Flexible integrated micro heater and preparation method thereof

Abstract

The invention discloses a flexible integrated micro-heater and a preparation method thereof, and belongs to the technical field of electric heating, the flexible integrated micro-heater comprises a flexible substrate and a micro-heater circuit arranged on the flexible substrate, the micro-heater circuit comprises streamline-shaped micro-heaters, the streamline-shaped micro-heaters are arranged in a regular array mode, and the streamline-shaped micro-heaters are arranged on the flexible substrate. The micro-heater is composed of a plurality of long-strip-shaped structures which are continuously bent and parallel to one another, the whole micro-heater extends on the flexible substrate in a reciprocating mode, streamline-shaped micro-heater electrodes are arranged at the two ends of the micro-heater, and a snakelike path is formed. According to the invention, highly uniform surface temperature distribution can be realized, the working temperature can be fed back and adjusted in real time, and the response time for reaching the set temperature is effectively shortened.

Description

Technical Field

[0001] This invention belongs to the field of electrothermal technology, and specifically relates to a flexible integrated microheater and its preparation method. Background Technology

[0002] ABO blood group system testing is crucial for transfusion safety, organ transplantation, and forensic medicine. Traditional serological methods are complex, time-consuming, and error-prone, while early molecular biology techniques (such as PCR-SSP and PCR-RFLP) have improved accuracy but still face challenges such as low throughput and high cost.

[0003] LAMP (Loop-mediated Isothermal Amplification) technology has shown great promise in ABO genotyping due to its high sensitivity, specificity, efficiency, and integration potential. It can design primers targeting ABO gene loci to accurately distinguish blood types and achieve high-throughput detection. The integration of automated equipment with LAMP can reduce human error. Current research has developed various integrated microfluidic LAMP schemes (such as digital chips, droplet coding, and hydrogel / aerosol binding), significantly improving detection performance.

[0004] LAMP is extremely sensitive to temperature, and its efficiency is highly dependent on the uniformity and response speed of the heating system. Various micro-heater structures (serpentine, spiral, etc.) and materials (gold, platinum, flexible substrates, etc.) have been studied, but current technology has not yet fully optimized the heating method. Existing instruments mostly use planar heating, which suffers from uneven temperature distribution, excessive heat loss, and low heating efficiency, thus affecting temperature control accuracy. Therefore, developing an intelligent temperature control platform that combines rapid response and high temperature uniformity is crucial. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible integrated microheater and its preparation method to solve the problems existing in the prior art. This invention can achieve a highly uniform surface temperature distribution, and can also provide real-time feedback adjustment of the working temperature, and effectively shorten the response time to reach the set temperature.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A flexible integrated micro heater includes a flexible substrate and a micro heater circuit disposed on the flexible substrate. The micro heater circuit includes a streamlined micro heater, which is arranged in a regular array and is composed of multiple continuously bent, parallel strip-shaped structures. The entire structure extends back and forth on the flexible substrate, and streamlined micro heater electrodes are provided at both ends to form a serpentine path. A micro-temperature sensor is arranged between several elongated structures in the middle of the streamlined micro heater. The micro-temperature sensor extends back and forth along the elongated structure and has micro-temperature sensor electrodes at both ends. The streamlined microheater electrode and the microtemperature sensor electrode are connected to the PID controller.

[0007] Furthermore, the flexible substrate is a PI film.

[0008] Furthermore, both the streamlined microheater and the microtemperature sensor are made of gold, and the current directions between two adjacent elongated structures in the streamlined microheater are opposite.

[0009] Furthermore, the streamlined microheater has a thickness of 300 nm and a width of 200 μm.

[0010] Furthermore, the width of the micro-temperature sensor is 40 μm.

[0011] A method for fabricating the flexible integrated microheater according to claim 1, comprising: Customized mask plates are designed based on the streamlined microheater pattern. Pre-treat the silicon wafer substrate to remove surface-adsorbed moisture; PDMS is uniformly coated onto the surface of a silicon wafer substrate using a spin coating method to form a buffer layer. The PI film was non-covalently bonded to the buffer layer by van der Waals forces, and interfacial bubbles were eliminated under vacuum conditions. ROL7133 negative photoresist was uniformly coated onto the surface of the PI film using a spin coating process to form a photoresist layer. The streamlined circuit pattern on the photomask is exposed to ultraviolet light using a contact lithography machine. Then, the exposed area is selectively etched using a developer to finally form a resist template for a streamlined micro heater on the PI film surface. A metal thin film is deposited on a resist template using an electron beam evaporation system; After metal deposition is completed, the sample is immersed in acetone solution for ultrasonic stripping to remove residual photoresist and redundant metal. The PI film is peeled off using a precision peeling process, and after being washed with ionized water and dried with nitrogen, a flexible integrated micro heater is obtained.

[0012] Furthermore, the thickness of the buffer layer is 250 μm.

[0013] Furthermore, the thickness of the PI film is 50 μm.

[0014] Furthermore, the thickness of the photoresist layer is 4.5 μm.

[0015] Furthermore, the deposition of a metal thin film on the resist template using an electron beam evaporation system specifically involves: depositing a metal thin film on a 5×10⁻⁶ substrate. -6 A 30 nm chromium adhesion layer was deposited under a vacuum of Pa, followed by the deposition of a 300 nm gold functional layer.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention proposes a flexible integrated micro heater solution, which not only provides a uniform temperature distribution, but also accurately measures the surface temperature of the streamlined micro heater by measuring the resistance change of a micro-temperature sensor. The temperature can then be controlled in real time by an external circuit. Moreover, compared with silicon wafer substrates, the flexible micro heater based on a PI film substrate has a wider range of applications and a faster heating rate.

[0017] The core of flexible electronic device packaging lies in building an integrated system that takes into account flexibility, thermal stability and interface reliability. It typically uses a PDMS / PI substrate combined with multilayer stacking (stress buffer layer, gas barrier film) and strain isolation encapsulation layer (UV-cured epoxy resin / silicon-based elastomer). The interface is strengthened by optimizing magnetron sputtering parameters and patterning is achieved by using micro-nano processing, ultimately achieving a balance between mechanical compliance and environmental protection.

[0018] This packaging solution provides key technical support for emerging fields such as wearable devices and flexible sensors, and also provides physical support for the subsequent construction of a flexible microheater platform for rapid ABO blood group gene detection, facilitating LAMP amplification around the EP tube. Attached Figure Description

[0019] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the flexible integrated microheater of the present invention; Figure 2 This is a structural development diagram of the flexible integrated microheater of the present invention; Figure 3 The flowchart shows the fabrication process of the flexible streamlined micro heater and micro temperature sensor, where (a) is surface treatment; (b) spin coating of PDMS; (c) bonding of polyimide film; (d) spin coating of photoresist; (e) exposure and development; (f) Cr vapor deposition; (g) Au vapor deposition; (h) metal stripping; and (i) stripping of polyimide film.

[0021] Among them, 1 is a micro temperature sensor; 2 is a streamlined micro heater; 3 is a micro temperature sensor electrode; and 4 is a streamlined micro heater electrode. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] Example 1 A flexible, integrated microheater with a streamlined geometry achieves a highly uniform surface temperature distribution. This invention integrates a closed-loop proportional-integral-derivative (PID) controller, enabling real-time feedback adjustment of the operating temperature and effectively shortening the response time to reach the set temperature. Specifically, as... Figure 1 and Figure 2 As shown, the present invention comprises the following core components: a streamlined microheater 2 with a streamlined structure, a micro-temperature sensor 1 for temperature monitoring, and a PID controller. Its operating mechanism is as follows: when a voltage is applied to the streamlined microheater electrodes 4 at both ends of the streamlined microheater 2, the current flowing through the conductor generates heat based on the Joule heating effect; the micro-temperature sensor 1, arranged adjacent to the heating area, can accurately sense and feedback surface temperature information based on its thermistor characteristics; the PID controller dynamically modulates the pulse duty cycle of the voltage applied across the streamlined microheater 2, adjusting its power input in real time, thereby precisely controlling the temperature rise rate and ultimately achieving a rapid temperature response.

[0025] The main highlight of this invention is that it proposes to use a combination of micro-nano lithography and magnetron sputtering technology to process streamlined micro heaters 2 and micro temperature sensors 1. This eliminates the need for complex metal corrosion processes and allows for the acquisition of the designed integrated flexible micro heater shape, greatly simplifying the processing technology and improving the precision of the processed structure. Furthermore, the use of a flexible substrate PI film makes the application scenarios of the integrated flexible micro heater more diversified.

[0026] The streamlined microheater 2 is arranged in a regular array and consists of multiple continuously bent, parallel strip-shaped structures. The whole extends back and forth on a flexible substrate, and streamlined microheater electrodes 4 are provided at both ends to form a serpentine path. Micro-temperature sensors 1 are arranged between several strip-shaped structures in the middle of the streamlined microheater 2. The micro-temperature sensors 1 are arranged back and forth along the strip-shaped structures and have micro-temperature sensor electrodes 3 at both ends. The streamlined microheater electrodes 4 and micro-temperature sensor electrodes 3 are connected to a PID controller.

[0027] Preferably, the micro-temperature sensor 1 is integrated inside the streamlined micro-heater 2, and both are made of gold; Preferably, the current directions between two adjacent elongated structures are opposite; Preferably, the streamlined microheater 2 has a thickness of 300 nm and a width of 200 μm, which can produce a uniform temperature distribution; Preferably, the micro temperature sensor 1 has a width of 40 μm, which can generate a sufficient change in resistance value when the temperature changes; Preferably, when processing the flexible integrated micro heater mold, the non-circuit area of ​​the PI film is covered with photoresist, so that the sputtered metal falls on the surface of the photoresist, and the excess metal can be removed using acetone.

[0028] This invention proposes and fabricates a novel flexible integrated microheater structure (streamlined), uses micro-nano lithography to fabricate the chip, and constructs a matching PID closed-loop temperature control system, realizing the integrated integration of microsensors and heaters.

[0029] Using the flexible integrated microheater established in this invention as the core unit of isothermal amplification, loop-mediated isothermal amplification (LAMP) technology is combined with a gold magnetic nanoparticle chromatography system with gold magnetic nanoparticles as the core carrier, realizing rapid, sensitive and visual detection of ABO blood group genes.

[0030] In the specific implementation process, DNA is first extracted from the blood sample to be tested. The 261st site (O and non-O genes) and 703rd site (B and non-B genes) of the ABO blood group gene are used as detection targets. Specific LAMP primer sets are designed and screened for the gene sites, and a LAMP amplification reaction system including specific primers, Bst 2.0 DNA polymerase, dNTPs, dUTPs, UDG enzyme, template DNA and nuclease-free water is constructed.

[0031] The LAMP amplification reaction system was added to an EP tube and placed on the LAMP amplification component that was tightly fitted with the flexible integrated microheater of the present invention. The EP tube was directly heated by the flexible integrated microheater array, and combined with a closed-loop temperature control algorithm, the reaction system was heated to the temperature required for the LAMP reaction within approximately 20 seconds and maintained stably at a constant temperature of 65 °C ± 1.5 °C. The reaction proceeded under these conditions for approximately 30 minutes to complete the LAMP amplification of the ABO blood group gene. During the amplification process, the reaction solution changed from clear to turbid, indicating that the amplification product was effectively generated, proving that the flexible integrated microheater of the present invention can stably achieve LAMP amplification of the ABO blood group gene.

[0032] After amplification, the amplification products undergo endpoint detection using a gold magnetic microparticle chromatography system. The digoxigenin and biotin dual labels carried in the amplification products specifically bind to the gold magnetic microparticles, forming a colored band on the detection band during chromatography. Unbound probes show color on the control band, thus validating the detection. Based on the color development of the detection and control bands, a positive or negative result for the ABO blood group gene can be directly determined, enabling the differentiation of different ABO blood group genotypes.

[0033] The LAMP rapid detection method established in this invention was used for ABO blood group gene detection. Under the isothermal amplification conditions provided by the flexible integrated microheater, the amplification products showed high specificity. The T-line was clearly visible and dark in the lateral flow chromatography detection. No obvious non-specific amplification phenomenon was observed, and it had good detection ability for low copy number samples.

[0034] Under the same sample conditions, the method of this invention was compared with commercial amplification equipment, including the Genie II isothermal amplification fluorescence detection system and an ABI PCR instrument 2720. The comparison results showed that the amplification time of the method of this invention was approximately 30 minutes, significantly shorter than the more than 45 minutes of the commercial equipment. Simultaneously, temperature fluctuations were controlled within ±1.5 ℃, resulting in higher amplification stability and superior specificity of the amplified bands compared to the commercial equipment. Furthermore, the system of this invention has significant advantages in terms of equipment size, energy consumption, and detection cost, making it more suitable for miniaturized, portable, and point-of-care testing applications.

[0035] Example 2 This invention utilizes micro-nano fabrication technology to prepare flexible integrated microheaters. The process mainly includes four stages: flexible substrate construction, photolithographic patterning, metal thin film deposition, and device lift-off. Specific experimental steps are as follows: Figure 3 First, the 4-inch silicon wafer substrate is pretreated by removing surface-adsorbed moisture through pre-baking. Then, polydimethylsiloxane (PDMS) is uniformly coated onto the silicon wafer substrate surface using a spin coater to form a buffer layer with a thickness of approximately 250 μm. After the PDMS cures, a polyimide (PI) film (50 μm thick) with excellent high-temperature resistance (temperature tolerance >300 ℃) is non-covalently bonded to the PDMS layer using van der Waals forces. The substrate is then placed in a vacuum chamber to eliminate interface bubbles and avoid pattern distortion caused by stress concentration during subsequent photolithography.

[0036] After the flexible substrate was fabricated, the microheater pattern was transferred. A spin-coating process was used to uniformly coat the PI surface with ROL7133 negative photoresist, forming a 4.5 μm thick photoresist layer. The streamlined circuit pattern (200 μm linewidth, 100 μm spacing) on ​​the photomask was then exposed to ultraviolet light using a contact lithography machine (KarlSuss MA6, 365 nm wavelength). Subsequently, selective etching of the exposed areas was performed using a developer, ultimately forming a precise microheater resist template on the PI substrate surface.

[0037] To establish conductive pathways, a metal thin film was deposited on a patterned PI substrate using an electron beam evaporation system. To enhance the bonding strength between the metal layer and the flexible substrate, a 5×10⁻⁶ layer was first deposited. -6 A 30 nm chromium (Cr) adhesion layer was deposited under a vacuum of Pa, followed by a 300 nm gold (Au) functional layer. After metal deposition, the sample was immersed in acetone solution for ultrasonic lift-off to remove residual photoresist and redundant metal, ultimately obtaining a microheater structure with high conductivity. The PI / PDMS composite flexible device was completely peeled from the silicon substrate using a precision lift-off process. After cleaning with deionized water and drying with nitrogen, a flexible microheater with excellent mechanical flexibility (bending radius < 3 mm) and thermal response characteristics was obtained.

[0038] Packaging technology for flexible electronic devices needs to balance mechanical compliance and environmental protection performance. Its core lies in constructing an integrated system that balances flexibility, thermal stability, and interface reliability. The packaging structure used in this invention specifically employs polydimethylsiloxane (PDMS) or polyimide (PI) as a flexible substrate, integrating a stress buffer layer and a gas barrier film through a multilayer stacking process, and constructing a strain-isolated encapsulation layer using UV-cured epoxy resin or a silicon-based elastomer. During the encapsulation process, magnetron sputtering deposition parameters need to be optimized to achieve interface strengthening between the conductive lines and the flexible substrate, while micro / nano fabrication technology is combined to achieve patterning of the encapsulation layer. The above description only illustrates the embodiments of the present invention, but it cannot be considered as the entire scope of protection of the present invention. Equivalent changes or modifications, or proportional enlargements or reductions made by the paradigm based on the design spirit of the present invention should all be considered to fall within the protection scope of the present invention.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A flexible integrated microheater, characterized in that, The device includes a flexible substrate and a micro heater circuit disposed on the flexible substrate. The micro heater circuit includes a streamlined micro heater (2). The streamlined micro heater (2) is arranged in a regular array and is composed of multiple continuously bent, parallel strip-shaped structures. The whole extends back and forth on the flexible substrate and has streamlined micro heater electrodes (4) at both ends to form a serpentine path. Micro temperature sensors (1) are arranged between several long strip structures in the middle of the streamlined micro heater (2). The micro temperature sensors (1) are arranged to extend back and forth along the long strip structure, and micro temperature sensor electrodes (3) are provided at both ends. The streamlined micro heater electrode (4) and the micro temperature sensor electrode (3) are connected to the PID controller.

2. The flexible integrated microheater according to claim 1, characterized in that, The flexible substrate is made of PI film.

3. The flexible integrated microheater according to claim 1, characterized in that, The streamlined micro heater (2) and the micro temperature sensor (1) are both made of gold, and the current direction between two adjacent long strip structures in the streamlined micro heater (2) is opposite.

4. The flexible integrated microheater according to claim 1, characterized in that, The streamlined microheater (2) has a thickness of 300 nm and a width of 200 μm.

5. A flexible integrated microheater according to claim 1, characterized in that, The width of the micro temperature sensor (1) is 40 μm.

6. A method for fabricating the flexible integrated microheater according to claim 1, characterized in that, include: Customized mask plates are designed based on the streamlined microheater pattern. Pre-treat the silicon wafer substrate to remove surface-adsorbed moisture; PDMS is uniformly coated onto the surface of a silicon wafer substrate using a spin coating method to form a buffer layer. The PI film was non-covalently bonded to the buffer layer by van der Waals forces, and interfacial bubbles were eliminated under vacuum conditions. ROL7133 negative photoresist was uniformly coated onto the surface of the PI film using a spin coating process to form a photoresist layer. The streamlined circuit pattern on the photomask is exposed to ultraviolet light by a contact lithography machine, and then the exposed area is selectively etched by a developer to finally form a resist template for a streamlined micro heater (2) on the PI film surface. A metal thin film is deposited on a resist template using an electron beam evaporation system; After metal deposition is completed, the sample is immersed in acetone solution for ultrasonic stripping to remove residual photoresist and redundant metal. The PI film is peeled off using a precision peeling process, and after being washed with ionized water and dried with nitrogen, a flexible integrated micro heater is obtained.

7. The method for fabricating a flexible integrated microheater according to claim 6, characterized in that, The thickness of the buffer layer is 250 μm.

8. A method for fabricating a flexible integrated microheater according to claim 6, characterized in that, The thickness of the PI film is 50 μm.

9. A method for fabricating a flexible integrated microheater according to claim 6, characterized in that, The thickness of the photoresist layer is 4.5 μm.

10. A method for fabricating a flexible integrated microheater according to claim 6, characterized in that, The method of depositing a metal thin film on a resist template using an electron beam evaporation system specifically involves: depositing a metal thin film on a 5×10⁻⁶ substrate. -6 A 30 nm chromium adhesion layer was deposited under a vacuum of Pa, followed by the deposition of a 300 nm gold functional layer.

Images