gradient temperature-controlled flexible electronic heating device prepared in the embodiments of the present invention under different applied bias voltages using a thermal imager: (a) 4V; (b) 6V; (c) 8V; (d) 10V.

[0039] Figure 10 for Figure 9 In the thermal imaging image in (b), the temperature distribution curve is shown at the location indicated by the white dashed line.

[0040] Figure 11Thermal images of the LIG heater induced by a monolayer PI film: (a): real-time temperature with an applied voltage of 3V; (b): real-time temperature with an applied voltage of 7V.

[0041] Figure 12 The real-time temperature of the gradient temperature-controlled flexible electronic heating device under different bending states was observed by a thermal imager when the bias voltage was 3.7V: (a) Unbent state (b) Bent state.

[0042] Figure 13 To observe the real-time temperature of a gradient temperature-controlled flexible electronic heating device adhered to different areas of human skin using a thermal imager: (a) Image of the heater adhered to the back of the hand with a bias voltage of 1.9V; (b) Image of the heater adhered to the wrist with a bias voltage of 2.3V.

[0043] Figure 14 The results of the mirror defogging test of the gradient temperature-controlled flexible electronic heating device prepared for the embodiments of the present invention are as follows: (a) physical photograph of the mirror containing a large amount of water mist before heating; (b) physical photograph of the mirror after the fog is removed after heating; (c) mirror image observed under a microscope after heating for 0s; (d) mirror image observed under a microscope after heating for 20s; (e) mirror image observed under a microscope after heating for 30s.

[0044] Figure 15 Enhanced thermal radiation test of the gradient temperature-controlled flexible electronic heating device prepared for an embodiment of the present invention: (a) a physical image of the laser-processed letters GZHU; (b) a thermal image after irradiation by a light source. Detailed Implementation

[0045] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0046] Example

[0047] The method for fabricating the gradient temperature-controlled flexible electronic heating device in this embodiment includes the following steps:

[0048] Step 1: Substrate Preparation. A three-layer composite insulating material is selected as the substrate. This material is composed of two layers of aramid paper (each approximately 50µm thick) and a middle layer of polyimide (PI) film (approximately 150µm thick) bonded together with an adhesive. Before the experiment, the surface of the material is cleaned with an air gun or a lint-free cloth.

[0049] Step 2: Partitioned Laser Direct Writing Process (Core Step) A CO2 pulsed laser marking machine (Hanslaser, CO2-D30) with a wavelength of 10.64 µm is used to perform line scanning laser direct writing on the substrate surface:

[0050] Processing parameters: Laser power is 1.9 W, processing area is... The scanning speed is 140-150 mm / s, and the scanning interval is 40 µm.

[0051] Technical Mechanism: In this process, the intermediate PI film plays a key "energy cutoff" role, blocking laser penetration, preventing substrate burn-through, and widening the process window; at the same time, by utilizing the unique disordered three-dimensional fiber structure of aramid paper, laser energy is scattered and absorbed between fibers, inducing the generation of a continuous three-dimensional porous graphene network without obvious periodic scanning traces, thereby eliminating micro hot spots and realizing an isotropic uniform conductive layer.

[0052] Step 3: Electrode encapsulation: Apply conductive silver paste to both ends of the processing area (i.e., the three-dimensional porous graphene network layer) and adhere copper foil as electrodes.

[0053] like Figure 1 As shown, the gradient temperature-controlled flexible electronic heating device of this embodiment includes an upper three-dimensional porous graphene network layer 2, a polyimide film 3, and a lower aramid paper layer 4. The three-dimensional porous graphene network layer has a pair of electrodes 1 arranged in relative positions. The upper three-dimensional porous graphene network layer 2 is generated by laser induction from aramid paper.

[0054] The gradient temperature-controlled flexible electronic heating device prepared in this embodiment was tested and characterized, and the results are as follows:

[0055] 1. SEM characterization

[0056] (1) The surfaces of the laser-processed three-layer composite material and the single-layer PI film were characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown in the figure, the laser processing power and spacing for the three-layer composite material and the single-layer PI film are 1.9 mW and 40 µm, respectively, and the scanning speeds are 140 mm / s and 160 mm / s, respectively.

[0057] Depend on Figure 2 In (a), a laser-induced three-dimensional porous graphene (LIG) structure can be observed on the surface of the three-layer composite material, and no periodic traces of laser scanning are observed, while the single-layer PI film exhibits a clear periodic structure after processing. Figure 2 (b)

[0058] (2) Using higher magnification SEM, the gradient temperature-controlled flexible electronic heating devices prepared at different scanning speeds: 140 mm / s and 150 mm / s were observed: at a scanning speed of 150 mm / s, a porous structure appeared on the surface, showing the effect of interconnection of the carbon skeleton (e.g. Figure 3As shown in (a)-(c), in contrast, although the samples processed at a scan rate of 140 mm / s showed a similar overall morphology, the reduced scan rate resulted in a higher laser flux, leading to more pronounced layer stacking (as shown in (a)-(c)). Figure 3 In (d)-(f), it is noteworthy that carbon nanostructures with a size of 50-100 nm were observed on the bone structure under both processing conditions. Although the paper-based LIG surface was fabricated using a line scan of 140 mm / s, no obvious periodic laser scanning trajectory was observed, ensuring a dense porous structure and a relatively uniform temperature distribution.

[0059] Meanwhile, in order to observe the carbon content of aramid paper after laser treatment, Figure 3 The structure of (b) was subjected to EDS analysis, such as Figure 4 As shown in the figure, the C element content is very high, proving that the framework structure is a high-carbon structure. Since the material used before induction is a three-layer material, to prove that LIG mainly originates from the paper substrate, the cross-section of the processed sample was characterized by SEM in this embodiment, as shown below. Figure 5 As shown, in Figure 5 In (a)-(c), a distinct three-layer structure is clearly observed. The middle PI layer was not laser-processed, and the depressions observed in the laser-induced LIG layer are due to the sample slices characterized by SEM of this cross-section. Furthermore, as... Figure 5 As shown in (d)-(f), cross-sectional EDS analysis confirms that the carbon content of the bottom three-dimensional porous graphene network layer is significantly higher than that of the unprocessed aramid paper and the intermediate layer, which proves that the LIG formation in this study is entirely derived from the paper substrate.

[0060] 2. Raman spectroscopy analysis and electrical performance testing

[0061] To further confirm the successful formation of the LIG structure, Raman spectroscopy was used to analyze the material composition before and after processing. The results showed that the laser-treated sample exhibited high performance at 1350 cm⁻¹. -1 (D-band), 1580cm -1 (G band) and 2700cm -1 A distinct characteristic peak was observed in the 2D band, confirming the presence of LIG. For example... Figure 6As shown in (a), by observing different laser processing parameters, the D-peak to G-peak ratios (referred to as ID / IG) of samples heater-1 (device with a scanning speed of 150 mm / s) and heater-2 (device with a scanning speed of 140 mm / s) are 0.80 and 0.77, respectively. A lower ID / IG generally indicates a more complete structure and fewer defects; however, defects in graphene introduce local potential field scattering, which reduces carrier mobility and leads to decreased conductivity. Therefore, heater-2 exhibits higher conductivity and relatively lower resistance. Furthermore, through... Figure 6 In Figure (b), the IV curves also show that the electrical performance of both heater-1 and heater-2 is very good, with resistance values ​​of 55Ω and 38Ω respectively. However, the IV curve of heater-2 has a higher slope and better electrical performance. Excellent electrical performance is beneficial for obtaining higher temperatures under the same applied power.

[0062] 3. Heating performance test:

[0063] Using a KEITHLEY 2231A-30-3 as the external power supply to provide the heater temperature rise, different peak temperatures are obtained by applying an external voltage of 4-10V. When the external power supply is turned on, the heater temperature rises rapidly over time until it reaches a steady-state temperature. Once the power is turned off, the heater temperature drops rapidly until it reaches room temperature, as shown in the following figures. Figure 7 As shown, it can be observed that the performance of heater-2 is better than that of heater-1.

[0064] 4. Long-term heating test and bending resistance test:

[0065] Using sample heater-2 (a device with a scan rate of 140 mm / s) as the test object, a bias voltage of 3.7V was continuously applied to the heater for 20 minutes, and the temperature remained stable at around 80°C (e.g., Figure 8 As shown in (a), this demonstrates the heater's ability to heat for extended periods. Furthermore, the heater underwent 10 cycles of heating-to-room-temperature testing (as shown in [reference]). Figure 8 As shown in (b), the heater exhibits excellent periodicity and a fast recovery time, indicating its applicability to environments with complex and variable requirements. Furthermore, the heater was repeatedly bent and restored 800 times using a self-made bending device. Its resistance was tested after every 100 cycles, revealing a change of approximately 0.1% in resistance after repeated bending. This demonstrates that the heater's performance does not rapidly decline or even lose function after repeated bending, indicating that its performance does not degrade after testing in complex environments, meeting the performance requirements of flexible electronic skin.

[0066] 5. Gradient thermal field testing: Using sample heater-2 (a device with a scanning speed of 140 mm / s) as the test object, a thermal imager (Fluke, Ti25, America) was used to observe the heating condition of the heater under different applied voltages. Figure 9 As shown in (a), when an external voltage of 4V is applied to the heater, its peak temperature can reach about 99℃, and the temperature distribution is relatively uniform. Furthermore, as the bias voltage increases, its temperature reaches 328℃ at 10V (as shown in Figure (a)). Figure 9 (as shown in (b)-(d))) close to Figure 7 The temperature-time image in Figure 9(b) shows that the peak temperature is reached in approximately 30 seconds, demonstrating the highly efficient performance of the heater prepared in this study, capable of reaching high temperatures in a short time. With increasing bias voltage, the temperature gradually exhibits a gradient distribution, with higher temperatures in the central region and lower temperatures in the peripheral region (Figure 9(b) and (c)). This temperature gradient phenomenon is particularly pronounced in Figure 9(c) and (d) with further increases in voltage, and can be further characterized through quantitative analysis. Specifically, to better quantify the temperature distribution, Figure 10 The transverse temperature distribution curve in Figure 9(b) is shown. This phenomenon is related to the unique thermodynamic properties of the three-layer matrix used in this application and the periodic structure of the three-dimensional porous graphene generated by laser-induced aramid paper. The aramid paper-PI-aramid paper three-layer composite structure results in a relatively uniform laser-induced LIG distribution, such as... Figure 2 As shown in (a). However, LIG ​​induced on a pure PI film exhibits a periodic stripe structure, as shown in [image 1]. Figure 2 As shown in (b), under different applied voltages, the temperature distribution in the processing area does not exhibit a similar gradient distribution, as... Figure 11 As shown, this stems from the laser-induced periodic structure.

[0067] 6. Heating test under bending conditions:

[0068] Using the sample heater-2 (a device with a scanning speed of 140 mm / s) as the test object, a self-made bending device was used for testing. Without bending and with a bias voltage of 3.7V, the overall temperature was observed to be approximately 90℃, with the core temperature reaching around 105℃. After applying a bending effect to the heater, it was found that the real-time overall temperature of the heater remained around 90℃. Figure 12(b) However, the temperature in the central region is lower than before bending, which is attributed to the specific structure of LIG. This reduction is due to the change in the conductive paths formed by the porous graphene structure on its surface during bending. When bending upwards, the current path decreases and the total resistance increases, thereby reducing the temperature rise at the same bias voltage. Therefore, at the same bias voltage, the real-time temperature of the heater observed by the thermal imager is slightly lower, exhibiting negative feedback thermal regulation characteristics during bending. This characteristic indicates that the heater of the present invention has the following features:

[0069] (1) "Strain response type" passive safety mechanism for preventing burns

[0070] Traditional flexible heaters, when applied to bent joints (such as knees and elbows), often experience tighter adhesion due to compression or heat buildup due to localized folding, easily leading to "localized overheating" and causing low-temperature burns. The heater of this invention exhibits "negative feedback thermal regulation characteristics." When a human joint (where the skin is stretched or compressed, making it more sensitive to heat) bends, the heater bends accordingly. Because the resistance of the LIG network increases slightly under stretching / bending conditions, the heating power automatically decreases, and the temperature moderately drops. This invention possesses an inherent bending-thermal power negative correlation characteristic. When applied to a human joint during significant activity, the device can sense the deformation and automatically fine-tune to reduce the output heat, preventing heat accumulation burns caused by skin folding and compression inside the joint, providing a passive safety protection mechanism without the need for additional sensors.

[0071] (2) It has excellent mechanical toughness

[0072] In traditional brittle materials, bending can cause drastic fluctuations in resistance or even open circuits. The temperature of the device in this invention only decreased slightly, indicating that the conductive network remained intact, with only the contact points undergoing elastic changes. This demonstrates the mechanical buffering and reconfiguration capabilities of the three-layer structure. The slight, controllable temperature drop during bending confirms that the LIG conductive network did not fracture brittlely, but rather underwent elastic contact reconfiguration based on the aramid fiber skeleton. This characteristic ensures that the device maintains a continuous conductive path under dynamic deformation, verifying the superiority of the three-layer composite structure in resisting mechanical fatigue.

[0073] (3) Possesses the dual-modal potential of "motion perception"

[0074] Bending causes changes in temperature (actually, resistance), so by monitoring changes in current, the bending angle of the joint can be deduced. This can be further upgraded to an integrated device combining "thermotherapy + motion monitoring." Based on the resistive response characteristics of the LIG layer to bending strain, this invention is not only a heater but also a flexible strain sensor. By monitoring current fluctuations during the heating process, it can provide real-time feedback on the patient's joint range of motion, offering a dual function of "thermal stimulation + motion data" for rehabilitation therapy.

[0075] (4) It is beneficial to energy saving and battery life.

[0076] Bending typically signifies being in a working / active state, or a more snug fit. In this situation, power consumption automatically decreases, effectively saving energy. Therefore, automatically reducing power consumption during deformation helps extend the battery life of portable power sources (such as button batteries or flexible batteries), aligning with the low-power, green design principles of wearable devices.

[0077] 7. Human body heating test

[0078] Using the sample heater-2 (a device with a scanning speed of 140 mm / s) as the test object, the heater was adhered to a joint of the human body, such as... Figure 13 As shown in (a), the heater was attached to the back of the test subject's hand and it was observed that it still worked normally and effectively. The comparison with the normal human body temperature (approximately 36°C) proves that the heater is wearable. At the same time, the device was also attached to the test subject's wrist and it was found that it could also be used normally. Figure 13 (b) proves that the sensor can be used as an electronic skin heater to achieve a heating therapy effect.

[0079] 8. Defogging test:

[0080] Using the sample heater-2 (a device with a scanning speed of 140 mm / s) as the test object, the heater (unprocessed side) was adhered to the back of the mirror using thermally conductive silicone. The heater and mirror, used for defogging testing, were placed in an environment with 40% humidity and 24°C. A fogging layer was created on the mirror surface using a moisture-generating device. Figure 14 In (a) (the mirror's state before the heater operates), a large number of water droplets can be observed accumulating on the mirror's surface. Subsequently, the heater is adhered to the back of the mirror, and a bias voltage of 4 V is applied to the heater. After approximately 35 seconds, the fog is successfully removed. Figure 14 As shown in (b), this image shows the surface of the mirror after it has been heated. Furthermore, to observe the process of water droplets evaporating from the mirror surface more closely, the mirror was examined under a microscope. It was found that when the heater was not subjected to a bias voltage, the water droplets were very dense (as shown in image). Figure 14In the middle (c)), after heating for 20 seconds, the volume of the water droplets gradually decreases (e.g. Figure 14 (d) , and after heating for 30 seconds, the water droplets gradually disappear (e.g. Figure 14 As shown in (e), this demonstrates that the heater has an excellent defogging function. By increasing the heating material area and encapsulation device of the heater, the fog on the mirror can be completely removed within 35 seconds. By increasing the area of ​​the heating substrate and encapsulation device, it can be applied to the defogging requirements of automotive rearview mirrors and is expected to be used in many defogging fields.

[0081] 9. Controllable processing

[0082] By combining laser processing technology with computer-controlled software, the initials of "Guangzhou University" were successfully processed onto the surface of aramid paper (e.g., ...). Figure 15 As shown in (a), due to the strong absorption rate of porous graphene structure over a wide spectral range, it appears black under visible light. Furthermore, according to Kirchhoff's law, an excellent absorber is also an excellent heat sink. LIG exhibits strong absorption and photothermal effects on light sources. When placed under a xenon lamp for 30 seconds and observed using an infrared thermal imager, it was found that the surface temperature of the four English letters after processing was higher than that of the unprocessed area (e.g., ...). Figure 15 In (b), the four letters GZHU were observed on the thermal imager by the temperature difference in different areas. The inconsistent brightness of the letters was caused by uneven illumination from the light source. Based on this study, the technology can be used for the design of anti-counterfeiting marks. Other characters or patterns can be processed by laser in the future, and it can be flexibly processed and applied to the field of light source detection.

[0083] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 method for fabricating a gradient temperature-controlled flexible electronic heating device, characterized in that, Includes the following steps: (1) A three-layer composite insulating material is selected as the substrate, wherein the three-layer composite insulating material consists of two layers of aramid paper and a polyimide film located between the two layers of aramid paper; (2) A pulsed laser is used to perform line scanning laser direct writing on one surface of the substrate to induce the generation of a three-dimensional porous graphene network layer. (3) An electrode is prepared on a three-dimensional porous graphene network layer to obtain a gradient temperature-controlled flexible electronic heating device; after a bias voltage is applied, the gradient temperature-controlled flexible electronic heating device forms a temperature gradient that gradually decreases from the central region to the edge region.

2. The method for preparing the gradient temperature-controlled flexible electronic heating device according to claim 1, characterized in that, The specific process parameters for the line scanning laser direct writing process described in step (2) are as follows: The laser power is 1.8~2.0 W, the scanning speed is 140~150 mm / s, and the scanning interval is 35~45 µm.

3. The method for preparing the gradient temperature-controlled flexible electronic heating device according to claim 2, characterized in that, The pulsed laser is a pulsed laser with a wavelength of 10.64µm.

4. The method for preparing the gradient temperature-controlled flexible electronic heating device according to claim 1, characterized in that, During the line scan laser direct writing process, the polyimide film blocks laser penetration, and laser induction is limited to the aramid paper on one of the surfaces.

5. The method for preparing the gradient temperature-controlled flexible electronic heating device according to claim 1, characterized in that, In the three-layer composite insulating material, the thickness of the aramid paper is 30~60µm, and the thickness of the polyimide film is 120~150µm.

6. The method for preparing the gradient temperature-controlled flexible electronic heating device according to claim 1, characterized in that, The preparation of electrodes on the three-dimensional porous graphene network layer specifically involves: the three-dimensional porous graphene network layer being square, with conductive silver paste applied to the edge regions of two opposite sides and copper foil adhered thereon as electrodes.

7. A gradient temperature-controlled flexible electronic heating device, characterized in that, It comprises, in sequence, a three-dimensional porous graphene network layer, a polyimide film, and a lower aramid paper layer; the three-dimensional porous graphene network layer is generated from aramid paper by laser induction.

8. The application of the gradient temperature-controlled flexible electronic heating device according to claim 7 in the preparation of mirror defogging patches, flexible medical physiotherapy skin patches, and light source detectors.

9. The application according to claim 8, characterized in that, When the flexible medical physiotherapy skin patch is used, a bias voltage of 2~2.5V is applied.

10. The application according to claim 8, characterized in that, When the flexible medical physiotherapy skin patch is used, the temperature of the central area is 45~55℃, and the temperature of the peripheral area is 37~40℃.

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