A self-adaptable fixed coagulation monitoring flexible pressure sensor and a preparation method and application thereof

Abstract

The application discloses a self-adaptable and fixable coagulation monitoring flexible pressure sensor and a preparation method thereof. The pressure-sensitive layer of the flexible pressure sensor is a nanofiber membrane with hundred-microstructure prepared by an electrospinning process. The nanofiber membrane is prepared by mixing polylactic acid with shape memory as a base material and multi-walled carbon nanotubes as a conductive substance. The preparation method of the flexible pressure sensor is simple, and the flexible pressure sensor has high sensitivity under small load. The pressure-sensitive layer of the sensor has an initial shape and a temporary shape, and can be transformed between the initial shape and the temporary shape under external stimulation driving. The installation and fixation of the flexible pressure sensor are realized by controlling the deformation process of the sensor. The nanofiber membrane is spontaneously deformed and inwards shrunk to be attached on a central venous catheter, so that the fixation is realized. The stability of the flexible pressure sensor is improved, the flexible pressure sensor is adaptively installed at the front end of the central venous catheter, and the blood flow pressure in the venous blood vessel can be monitored in real time.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and relates to a flexible sensor for coagulation monitoring and its preparation method, particularly to a flexible pressure sensor for coagulation monitoring that can be adaptively fixed, its preparation method, and its application. Background Technology

[0002] Peripherally inserted central catheters (PICCs) provide patients with a long-term treatment pathway, ensuring catheter stability, reducing drug irritation to blood vessels, and improving treatment efficacy. However, as a foreign body, PICCs carry risks of complications during placement, with deep vein thrombosis (DVT) in the upper extremities being particularly serious. PICC-related upper extremity DVT often presents without obvious symptoms, leading to a high rate of missed diagnoses. Delayed treatment can damage venous structures and even trigger life-threatening pulmonary embolism. Studies have shown that timely detection and management of DVT are crucial for patient prognosis. Close monitoring for complications, especially upper extremity DVT, is necessary for patients receiving PICC treatment to ensure timely diagnosis and treatment. Therefore, developing a compact, stable monitoring device capable of real-time coagulation monitoring is of great significance, as it can ensure patient safety and reduce costs.

[0003] Wearable health monitoring systems have garnered significant public attention due to their immense potential. Their core component—the flexible pressure sensor—can continuously track physiological signals such as body movement and heart rate. Possessing exceptional flexibility and stretchability, it can accurately reflect an individual's health status, providing data support for disease prevention, health management, and telemedicine.

[0004] However, due to the size mismatch between traditional flexible pressure sensors and central venous catheters, and the need for adhesive to bond the flexible sensor to the catheter, the diameter of the flexible sensor in the blood vessel is significantly increased, thereby increasing the probability of thrombosis; prolonged use may also lead to dangerous situations such as adhesive detachment and vascular blockage.

[0005] Based on this, the present invention proposes a flexible pressure sensor that can be adaptively installed and fixed. It is inserted into the body together with a central venous catheter to monitor pressure changes around the catheter in real time to determine whether coagulation has occurred. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an adaptive and fixed flexible pressure sensor for coagulation monitoring and its preparation method. This flexible pressure sensor is mainly fabricated in one step using an electrospinning process to obtain a nanofiber membrane with a 100-mesh microstructure. The preparation method of this pressure sensor is simple, it has high sensitivity under low load, and since the substrate material is polylactic acid with shape memory, the sensor can be more closely installed at the front end of a central venous catheter, enabling real-time monitoring of blood flow pressure in venous vessels.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for fabricating an adaptively fixed flexible pressure sensor for coagulation monitoring, wherein the pressure-sensitive layer of the flexible pressure sensor is a nanofiber membrane with a 100-mesh microstructure. The pressure-sensitive layer is prepared by electrospinning a spinning solution made of shape memory polylactic acid (SMP-PLA) and multi-walled carbon nanotubes (MWCNTs), and receiving the signal through a receiver with a 100-mesh microstructure during spinning. The flexible pressure sensor can be adaptively fixed to an implantable venous catheter for monitoring coagulation after implantation.

[0009] In the above technical solution, the flexible pressure sensor is further formed with a multi-layer structure, including an electrode layer, a pressure-sensitive layer, and a waterproof layer. The pressure-sensitive layer is a hollow cylindrical membrane, and the electrode layer is disposed on the inner side of the hollow cylindrical membrane. The electrode layer is made by screen printing silver paste on a PI film. The silver paste side is in contact with the hollow cylindrical membrane, and the PI film side is in contact with the implanted venous catheter. The shape memory function of the pressure-sensitive layer enables the flexible pressure sensor and the implanted venous catheter to be adaptively fixed. The waterproof layer is encapsulated on the outside of the pressure-sensitive layer.

[0010] Furthermore, the method specifically includes the following:

[0011] SMP-PLA and MWCNTs were added to a mixed solvent of dichloromethane and N,N-dimethylformamide and thoroughly mixed and dispersed to obtain a spinning solution. A steel mesh with a 100-mesh microstructure was fixed onto a steel tube of the required diameter. The resulting steel tube was then fitted onto a tubular support receiver, and electrospinning was performed to obtain an SMP-PLA / MWCNTs composite hollow cylindrical membrane. The composite hollow cylindrical membrane was fixed onto an electrode layer, which was then attached to the outside of an implantable venous catheter. Adaptive fixation was achieved through the shape memory process of the pressure-sensitive layer, and finally, a waterproof layer was used for encapsulation.

[0012] Furthermore, the volume ratio of dichloromethane to the mixed solution is 70% to 80%, and the volume ratio of N,N-dimethylformamide to the mixed solution is 20% to 30%.

[0013] Furthermore, the concentration of SMP-PLA in the spinning solution is 16-17 wt%.

[0014] Furthermore, the amount of MWCNTs used is 11 to 15 wt% of SMP-PLA, more preferably 14%.

[0015] Furthermore, the thickness of the SMP-PLA / MWCNTs composite hollow cylindrical membrane is 130–200 μm.

[0016] Furthermore, the SMP-PLA / MWCNTs composite hollow cylinder membrane is heat-pressed to improve its performance stability. The heat pressing is usually to fix the tubular nanofiber membrane on the hollow cylinder fitting structure prepared with PDMS and heat-press at 120 °C for 5 to 6 hours.

[0017] A flexible pressure sensor for coagulation monitoring with self-adaptive fixation is prepared by the method described in any one of the above.

[0018] An implantable venous catheter for monitoring coagulation, on which there is the flexible pressure sensor for coagulation monitoring with self-adaptive fixation described above. The sensor is adaptively installed and fixed on the venous catheter and is used to monitor the blood flow pressure in the venous blood vessel in real time to monitor the coagulation situation. The self-adaptive fixation is to increase the tube diameter of the hollow cylinder membrane under the action of temperature rise (T≥Tg) and external force, and then cool down (T<Tg) and remove the external force to fix its temporary shape; nest it on the electrode layer pre-attached to the outside of the implantable venous catheter in vitro, and heat it again (T≥Tg). Due to the nature of the material itself, the hollow cylinder membrane will actively shrink inward to achieve the fixation effect, and finally encapsulate it with a waterproof layer.

[0019] The conductivity range of the conductive fiber membrane (i.e., the composite hollow cylinder membrane) prepared by the present invention is 2.65 - 12.65 μS / cm. The thickness of the conductive fiber membrane is 0.13 - 0.2 mm.

[0020] Combining the conductive fiber membrane with the electrode layer and the waterproof layer can obtain a flexible pressure sensor with excellent signal stability. For example: form the electrode layer by screen-printing silver paste with a certain viscosity on the PI film. The electrode layer contacts the conductive fiber membrane to lead out electrical signals to form the sensor body, and then wrap the sensor body with a 5-μm PET film on its outside to form a tubular flexible sensor. This sensor can monitor the coagulation situation, has biocompatibility and hydrophobicity, and can ensure long-term stability.

[0021] This flexible sensor is primarily fabricated in one step using an electrospinning process to obtain a nanofiber membrane with a 100-mesh microstructure. The nanofiber membrane is made by mixing polylactic acid (PLA) with shape memory as the substrate material and multi-walled carbon nanotubes (MWCNTs) as the conductive material. By adjusting the mass ratio of MCCNTs, the threshold of the final conductive composite material is controlled. Under different pressures, the contact area of ​​the conductive fibers in the nanofiber membrane changes, leading to a corresponding adjustment in the effective resistance, thus achieving the sensing function. This sensor has a simple fabrication method, high sensitivity under low loads, and because the substrate material is PLA with shape memory, the sensor has an initial shape and a temporary shape, which can change between the initial shape and the temporary shape under external stimuli. This invention controls the installation and fixation of the flexible pressure sensor through the deformation process of the shape-memory nanofiber membrane. Fixation is achieved by the spontaneous deformation and inward contraction of the nanofiber membrane to adhere to the implanted venous catheter, improving the stability of the flexible pressure sensor. This allows the flexible pressure sensor to be adaptively installed at the front end of the implanted venous catheter, enabling real-time monitoring of blood flow pressure within the vein. Attached Figure Description

[0022] Figure 1 A schematic diagram of a flexible pressure sensor that is adaptively fixed to the end of an implanted venous catheter. Detailed Implementation

[0023] The described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any inventive effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.196 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour. Then, the solution was sonicated for 30 minutes to prepare an electrospinning solution, wherein the concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 11 wt%.

[0026] (2) Fix the steel mesh with a 100-mesh microstructure onto a steel tube with the same diameter as the central venous catheter, and fix the steel tube onto the tubular stent receiver for electrospinning;

[0027] (3) Transfer the prepared solution to a syringe (5 ml) equipped with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm from the collector. Finally, the obtained SMP-PLA / MWCNTs fiber tubular spun membrane was dried in a 60℃ constant temperature oven for 20 h. The thickness of the pressure-sensitive layer was approximately 134 μm, and the conductivity was 2.65 μS / cm.

[0028] (4) Place the thin tube in PDMS solution in advance, and after solidification, remove the thin tube to form a hollow mold. Divide it into two halves to form a hot-pressing mold. After hot-pressing the tubular spun membrane obtained in (3), make an electrode layer by screen printing silver paste on a PI film, attach it to the central venous catheter, and put the tubular spun membrane on it. After adaptive fixation, wrap its outer side with a 5μm PET film to form a tubular flexible pressure sensor. Its structure is as follows: Figure 1 As shown.

[0029] Example 2

[0030] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.216 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour, followed by sonication for 30 minutes to prepare an electrospinning solution. The concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 12 wt%.

[0031] (2) Fix the steel mesh with a 100-mesh microstructure onto a steel tube with the same diameter as the central venous catheter, and fix the steel tube with the microstructure onto the tubular stent receiver for electrospinning.

[0032] (3) Transfer the prepared solution to a syringe (5 ml) with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm from the collector. Finally, the SMP-PLA / MWCNTs fiber tubular spun membrane was dried in a 60℃ constant temperature oven for 20 h. The thickness of the pressure-sensitive layer was approximately 174 μm, and the conductivity was 3.22 μS / cm.

[0033] (4) After hot pressing with a hot pressing mold, an electrode layer is made by screen printing silver paste on a PI film and attaching it to a central venous catheter. A tubular spun membrane is then placed on top of it. After self-adaptive fixation, the sensor is wrapped with a 5μm PET film to form a closed tubular flexible pressure sensor.

[0034] Example 3

[0035] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.236 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour, followed by sonication for 30 minutes to prepare an electrospinning solution. The concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 13 wt%.

[0036] (2) Fix the steel mesh with a 100-mesh microstructure onto a steel tube with the same diameter as the central venous catheter, and fix the steel tube with the microstructure onto the tubular stent receiver for electrospinning.

[0037] (3) Transfer the prepared solution to a syringe (5 ml) with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm for collection. Finally, the SMP-PLA / MWCNTs fiber tubular spun membrane was placed in a 60℃ constant temperature oven for drying for 20 h. The thickness of the pressure-sensitive layer was approximately 200 μm, and the conductivity was 4.04 μS / cm.

[0038] (4) After hot pressing with a hot pressing mold, an electrode layer is made by screen printing silver paste on a PI film and attaching it to a central venous catheter. A tubular spun membrane is then placed on top of it. After self-adaptive fixation, the sensor is wrapped with a 5μm PET film to form a closed tubular flexible pressure sensor.

[0039] Example 4

[0040] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.258 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour, followed by sonication for 30 minutes to prepare an electrospinning solution. The concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 14 wt%.

[0041] (2) Fix the steel mesh with a 100-mesh microstructure onto a steel tube with the same diameter as the central venous catheter, and fix the steel tube with the microstructure onto the tubular stent receiver for electrospinning.

[0042] (3) Transfer the prepared solution to a syringe (5 ml) with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm from the collector. Finally, the SMP-PLA / MWCNTs fiber tubular spun membrane was dried in a 60℃ constant temperature oven for 20 h. The thickness of the pressure-sensitive layer was approximately 173 μm, and the conductivity was 6.41 μS / cm.

[0043] (4) After hot pressing with a hot pressing mold, an electrode layer is made by screen printing silver paste on a PI film and attaching it to a central venous catheter. A tubular spun membrane is then placed on top of it. After self-adaptive fixation, the sensor is wrapped with a 5μm PET film to form a closed tubular flexible pressure sensor.

[0044] Example 5

[0045] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.279 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour, followed by sonication for 30 minutes to prepare an electrospinning solution. The concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 15 wt%.

[0046] (2) Fix the steel mesh with a 100-mesh microstructure onto a steel tube with the same diameter as the central venous catheter, and fix the steel tube with the microstructure onto the tubular stent receiver for electrospinning.

[0047] (3) Transfer the prepared solution to a syringe (5 ml) with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm from the collector. Finally, the SMP-PLA / MWCNTs fiber tubular spun membrane was dried in a 60℃ constant temperature oven for 20 h. The thickness of the pressure-sensitive layer was approximately 185 μm, and the conductivity was 12.65 μS / cm.

[0048] (4) After hot pressing, an electrode layer is made by screen printing silver paste on the PI film and attaching it to the central venous catheter. A tubular spun membrane is then placed on top of it. After self-adaptive fixation, the sensor is wrapped with a 5μm PET film to form a closed tubular flexible pressure sensor.

[0049] Example 6

[0050] (1) Polylactic acid particles (1.586 g) were dissolved in dichloromethane solvent (7.2 ml CH2Cl2) and stirred electromagnetically for 2 hours. After the particles were completely dissolved, multi-walled carbon nanotube powder (0.258 g) and N,N-dimethylformamide solvent (2.4 ml DMF) were added to the solution and stirred for 1 hour, followed by sonication for 30 minutes to prepare an electrospinning solution. The concentration of multi-walled carbon nanotubes in the SMP-PLA / MWCNTs composite material was 14 wt%.

[0051] (2) Then adjust the electrospinning parameters and receive the data through a roller receiver (without a 100-mesh microstructure steel mesh) for electrospinning.

[0052] (3) Transfer the prepared solution to a syringe (5 ml) with a 21G needle. Electrospinning was performed for 30 min at a voltage of 20 kV, a feed rate of 0.1 mm / s, and a needle distance of 10 cm from the collector. Finally, the SMP-PLA / MWCNTs fiber tubular spun membrane was dried in a 60℃ constant temperature oven for 20 h. The thickness of the pressure-sensitive layer was approximately 192 μm, and the conductivity was 6.32 μS / cm.

[0053] (4) After hot pressing with a hot pressing mold, an electrode layer is made by screen printing silver paste on a PI film and attaching it to a central venous catheter. A tubular spun membrane is then placed on top of it. After self-adaptive fixation, the sensor is wrapped with a 5μm PET film to form a closed tubular flexible pressure sensor.

[0054] Coagulation monitoring

[0055] First, COMSOL was used to simulate the pressure on the central venous catheter wall. A central venous catheter was constructed at the center of the vein model, and then thrombi of different sizes were introduced for fluid-structure interaction simulation. When there was no blood clot around the central venous catheter, the maximum blood flow velocity in the vessel during one heartbeat cycle was 0.36 m / s, and the maximum pressure of the blood on the central venous catheter wall was approximately 400 Pa. When blood clots formed around the central venous catheter (V = 5.22 mm), the pressure was significantly lower. 3 During one heartbeat cycle, the maximum blood flow velocity drops to 0.32 m / s, and the maximum pressure of blood against the central venous catheter wall increases to approximately 1 kPa. Simulation results show that as the thrombus grows, the blood flow velocity within the blood vessel slows down, and the pressure of blood against the central venous catheter wall increases, with a maximum pressure of 1 kPa, thus guiding the sensor's measurement range design (<1 kPa).

[0056] This flexible pressure sensor is inserted into the body along with a central venous catheter. It monitors pressure changes around the catheter in real time to determine the presence of thrombi within the blood vessel; an increase in monitored pressure indicates the formation of blood clots. To improve the sensor's ability to detect the pressure during deep vein thrombosis (DVT), this study used electrospinning to prepare tubular nanofiber films with a 100-mesh microstructure. Because the receiver has a 100-mesh steel mesh, the nanofibers are selectively distributed in non-porous areas rather than uniformly on the receiver, thus constructing a matrix-like conductive microstructure. This microstructure increases the effective concentration of carbon nanotubes; therefore, with the same carbon nanotube content, the conductive network with the microstructure has a more concentrated conductive path and significantly higher sensitivity than a random network. Furthermore, the nanofiber membrane prepared by electrospinning has a larger specific surface area and volume ratio, resulting in a multi-layered microstructure that further enhances its sensitivity. The nanofiber membrane with the 100-mesh microstructure provides better monitoring of blood pressure around the central venous catheter compared to nanofiber membranes without microstructure. To delve into the properties of SMP-PLA / MWCNTs composites, we systematically investigated the solution characteristics of different ratios, focusing on their impact on the stability of the nanospun membrane. Through a series of experiments and summaries, we found that when the mass ratio of carbon nanotubes to SMP-PLA in the electrospinning solution was less than 14 wt%, the prepared nanofiber membrane exhibited poor conductivity and insufficient pressure response. However, when the carbon nanotube content was above 14 wt%, significant differences in fiber diameter occurred within the spun membrane, leading to the aggregation of multiple fibers, forming fibers approaching 20 micrometers in size, and the spinning process became difficult to reproduce. At a carbon nanotube content of 14 wt%, the nanospun membrane exhibited superior structural stability and more sensitive electrical properties. Under different pressure loads, the recovery performance of the membrane with a carbon nanotube to SMP-PLA content of 14 wt% was very stable, with a sensitivity as high as 204 kPa. -1 The formation of 100-mesh microstructures can effectively improve the sensitivity of flexible pressure sensors, with the nanofiber membrane without 100-mesh microstructures (Example 6) having a sensitivity of only 132.2 kPa. -1 In addition to its high sensitivity, this sensor also features an ultra-low detection limit (150 Pa) and a stable response plateau with a resolution of 100 Pa under increasing pressure. It can respond to minute pressure changes within a low-pressure range, detecting even the slight pressure required for thrombus formation. The flexible pressure sensor for coagulation monitoring has a response time of 28 ms, meeting the requirements of real-time medical monitoring and enabling early detection and timely treatment.

[0057] The sensor of the present invention utilizes polylactic acid with shape memory to achieve the fixation and installation of the flexible pressure sensor through the shape memory property of the material itself. Through DMA testing, it can be understood that the shape fixation rate of the SMP-PLA / MWCNTs film always remains above 97.5%, and the shape recovery rate gradually increases, rising from 66.14% in the first time to 96.37% in the fourth time. The tubular nanofiber membrane with shape memory changes its initial shape under thermal stimulation (T≥Tg) and external force, withdraws the thermal stimulation (T<Tg) and maintains the external force to obtain a temporary shape, and the temporary shape is fixed after withdrawing the external force. The temporary shape of the tubular nanofiber membrane is designed to have an increased tube diameter, and then it is sleeved into the position to be fixed; then, under the action of thermal stimulation (T≥Tg), it is restored to its initial shape and actively shrinks inward to achieve the fixation effect.

[0058] The present invention illustrates the detailed method of the present invention through the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, and the selection of specific methods and conditions, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for fabricating a flexible pressure sensor for coagulation monitoring that can be adaptively fixed, characterized in that, The flexible pressure sensor has a multi-layer structure, including an electrode layer, a pressure-sensitive layer, and a waterproof layer. The pressure-sensitive layer is made by electrospinning a spinning solution composed of shape-memory polylactic acid (SMP-PLA) and multi-walled carbon nanotubes (MWCNTs). During electrospinning, a receiver with a 100-mesh microstructure is used to receive the resulting composite hollow cylindrical membrane. The electrode layer is located on the inner side of the composite hollow cylindrical membrane and is made by screen-printing silver paste onto a PI film. One side of the screen-printed silver paste contacts the composite hollow cylindrical membrane, and the opposite side contacts the implanted venous catheter. The shape-memory function of the pressure-sensitive layer enables the flexible pressure sensor to adaptively fix itself to the implanted venous catheter. The waterproof layer is encapsulated on the outside of the pressure-sensitive layer. The flexible pressure sensor is adaptively fixed to the implanted venous catheter for monitoring coagulation after insertion. When the monitored pressure increases, it indicates that blood clots are beginning to form in the vein. The preparation method includes the following steps: Shape memory polylactic acid (SMP-PLA) and multi-walled carbon nanotubes (MWCNTs) were added to a mixed solution of dichloromethane and N,N-dimethylformamide. After thorough mixing and dispersion, a spinning solution was obtained. A steel mesh with a 100-mesh microstructure was fixed onto a steel tube of the desired diameter. The resulting steel tube was then fitted onto a tubular support receiver, and electrospinning was performed to obtain the pressure-sensitive layer. One side of the screen-printed silver paste of the electrode layer was fixed to the inner side of the pressure-sensitive layer, and the other side of the electrode layer, opposite to the screen-printed silver paste side, was attached to the outer side of the wall of the implantable venous catheter. The shape memory function of the pressure-sensitive layer was then used to achieve adaptive fixation to the implantable venous catheter. Finally, a waterproof layer was used for encapsulation.

2. The preparation method according to claim 1, characterized in that, The volume ratio of dichloromethane to the mixed solution is 70% to 80%, and the volume ratio of N,N-dimethylformamide to the mixed solution is 20% to 30%.

3. The preparation method according to claim 1, characterized in that, The concentration of shape memory polylactic acid (SMP-PLA) in the spinning solution is 16-17 wt%.

4. The preparation method according to claim 1, characterized in that, The concentration of multi-walled carbon nanotubes (MWCNTs) in the spinning solution is 11-15 wt%.

5. The preparation method according to claim 1, characterized in that, The concentration of multi-walled carbon nanotubes (MWCNTs) in the spinning solution is 14 wt%.

6. The preparation method according to claim 1, characterized in that, The composite hollow cylindrical membrane has a thickness of 130~200μm.

7. A flexible pressure sensor manufactured using the method for preparing an adaptively fixed flexible pressure sensor for coagulation monitoring as described in any one of claims 1-6, characterized in that, The flexible pressure sensor has a multi-layer structure, including an electrode layer, a pressure-sensitive layer, and a waterproof layer. The pressure-sensitive layer is made by electrospinning a spinning solution composed of shape memory polylactic acid (SMP-PLA) and multi-walled carbon nanotubes (MWCNTs). During electrospinning, a receiver with a 100-mesh microstructure is used to receive the composite hollow cylindrical membrane. The electrode layer is located on the inner side of the composite hollow cylindrical membrane and is made by screen printing silver paste on a PI film. One side of the screen-printed silver paste is in contact with the composite hollow cylindrical membrane, and the other side, opposite to the screen-printed silver paste side, is in contact with the implanted venous catheter. The shape memory function of the pressure-sensitive layer enables the flexible pressure sensor to adaptively fix itself to the implanted venous catheter. The waterproof layer is encapsulated on the outside of the pressure-sensitive layer. The flexible pressure sensor is adaptively fixed to the implanted venous catheter for monitoring coagulation after insertion; when the monitored pressure increases, it indicates that blood clots are beginning to form in the vein.

Images