Conductive hydrophilic flexible foam polyurethane as well as preparation method and application thereof

Abstract

The invention relates to conductive hydrophilic flexible foam polyurethane as well as a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing polyether glycol, diisocyanate and a tin catalyst to form a prepolymer, and then adding a foaming agent to obtain hydrophilic flexible foam polyurethane; (2) immersing the hydrophilic flexible foam polyurethane into the polyelectrolyte raw material solution, taking out and drying to obtain conductive hydrophilic flexible foam polyurethane; the polyelectrolyte raw material solution in the step (2) comprises a vinyl nitrogen heterocyclic compound, an acrylic acid compound, an initiator, an amine catalyst and water. Compared with the prior art, the conductive hydrophilic flexible foam polyurethane material prepared by the preparation method disclosed by the invention has good hydrophilicity and mechanical properties, introduces electrochemical response characteristics to the material, and can be used for preparing a sweat environment strain sensor with good strain responsiveness and humidity sensitivity.

Description

Technical Field

[0001] The present invention relates to the interdisciplinary technical field of material science and communication technology, and in particular to a conductive hydrophilic soft foam polyurethane and a preparation method and application thereof. Background Art

[0002] In recent years, flexible wearable sensors have attracted much attention due to their unique performance in the fields of human health monitoring, electronic skin and artificial intelligence. Among them, sweat is an important biomarker for real-time health monitoring, and its electrochemical detection depends on highly sensitive and fast-response sensing materials. However, existing sensor materials have significant bottlenecks in simultaneously meeting the requirements of deformation sensing and sweat response: although traditional polyurethane foam has excellent mechanical flexibility and processability, its inherent hydrophobicity limits its compatibility with sweat, resulting in poor signal stability and insufficient biocompatibility. In addition, although existing conductive modification methods (such as impregnation of carbon nanotubes, graphene, etc.) can improve conductivity, they often sacrifice the hydrophilicity and mechanical resilience of the material, making it difficult to adapt to long-term use requirements in dynamic humid environments.

[0003] Previous studies have attempted to overcome these limitations through material modification, but the hydrophobic matrix itself is difficult to absorb sweat, resulting in poor response to changes in sweat humidity. While conventional polyurethane foam sensors can monitor large-strain human motion, the complex preparation process and high cost limit their large-scale application. These studies demonstrate that while polyurethane foam has potential in motion sensing, the conflict between its hydrophobic properties and sweat responsiveness remains a technical challenge.

[0004] Hydrophilic soft polyurethane foam, with its porous structure, high water absorption rate, and mechanical stability, offers a new approach to solving these problems. Its hydrophilic pore walls rapidly absorb sweat while maintaining the stability of the conductive pathway. Furthermore, its multi-level pore structure achieves reversible resistance changes through contact and separation of the pore walls during compression deformation. However, existing technologies have yet to effectively integrate the moisture sensitivity of hydrophilic polyurethane with conductive modification strategies, making it difficult to implement sweat-induced strain sensing.

[0005] Chinese patent document CN115979112A discloses a method for preparing a high-performance strain / humidity sensor with a hydrophobic surface by combining electrospinning and ultrasonic cavitation technology. The strain / humidity sensor consists of a TPU fiber membrane prepared by electrospinning and a conductive dispersion layer of carbon nanotubes loaded with silver nanoparticles. The invention enhances the mechanical properties of the material through a thermoplastic polyurethane elastomer substrate, but as a humidity sensor, it cannot accurately respond to specific humidity conditions.

[0006] Chinese patent publication CN115219565A discloses a porous polymer humidity sensing material with fast response and recovery characteristics and a preparation method thereof. The porous polymer humidity sensing material is composed of a water-soluble polymer and a conductive filler. The porous polymer humidity sensing material can achieve a response within a humidity range of 20-84%. However, the response time and recovery time of the porous polymer humidity sensing material are too long.

[0007] Therefore, it is of great significance to develop a sweat environmental strain sensing material with simple preparation process, mild reaction conditions, high sensitivity, and rapid response and recovery characteristics. Summary of the Invention

[0008] The purpose of the present invention is to provide a conductive hydrophilic soft foam polyurethane and its preparation method and application, so as to solve the problems in the prior art such as poor sweat responsiveness caused by the hydrophobicity of polyurethane foam and complex conductive modification process.

[0009] The purpose of the present invention can be achieved by the following technical solution: A method for preparing a conductive hydrophilic soft foam polyurethane comprises the following steps:

[0010] (1) mixing polyether diol, diisocyanate and tin catalyst to form a prepolymer, and then adding a foaming agent to obtain a hydrophilic soft foam polyurethane;

[0011] (2) immersing the hydrophilic soft foam polyurethane into a polyelectrolyte raw material solution, taking it out and drying it to obtain a conductive hydrophilic soft foam polyurethane;

[0012] The polyelectrolyte raw material solution in step (2) comprises a vinyl nitrogen heterocyclic compound, an acrylic compound, an initiator, an amine catalyst and water.

[0013] In the present invention, the polymerization reaction of the vinyl nitrogen heterocyclic compound and the acrylic compound in step (2) forms a polyelectrolyte network through free radical polymerization, and the polyelectrolyte network is embedded in the polyurethane foam pore wall in a chemical bonding manner, giving the material ionic conductivity to form a conductive hydrophilic soft foam polyurethane material.

[0014] Preferably, the polyether diol in step (1) is at least one of polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetramethylene glycol (PTMG), and has a number average molecular weight of 400-100,000.

[0015] More preferably, the polyether diol is polyethylene glycol.

[0016] Preferably, the diisocyanate in step (1) is at least one of hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI).

[0017] More preferably, the diisocyanate is hexamethylene diisocyanate.

[0018] Preferably, the tin catalyst in step (1) is one of stannous octoate and dibutyltin dilaurate.

[0019] Preferably, the foaming agent in step (1) is one of water, sodium hydroxide solution, ammonia water, hydrochloric acid solution, acetic acid solution, and adipic acid dihydrazide solution.

[0020] Preferably, the molar ratio of the polyether diol to the diisocyanate in step (1) is 1:1-4, and the amount of the foaming agent used is 10-300% of the mass of the prepolymer.

[0021] Preferably, step (1) comprises the following steps:

[0022] The polyether diol is melted at 30-200°C, diisocyanate and tin catalyst are added, mixed and reacted at 30-160°C for 2-30 minutes to form a prepolymer, and then a foaming agent is added. After stirring and foaming, it is injected into a mold and cured at 30-100°C for 0.5-24 hours to obtain a hydrophilic soft foam polyurethane.

[0023] Preferably, the vinyl nitrogen heterocyclic compound in step (2) is at least one of 1-vinylimidazole, 1-vinylpyrrolidone, 2-vinylpyrrole, and N-vinylcarbazole.

[0024] Preferably, the acrylic compound in step (2) is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and acrylamide.

[0025] Preferably, the initiator in step (2) is at least one of potassium persulfate and ammonium persulfate.

[0026] Preferably, the amine catalyst in step (2) is at least one of tetramethylethylenediamine (TMEDA) and tetraethylethylenediamine (TEEDA).

[0027] Preferably, the mass ratio of the vinyl nitrogen heterocyclic compound to the acrylic compound in step (2) is 1:1-5, which are dissolved in deionized water to form a 5-30wt% mixed solution, and 0.1-5wt% of an initiator and a few drops of an amine catalyst are added and stirred evenly to obtain the polyelectrolyte raw material solution.

[0028] Preferably, in step (2), the hydrophilic soft foam polyurethane is immersed in the polyelectrolyte raw material solution for 1-30 seconds, taken out and squeezed to remove excess solution, and dried at 30-100° C. for 0.5-24 hours to obtain the conductive hydrophilic soft foam polyurethane.

[0029] A conductive hydrophilic soft foam polyurethane is prepared by adopting the above preparation method.

[0030] Preferably, the conductive hydrophilic soft polyurethane foam has the following characteristics:

[0031] It has a multi-level pore structure with a pore size range of 50-1000μm and a porosity greater than 30%;

[0032] It has conductive properties, and the conductive properties are adjustable with deformation. The resistance change rate is greater than 20% within the range of 0-99% compression strain;

[0033] It is humidity responsive, with the impedance changing by more than 0.1 orders of magnitude within the relative humidity range of 10-95%.

[0034] Preferably, the conductive hydrophilic soft polyurethane foam has the following characteristics:

[0035] In a simulated sweat (0.1-10wt% NaCl solution) environment, the water absorption rate is greater than 100%; the response time to humidity changes is less than 10 seconds.

[0036] An application of the above-mentioned conductive hydrophilic soft foam polyurethane is to use the conductive hydrophilic soft foam polyurethane in a wearable sensor.

[0037] Preferably, the conductive hydrophilic soft polyurethane foam is used as a sweat environment strain sensor to monitor human joint movements (such as finger bending, elbow extension) and sweat secretion in real time;

[0038] Alternatively, the conductive hydrophilic soft foam polyurethane is used as the inner lining of sports equipment to dynamically feedback the sports posture and perspiration status.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The conductive hydrophilic soft foam polyurethane material prepared by the present invention has a formula that takes into account both good hydrophilicity and mechanical properties, while introducing electrochemical response characteristics into the material, which can be used to prepare a sweat environment strain sensor with good strain responsiveness and humidity sensitivity.

[0041] 2. The present invention can solve the problems in the prior art such as poor sweat responsiveness caused by the hydrophobicity of polyurethane foam and complex conductive modification process.

[0042] 3. The conductive hydrophilic soft foam polyurethane material of the present invention adopts a prepolymer foaming-functionalization process to simplify the preparation process, and the process is simple.

[0043] 4. The conductive hydrophilic soft polyurethane foam material of the present invention has stable performance in a humid environment and integrates humidity sensing and strain sensing functions.

[0044] 5. The present invention provides a sweat environment strain sensing material with simple preparation process, mild reaction conditions, high sensitivity, and rapid response and recovery characteristics.

[0045] 6. The present invention prepares hydrophilic soft foam polyurethane through prepolymerization-foaming, and adopts the in-situ polymerization method to prepare conductive hydrophilic soft foam polyurethane material. The prepared material has a multi-level pore structure, hydrophilicity, deformation responsiveness, and humidity responsiveness, and realizes the synchronous monitoring of deformation, sweat secretion and humidity changes on a single material platform, expanding its application in wearable health management, smart medical and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The figure is a flow chart for preparing conductive hydrophilic soft foam polyurethane material;

[0047] Figure 2 This is the infrared spectrum of conductive hydrophilic soft foam polyurethane;

[0048] Figure 3 This is a scanning electron microscope image of a conductive hydrophilic soft foam polyurethane material;

[0049] Figure 4 The resistance change curve of the conductive hydrophilic soft polyurethane foam material during the compression-release cycle;

[0050] Figure 5 This is the impedance response curve of the conductive hydrophilic soft polyurethane foam material under humidity gradient;

[0051] Figure 6 Schematic diagram of finger motion monitoring using conductive hydrophilic soft polyurethane foam material as a wearable sensor;

[0052] Figure 7 Diagram of the sweat evaporation device simulating conductive hydrophilic soft polyurethane foam;

[0053] Figure 8 This is the impedance change curve of conductive hydrophilic soft polyurethane foam over time. DETAILED DESCRIPTION

[0054] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0055] A conductive hydrophilic soft foam polyurethane is composed of polyether diol, diisocyanate, a foaming agent, a tin catalyst, a vinyl nitrogen heterocyclic compound, an acrylic compound, an initiator, and an amine catalyst.

[0056] A method for preparing conductive hydrophilic soft foam polyurethane, such as Figure 1 As shown, the following steps are included:

[0057] (1) The polyether diol is melted, and then diisocyanate and a tin catalyst are added to the melted polyether polyol to mix and perform prepolymerization. After a period of time, a foaming agent is added and stirred to obtain a hydrophilic soft foam polyurethane material.

[0058] (2) A vinyl nitrogen heterocyclic compound and an acrylic compound are prepared into a solution, an initiator and an amine catalyst are added, a hydrophilic soft foam polyurethane material is quickly immersed in the solution and taken out and squeezed dry, an in-situ polymerization reaction is carried out in the hydrophilic soft foam polyurethane, and finally the conductive hydrophilic soft foam polyurethane material is obtained by drying.

[0059] As a preferred technical solution, a method for preparing a conductive hydrophilic soft foam polyurethane comprises the following steps:

[0060] (1) Melting polyether diol at 30-200° C., adding diisocyanate and a tin catalyst at a molar ratio of polyether diol to diisocyanate of 1:1-4, mixing and reacting at 30-160° C. for 2-30 minutes to form a prepolymer; then adding a foaming agent in an amount of 10-300% of the mass of the prepolymer, stirring and foaming, and then injecting into a mold, and curing at 30-100° C. for 0.5-24 hours to obtain a hydrophilic soft foam polyurethane material;

[0061] (2) dissolving a vinyl nitrogen heterocyclic compound and an acrylic compound in deionized water at a mass ratio of 1:1-5 to prepare a 5-30 wt% mixed solution, adding 0.1-5 wt% of an initiator and a few drops of a catalyst, and stirring evenly; quickly immersing the hydrophilic soft foam polyurethane material obtained in step (1) in the solution for 1-30 s, taking it out and squeezing out excess solution, and drying it at 30-100° C. for 0.5-24 hours to obtain a conductive hydrophilic soft foam polyurethane material.

[0062] As a more preferred technical solution, the preparation method of the conductive hydrophilic soft foam polyurethane comprises the following steps:

[0063] First, a polyether diol (such as PEG, PPG, or PTMG) with a number average molecular weight of 400-10,000 is melted and mixed with a diisocyanate (HDI, MDI, HMDI, IPDI, or TDI) in a molar ratio of 1:1-4. A tin catalyst (stannous octoate or dibutyltin diisocyanate) is added, and the mixture is reacted at 30-160° C. for 2-30 minutes to form a prepolymer. A blowing agent (water, sodium hydroxide solution, ammonia water, hydrochloric acid solution, acetic acid solution, or adipic acid dihydrazide solution) is added at 10-300% by weight of the prepolymer. The mixture is stirred and foamed, and then injected into a mold for curing to obtain a hydrophilic soft foam polyurethane matrix having a pore size of 50-1000 μm and a porosity greater than 30%.

[0064] Secondly, a vinyl nitrogen heterocyclic compound (1-vinylimidazole, 1-vinylpyrrolidone, 2-vinylpyrrole or N-vinylcarbazole) and an acrylic compound (hydroxyethyl acrylate, hydroxyethyl methacrylate or acrylamide) are dissolved in deionized water at a mass ratio of 1:1-5 to prepare a 5-30wt% mixed solution, 0.1-5wt% of an initiator (potassium persulfate or ammonium persulfate) and a few drops of a catalyst (TMEDA or TEEDA) are added; the foam obtained in step (1) is quickly immersed in the solution for 1-30s, the excess solution is squeezed out and then dried to obtain a conductive hydrophilic soft foam polyurethane material.

[0065] The following describes it in detail with reference to specific embodiments.

[0066] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0067] Example 1

[0068] First, polyethylene glycol (6.0 g) was weighed and melted in a glass beaker. Hexamethylene diisocyanate (HDI, 2.0 g) and stannous octoate (50 μL) were then added and reacted at 90°C for 5 minutes to form a prepolymer. Adipic acid dihydrazide solution was added as a blowing agent, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to produce a hydrophilic flexible polyurethane foam matrix. 1-vinylimidazole (500 mg) and acrylamide (2.0 g) were weighed and dissolved in deionized water. Ammonium persulfate initiator (50 mg) and a few drops of TMEDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam APUF-PAmVI described in the example.

[0069] Example 2

[0070] First, polypropylene glycol (6.5 g) weighed by weight or calculated by equivalent ratio was added to a glass beaker. After melting, cyclohexylmethane diisocyanate (HMDI, 2.3 g) and stannous octoate (50 μL) were added and reacted at 90°C for 5 minutes to form a prepolymer. A sodium hydroxide solution was added as a blowing agent, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to obtain a hydrophilic flexible polyurethane foam matrix. Then, 1-vinyl pyrrolidone (500 mg) and hydroxyethyl acrylate (2.0 g) weighed by weight or calculated by equivalent ratio were dissolved in deionized water. Potassium persulfate initiator (50 mg) and a few drops of TEEDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam material described in the example.

[0071] Example 3

[0072] First, polytetramethylene ether glycol (8.0 g) weighed by weight or calculated by equivalent ratio was added to a glass beaker. After melting, diphenylmethane diisocyanate (MDI, 2.3 g) and stannous octoate (50 μL) were added and reacted at 90°C for 5 minutes to form a prepolymer. Ammonia was added as a blowing agent, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to obtain a hydrophilic flexible polyurethane foam matrix. Then, 2-vinylpyrrole (500 mg) and hydroxyethyl methacrylate (2.0 g) weighed by weight or calculated by equivalent ratio were dissolved in deionized water. Ammonium persulfate initiator (50 mg) and a few drops of TEMDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam material described in the example.

[0073] Example 4

[0074] First, polyethylene glycol (6.0 g) weighed by weight or calculated by equivalent ratio was added to a glass beaker. After melting, toluene diisocyanate (TDI, 2.1 g) and stannous octoate (50 μL) were added and reacted at 90°C for 5 minutes to form a prepolymer. A hydrochloric acid solution was added as a blowing agent, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to obtain a hydrophilic flexible polyurethane foam matrix. Then, N-vinyl carbazole (500 mg) and acrylamide (2.0 g) weighed by weight or calculated by equivalent ratio were dissolved in deionized water. Potassium persulfate initiator (50 mg) and a few drops of TEEDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam material described in the example.

[0075] Example 5

[0076] First, polypropylene glycol (6.5 g) weighed by weight or calculated by equivalent ratio was added to a glass beaker. After melting, isophorone diisocyanate (IPDI, 2.8 g) and stannous octoate (50 μL) were added and reacted at 90°C for 5 minutes to form a prepolymer. An acetic acid solution was added as a blowing agent, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to obtain a hydrophilic flexible polyurethane foam matrix. Then, 1-vinylimidazole (500 mg) and hydroxyethyl acrylate (2.0 g) weighed by weight or calculated by equivalent ratio were dissolved in deionized water. Ammonium persulfate initiator (50 mg) and a few drops of TMEDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam material described in the example.

[0077] Example 6

[0078] First, polytetramethylene ether glycol (8.0 g) weighed by weight or calculated by equivalent ratio was added to a glass beaker. After melting, hexamethylene diisocyanate (HDI, 2.0 g) and stannous octoate (50 μL) were added and reacted at 90°C for 5 minutes to form a prepolymer. A water-based foaming agent was added, stirred and foamed, and then injected into a mold and cured at 40°C for 2 hours to obtain a hydrophilic flexible polyurethane foam matrix. Then, 1-vinyl pyrrolidone (500 mg) and hydroxyethyl methacrylate (2.0 g) weighed by weight or calculated by equivalent ratio were dissolved in deionized water. Potassium persulfate initiator (50 mg) and a few drops of TEEDA catalyst were added to prepare a polyelectrolyte raw material solution. The hydrophilic flexible polyurethane foam matrix was quickly immersed in the solution for 10 seconds, squeezed to remove excess solution, and dried to obtain the conductive hydrophilic flexible polyurethane foam material described in the example.

[0079] Example 7

[0080] The conductive hydrophilic soft polyurethane foam prepared in Example 1 was tested in the following manner. The conductive hydrophilic soft polyurethane foam was characterized using an infrared spectrometer. The results are shown in FIG. Figure 2 As shown, at 1721cm -1 and 1618cm -1 The peak corresponds to the C=O stretching vibration of polyurethane. The conductive hydrophilic soft foam polyurethane was characterized using scanning electron microscopy. The results are as follows Figure 3 As shown, the prepared conductive hydrophilic soft foam polyurethane material has a multi-level pore structure, a pore size range of 50-1000 μm, and a porosity greater than 30%.

[0081] Example 8

[0082] The conductive hydrophilic soft polyurethane foam prepared in Example 1 was tested in the following manner. The conductive hydrophilic soft polyurethane foam was placed on the test platform of a universal testing machine, with the upper and lower ends of the material in close contact with a copper sheet. A digital multimeter was connected to the copper sheet to record the change in resistance. As the pressure increased, the conductive hydrophilic soft polyurethane foam produced strain, and the material's resistance changed accordingly. The resistance change curve of the conductive hydrophilic soft polyurethane foam during the compression-release cycle is shown in Figure 2. Figure 4 As shown in the figure, the resistance change rate is stable at about 70% under 90% compressive strain, indicating that the conductive hydrophilic soft polyurethane foam has good cycle stability.

[0083] Example 9

[0084] The conductive hydrophilic soft polyurethane foam prepared in Example 1 was tested in the following manner. The resistance of the conductive hydrophilic soft polyurethane foam was compared under different humidity conditions, including the adsorption process from low humidity to high humidity. The impedance response curve of the conductive hydrophilic soft polyurethane foam under humidity gradient is shown in FIG. Figure 5 As shown in the graph, when the humidity changes from 30% to 90%, the impedance drops from 1.04 MΩ to 0.11 MΩ, indicating that the conductive hydrophilic soft foam polyurethane has good humidity responsiveness.

[0085] Example 10

[0086] The conductive hydrophilic soft polyurethane foam prepared in Example 1 was tested in the following manner. A copper sheet of conductive hydrophilic soft polyurethane foam was attached to a volunteer's finger and connected in series with a Keithley 2400. The change in current during bending was tracked, and a response curve of the resistance change rate as the volunteer's movement was calculated. The voltage was set to 5V. A schematic diagram of the conductive hydrophilic soft polyurethane foam used as a wearable sensor for finger motion monitoring is shown in the figure below. Figure 6 As shown, the conductive hydrophilic soft foam polyurethane material can achieve good recognition of different hand movements.

[0087] Example 11

[0088] The conductive hydrophilic soft polyurethane foam prepared in Example 1 was tested in the following manner. Figure 7As shown, a piece of non-woven fabric is placed on a hot plate set to 37°C to simulate the human body temperature environment. A dry conductive super hydrophilic soft foam polyurethane material is placed on top of the non-woven fabric. During the experiment, a small amount of sodium chloride solution with a concentration of 0.45wt% is taken with a plastic dropper to simulate the sweat of the human body (salt concentration is about 0.45wt%), and then dripped onto the non-woven fabric. The non-woven fabric slowly wets to simulate the sweating process of the human body; then, a piece of dry non-woven fabric is used to replace the non-woven fabric soaked in salt water in the previous experiment, and the conductive super hydrophilic soft foam polyurethane gradually dries over time to simulate the sweat evaporation process. Subsequently, the impedance change curve of the conductive hydrophilic soft foam polyurethane over time is obtained. The schematic diagram of the impedance change curve of the conductive hydrophilic soft foam polyurethane over time is shown as follows Figure 8 As shown, during simulated sweating, the impedance of the conductive hydrophilic soft polyurethane foam rapidly decreased from 1.04 MΩ to 0.2 MΩ within 100 seconds, then slowly decreased until the impedance remained essentially stable. When the solution absorption rate reached 500%, the impedance remained essentially stable and did not change. During simulated sweat evaporation, the impedance slowly increased from 0.1 MΩ to 1.04 MΩ. This dynamic impedance-humidity response shows that the material can reflect changes in sweat volume in real time.

[0089] The conductive hydrophilic soft foam polyurethane material of the present invention has a multi-level pore structure, hydrophilicity, strain responsiveness, and humidity responsiveness, and realizes the synchronous monitoring of strain and humidity changes on a single material platform. It can be used for wearable sports monitoring, smart medical dressings, and human-computer interaction interfaces.

[0090] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a conductive hydrophilic soft foam polyurethane, characterized in that: The following steps are involved: (1) mixing polyether diol, diisocyanate and tin catalyst to form a prepolymer, and then adding a foaming agent to obtain a hydrophilic soft foam polyurethane; (2) immersing the hydrophilic soft foam polyurethane into a polyelectrolyte raw material solution, taking it out and drying it to obtain a conductive hydrophilic soft foam polyurethane; The polyelectrolyte raw material solution in step (2) comprises a vinyl nitrogen heterocyclic compound, an acrylic compound, an initiator, an amine catalyst and water.

2. The method for preparing a conductive hydrophilic soft polyurethane foam according to claim 1, wherein: The polyether diol in step (1) is at least one of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and has a number average molecular weight of 400-100000; The diisocyanate in step (1) is at least one of hexamethylene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate; The tin catalyst in step (1) is one of stannous octoate and dibutyltin dilaurate; The foaming agent in step (1) is one of water, sodium hydroxide solution, ammonia water, hydrochloric acid solution, acetic acid solution, and adipic acid dihydrazide solution.

3. The method for preparing a conductive hydrophilic soft polyurethane foam according to claim 1, wherein: The molar ratio of the polyether diol to the diisocyanate in step (1) is 1:1-4, and the amount of the foaming agent is 10-300% of the mass of the prepolymer.

4. The method for preparing a conductive hydrophilic soft polyurethane foam according to claim 1, wherein: Step (1) includes the following steps: The polyether diol is melted at 30-200°C, diisocyanate and tin catalyst are added, mixed and reacted at 30-160°C for 2-30 minutes to form a prepolymer, and then a foaming agent is added. After stirring and foaming, it is injected into a mold and cured at 30-100°C for 0.5-24 hours to obtain a hydrophilic soft foam polyurethane.

5. The method for preparing the conductive hydrophilic soft polyurethane foam according to claim 1, wherein: The vinyl nitrogen heterocyclic compound in step (2) is at least one of 1-vinylimidazole, 1-vinylpyrrolidone, 2-vinylpyrrole, and N-vinylcarbazole; The acrylic compound in step (2) is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and acrylamide; The initiator in step (2) is at least one of potassium persulfate and ammonium persulfate; The amine catalyst in step (2) is at least one of tetramethylethylenediamine and tetraethylethylenediamine.

6. The method for preparing a conductive hydrophilic soft polyurethane foam according to claim 1, characterized in that: In step (2), the vinyl nitrogen heterocyclic compound and the acrylic compound are dissolved in deionized water at a mass ratio of 1:1-5 to form a 5-30 wt% mixed solution, 0.1-5 wt% of an initiator and a few drops of an amine catalyst are added, and the mixture is stirred to obtain the polyelectrolyte raw material solution.

7. The method for preparing a conductive hydrophilic soft polyurethane foam according to claim 1, wherein: Step (2) immersing the hydrophilic soft foam polyurethane into the polyelectrolyte raw material solution for 1-30 seconds, taking it out and squeezing out the excess solution, and drying it at 30-100° C. for 0.5-24 hours to obtain the conductive hydrophilic soft foam polyurethane.

8. A conductive hydrophilic soft polyurethane foam, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7, having a multi-level pore structure, a pore size range of 50-1000 μm, and a porosity greater than 30%; It is hydrophilic, with a water contact angle of less than 90° and a water absorption rate greater than 100%; It has conductive properties, and the conductive properties are adjustable with deformation. The resistance change rate is greater than 20% within the range of 0-99% compression strain; It is humidity responsive, with the impedance changing by more than 0.1 orders of magnitude within the relative humidity range of 10-95%.

9. An application of the conductive hydrophilic soft polyurethane foam according to claim 8, characterized in that: The conductive hydrophilic soft polyurethane foam is used in wearable sensors.

10. The use of the conductive hydrophilic soft polyurethane foam according to claim 9, characterized in that: The conductive hydrophilic soft polyurethane foam is used as a sweat environment strain sensor to monitor human joint movement and sweat secretion in real time; Alternatively, the conductive hydrophilic soft foam polyurethane is used as the inner lining of sports equipment to dynamically feedback the sports posture and perspiration status.

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