CN114618006B

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

Info

Publication number: CN114618006B
Application number: CN202210371111.8A
Authority: CN
Inventors: 汪滨; 丁姗姗; 牛泽浩; 王杰; 金旭; 马佳瑜; 张延萍; 李秀艳
Original assignee: Beijing Institute Fashion Technology
Current assignee: Beijing Institute Fashion Technology
Priority date: 2022-04-11
Filing date: 2022-04-11
Publication date: 2022-11-25
Anticipated expiration: 2042-04-11
Also published as: CN114618006A

Abstract

The invention relates to the technical field of wound dressings, in particular to an intelligent wound dressing, a preparation method and application thereof 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 chitosan hemostatic sponge; the functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber membrane. The intelligent wound dressing has good responsiveness to humidity and pressure.

Description

Intelligent wound dressing, preparation method and application thereof, and flexible sensor

Technical Field

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

Background

Pathogenic infections have become a global health care challenge as the most common complication of chronic wounds, and detection of wound healing processes has become of particular importance. Currently, dressings in the form of films, sponges and hydrogels are the main choice for clinical wound treatment. However, current wound dressings are essentially passive therapies, making it difficult to achieve both actual wound therapy and the need for dynamic healing monitoring of chronic wounds. Therefore, there is a great need for an intelligent wound dressing system to enable real-time monitoring of wound healing status and on-demand therapy. With the advent of the internet of things and smart wearable devices, new generation smart wound dressings with smart wearable sensors as the core can solve the above problems faced by current wound dressings by detecting physicochemical signals related to the wound healing process. Among them, wound moisture, which is closely related to the verification of the wound site and the infection state, and the change in the pressure value of the surrounding skin during the wound healing process are considered as the most important and promising monitoring indexes.

Disclosure of Invention

The invention aims to provide an intelligent wound dressing, a preparation method and application thereof and a flexible sensor. The intelligent wound dressing has good responsiveness to humidity and pressure.

In order to achieve the above object, the present invention provides the following technical solutions:

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 chitosan hemostatic sponge;

the functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber membrane.

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

the invention also provides a preparation method of the intelligent wound dressing, which comprises the following steps:

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

and (3) performing electrostatic spinning on the composite spinning solution by taking chitosan hemostatic sponge as a substrate to obtain the intelligent wound dressing.

Preferably, the mass concentration of the 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 comprises N, N-dimethylformamide and tetrahydrofuran;

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

preferably, the electrostatic spinning adopts 2-4 nozzle spinning;

the temperature of the electrostatic spinning is 30-50 ℃, the positive voltage is 10-24 kV, the negative voltage is-5 to-1 kV, the time is 1-5 h, the propelling speed is 1-3 mL/h, and the receiving distance is 10-18 cm.

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

The invention also provides a flexible sensor for wound intelligent monitoring, which comprises the intelligent wound dressing in the technical scheme or the intelligent wound dressing prepared by the preparation method in the technical scheme and an electrode layer arranged on the surface of the functional layer in the intelligent wound dressing.

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

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 chitosan hemostatic sponge; the functional layer is a citric acid-thermoplastic elastomer polyurethane composite nanofiber membrane.

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

1) Hydroxyl and carboxyl in the citric acid easily form a hydrogen bond connected network structure, the hydroxyl exposed on the surface of the citric acid can form a hydrogen bond with external water molecules, three carboxyl groups contained in the citric acid can also form intermolecular hydrogen bonds with the water molecules, and the ultrahigh humidity response sensitivity can be achieved by adding the hydroxyl and the carboxyl into a nanofiber membrane;

2) The nano-fiber membrane structure is characterized in that nano-fibers under the microcosmic condition are arranged in a staggered mode, and a microstructure with an uneven surface is constructed in the functional layer, so that the sensitivity and the response time of the microstructure can be effectively improved; meanwhile, the citric acid-thermoplastic elastomer polyurethane composite nanofiber membrane has the characteristics of softness, stretchability and air permeability, has good biocompatibility, can not cause damage to human bodies when used on human skins, can be combined with chitosan hemostatic sponge to form a wound dressing for intelligently monitoring the healing condition of open wounds, has a hemostatic effect on the wounds, and is used for monitoring the health of the open wounds;

3) The intelligent wound dressing can be used as an early prediction index of pathological infection by detecting the humidity and pressure change of the wound in real time and judging the wound healing condition;

4) The chitosan hemostatic sponge has water-absorbing expansion performance, can rapidly absorb water in blood to stop bleeding, can agglutinate red blood cells by combining polycation of chitosan with anions on the surface of a red blood cell membrane, and simultaneously activates platelet aggregation and thrombin, thereby achieving the purpose of rapid hemostasis; has solubility, and can form uniform chitosan gel layer on the surface of bleeding wound to protect the surface of wound and stop bleeding.

Drawings

Fig. 1 is an SEM image of a functional layer in the smart wound dressings prepared in examples 1 to 3 and comparative example 1;

fig. 2 is an XRD pattern of the functional layers in the smart wound dressings prepared in examples 1 to 3 and comparative example 1;

FIG. 3 is a FT-TR graph of the functional layer and pure CA in the smart wound dressings prepared in examples 1-3 and comparative example 1;

fig. 4 is a TG curve of the functional layer in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1;

FIG. 5 shows the mechanical property test results of the functional layers in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1;

fig. 6 is a water contact angle test result of the functional layer in the smart wound dressings prepared in examples 1 to 3 and comparative example 1;

fig. 7 is a result of biocompatibility testing of a functional layer in the smart wound dressing prepared in example 3;

FIG. 8 is a humidity response performance test result of the flexible sensor according to examples 4-6;

FIG. 9 shows the results of the pressure response performance test of the flexible sensor according to example 6;

FIG. 10 shows the results of the permeability test of the flexible sensor according to example 6.

Detailed Description

the substrate is chitosan hemostatic sponge;

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

In the present invention, the thickness of the functional layer is preferably 30 to 60 μm, more preferably 35 to 50 μm, and 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 membrane is preferably (0.05 to 0.15): 1, more preferably (0.10 to 0.15): 1.

mixing Citric Acid (CA), thermoplastic elastomer polyurethane (TPU) and a solvent to obtain a composite spinning solution;

and performing electrostatic spinning on the composite spinning solution by taking chitosan hemostatic sponge as a substrate to obtain the intelligent wound dressing.

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

According to the invention, citric acid, thermoplastic elastomer polyurethane and a solvent are mixed to obtain a composite spinning solution.

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

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

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

in the present invention, the mixing is preferably performed by mixing citric acid and a solvent under ultrasonic conditions, adding a thermoplastic elastomer polyurethane, and stirring and mixing. In the invention, the power of the ultrasound is preferably 400W, and the time is preferably 15min; the stirring and mixing conditions are not particularly limited in the present invention, and the stirring and mixing conditions are well known to those skilled in the art, and the obtained composite spinning solution is uniformly mixed.

After the composite spinning solution is obtained, the chitosan hemostatic sponge is used as a substrate, and the composite spinning solution is subjected to electrostatic spinning to obtain the intelligent wound dressing.

In the present invention, the electrospinning preferably employs 2 to 4-nozzle spinning. The temperature of the electrostatic spinning is preferably 30-50 ℃, more preferably 35-45 ℃, and most preferably 38-42 ℃; the positive voltage is preferably 10 to 24kV, more preferably 13 to 20kV, and most preferably 15 to 18kV; the negative voltage is preferably-5 to-1 kV, more preferably-4 to-2 kV; the time is preferably 1 to 5 hours, more preferably 2 to 4 hours, and most preferably 2.5 to 3.5 hours; the propelling speed is preferably 1-3 mL/h, more preferably 1.5-2.5 mL/h, and most preferably 1.8-2.2 mL/h; the receiving distance is preferably 10 to 18cm, more preferably 12 to 16cm, most preferably 13 to 15cm.

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

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

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 with a conductive patch.

In the present invention, the flexible sensor further preferably includes a wire; the lead is connected with two opposite sides of the electrode layer; the wire is preferably a copper wire.

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

In the present invention, the method for manufacturing the flexible sensor preferably includes the steps of:

preparing an intelligent wound dressing;

preparing an electrode layer on the surface of a functional layer in the intelligent wound dressing by adopting a screen printing mode, and connecting wires on two opposite sides of the electrode layer to obtain the flexible sensor;

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

In the present invention, the method for preparing the intelligent wound dressing is preferably performed by using the preparation method described in the above technical scheme, and details are not repeated herein.

After the intelligent wound dressing is obtained, an electrode layer is prepared on the surface of a functional layer in the intelligent wound dressing in a screen printing mode, and the flexible sensor is obtained.

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

providing a conductive ink;

and covering a screen printing plate on the functional layer, pouring the conductive ink on the screen printing plate, pushing the conductive ink away and spreading by using a scraper blade, and airing to obtain the electrode layer.

In the present invention, the conductive ink is preferably one or more of a conductive silver paste, a carbon nanotube-containing ink and a graphene-containing ink, and the present invention does not have any particular limitation on the composition of the conductive silver paste, the carbon nanotube-containing ink and the graphene-containing ink, and may adopt commercially available products well known to those skilled in the art.

The intelligent wound dressing, the preparation method and application thereof, and the flexible sensor provided by the present invention are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.

Example 1

Mixing 0.25g of CA with 20mL of a mixed solution of N, N-dimethylformamide and tetrahydrofuran in a volume ratio of 1, performing ultrasonic treatment at 400W for 15min, adding 5g of TPU, and stirring until the TPU is completely dissolved to obtain a composite spinning solution;

transferring the composite spinning solution into two 10mL injectors, installing the injectors on a spinning machine, attaching chitosan hemostatic sponge serving as a substrate to a receiving roller of the spinning machine, and adjusting spinning conditions (the temperature is 30 ℃, the positive voltage is 18kV, the negative voltage is 2kV, the time is 3h, the propelling speed is 1mL/h, and the receiving distance is 10 cm) to obtain the intelligent wound dressing (the mass ratio of citric acid to thermoplastic elastomer polyurethane in the functional layer is 0.05.

Example 2

With reference to example 1, except that the amount of CA was 0.5g, an intelligent wound dressing was prepared (mass ratio of citric acid to thermoplastic elastomer polyurethane in the functional layer 0.1, noted CA/TPU-10%).

Example 3

Referring to example 1, except that the amount of CA was 0.75g, a smart wound dressing was prepared (mass ratio of citric acid to thermoplastic elastomer polyurethane in the functional layer 0.15, noted CA/TPU-15%).

Example 4

Covering a screen printing plate on the surface of the functional layer in the embodiment 1, pouring carbon nanotube ink on the screen printing plate, pushing the conductive ink away and flatly spreading by using a scraper, and naturally airing to obtain the electrode layer;

conductive copper wires were bonded to opposite ends of the electrode layer to yield a flexible sensor (noted CTHPS-5%).

Example 5

Referring to example 4, except that an electrode layer was prepared on the surface of the functional layer described in example 2, a flexible sensor (noted as CTHPS-10%) was obtained.

Example 6

Referring to example 4, except that an electrode layer was prepared on the surface of the functional layer described in example 3, a flexible sensor (noted as CTHPS-15%) was obtained.

Comparative example 1

Reference is made to example 1, the only difference being that no CA is added.

Test example

SEM tests were performed on the functional layers in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1, and the test results are shown in fig. 1, in which (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 FIG. 1, the functional layer fibers without CA addition in comparative example 1 were smooth and continuous and had uniform diameter distribution (average diameter of about 582. + -. 7.2 nm), forming a three-dimensionally arranged lattice structure; in example 1, a small amount of CA particles are loaded on the surface of the fiber, and with the increase of the addition amount of CA, the loading amount of the CA particles on the surface of the citric acid/thermoplastic elastomer polyurethane (CA/TPU) composite nanofiber is increased, and the CA particles are distributed uniformly, and in addition, as the addition amount of CA is increased, the surface tension required to be overcome in the electrostatic spinning process is reduced, so that the diameter of the fiber is reduced to 525 ± 6.5nm, and thus more microstructures are formed in the film, which is beneficial to improving the humidity and pressure sensing performance of the fiber film;

XRD tests are carried out on the functional layers in the intelligent wound dressings prepared by the embodiments 1-3 and the comparative example 1 (pure TPU), the test results are shown in figure 2, XRD spectral lines of CA/TPU-5% and CA/TPU-10% are basically consistent with those of the pure TPU, and therefore, the fact that the crystal structure of the TPU is not changed obviously by doping of CA is inferred. And with the increase of the doping amount, the characteristic diffraction peak of the CA particles in XRD is more obvious, which shows that the CA particles are successfully doped into the TPU nanofiber membrane;

FT-TR test was performed on the functional layer and pure CA in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1, and the test result is shown in FIG. 3, and it can be seen from FIG. 3 that pure TPU is 3000cm ^-1 And 1750cm ^-1 The peak values are respectively-N-H-stretching vibration absorption peak and C ≡ O stretching vibration absorption peak, which are very obvious in FT-IR of the CA/TPU composite nanofiber membrane, and the basic structure of the TPU can not be damaged by blending electrostatic spinning of the TPU and the CA. In addition, the thickness is 1736-1720 cm ^-1 A new absorption band appears in the CA/TPU composite nanofiber membrane, is a C = O stretching vibration peak and belongs to a characteristic peak of CA, and the fact that the TPU membrane successfully loads CA is proved;

the functional layers in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1 (pure TPU) were TG tested, and the test results are shown in fig. 4, and it can be seen from fig. 4 that pure TPU and all CA/TPU composite nanofiber films have a small weight loss due to the loss of adsorbed water when the temperature is below 200 ℃. Between 200 and 450 ℃, pure TPU and CA/TPU composite nanofiber membranes show severe mass loss due to decomposition of the polymer. With the increase of the doping amount of CA, the residual mass percentage of the CA/TPU composite nanofiber membrane is increased, and the residual weight of the CA/TPU-15% is 10.5%, which indicates that CA is successfully doped into TPU;

the functional layers in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1 (pure TPU) were subjected to mechanical property tests, and the stress-strain curve is shown in fig. 5, and it can be seen from fig. 5 that the ultimate stress monotonically increases from 0.7MPa to 1.3MPa as the CA content increases from 0 to 10 wt%. When the doping amount of CA 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 nanofiber membrane is always kept above 350%, and the elongation at break is also kept at a higher level (about 470%), which shows that the CA/TPU nanofiber membrane has good flexibility and stretchability, and is not easy to break when attached to the skin;

the functional layers in the intelligent wound dressings prepared in examples 1 to 3 and comparative example 1 (pure TPU) were subjected to a water contact angle test, and the test result is shown in fig. 6, as can be seen from fig. 6, the water contact angle of comparative example 1 is 132 °, the water contact angles of examples 1 to 3 are 72 °, 57 ° and 46 °, respectively, and thus it can be seen that the water contact angle of the composite nanofiber membrane doped with CA is reduced, which indicates that the wettability of the composite nanofiber membrane is improved by the addition of CA, and the hydrophilic property of the composite nanofiber membrane is enhanced. The CA molecules contain a plurality of carboxyl and hydroxyl groups, and the carboxyl and the hydroxyl groups can form intermolecular hydrogen bonds with water molecules in the air, so that the water molecules are adsorbed on the surface of the nanofiber membrane in a physical adsorption mode and are the basis of humidity response;

the functional layer in the intelligent wound dressing prepared in example 3 was subjected to a biocompatibility test, and the test results are shown in fig. 7, where (a) is a fluorescence image of HaCaT cells cultured on a Roswell Park Memorial Institute-1640 standard medium for 4 days, (b) is a fluorescence image of HaCaT cells cultured on the functional layer in the intelligent wound dressing prepared in example 3, (c) is a fluorescence image of HaCaT cells cultured on a blank cell culture medium, and (d) is an OD value of HaCaT cells cultured on a Roswell Park Memorial Institute-1640 standard medium, the functional layer in the intelligent wound dressing prepared in example 3, and the cell culture medium for different blank times, respectively, and it can be seen from fig. 7 that the functional layer in the intelligent wound dressing prepared in example 3 has no significant cytotoxicity effect on HaCaT a wavelength of 450nm, and the cell survival rate is measured after culturing on the functional layer in the intelligent wound dressing prepared in example 3 for 4 days, and the absorbance at a wavelength of 450nm is not significantly reduced. The functional layer in the intelligent wound dressing prepared in example 3 is biocompatible and can be directly used on the skin or open wounds;

the humidity response performance of the flexible sensors described in examples 4 to 6 was tested, and the test results are shown in fig. 8, wherein (a) is a humidity-relative resistance change curve of the flexible sensors described in examples 4 to 6 at 20 to 90 RH, and (b) is a hysteresis curve of the flexible sensors described in example 6 at 20 to 90 RH, and from (a), it was found that the relative resistance of the flexible sensors increased with increasing humidity, and in the low humidity range (20 to 50 RH), the humidity sensitivity of the flexible sensors was approximately the same as 0.6 RH, and in the high humidity range (50% to 90% RH), the CTHPS-15% humidity sensitivity was the highest and was approximately 2.15% RH, while CTHPS-5% and CTHPS-10% were respectively 1.32/% RH and 1.88%/RH. Therefore, as the doping amount of CA is increased, the humidity sensing performance of the flexible sensor is enhanced, so that the optimal doping amount of CA is 15%; from (b), the humidity hysteresis of CTHPS-15% was 10% in the humidity range of 20% -90% RH, demonstrating good stability of the sensor over a wide humidity range;

the flexible sensor of example 6 was subjected to a pressure response performance test, and the test results are shown in fig. 9, in which (a) is a pressure sensitivity curve, (b) is a time response curve, and (c) is a response recovery curve; as can be seen from (a), the pressure sensitivity is divided into three linear regions: s in the low pressure range (0 to 2.25 kPa) _P1 S in the medium pressure range (2.25 to 11.25 kPa) _P2 And S in a high pressure range (11.25 to 26.25 kPa) _P3 . CTHPS-15% vs S _P1 、S _P2 And S _P3 Sensitivity of 10.53, 2.56 and 0.3kPa, respectively ^-1 The inside of the electrospun nanofiber membrane has a large number of pores and gaps. The presence of pores and gaps results in poor contact between the conductive CNTs, resulting in a large initial resistance of the CTHPS without applying pressure, and once pressure is applied to the sensor, compressive deformation occurs, the pores and gaps between the nanofibers decrease, the contact between the fibers and the conductive carbon nanotubes increases greatly, and when a small pressure (0 to 2) is applied25 kPa), the carbon nanotube electrode comes into closer contact with the nanofiber membrane, resulting in a sharp increase in conductivity, at which the sensitivity is higher. When the applied pressure is increased (2.25-11.25 kPa), the layers of nanofibers are tightly compressed together, resulting in a further increase in conductivity and a decrease in resistance. According to clinical data, the pressure value of the open wound of the human abdomen is usually lower than 10kPa, therefore, CTHPS can be used for open intelligent wound dressing, and the wound healing degree is monitored according to the pressure value change of the surrounding skin in the wound healing process. As the pressure increased (11.25-26.25 kPa), the sensitivity of the sensor decreased to 0.3kPa ^-1 . This is because the mutual contact of the conductive carbon nanotubes cannot be improved, and the output resistance hardly changes; as can be seen from (b), CTHPS-15% exhibits a fast response (88 ms) and a recovery time (90 ms), indicating that the sensor has a fast response; from (c), the response recovery curve of CTHPS-15% under 200 times of cycle test shows that the sensor has good cycle stability;

the air permeability test of the flexible sensor described in example 6, the TPU nanofiber membrane described in comparative example 1, and the PDMS membrane was performed, and the test result is shown in fig. 10, and it can be seen from fig. 10 that the air permeability of the TPU nanofiber membrane was 192mm/s, which is superior to that of the PDMS membrane (0 mm/s) commonly used in the flexible pressure sensor, and similar to that of the polypropylene melt-blown nonwoven fabric (air permeability of about 198 mm/s) used as a filter in the medical protective mask. The permeability of CTHPS-15% was 171mm/s, which was slightly less than that of pure TPU, but still exhibited good permeability, indicating excellent permeability of CTHPS-15%.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A flexible sensor for wound intelligent monitoring is characterized by comprising an intelligent wound dressing and an electrode layer arranged on the surface of a functional layer in the intelligent wound dressing;

the intelligent wound dressing comprises a substrate and a functional layer arranged on the surface of the substrate;

the substrate is chitosan hemostatic sponge;

2. The flexible sensor of claim 1, wherein the mass ratio of the citric acid to the thermoplastic elastomer polyurethane in the citric acid-thermoplastic elastomer polyurethane composite nanofiber membrane is (0.05 to 0.15): 1.

3. the flexible sensor of claim 1 or 2, wherein the method of making the intelligent wound dressing comprises the steps of:

4. The flexible sensor according to claim 3, wherein the mass concentration of the thermoplastic elastomer polyurethane in the composite spinning solution is 15 to 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 to 0.15): 1.

6. the flexible sensor of claim 5, wherein the solvent comprises N, N-dimethylformamide and tetrahydrofuran;

7. the flexible sensor according to claim 3, wherein the electrostatic spinning is performed by using 2 to 4 nozzles;

the electrostatic spinning temperature is 30 to 50 ℃, the positive voltage is 10 to 24kV, the negative voltage is-5 to-1 kV, the time is 1 to 5h, the propelling speed is 1 to 3mL/h, and the receiving distance is 10 to 18cm.

8. The flexible sensor according to claim 1, wherein the thickness of the electrode layer is 50 to 60nm.