CN114618006B - Intelligent wound dressing, preparation method and application thereof, and flexible sensor - Google Patents

Abstract

The invention relates to the technical field of wound dressings, in particular to an intelligent wound dressing, its preparation method and application, and a flexible sensor. The invention provides an intelligent wound dressing, which comprises a substrate and a functional layer arranged on the surface of the substrate; the substrate is a chitosan hemostatic sponge; and the functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber film. The smart wound dressing has better responsiveness to humidity and pressure.

Description

A kind of intelligent wound dressing and its preparation method and application, flexible sensor

technical field

The invention relates to the technical field of wound dressings, in particular to an intelligent wound dressing, its preparation method and application, and a flexible sensor.

Background technique

Pathogenic infection, as the most common complication of chronic wounds, has become a global healthcare challenge, and the detection of wound healing process has become particularly important. Currently, dressings in the form of films, sponges, and hydrogels are the main options for clinical wound management. However, the current wound dressings are basically passive treatments, and it is difficult to achieve actual wound treatment and meet the needs of dynamic healing monitoring of chronic wounds at the same time. Therefore, there is a great need for an intelligent wound dressing system for real-time monitoring of wound healing status and on-demand treatment. With the emergence of the Internet of Things and smart wearable devices, a new generation of smart wound dressings with smart wearable sensors as the core can solve the above-mentioned problems faced by current wound dressings by detecting physical and chemical signals related to the wound healing process. Among them, the humidity at the wound, which is closely related to the verification and infection status of the wound site, and the pressure value change of the surrounding skin during the wound healing process are considered to be the most important and promising monitoring indicators.

Contents of the invention

The object of the present invention is to provide an intelligent wound dressing, its preparation method and application, and a flexible sensor. The smart wound dressing has better responsiveness to humidity and pressure.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides an intelligent wound dressing, comprising a substrate and a functional layer arranged on the surface of the substrate;

The base is chitosan hemostatic sponge;

The functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber film.

Preferably, the mass ratio of citric acid to thermoplastic elastomer polyurethane in the citric acid-thermoplastic elastomer polyurethane composite nanofiber film is (0.05-0.15):1.

The present invention also provides a preparation method for the intelligent wound dressing described in the above technical solution, comprising the following steps:

mixing citric acid, thermoplastic elastomer polyurethane and a solvent to obtain a composite spinning solution;

Using the chitosan hemostatic sponge as a base, the composite spinning solution is electrospun to obtain the intelligent wound dressing.

Preferably, the mass concentration of thermoplastic elastomer polyurethane in the composite spinning solution is 15-30%.

Preferably, the mass ratio of the citric acid to the thermoplastic elastomer polyurethane is (0.05-0.15):1.

Preferably, the solvent includes N,N-dimethylformamide and tetrahydrofuran;

The volume ratio of the N,N-dimethylformamide to tetrahydrofuran is (0.5-2.5):1.

Preferably, the electrospinning uses 2 to 4 nozzles for spinning;

The temperature of the electrospinning is 30-50°C, the positive voltage is 10-24kV, the negative voltage is -5--1kV, the time is 1-5h, the advancing speed is 1-3mL/h, and the receiving distance is 10-18cm .

The present invention also provides the application of the intelligent wound dressing described in the above technical solution or the intelligent wound dressing prepared by the preparation method described in the above technical solution in the field of intelligent wound monitoring.

The present invention also provides a flexible sensor for intelligent monitoring of wounds, comprising the intelligent wound dressing described in the above technical solution or the intelligent wound dressing prepared by the preparation method described in the above technical solution and a functional layer arranged in the intelligent wound dressing surface electrode layer.

Preferably, the thickness of the electrode layer is 50-60 nm.

The invention provides an intelligent wound dressing, which comprises a substrate and a functional layer arranged on the surface of the substrate; the substrate is a chitosan hemostatic sponge; and the functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber film.

Compared with the prior art, the present invention has the following advantages:

1) Hydroxyl and carboxyl in the citric acid of the present invention are easy to form the network structure that hydrogen bond connects, and the hydroxyl that citric acid surface exposes can form hydrogen bond with external water molecule, and three carboxyls contained in citric acid also can be with water Molecules form intermolecular hydrogen bonds, which can be added to nanofiber membranes to achieve ultra-high humidity response sensitivity;

2) The nanofiber membrane structure has nanofibers staggered at the microscopic level, and the microstructure with uneven surface, constructing the above-mentioned microstructure in the functional layer can effectively improve its sensitivity and response time; at the same time, the citric acid- The thermoplastic elastomer polyurethane composite nanofiber membrane is also soft, stretchable and breathable, and has good biocompatibility. It will not cause harm to the human body when used on human skin. Combined with chitosan hemostatic sponge, It can be combined into a wound dressing that intelligently monitors the healing status of open wounds, and has a hemostatic effect on wounds, and is used for monitoring human health in open wounds;

3) The smart wound dressing of the present invention can detect changes in humidity and pressure at the wound in real time as an early predictor of pathological infection and judge wound healing;

4) The chitosan hemostatic sponge has water-absorbing swelling properties, can quickly absorb moisture in the blood to stop bleeding, and can also agglutinate red blood cells through the combination of polycations of chitosan and anions on the surface of red blood cell membranes, while activating platelet aggregation and activating blood coagulation Enzyme, so as to achieve the purpose of rapid hemostasis; it is soluble, and forms a uniform chitosan gel layer on the oozing wound to protect the wound and stop bleeding.

Description of drawings

Fig. 1 is the SEM picture of the functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 2 is the XRD diagram of the functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 3 is the FT-TR diagram of the functional layer and pure CA in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 4 is the TG curve of the functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 5 is the mechanical performance test result of the functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 6 is the water contact angle test result of the functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1;

Fig. 7 is the biocompatibility test result of the functional layer in the smart wound dressing prepared in Example 3;

Fig. 8 is the humidity response performance test result of the flexible sensor described in embodiments 4-6;

Fig. 9 is the pressure response performance test result of the flexible sensor described in embodiment 6;

Fig. 10 is the gas permeability test result of the flexible sensor described in Example 6.

Detailed ways

The invention provides an intelligent wound dressing, comprising a substrate and a functional layer arranged on the surface of the substrate;

The base is chitosan hemostatic sponge;

The functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber film.

In the present invention, the thickness of the chitosan hemostatic sponge is preferably 0.5-3 mm, more preferably 1-2 mm, most preferably 1.8 mm.

In the present invention, the thickness of the functional layer is preferably 30-60 μm, more preferably 35-50 μm, most preferably 44 μm.

In the present invention, the mass ratio of citric acid to thermoplastic elastomer polyurethane in the citric acid-thermoplastic elastomer polyurethane composite nanofiber film is preferably (0.05-0.15):1, more preferably (0.10-0.15):1.

The present invention also provides a preparation method for the intelligent wound dressing described in the above technical solution, comprising the following steps:

Mixing citric acid (CA), thermoplastic elastomer polyurethane (TPU) and a solvent to obtain a composite spinning solution;

Using the chitosan hemostatic sponge as a base, the composite spinning solution is electrospun to obtain the smart wound dressing.

In the present invention, unless otherwise specified, all preparation materials are commercially available products well known to those skilled in the art.

The invention mixes citric acid, thermoplastic elastomer polyurethane and solvent to obtain composite spinning solution.

In the present invention, the solvent preferably includes N,N-dimethylformamide and tetrahydrofuran; the volume ratio of N,N-dimethylformamide and tetrahydrofuran is preferably (0.5-2.5):1, more preferably 1:1.

In the present invention, the mass concentration of thermoplastic elastomer polyurethane in the composite spinning solution is preferably 15-30%, more preferably 18-26%, most preferably 20-23%.

In the present invention, the mass ratio of the citric acid to the thermoplastic elastomer polyurethane is preferably (0.05-0.15):1, more preferably (0.10-0.15):1.

In the present invention, the mixing is preferably mixing the citric acid and the solvent under ultrasonic conditions, and then adding the thermoplastic elastomer polyurethane for stirring and mixing. In the present invention, the power of the ultrasonic wave is preferably 400W, and the time is preferably 15min; the present invention does not have any special restrictions on the conditions of the stirring and mixing, and the conditions known to those skilled in the art are used to carry out and make the resulting composite spinning The solution is mixed evenly.

After the composite spinning solution is obtained, the invention uses the chitosan hemostatic sponge as a base, and carries out electrostatic spinning on the composite spinning solution to obtain the intelligent wound dressing.

In the present invention, the electrospinning preferably adopts 2-4 nozzles for spinning. The temperature of the electrospinning is preferably 30-50°C, more preferably 35-45°C, most preferably 38-42°C; the positive voltage is preferably 10-24kV, more preferably 13-20kV, most preferably 15-20kV 18kV; the negative voltage is preferably -5~-1kV, more preferably -4~-2kV; the time is preferably 1~5h, more preferably 2~4h, most preferably 2.5~3.5h; the propulsion speed is preferably 1~3mL /h, more preferably 1.5-2.5mL/h, most preferably 1.8-2.2mL/h; receiving distance is preferably 10-18cm, more preferably 12-16cm, most preferably 13-15cm.

The present invention also provides the application of the intelligent wound dressing described in the above technical solution or the intelligent wound dressing prepared by the preparation method described in the above technical solution in the field of intelligent wound monitoring.

The present invention also provides a flexible sensor for intelligent monitoring of wounds, comprising the intelligent wound dressing described in the above technical solution or the intelligent wound dressing prepared by the preparation method described in the above technical solution and a functional layer arranged in the intelligent wound dressing surface electrode layer.

In the present invention, the electrode layer has a mesh structure.

In the present invention, the thickness of the electrode layer is preferably 50-60 nm, more preferably 53-56 nm.

In the present invention, the material of the electrode layer preferably includes one or more of silver, carbon nanotubes and graphene.

In the present invention, the electrode layer is preferably replaced by a conductive paste.

In the present invention, the flexible sensor further preferably includes wires; the wires are connected to opposite sides of the electrode layer; the wires are preferably copper wires.

In the present invention, the flexible sensor is preferably electrically connected with a monitoring device when in use.

In the present invention, the preparation method of the flexible sensor preferably includes the following steps:

Preparation of smart wound dressings;

Using screen printing, after preparing an electrode layer on the surface of the functional layer in the intelligent wound dressing, connecting wires on opposite sides of the electrode layer to obtain the flexible sensor;

Or after pasting a layer of conductive paste on the surface of the functional layer in the intelligent wound dressing, connecting wires on opposite sides of the electrode layer to obtain the flexible sensor.

In the present invention, the method for preparing the smart wound dressing is preferably carried out by using the preparation method described in the above technical solution, which will not be repeated here.

After the smart wound dressing is obtained, the present invention uses screen printing to prepare an electrode layer on the surface of the functional layer in the smart wound dressing to obtain the flexible sensor.

In the present invention, the preparation process of the electrode layer preferably includes:

Provide conductive ink;

A screen printing plate is covered on the functional layer, the conductive ink is poured on the screen printing plate, the conductive ink is pushed away by a scraper, and dried to obtain the electrode layer.

In the present invention, the conductive ink is preferably one or more of conductive silver paste, ink containing carbon nanotubes, and ink containing graphene. The composition of the vinyl ink is not particularly limited, and commercially available products well known to those skilled in the art can be used.

The smart wound dressing provided by the present invention, its preparation method and application, and the flexible sensor will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

Example 1

Mix 0.25g of CA with 20mL of a mixture of N,N-dimethylformamide and tetrahydrofuran at a volume ratio of 1:1, and after ultrasonication at 400W for 15 minutes, add 5g of TPU and stir until the TPU is completely dissolved to obtain a composite spinning solution;

The composite spinning solution is transferred to two 10mL syringes, installed on the spinning machine, with the chitosan hemostatic sponge as the base, attached to the receiving drum of the spinning machine, and adjusting the spinning conditions (the temperature is 30 ° C, The positive voltage is 18kV, the negative voltage is 2kV, the time is 3h, the propulsion speed is 1mL/h, and the receiving distance is 10cm), to obtain a smart wound dressing (the mass ratio of citric acid and thermoplastic elastomer polyurethane in the functional layer is 0.05:1, record is CA/TPU-5%).

Example 2

Referring to Example 1, the only difference is that the amount of CA is 0.5g, and a smart wound dressing is prepared (the mass ratio of citric acid and thermoplastic elastomer polyurethane in the functional layer is 0.1:1, denoted as CA/TPU-10%).

Example 3

Referring to Example 1, the only difference is that the amount of CA is 0.75g, and a smart wound dressing is prepared (the mass ratio of citric acid and thermoplastic elastomer polyurethane in the functional layer is 0.15:1, denoted as CA/TPU-15%).

Example 4

Cover the screen printing plate on the surface of the functional layer described in Example 1, pour the carbon nanotube ink on the screen printing plate, push the conductive ink away and spread it with a scraper, and let it dry naturally. obtaining the electrode layer;

Conductive copper wires were glued to the opposite ends of the electrode layer to obtain a flexible sensor (denoted as CTHPS-5%).

Example 5

Referring to Example 4, the only difference is that an electrode layer is prepared on the surface of the functional layer described in Example 2 to obtain a flexible sensor (referred to as CTHPS-10%).

Example 6

Referring to Example 4, the only difference is that an electrode layer is prepared on the surface of the functional layer described in Example 3 to obtain a flexible sensor (denoted as CTHPS-15%).

Comparative example 1

Referring to Example 1, the only difference is that no CA is added.

test case

The functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1 was subjected to SEM testing, and the test results are shown in Figure 1, wherein (a) corresponds to Comparative Example 1, (b) corresponds to Example 1, ( c) corresponds to Example 2, and (d) corresponds to Example 3; as can be seen from Figure 1, the fibers of the functional layer without adding CA in Comparative Example 1 are smooth and continuous with uniform diameter distribution (the average diameter is about 582±7.2nm), forming a three-dimensional Arranged grid structure; a small amount of CA particles loaded on the fiber surface in Example 1, along with the increase of CA addition, the load of CA particles on the surface of citric acid/thermoplastic elastomer polyurethane (CA/TPU) composite nanofibers also increases with In addition, due to the increase of CA addition, the surface tension to be overcome in the electrospinning process is reduced, so the fiber diameter is reduced to 525±6.5nm, thereby forming more microstructures in the film, It is beneficial to improve the humidity and pressure sensing performance of the fiber membrane;

The functional layer in the smart wound dressing prepared in Examples 1 to 3 and Comparative Example 1 (pure TPU) is subjected to XRD testing, and the test results are as shown in Figure 2, CA/TPU-5% and CA/TPU-10% The XRD spectrum is basically consistent with that of pure TPU, so it can be inferred that the doping of CA will not significantly change the crystal structure of TPU. And as the doping amount increases, the characteristic diffraction peaks of CA particles in XRD are more obvious, indicating that CA particles are successfully incorporated into the TPU nanofiber film;

The functional layer and pure CA in the smart wound dressings prepared in Examples 1-3 and Comparative Example 1 were tested by FT-TR. The test results ^are shown in Figure 3. It can be seen from Figure 3 that the pure TPU ^3000cm The peaks at ¹ are -NH- stretching vibration absorption peak and C≡O stretching vibration absorption peak, which are very obvious in FT-IR of CA/TPU composite nanofibrous membrane, indicating that TPU and CA blended electrospinning Will not destroy the basic structure of TPU. In addition, at 1736-1720 cm ^-1 , a new absorption band appeared in the CA/TPU composite nanofiber membrane, which is the C=O stretching vibration peak, which belongs to the characteristic peak of CA, which proves that the TPU membrane has successfully loaded CA;

The functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1 (pure TPU) was tested by TG, and the test results are shown in Figure 4. It can be seen from Figure 4 that when the temperature is lower than 200°C, the pure TPU TPU and all CA/TPU composite nanofibrous membranes had a small weight loss due to the loss of adsorbed water. Between 200 and 450 °C, pure TPU and CA/TPU composite nanofibrous membranes exhibit severe mass loss due to the decomposition of the polymer. With the increase of CA doping amount, the remaining mass percentage of CA/TPU composite nanofibrous membrane showed an increasing trend, and the remaining weight of CA/TPU-15% was 10.5%, indicating that CA had been successfully doped into TPU;

The functional layer in the smart wound dressing prepared in Examples 1-3 and Comparative Example 1 (pure TPU) was tested for mechanical properties. The stress-strain curve is shown in Figure 5. It can be seen from Figure 5 that as the CA content increases from 0 Up to 10wt%, the ultimate stress increases monotonically from 0.7MPa to 1.3MPa. When the CA doping amount is 15%, the tensile strain of the CA/TPU composite nanofiber membrane is about 350%, and the elongation at break is about 450%. The tensile strain of the CA/TPU composite nanofibrous membrane was always maintained above 350%, and the elongation at break was also maintained at a high level (about 470%), indicating that the CA/TPU nanofibrous membrane has good flexibility and stretchability , not easy to break when attached to the skin;

The functional layer in the smart wound dressing prepared in Examples 1 to 3 and Comparative Example 1 (pure TPU) was tested for water contact angle, and the test results are shown in Figure 6. As can be seen from Figure 6, the water contact angle of Comparative Example 1 is 132°, and the water contact angles of Examples 1 to 3 are 72°, 57° and 46° respectively. It can be seen that the water contact angle of the composite nanofibrous membrane doped with CA decreases, indicating that the addition of CA improves the composite nanofiber membrane. The wettability of the nanofibrous membrane enhances the hydrophilic property of the composite nanofibrous membrane. This is because CA molecules contain multiple carboxyl groups and hydroxyl groups, and carboxyl groups and hydroxyl groups can form intermolecular hydrogen bonds with water molecules in the air, and adsorb water molecules on the surface of nanofiber membranes in the form of physical adsorption, which is the basis of humidity response. ;

The functional layer in the smart wound dressing prepared in Example 3 was subjected to a biocompatibility experiment, and the test results are shown in Figure 7, wherein (a) is HaCaT cultured on Roswell Park Memorial Institute-1640 standard medium for 4 days. Fluorescent image of cells, (b) is a fluorescent image of HaCaT cells cultured on the functional layer in the smart wound dressing prepared in Example 3, (c) is a fluorescent image of HaCaT cells cultured on blank cell culture medium, (d ) is the OD value of the HaCaT cells cultured at different times on the Roswell Park Memorial Institute-1640 standard medium, the functional layer in the smart wound dressing prepared in Example 3, and the blank cell medium, as can be seen from Figure 7. 3 The functional layer in the smart wound dressing prepared in Example 3 has no obvious cytotoxic effect on HaCaT cells, which is very close to the standard cell culture medium. After culturing for 4 days on the functional layer in the smart wound dressing prepared in Example 3, the specific The absorbance was measured at a wavelength of 450nm, and the survival rate of HaCaT cells was not significantly reduced. It shows that the functional layer in the smart wound dressing prepared in Example 3 has biocompatibility and can be used directly on the skin or on an open wound;

The flexible sensor described in Examples 4-6 was tested for humidity response performance, and the test results are shown in Figure 8, wherein (a) is the humidity of the flexible sensor described in Examples 4-6 at 20-90% RH- The relative resistance change curve, (b) is the hysteresis curve of the flexible sensor described in embodiment 6 at a humidity of 20 to 90% RH, as can be seen from (a), the relative resistance of the flexible sensor changes with the increase of humidity Larger, in the low humidity range (20-50% RH), the humidity sensitivity of the flexible sensor is roughly the same, the higher the 0.6% RH, in the high humidity range (50%-90% RH), the CTHPS-15% sensitivity The wet sensitivity is the largest at about 2.15%RH, while CTHPS-5% and CTHPS-10% are 1.32/%RH and 1.88/%RH, respectively. It can be seen that with the increase of the doping amount of CA, the moisture-sensing performance of the flexible sensor is enhanced, so the optimal doping amount of CA is 15%; it can be seen from (b) that in the humidity range of 20% to 90% RH Within, the humidity hysteresis of CTHPS-15% is 10%, which proves that the sensor has good stability in a wide range of humidity;

The flexible sensor described in Example 6 is tested for pressure response performance, and the test results are as shown in Figure 9, wherein (a) is a pressure sensitivity curve, (b) is a time response curve, and (c) is a response recovery curve; by (a ) shows that the pressure sensitivity is divided into three linear regions: _SP1 in the low pressure range (0-2.25kPa), _SP2 in the medium-pressure range (2.25-11.25kPa) and _SP3 in the high-pressure range (11.25-26.25kPa). The sensitivities of CTHPS-15% to _SP1 , _SP2 and _SP3 are 10.53, 2.56 and 0.3kPa ^-1 respectively, because there are a lot of pores and gaps inside the electrospun nanofibrous membrane. The existence of pores and gaps leads to poor contact between conductive CNTs, resulting in a large original resistance of CTHPS without applying pressure, once the pressure is applied to the sensor, compression deformation occurs, and the pores and gaps between nanofibers will be Reduced, the contact between the fiber and the conductive carbon nanotube will be greatly increased. When a small pressure (0 ~ 2.25kPa) is applied, the carbon nanotube electrode is in closer contact with the nanofiber film, resulting in a sharp increase in conductivity. At this time The sensitivity is relatively high. When the applied pressure increases (2.25–11.25 kPa), the multilayer nanofibers are tightly compressed together, resulting in a further increase in electrical conductivity and a decrease in electrical resistance. According to clinical data, the pressure value of open wounds in the human abdomen is usually lower than 10kPa. Therefore, CTHPS can be used in open smart wound dressings to monitor the degree of wound healing according to the changes in the pressure value of the surrounding skin during the wound healing process. As the pressure increases (11.25 ~ 26.25kPa), the sensitivity of the sensor drops to 0.3kPa ^-1 . This is because the mutual contact of conductive carbon nanotubes cannot be improved, and the output resistance has almost no change; as can be seen from (b), CTHPS-15% shows a fast response (88ms) and recovery time (90ms), indicating that the sensor has a fast response; It can be seen from (c) that the response recovery curve of CTHPS-15% under 200 cycle tests shows that the sensor has good cycle stability;

The flexible sensor described in Example 6, the TPU nanofiber membrane described in Comparative Example 1, and the PDMS membrane were tested for gas permeability, and the test results are as shown in Figure 10. As can be seen from Figure 10, the gas permeability of the TPU nanofiber membrane is 192mm/ s, better than PDMS membrane (0mm/s) commonly used in flexible pressure sensors, and similar to polypropylene melt-blown nonwovens used as filters in medical protective masks (air permeability about 198mm/s). The air permeability of CTHPS-15% is 171mm/s, which is slightly weaker than that of pure TPU, but still shows good air permeability, indicating the superior air permeability of CTHPS-15%.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (8)

1. A flexible sensor for intelligent monitoring of wounds, characterized in that it comprises an intelligent wound dressing and an electrode layer arranged on the surface of a functional layer in the intelligent wound dressing; The smart wound dressing includes a substrate and a functional layer arranged on the surface of the substrate; The base is chitosan hemostatic sponge; The functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber film. 2 . The flexible sensor according to claim 1 , wherein the mass ratio of citric acid to thermoplastic elastomer polyurethane in the citric acid-thermoplastic elastomer polyurethane composite nanofiber film is (0.05-0.15):1. 3. The flexible sensor according to claim 1 or 2, wherein the preparation method of the intelligent wound dressing comprises the following steps: mixing citric acid, thermoplastic elastomer polyurethane and a solvent to obtain a composite spinning solution; Using the chitosan hemostatic sponge as a base, the composite spinning solution is electrospun to obtain the smart wound dressing. 4. The flexible sensor according to claim 3, wherein the mass concentration of thermoplastic elastomer polyurethane in the composite spinning solution is 15-30%. 5. The flexible sensor according to claim 3 or 4, wherein the mass ratio of the citric acid to the thermoplastic elastomer polyurethane is (0.05-0.15):1. 6. The flexible sensor according to claim 5, wherein the solvent comprises N,N-dimethylformamide and tetrahydrofuran; The volume ratio of N,N-dimethylformamide to tetrahydrofuran is (0.5-2.5):1. 7. The flexible sensor according to claim 3, wherein the electrospinning adopts 2 to 4 nozzles for spinning; The temperature of the electrospinning is 30~50°C, the positive voltage is 10~24kV, the negative voltage is -5~-1kV, the time is 1~5h, the advancing speed is 1~3mL/h, and the receiving distance is 10~18cm . 8. The flexible sensor according to claim 1, wherein the electrode layer has a thickness of 50-60 nm.

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