Hydrogel microchannel evaporative coolers for mitigating tbi and methods of making the same

Abstract

The application discloses a hydrogel microchannel evaporative cooler for relieving TBI and a preparation method thereof, the cooler is integrally composed of a degradable and adhesive hydrogel material, is of an integrated structure, and is internally provided with parallel arranged microchannel structures, adjacent microchannel structures are connected through semicircular structures, and the whole forms a serpentine microchannel structure, double inlets and a single outlet are arranged, and the double inlets and the single outlet are respectively connected with a nitrogen channel and a cooling liquid supply channel, the two independent inlets are jointly connected at one end of the serpentine microchannel structure, and the other end of the serpentine microchannel structure is connected with the outlet; the hydrogel material is prepared from deionized water, chitosan, acrylic acid, aluminum nitrate nonahydrate, a BACA crosslinking agent and a photoinitiator, through the synergistic design of structural innovation and material innovation, the implantable hydrogel microchannel realizes controllable evaporative cooling and biodegradation in the brain tissue, and precise hypothermia protection of the brain injury area is realized.

Description

Technical Field

[0001] This invention relates to the field of hypothermia treatment technology for traumatic brain injury, and in particular to a hydrogel microchannel evaporative cooler for relieving TBI and its preparation method. Background Technology

[0002] Traumatic brain injury (TBI) is the destruction of brain tissue structure and dysfunction caused by external forces such as falls, car accidents, and blows. It can lead to severe secondary brain damage, such as cerebral edema, impaired or even lost neurological function. TBI is one of the leading causes of death and disability worldwide. Its pathological process includes not only primary mechanical injury but also secondary injury, such as cerebral edema, increased intracranial pressure, expanded brain tissue damage, and impaired or even lost neurological function. Secondary brain injury can lead to increased neuronal apoptosis, cognitive impairment, emotional disorders, stress dysfunction, and even serious adverse tendencies such as anxiety, depression, and suicide. These secondary pathological processes can persist for hours or even days after the injury, seriously affecting the patient's neurological function recovery. Clinical studies have shown that Mild Hypothermia Therapy (MHT) can significantly alleviate secondary brain injury by lowering brain tissue temperature to 32-35°C, effectively inhibiting cell metabolic rate, reducing excitotoxic reactions and cell apoptosis. However, existing cooling methods still face significant bottlenecks in terms of precise local temperature control and biosafety.

[0003] Currently, commonly used methods for brain cooling include cooling blankets, extracranial cold caps, nasal cooling, and cold saline infusion. These methods generally have the following problems: (1) slow cooling rate, unable to achieve a rapid decrease in local brain temperature in a short time; (2) long heat conduction path, low cooling efficiency and uneven temperature; (3) systemic cooling can cause side effects such as chills, coagulation abnormalities, arrhythmias, and hypotension, resulting in insufficient clinical safety; (4) external cooling methods are difficult to achieve precise, controllable, and sustainable local cooling of the brain injury area. Therefore, developing an implantable local cooling device has become an important direction for brain injury treatment research.

[0004] In recent years, microchannel evaporative cooling technology has shown great potential in electronic devices, chip cooling, and thermal management of biological tissues due to its highly efficient heat transfer characteristics. Its core principle is to achieve rapid local temperature reduction through the heat absorption of liquid evaporation. However, existing microchannel cooling devices mainly use silicon-based, metal, or polymer materials, which present the following key challenges in biological implantation scenarios:

[0005] 1. The material is non-degradable: it requires a second surgery to remove after implantation, increasing the risk of infection.

[0006] 2. High interfacial thermal resistance: Due to insufficient thermal contact between the device and brain tissue, local thermal resistance is high and cooling is unstable.

[0007] 3. Limited cooling precision: Traditional single-phase heat exchange systems have difficulty in accurately controlling the cooling rate, resulting in problems such as unstable cooling effect or temperature control lag.

[0008] Hydrogel materials, due to their excellent flexibility, biocompatibility, and tunable physicochemical properties, have become ideal substrates for research on bio-implantable devices. However, existing hydrogel materials used for temperature control or thermal management still face the following challenges:

[0009] (1) Most hydrogel materials lack adhesion and are difficult to achieve a stable fit with the surface of brain tissue, thus limiting the efficient transfer of heat.

[0010] (2) Most hydrogels are not biodegradable and require a second surgery to remove after implantation, increasing the risk of infection.

[0011] (3) Existing hydrogel microchannel cooling systems mainly rely on single-phase water cooling, which has limited cooling effect, lagging temperature control and difficulty in precise temperature control.

[0012] In summary, there is an urgent need for a novel implantable cooling device in the field of hypothermia treatment for traumatic brain injury that combines high cooling capacity, biodegradability, and adhesion, in order to achieve rapid, precise, stable, and safe temperature regulation in local brain tissue. Summary of the Invention

[0013] To overcome the above problems, the purpose of this invention is to provide a hydrogel microchannel evaporative cooler for alleviating TBI and its preparation method. This hydrogel microchannel evaporative cooler achieves the dual functions of controllable evaporative cooling and biodegradation of implantable hydrogel microchannels in brain tissue through the synergistic design of structural and material innovation, thereby achieving precise sub-low temperature protection for brain injury areas.

[0014] The technical solution adopted in this invention is:

[0015] A hydrogel microchannel evaporative cooler for alleviating TBI (Total Biomarker Intake) is constructed entirely of a biodegradable and adhesive hydrogel material in an integrated structure. The internal design incorporates parallel microchannel structures connected by semicircular structures, forming a serpentine microchannel structure. This serpentine microchannel structure features dual inlets and a single outlet. One inlet connects to a nitrogen channel, and the other connects to a cooling liquid supply channel. Both inlets are connected to one end of the serpentine microchannel structure, while the other end connects to the outlet.

[0016] As a further description of the present invention, the hydrogel material is prepared from deionized water, chitosan, acrylic acid, aluminum nitrate nonahydrate, BACA crosslinking agent, and photoinitiator, and the specific content of each component is as follows:

[0017] 60 mL of deionized water was used as the reaction solvent and dispersion medium.

[0018] Chitosan 0.35g provides adhesion and biocompatibility.

[0019] 20 mL of acrylic acid was used as the main scaffold monomer for the hydrogel.

[0020] 3.6g of aluminum nitrate nonahydrate was used as an ion crosslinking aid to enhance mechanical strength.

[0021] 0.4g of BACA crosslinking agent provides a degradable crosslinking structure, which can induce the degradation of cysteine ​​in vivo.

[0022] 0.16g of photoinitiator initiates the photopolymerization reaction, forming a three-dimensional cross-linked network.

[0023] As a further description of the present invention, the spacing between the parallel microchannel structures of the serpentine microchannel structure is... The cross-sectional shape of the serpentine microchannel structure is either square or circular. The length and height of the square structure are the same as the spacing between the microchannel structures, and the radius of the circular structure is the same as the spacing between the microchannel structures. .

[0024] As a further description of the present invention, the cooling liquid is deionized water.

[0025] As a further description of the present invention, the inner diameter of the inlet of the cooling liquid supply channel in the dual inlet is 0.5-2 mm, the inner diameter of the inlet of the nitrogen channel is 0.3-1 mm, and the inner diameter of the outlet is 1-3 mm.

[0026] As a further description of the present invention, the inlet is connected to a nitrogen pumping device, which is used to reduce the saturated vapor pressure at the gas-liquid interface within the microchannel structure, accelerate the evaporation of the cooling liquid within the serpentine microchannel structure, and discharge the vapor.

[0027] As a further description of the present invention, the hydrogel microchannel evaporative cooler is directly attached to the surface of brain tissue at the site of traumatic brain injury during use. It achieves in-situ fixation through the adhesiveness of the hydrogel and utilizes the evaporative heat absorption effect of the cooling liquid in the microchannel to achieve local cooling.

[0028] As a further description of the present invention, when the hydrogel material is in the presence of cysteine ​​in a brain tissue environment, its BACA cross-linked structure degrades, with a degradation cycle of 7 to 30 days. The degradation products are non-toxic small molecules that can be metabolized and cleared by the body.

[0029] A method for preparing a hydrogel microchannel evaporative cooler for alleviating TBI includes the following steps:

[0030] S1: Solution preparation: Dissolve 0.35g of chitosan in 40mL of deionized water at room temperature, and heat in a 60-80℃ incubator until completely melted into syrup to form a chitosan solution.

[0031] S2: Add 20 mL of acrylic acid to the chitosan solution and stir continuously to form a homogeneous and transparent solution, i.e., a chitosan-acrylic acid mixed solution.

[0032] S3: Dissolve 3.6g of aluminum nitrate nonahydrate in 10mL of deionized water to obtain an aluminum salt solution; separately dissolve 0.4g of BACA crosslinking agent and 0.16g of photoinitiator in 10mL of deionized water to prepare a crosslinking agent / initiator solution.

[0033] S4: Under vigorous stirring, the aluminum salt solution is slowly added dropwise to the chitosan-acrylic acid mixed solution, followed by the addition of the crosslinking agent / initiator solution and thorough mixing. At the same time, degassing is performed to remove air bubbles, and finally a homogeneous hydrogel precursor solution is obtained.

[0034] S5: Mold preparation and injection molding. A microchannel structure is made using polytetrafluoroethylene. The prepared hydrogel precursor solution is injected into the mold cavity and placed in a vacuum autoclave until no air bubbles are present.

[0035] S6: Photocuring molding. The cavity after injection molding is placed under an ultraviolet light irradiation device for 40 minutes to complete the photo-initiated polymerization reaction. After curing, a hydrogel microchannel layer is obtained.

[0036] S7: Demolding and post-processing. After curing, demold and polymerize a hydrogel layer and a microchannel layer to obtain a complete hydrogel microchannel evaporative cooler.

[0037] As a further description of the present invention, the ultraviolet irradiation device in S6 is an irradiation device with a light intensity of 50W and a wavelength of 365nm.

[0038] The beneficial effects of this invention are:

[0039] This invention relates to a hydrogel microchannel evaporative cooler for alleviating traumatic brain injury (TBI). The cooler is entirely constructed of a biodegradable and adhesive hydrogel material and can be used as an implantable hypothermic brain cooling device in the treatment of TBI. The cooler's internal design incorporates parallel-arranged microchannel structures with channel width, height, and spacing within a specific range. The system employs a semi-circular transition connection to form an evaporation channel with low flow resistance and a high heat transfer area ratio, ensuring effective cooling during use. Furthermore, the dual-inlet synergistic cooling strategy includes two independent inlets for introducing cooling liquid (water) and gas (nitrogen), respectively. This allows nitrogen to form a two-phase flow within the microchannel, enabling dynamic control of the evaporation process. The nitrogen flow promotes liquid film disturbance and vapor discharge, creating a non-steady-state enhanced evaporation mechanism. Compared to single-phase water cooling, this significantly improves the cooling rate and cooling effect, and the cooling effect is more stable, achieving highly efficient local cooling. This, in turn, helps to suppress secondary brain injury through temperature regulation.

[0040] This invention relates to a hydrogel microchannel evaporative cooler for alleviating tissue injury (TBI). The hydrogel material incorporates a cross-linking agent, BACA, with degradable sites, and natural chitosan, creating a hydrogel system that combines adhesion and degradability. This solves the problem of traditional inorganic or metal microchannel coolers failing to degrade after implantation and requiring secondary removal. Furthermore, the hydrogel system possesses high water content and heat capacity, enabling efficient evaporative cooling and flexible adhesion to tissue surfaces. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the hydrogel microchannel evaporative cooler structure proposed in this invention for alleviating TBI.

[0042] Figure 2 This is a schematic diagram illustrating the evaporation principle of the hydrogel microchannel evaporative cooler proposed in this invention for alleviating TBI.

[0043] Figure 3 This is a schematic diagram illustrating the fabrication principle of the hydrogel microchannel evaporative cooler for alleviating TBI proposed in this invention.

[0044] Figure 4 This is a schematic diagram illustrating the hydrogel adhesion characterization of the hydrogel microchannel evaporative cooler for alleviating TBI proposed in this invention.

[0045] Figure 5 This is a schematic diagram illustrating the hydrogel degradability of the hydrogel microchannel evaporative cooler proposed in this invention for alleviating TBI.

[0046] Figure 6 This is a comparison curve of the hydrogel microchannel evaporative cooler and forced water cooling proposed in this invention for alleviating TBI.

[0047] Figure 7 The figure shows the results of an intracranial cooling experiment in rats using the hydrogel microchannel evaporative cooler proposed in this invention to alleviate TBI.

[0048] Figure 8This is a flowchart of the preparation method of the hydrogel microchannel evaporative cooler for alleviating TBI proposed in this invention.

[0049] Figure 9 This is a physical image of the hydrogel microchannel evaporative cooler proposed in this invention for alleviating TBI.

[0050] Explanation of reference numerals in the attached figures

[0051] 1. Microchannel structure.

[0052] 2. Snake-shaped microchannel structure.

[0053] 3. Imports.

[0054] 4. Exports. Detailed Implementation

[0055] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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 protection scope of the present invention.

[0056] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0057] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0058] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0059] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0060] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0061] like Figures 1-9 As shown, it illustrates a specific embodiment of the present invention.

[0062] Example 1:

[0063] A hydrogel microchannel evaporative cooler for alleviating TBI (Total Biomarker Infection) is constructed entirely of a biodegradable and adhesive hydrogel material in an integrated structure. The internal design incorporates parallel microchannel structures 1, connected by semi-circular structures to form a serpentine microchannel structure 2. This serpentine microchannel structure 2 has two inlets 3 and a single outlet 4. One inlet 3 connects to a nitrogen channel, and the other inlet 3 connects to a cooling liquid supply channel. Both inlets 3 are connected to one end of the serpentine microchannel structure 2, while the other end connects to the outlet 4.

[0064] Specifically, the cooling liquid is deionized water.

[0065] Specifically, the hydrogel material is prepared from deionized water, chitosan, acrylic acid, aluminum nitrate nonahydrate, BACA crosslinking agent, and photoinitiator. The content and function of each component are shown in Table 1 below.

[0066] Table 1. Hydrogel component content and functional description

[0067] Deionized water 60 mL Reaction solvent and dispersion medium Chitosan 0.35 g Provides adhesion and biocompatibility acrylic acid 20 mL Hydrogel main skeleton monomer Aluminum nitrate nonahydrate 3.6 g Ion crosslinking aids enhance mechanical strength BACA crosslinking agent 0.4 g It provides a degradable cross-linked structure, and cysteine ​​can induce degradation in vivo. Photoinitiator 0.16 g Initiating a photopolymerization reaction to form a three-dimensional cross-linked network

[0068] Specifically, the spacing between the parallel microchannel structures 1 of the serpentine microchannel structure 2 is... The cross-sectional shape of the serpentine microchannel structure 2 is either a square or a circular structure. The length and height of the square structure are the same as the spacing between the microchannel structures 1, and the radius of the circular structure is the same as the spacing between the microchannel structures 1. .

[0069] Specifically, the inner diameter of the inlet 3 of the cooling liquid supply channel in the dual inlet 3 is 0.5-2 mm, the inner diameter of the inlet 3 of the nitrogen channel is 0.3-1 mm, and the inner diameter of the outlet 4 is 1-3 mm.

[0070] Specifically, the inlet 3 is connected to a nitrogen pumping device, which is used to reduce the saturated vapor pressure at the gas-liquid interface within the microchannel structure 1, accelerate the evaporation of the cooling liquid within the serpentine microchannel structure 2, and discharge the vapor.

[0071] In this embodiment, as Figure 1 As shown, this hydrogel microchannel evaporative cooler is entirely composed of a biodegradable and adhesive hydrogel material. Through a dual-inlet design (with separate inlet for liquid and inert gas), it constructs a controllable gas-liquid mixing evaporation system, achieving rapid, efficient, and precise localized evaporative cooling. The use of an adhesive and biodegradable hydrogel material as the overall structure ensures stable thermal contact and biocompatibility between the implantation site and brain tissue. By optimizing the microchannel geometry and gas-liquid flow characteristics, the cooler achieves uniform temperature distribution and adjustable cooling rates. Through the synergistic design of structural and material innovations, this cooler realizes the dual functions of controllable evaporative cooling and biodegradation of implantable hydrogel microchannels in brain tissue, providing a novel engineered solution for TBI hypothermia treatment.

[0072] In this embodiment, the hydrogel microchannel evaporative cooler is an integrated hydrogel structure, possessing soft, adherent, and biodegradable properties. The serpentine microchannel structure 2 serves as the evaporation region of the device. In this embodiment, it comprises six rows of parallel, straight-through microchannels, with a channel spacing, width, and height all of 400 micrometers. Adjacent channels are connected by a semi-circular structure to reduce fluid stagnation and improve gas-liquid distribution uniformity. One end of the device has a dual-inlet structure, with one inlet connected to the liquid supply system and the other to the nitrogen channel. The outlet is a single discharge port. During operation, liquid water enters the microchannel through the liquid inlet, forming a liquid film layer on the channel surface; simultaneously, nitrogen enters from the gas inlet and forms a parallel gas-liquid two-phase flow with the liquid water. Gas disturbance disrupts the stability of the liquid film surface, increasing the evaporation surface area and evaporation rate, thereby significantly enhancing the evaporative cooling intensity. The absorption of latent heat of evaporation rapidly lowers the temperature of the device and its attached tissue, achieving localized sub-low temperature regulation.

[0073] Example 2:

[0074] Specifically, the hydrogel microchannel evaporative cooler is directly attached to the surface of brain tissue at the site of traumatic brain injury. It achieves in-situ fixation through the adhesiveness of the hydrogel and utilizes the evaporative heat absorption effect of the cooling liquid within the microchannel to achieve local cooling.

[0075] Specifically, when the hydrogel material is in the presence of cysteine ​​in a brain tissue environment, its BACA cross-linked structure degrades, with a degradation cycle of 7 to 30 days. The degradation products are non-toxic small molecules that can be metabolized and cleared by the body.

[0076] Example 3:

[0077] This embodiment provides a hydrogel microchannel evaporative cooler for alleviating traumatic brain injury and its preparation method.

[0078] I. Preparation of hydrogel precursor solution.

[0079] At room temperature, 0.35 g of chitosan was dissolved in 40 mL of deionized water and heated in an incubator at 60–80 °C until completely melted into a syrup, forming a chitosan solution. Then, 20 mL of acrylic acid was added to the chitosan solution and mixed thoroughly under continuous stirring to form a homogeneous and transparent chitosan-acrylic acid mixed solution.

[0080] Prepare aluminum salt solution and crosslinking agent / initiator solution separately: Dissolve 3.6g of aluminum nitrate nonahydrate in 10mL of deionized water to obtain aluminum salt solution; separately dissolve 0.4g of BACA crosslinking agent (N,N′-bisacrylcysteine) and 0.16g of photoinitiator (e.g., 2-hydroxy-2-methyl-1-phenyl-1-propanone, photoinitiator 1173) in 10mL of deionized water to prepare crosslinking agent / initiator solution.

[0081] Under vigorous stirring conditions, the aluminum salt solution was slowly added dropwise to the chitosan-acrylic acid mixed solution, followed by the addition of a crosslinking agent / initiator solution and thorough mixing. Simultaneously, degassing was performed to remove air bubbles, ultimately yielding a homogeneous hydrogel precursor solution.

[0082] II. Preparation of microchannel structure molds.

[0083] A microchannel structure mold is fabricated using polytetrafluoroethylene (PTFE) material. The mold cavity contains parallel-arranged microchannel forming protrusions, which are connected by semi-circular connecting structures, forming a serpentine microchannel structure within the mold cavity. The spacing between the microchannel forming protrusions is [missing information]. The cross-sectional shape is either square or circular—the length and height of the square cross-section are the same as the microchannel spacing, and the radius of the circular cross-section is the same as the microchannel spacing. One end of the mold is equipped with a dual-inlet molding structure, one inlet of which is used to connect to the nitrogen gas channel (inner diameter). Another inlet is used to connect to the cooling fluid supply channel (inner diameter). The other end of the mold is equipped with a single outlet forming structure (inner diameter). ).

[0084] III. Injection molding and photopolymerization.

[0085] The prepared hydrogel precursor solution was injected into a polytetrafluoroethylene (PTFE) mold cavity, and then placed in a vacuum autoclave to evacuate until no air bubbles were present, ensuring that the precursor solution fully filled all the microstructures within the mold. The molded cavity was then placed under a UV irradiation device and irradiated with 50W UV light at a wavelength of 365nm for 40 minutes to complete the photoinitiated polymerization reaction and form a three-dimensional cross-linked network. After curing, a hydrogel microchannel layer with a serpentine microchannel structure was obtained.

[0086] IV. Demolding and Assembly.

[0087] After curing, the hydrogel microchannel layer is removed from the polytetrafluoroethylene mold through a demolding process. A hydrogel overlay layer is then fabricated on top of the microchannel layer. The hydrogel layer and the microchannel layer are then bonded together via in-situ polymerization to form a complete, integrated hydrogel microchannel evaporative cooler. The cooler is constructed entirely of a biodegradable and adhesive hydrogel material and features a complete flow path structure with dual inlets, serpentine microchannels, and a single outlet.

[0088] V. Product Structure.

[0089] The resulting hydrogel microchannel evaporative cooler is an integrated structure with parallel microchannels arranged internally. Adjacent microchannels are connected by semi-circular structures, forming a serpentine microchannel pattern. One end of the serpentine microchannel has two independent inlets—one connected to a nitrogen channel and the other to a deionized water supply channel; the other end has a single outlet. In use, the cooler is directly attached to the surface of the brain tissue at the site of traumatic brain injury, achieving in-situ fixation through the adhesive properties of the hydrogel. Activating the nitrogen pump causes a rapid decrease in the saturated vapor pressure at the gas-liquid interface within the microchannel, allowing deionized water to continuously evaporate within the serpentine microchannel. This evaporative endothermic effect achieves localized cooling of the injured area. The nitrogen channel assists in expelling the water vapor generated during evaporation, maintaining the continuous evaporation process.

[0090] VI. Degradation characteristics.

[0091] In a brain tissue environment, the BACA cross-linked structure of this hydrogel microchannel evaporator can be degraded under cysteine ​​induction, with a degradation cycle of 7 to 30 days. The degradation products are non-toxic small molecules that can be metabolized and cleared by the body, eliminating the need for a second surgery to remove them.

[0092] Example 4:

[0093] The performance of the hydrogel microchannel evaporator prepared in Example 3 was tested.

[0094] (a) Adhesion test.

[0095] The adhesion strength of the hydrogel microchannel evaporative cooler was tested by attaching it to the surface of pig brain tissue using an overlap shear test. The results showed that the adhesion strength of the hydrogel material to the brain tissue surface met the requirements for in-situ fixation.

[0096] Furthermore, adhesion tests were conducted on human skin surfaces. The hydrogel material was found to adhere stably to the skin surface, demonstrating its adhesive properties. Figure 4 As shown.

[0097] (ii) Evaporative cooling performance test.

[0098] A hydrogel microchannel evaporator was attached to the surface of a heating element simulating brain tissue. Under constant temperature control, deionized water was introduced and a nitrogen pump was activated, with a flow rate of... The nitrogen pressure was 150 kPa, and the temperature at the center of the microchannel evaporation region was recorded using thermocouples. The results showed that the temperature could drop by 35°C within 2 minutes and maintain a stable cooling effect for 5 minutes. Under the same pump power, the temperature reduction was 2.2 times that of forced water cooling. This cooler exhibits excellent localized cooling performance.

[0099] (iii) Degradation performance test.

[0100] Prepare a mixture of physiological saline and L-cysteine ​​as a simulated body fluid, with the cysteine ​​content being [missing information]. The hydrogel completely degraded within 72 hours. The degradation products were non-toxic small molecules, and no obvious inflammatory response was observed.

[0101] Example 5:

[0102] The hydrogel microchannel cooler prepared using the formulation in Example 3 was tested in the intracranial cavity of rats. The hydrogel microchannel cooler adhered to the dura mater of the rats, and the temperature of its cooling surface could be reduced from 37°C to approximately [temperature missing]. The temperature was maintained stable for 4 hours. After cooling was stopped, the rat's brain temperature gradually returned to normal.

[0103] In summary, the hydrogel microchannel evaporative cooler for alleviating TBI proposed in this invention is specifically manifested in terms of structure, materials, and functional implementation as follows:

[0104] At the materials level: By introducing the cross-linking agent BACA with degradable sites and the natural polymer chitosan, a hydrogel system that combines adhesion and degradability was constructed, solving the problem that traditional inorganic or metal microchannel coolers cannot degrade after implantation and require secondary removal. At the same time, the hydrogel system has high water content and heat capacity, enabling efficient evaporative heat dissipation and flexible adhesion to tissue surfaces.

[0105] At the structural level: the cooler adopts a parallel straight-through microchannel structure design, with the same channel width, height, and spacing. And a low flow resistance flow field is formed through a semi-circular transition connection.

[0106] At the functional implementation level: the cooler's dual-inlet synergistic cooling strategy (nitrogen inlet + water inlet) enables dynamic control of the evaporation process. Nitrogen flow promotes liquid film disturbance and steam discharge, forming a non-steady-state enhanced evaporation mechanism. Compared with the single-phase water cooling mode, it significantly improves the cooling rate and cooling effect, and the cooling effect is more stable.

[0107] At the application level: Hydrogel microchannel evaporative cooling technology was applied to hypothermic brain protection in a traumatic brain injury (TBI) model. In rat model experiments, the implanted hydrogel cooler lowered the rat brain temperature from 37°C to 33°C and maintained it stably for 4 hours without tissue necrosis or obvious inflammatory response, demonstrating the safety and feasibility of this device in biological tissue temperature control.

[0108] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0109] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A hydrogel microchannel evaporative cooler for alleviating TBI, characterized in that, The microchannel evaporative cooler is made of a biodegradable and adhesive hydrogel material and is an integrated structure. It has parallel microchannel structures (1) inside, and adjacent microchannel structures (1) are connected by a semi-circular structure to form a serpentine microchannel structure (2). The serpentine microchannel structure (2) is provided with two inlets (3) and a single outlet (4). One inlet (3) is connected to a nitrogen channel, and the other inlet (3) is connected to a cooling liquid supply channel. The two independent inlets (3) are connected to one end of the serpentine microchannel structure (2), and the other end of the serpentine microchannel structure (2) is connected to the outlet (4).

2. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The hydrogel material is prepared from deionized water, chitosan, acrylic acid, aluminum nitrate nonahydrate, BACA crosslinking agent, and photoinitiator. The specific content of each component is as follows: 60 mL of deionized water was used as the reaction solvent and dispersion medium. Chitosan 0.35g provides adhesion and biocompatibility; 20 mL of acrylic acid was used as the main structural monomer of the hydrogel. 3.6g of aluminum nitrate nonahydrate was used as an ion crosslinking aid to enhance mechanical strength. 0.4g of BACA crosslinking agent provides a degradable crosslinking structure, which can be induced to degrade by cysteine ​​in vivo; 0.16g of photoinitiator initiates the photopolymerization reaction, forming a three-dimensional cross-linked network.

3. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The serpentine microchannel structure (2) has parallel microchannel structures (1) with a spacing of [missing information]. The cross-sectional shape of the serpentine microchannel structure (2) is either a square structure or a circular structure. The length and height of the square structure are the same as the spacing of the microchannel structure (1), and the radius of the circular structure is the same as the spacing of the microchannel structure (1). .

4. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The cooling liquid is deionized water.

5. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The inner diameter of the inlet (3) of the cooling liquid supply channel in the dual inlet (3) is 0.5-2 mm, the inner diameter of the inlet (3) of the nitrogen channel is 0.3-1 mm, and the inner diameter of the outlet (4) is 1-3 mm.

6. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The inlet (3) is connected to a nitrogen pumping device, which is used to reduce the saturated vapor pressure at the gas-liquid interface in the microchannel structure (1), accelerate the evaporation of the cooling liquid in the serpentine microchannel structure (2), and discharge the vapor.

7. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 1, characterized in that, The hydrogel microchannel evaporative cooler is applied directly to the surface of brain tissue at the site of traumatic brain injury. It achieves in-situ fixation through the adhesiveness of the hydrogel and utilizes the evaporative endothermic effect of the cooling liquid within the microchannel to achieve localized cooling.

8. The hydrogel microchannel evaporative cooler for alleviating TBI according to claim 2, characterized in that, When the hydrogel material is in the presence of cysteine ​​in a brain tissue environment, its BACA cross-linked structure degrades, with a degradation cycle of 7 to 30 days. The degradation products are non-toxic small molecules that can be metabolized and cleared by the body.

9. A preparation method for preparing the hydrogel microchannel evaporative cooler for alleviating TBI as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Solution preparation: Dissolve 0.35g of chitosan in 40mL of deionized water at room temperature, and heat in a 60-80℃ incubator until completely melted into syrup to form a chitosan solution. S2: Add 20 mL of acrylic acid to the chitosan solution and stir continuously to form a homogeneous and transparent solution, i.e., a chitosan-acrylic acid mixed solution; S3: Dissolve 3.6g of aluminum nitrate nonahydrate in 10mL of deionized water to obtain an aluminum salt solution; separately dissolve 0.4g of BACA crosslinking agent and 0.16g of photoinitiator in 10mL of deionized water to prepare a crosslinking agent / initiator solution; S4: Under vigorous stirring, the aluminum salt solution is slowly added dropwise to the chitosan-acrylic acid mixed solution, followed by the addition of the crosslinking agent / initiator solution and thorough mixing. At the same time, degassing is performed to remove air bubbles, and finally a homogeneous hydrogel precursor solution is obtained. S5: Mold preparation and injection molding. A microchannel structure was made using polytetrafluoroethylene (1). The prepared hydrogel precursor solution was injected into the mold cavity and placed in a vacuum kettle until no air bubbles were present. S6: Photocuring molding. The cavity after injection molding is placed under an ultraviolet light irradiation device for 40 minutes to complete the photo-initiated polymerization reaction. After curing, a hydrogel microchannel layer is obtained. S7: Demolding and post-processing. After curing, demold and polymerize a hydrogel layer and a microchannel layer to obtain a complete hydrogel microchannel evaporative cooler.

10. The method for preparing a hydrogel microchannel evaporative cooler for alleviating TBI according to claim 9, characterized in that, The ultraviolet irradiation device in S6 is an irradiation device with a light intensity of 50W and a wavelength of 365nm.

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