High-durability self-healing polyimide-based flexible sensing base material and preparation method thereof

Abstract

The invention relates to a high-durability self-healing polyimide-based flexible sensing base material and a preparation method of the high-durability self-healing polyimide-based flexible sensing base material. The high-durability self-healing polyimide-based flexible sensing base material is prepared from the following components in parts by weight: 80 to 90 parts of dynamic modified polyimide matrix, 5 to 10 parts of silane coupling agent KH-580 modified Ti < 3 > C < 2 > T < x > MXene, 4 to 8 parts of self-healing microcapsule and 1 to 3 parts of polycaprolactone-polyethylene glycol segmented copolymer, wherein the dynamic modified polyimide matrix is prepared by copolymerization of 3, 3 ', 4, 4'-benzophenone tetracarboxylic dianhydride, 4, 4 '-diaminodiphenyl disulfide and dimercaptopropionic acid; a core material of the self-healing microcapsule is an isocyanate-polyol prepolymer, and a wall material of the self-healing microcapsule is urea resin. The high-durability self-healing polyimide-based flexible sensing base material disclosed by the invention is high in self-healing capability and high in durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible electronic materials, in particular to a high-durability self-healing polyimide-based flexible sensing substrate and a preparation method thereof. BACKGROUND

[0002] With the rapid development of flexible electronic devices, wearable devices and intelligent robot technologies, flexible sensing substrates, as core component substrates capable of sensing functions such as pressure, temperature and strain, are attracting increasing attention, and their applications have penetrated into key fields such as medical rehabilitation and robot interaction. These applications not only require flexible sensing substrates to have excellent sensing performance, but also require them to maintain mechanical and electrical reliability and stability under complex mechanical deformation and long-term wear and tear environments.

[0003] However, during the actual long-term use of the flexible sensing substrate, microcracks are easily generated due to frequent bending, stretching or friction, such microcracks hinder the formation and maintenance of conductive paths, leading to the attenuation of piezoresistive performance, and such microcracks destroy the structural integrity of the flexible sensing substrate, causing the damping characteristics of the flexible sensing substrate to fail.

[0004] To solve the above problems, the flexible sensing substrate of the prior art often uses a self-healing polymer system based on a single type of dynamic covalent bond to improve the self-repairing ability. However, the self-healing rate of such flexible sensing substrate with a self-healing polymer system is generally low, for example, the 1h self-healing rate is usually less than 80%, and the damping coefficient decreases by more than 30% after healing, and the recovery rate is also low. In addition, the interface between the polyimide matrix and the conductive filler such as MXene used in the existing flexible sensing substrate is weak, and the retention rate of key performance such as resistance and piezoresistive sensitivity of the flexible sensing substrate is often less than 70% after experiencing thousands of cycles of stretching, which is difficult to meet the demand for long-term stable use of devices in the fields of medical rehabilitation and robot interaction. SUMMARY

[0005] Therefore, it is necessary to provide a high-durability self-healing polyimide-based flexible sensing substrate with high self-healing efficiency and strong durability and stability, and a preparation method thereof, in view of the above technical problems.

[0006] In a first aspect, the present application provides a high-durability self-healing polyimide-based flexible sensing substrate, which comprises the following components by weight: a dynamically modified polyimide matrix 80-90 parts, a silane coupling agent KH-580 modified Ti3C2T x MXene 5-10 parts, self-healing microcapsules 4-8 parts, and polycaprolactone-polyethylene glycol block copolymer 1-3 parts. The dynamic modified polyimide matrix is prepared by copolymerization of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercaptopropanoic acid; Ti3C2T modified by silane coupling agent KH-580 x The MXene is Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T modified by 3-5% silane coupling agent KH-580; The core material of the self-healing microcapsule is an isocyanate-polyol prepolymer, and the wall material is a urea-formaldehyde resin.

[0007] Preferably, the content of dimercaptopropanoic acid in the dynamic modified polyimide matrix is 8-15 wt%, and the molar ratio of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-diamino diphenyl disulfide is 1:1.

[0008] Preferably, Ti3C2T modified by silane coupling agent KH-580 x The MXene has a sheet thickness of 1-5 nm and a lateral size of 0.5-2 mu m.

[0009] Preferably, the particle size of the self-healing microcapsule is 1-5 mu m, and the wall material thickness of the self-healing microcapsule is 150-250 nm. The mass ratio of isocyanate to polyol in the core material of the self-healing microcapsule is 1:1.2-1.5.

[0010] Preferably, the content of dimercaptopropanoic acid in the dynamic modified polyimide matrix is 10-12 wt%.

[0011] Preferably, Ti3C2T modified by silane coupling agent KH-580 x The MXene has a weight fraction of 7-9 parts and a sheet thickness of 2-3 nm.

[0012] In a second aspect, the application also provides a preparation method of a high-durability self-healing polyimide-based flexible sensing substrate, which is used for preparing the high-durability self-healing polyimide-based flexible sensing substrate and comprises the following steps: Step 1: 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercaptopropanoic acid are added into dimethylacetamide, and stirred at 60-80 DEG C for 3-5 h to prepare a dynamic polyamide acid solution; the dynamic polyamide acid solution contains 85 wt% dimethylacetamide; Step 2: Ti3C2T modified by silane coupling agent KH-580 xMXene is added into dimethylacetamide, and ultrasonic dispersion is carried out for 40-60 min to prepare a MXene dispersion liquid; the MXene dispersion liquid contains 85wt% dimethylacetamide; Step 3: self-healing microcapsules and polycaprolactone-polyethylene glycol block copolymers are added into the MXene dispersion liquid, and mechanical stirring is carried out for 2-3 h to prepare a composite filler liquid; Step 4: the composite filler liquid is added into a dynamic polyamide acid solution, and stirring is carried out at 70-90℃ for 4-6 h to form a slurry; Step 5: the slurry is coated on a substrate, and heat treatment is carried out in sequence at 100℃ / 1.5h, 200℃ / 1h and 300℃ / 1h, and after cooling, the high-durability self-healing polyimide-based flexible sensing substrate is prepared by peeling.

[0013] Preferably, the material of the substrate in step 5 is PET or polytetrafluoroethylene.

[0014] The present application has the following beneficial effects: (1) The dynamic modified polyimide matrix prepared by copolymerization of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercapto propionic acid introduces disulfide bonds into the flexible sensing substrate polymer network, which can break and recombine at room temperature, thereby improving the self-healing performance of the flexible sensing substrate; (2) The present application modifies Ti3C2T x The surface of MXene is modified by silane coupling agent KH-580, so that the hydroxyl groups on the surface form strong hydrogen bond interactions with the mercapto groups in the dynamic modified polyimide matrix. This interface strengthening effect cooperates with the disulfide bonds in the matrix to significantly enhance the dynamic bonding and interface compatibility between the conductive filler and the dynamic modified polyimide matrix, thereby improving the durability and stability of the flexible sensing substrate; (3) The self-healing microcapsules in the present application can break when cracks occur in the flexible sensing substrate, releasing the core material to react with the mercapto groups of the dynamic modified polyimide matrix to form new crosslinking structures to repair the cracks, further improving the self-healing ability of the flexible sensing substrate; (4) Experimental verification shows that the high-durability self-healing polyimide-based flexible sensing substrate of the present application has significantly better comprehensive performance than existing flexible sensing substrates; the flexible sensing substrate of the present application can realize rapid healing at room temperature, and the self-healing efficiency can reach more than 90% in 1h, and the recovery rate of piezoresistive sensitivity after healing is higher than 91%, and the recovery rate of damping coefficient is higher than 88%, which has excellent self-healing performance; at the same time, the flexible sensing substrate of the present application has a tensile strength retention rate of more than 86% after 5000 cycles of stretching, and a resistance change rate of less than 5% after 1000 cycles of bending, which has strong interface stability and high durability, and can meet the demand for long-term stable use of devices in the fields of medical rehabilitation and robot interaction. DETAILED DESCRIPTION

[0015] For the purpose of facilitating the understanding of the present application, a more comprehensive description of the present application will be provided below. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0016] The high-durability self-healing polyimide-based flexible sensing substrate of the present application comprises the following components by weight: dynamic modified polyimide matrix 80-90 parts, silane coupling agent KH-580 modified Ti3C2T x MXene 5-10 parts, self-healing microcapsule 4-8 parts, polycaprolactone-polyethylene glycol block copolymer 1-3 parts.

[0017] The dynamic modified polyimide matrix is prepared by copolymerization of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercaptopropanoic acid. The disulfide bond can be broken and recombined at room temperature during the copolymerization process, realizing self-healing of the flexible sensing substrate.

[0018] The silane coupling agent KH-580 modified Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T

[0019] The Ti3C2T x The MXene is a two-dimensional transition metal carbon material, and the specific chemical name of the silane coupling agent KH-580 is γ-mercaptopropyl triethoxysilane. The silane coupling agent KH-580 accounts for 3-5% of the modified Ti3C2T x The MXene is Ti3C2T x The MXene is Ti3C2T

[0020] The core material of the self-healing microcapsule is an isocyanate-polyol prepolymer, and the wall material is a urea-formaldehyde resin. When the flexible sensing substrate is bent to generate a crack, the wall material of the self-healing microcapsule will break, releasing the core material to react with the mercapto group in the dynamically modified polyimide matrix to form a crosslinked structure to repair the crack, thereby realizing self-healing of the flexible sensing substrate.

[0021] Specifically, the content of dimercapto propionic acid in the dynamically modified polyimide matrix is 8-15wt%, and the molar ratio of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-diamino diphenyl disulfide is 1:1.

[0022] In this embodiment, the silane coupling agent KH-580 is used to modify Ti3C2T x The sheet thickness of MXene is 1-5nm, and the lateral size is 0.5-2μm. The particle size of the self-healing microcapsule is 1-5μm, and the wall material thickness of the self-healing microcapsule is 150-250nm; the mass ratio of isocyanate to polyol in the core material of the self-healing microcapsule is 1:1.2-1.5.

[0023] The high-durability self-healing polyimide-based flexible sensing substrate of the present embodiment fully combines the inherent self-healing ability of disulfide bonds and the active repair ability of microcapsules, achieving efficient and rapid self-healing. By modifying MXene with a silane coupling agent KH-580, the interfacial bonding force between MXene and the polyimide matrix is enhanced, and the durability and stability of the material are improved.

[0024] Preferably, the content of dimercapto propionic acid in the dynamically modified polyimide matrix is 10-12wt%. The silane coupling agent KH-580 is used to modify Ti3C2T x The weight fraction of MXene is 7-9 parts, and the sheet thickness is 2-3nm.

[0025] The preparation method of the high-durability self-healing polyimide-based flexible sensing substrate of the present application comprises the following steps: Step 1, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercapto propionic acid are added to dimethylacetamide, stirred at 60-80℃ for 3-5h to prepare a dynamic polyamide acid solution; the dynamic polyamide acid solution contains 85wt% dimethylacetamide; Step 2, the silane coupling agent KH-580 is used to modify Ti3C2T x MXene is added to dimethylacetamide and ultrasonically dispersed for 40-60min to prepare a MXene dispersion liquid; the MXene dispersion liquid contains 85wt% dimethylacetamide; Step 3, the self-healing microcapsule and the polycaprolactone-polyethylene glycol block copolymer are added to the MXene dispersion liquid, and mechanically stirred for 2-3h to prepare a composite filler liquid; Step 4, add the composite filler liquid into the dynamic polyamic acid solution, stir at 70-90℃ for 4-6h to form a slurry; Step 5, coat the slurry on the substrate, and sequentially go through 100℃ / 1.5h, 200℃ / 1h, 300℃ / 1h heat treatment, and then peel off after cooling to obtain a high-durability self-healing polyimide-based flexible sensing substrate.

[0026] In step 5, the material of the substrate is PET or polytetrafluoroethylene. It should be noted that the thickness of the slurry in this embodiment is not required, and uniform coating is sufficient. The thickness of the high-durability self-healing polyimide-based flexible sensing substrate peeled off finally is different under different slurry thicknesses and different preparation parameters.

[0027] The high-durability self-healing polyimide-based flexible sensing substrate of the present application can be applied in medical rehabilitation or human-robot interaction. For example, in medical rehabilitation, the high-durability self-healing polyimide-based flexible sensing substrate of the present application can be used as a local heat therapy patch or a human body characterization information acquisition device substrate; in human-robot interaction, the high-durability self-healing polyimide-based flexible sensing substrate of the present application can be used as a simulated skin of a robot.

[0028] The following is a specific embodiment.

[0029] Embodiment 1 In this embodiment, the high-durability self-healing polyimide-based flexible sensing substrate contains the following components by weight: dynamic modified polyimide matrix 85 parts, silane coupling agent KH-580 modified Ti3C2T x MXene 7 parts, self-healing microcapsule 6 parts, and polycaprolactone-polyethylene glycol block copolymer 2 parts.

[0030] In the process of copolymerization of the dynamic modified polyimide matrix, the content of dimercaptopropanoic acid is 10wt%, the particle size of the self-healing microcapsule is 3μm, the thickness of the wall material is 200nm, and the silane coupling agent KH-580 modified Ti3C2T x MXene has a sheet thickness of 3nm and a lateral size of 1μm.

[0031] The mass ratio of isocyanate to polyol in the core material of the self-healing microcapsule is 1:1.2.

[0032] The preparation method of the high-durability self-healing polyimide-based flexible sensing substrate of this embodiment includes the following steps: (1) 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-diamino diphenyl disulfide and dimercaptopropanoic acid are added to dimethylacetamide, stirred at 70℃ for 4h to obtain a dynamic polyamic acid solution; (2) silane coupling agent KH-580 modified Ti3C2Tx MXene was added into dimethylacetamide and dispersed for 50 min by ultrasonic to prepare a MXene dispersion liquid; (3) The self-healing microcapsules and polycaprolactone-polyethylene glycol block copolymer were added into the MXene dispersion liquid and mechanically stirred for 2.5 h to prepare a composite filler liquid; (4) The composite filler liquid was added into the dynamic polyamic acid solution and stirred at 80℃ for 5 h to form a slurry; (5) The slurry was coated on a substrate, and was subjected to heat treatment at 100℃ / 1.5 h, 200℃ / 1 h and 300℃ / 1 h in sequence, and was peeled off after cooling to prepare a high-durability self-healing polyimide-based flexible sensing substrate with a thickness of 150 μm. It should be noted that the coating thickness of the slurry in this embodiment needs to meet the requirement that the thickness of the flexible sensing substrate after cooling and peeling off is 150 μm.

[0033] Example 2 The other features of this embodiment are the same as those of Example 1, except that the high-durability self-healing polyimide-based flexible sensing substrate in this embodiment contains the following components by weight: a dynamic modified polyimide matrix 83 parts, a silane coupling agent KH-580 modified Ti3C2T x MXene 8 parts, and self-healing microcapsules 7 parts.

[0034] In this embodiment, the content of dimercaptopropanoic acid in the preparation of the dynamic modified polyimide matrix by copolymerization is 12 wt%, the particle size of the self-healing microcapsules is 2 μm, the thickness of the wall material is 150 nm, the silane coupling agent KH-580 modified Ti3C2T x MXene has a sheet thickness of 2 nm and a lateral size of 0.8 μm.

[0035] Example 3 The other features of this embodiment are the same as those of Example 1, except that the high-durability self-healing polyimide-based flexible sensing substrate in this embodiment contains the following components by weight: a dynamic modified polyimide matrix 90 parts, a silane coupling agent KH-580 modified Ti3C2T x MXene 6 parts, self-healing microcapsules 4 parts, and polycaprolactone-polyethylene glycol block copolymer 1.5 parts.

[0036] In this embodiment, the content of dimercaptopropanoic acid in the preparation of the dynamic modified polyimide matrix by copolymerization is 12 wt%, the particle size of the self-healing microcapsules is 4 μm, the thickness of the wall material is 250 nm, the silane coupling agent KH-580 modified Ti3C2T x MXene has a sheet thickness of 4 nm and a lateral size of 1.5 μm.

[0037] Example 4 The other features of this embodiment are the same as those of embodiment 1, except that the high-durability self-healing polyimide-based flexible sensing substrate in this embodiment comprises the following components in parts by weight: a dynamically modified polyimide matrix 80, a silane coupling agent KH-580 modified Ti3C2T MXene 10, self-healing microcapsules 8, and a polycaprolactone-polyethylene glycol block copolymer 3. x MXene 10, self-healing microcapsules 8, and a polycaprolactone-polyethylene glycol block copolymer 3.

[0038] The content of dimercaptopropanoic acid in the preparation of the dynamically modified polyimide matrix by copolymerization is 15 wt%, the particle size of the self-healing microcapsules is 1 pm, the thickness of the wall material is 150 nm, the silane coupling agent KH-580 modified Ti3C2T MXene is 10, the self-healing microcapsules are 8, and the polycaprolactone-polyethylene glycol block copolymer is 3. x The sheet thickness of the MXene is 1 nm, and the lateral size is 0.5 pm.

[0039] Embodiment 5 The other features of this embodiment are the same as those of embodiment 1, except that the high-durability self-healing polyimide-based flexible sensing substrate in this embodiment comprises the following components in parts by weight: a dynamically modified polyimide matrix 84, a silane coupling agent KH-580 modified Ti3C2T MXene 7, self-healing microcapsules 6, and a polycaprolactone-polyethylene glycol block copolymer 2. x MXene 7, self-healing microcapsules 6, and a polycaprolactone-polyethylene glycol block copolymer 2.

[0040] The content of dimercaptopropanoic acid in the preparation of the dynamically modified polyimide matrix by copolymerization is 11 wt%, the particle size of the self-healing microcapsules is 3 pm, the thickness of the wall material is 250 nm, the silane coupling agent KH-580 modified Ti3C2T MXene is 7, the self-healing microcapsules are 6, and the polycaprolactone-polyethylene glycol block copolymer is 2. x The sheet thickness of the MXene is 3 nm, and the lateral size is 2 pm.

[0041] Embodiment 6 The other features of this embodiment are the same as those of embodiment 1, except that the high-durability self-healing polyimide-based flexible sensing substrate in this embodiment comprises the following components in parts by weight: a dynamically modified polyimide matrix 86, a silane coupling agent KH-580 modified Ti3C2T MXene 5, self-healing microcapsules 7, and a polycaprolactone-polyethylene glycol block copolymer 1. x MXene 5, self-healing microcapsules 7, and a polycaprolactone-polyethylene glycol block copolymer 1.

[0042] The content of dimercaptopropanoic acid in the preparation of the dynamically modified polyimide matrix by copolymerization is 9 wt%, the particle size of the self-healing microcapsules is 5 pm, the thickness of the wall material is 200 nm, the silane coupling agent KH-580 modified Ti3C2T MXene is 5, the self-healing microcapsules are 7, and the polycaprolactone-polyethylene glycol block copolymer is 1. x The sheet thickness of the MXene is 5 nm, and the lateral size is 1.2 pm.

[0043] Embodiment 7 Other features of this embodiment are the same as those of Embodiment 1, except that the mass ratio of isocyanate to polyol in the core material of the self-healing microcapsule is 1:1.5.

[0044] Comparative Example 1 In this embodiment, the flexible sensing substrate comprises, by weight, 92 parts of dynamically modified polyimide matrix with a dimercaptopropionic acid content of 10 wt% and unmodified Ti3C2T. x The substrate contains 7 parts of MXene, excluding polycaprolactone-polyethylene glycol block copolymer and self-healing microcapsules. The preparation method of the flexible sensing substrate in this embodiment is the same as that in Example 1. First, a dynamic polyamic acid solution is prepared, then an MXene dispersion is prepared, and then the two are mixed to form a slurry which is coated onto a substrate. After cooling, the flexible sensing substrate of this embodiment is obtained.

[0045] Comparative Example 2 In this embodiment, the flexible sensing substrate comprises, by weight, 85 parts of pure polyimide and silane coupling agent KH-580 modified Ti3C2T. x The mixture contains 7 parts MXene, 6 parts self-healing microcapsules, and 2 parts polycaprolactone-polyethylene glycol block copolymer. The preparation method of the flexible sensing substrate in this embodiment is the same as that in Example 1.

[0046] Test Example 1 The high-durability self-healing polyimide-based flexible sensing substrates prepared in Examples 1-7 and the flexible sensing substrates prepared in Comparative Examples 1-2 were tested for 1-hour self-healing efficiency, 1-hour healing piezoresistive sensitivity recovery rate, 1-hour healing damping coefficient recovery rate, tensile strength retention rate after 5000 cycles of stretching, and resistance change rate after 1000 cycles of bending.

[0047] All performance tests were conducted under simulated ambient temperature conditions: 23℃ (error not exceeding 2℃) and 50% humidity (error not exceeding 5%). The test procedures are as follows: The 1-hour self-healing efficiency refers to the ability of a flexible sensing substrate to recover its mechanical integrity after being subjected to standardized mechanical damage and left to heal for 1 hour. By comparing the tensile strength of the material before and after healing, the strength recovery rate can be calculated, which is the self-healing efficiency. It reflects the ability of the flexible sensing substrate to restore its mechanical integrity after damage. The 1-hour self-healing efficiency test process is as follows: (1) Three standard tensile specimens were prepared by cutting the flexible sensing substrate to be tested. For example, the length, width and thickness of the standard tensile specimens were 150 mm, 10 mm and 150 μm, respectively.

[0048] (2) On a universal testing machine, the initial tensile strength of each standard tensile specimen was tested at a tensile rate of 5 mm / min. The average of the initial tensile strengths of the three standard tensile specimens was taken as the initial tensile strength σ0 of the flexible sensing substrate to be tested.

[0049] (3) Cut the flexible sensing substrate to be tested into three standard tensile specimens. Use a blade to cut a cut perpendicular to the tensile direction at the center of the three standard tensile specimens. Control the depth of the cut to be half the thickness of the specimen and the width to be 0.5 mm.

[0050] (4) Place the damaged specimen in (3) in a room temperature simulation environment for self-healing for 1 hour, without applying any additional pressure or heat.

[0051] (5) Take out the healed specimen and test the tensile strength of the three healed specimens at a tensile rate of 5 mm / min on a universal testing machine. Take the average value to obtain the tensile strength σ1 after healing.

[0052] (6) Calculate the self-healing efficiency η = (σ1 / σ0) × 100%. The data of σ0, σ1 and η are all rounded to one decimal place.

[0053] Piezoresistive sensitivity is the ratio of the relative rate of change of resistance to the rate of change of pressure. By comparing the sensitivity before and after 1 hour of healing, the piezoresistive sensitivity recovery rate can be calculated, which determines the recovery capability of the electrical response of the flexible sensing substrate after damage. The piezoresistive sensitivity recovery rate test process after 1 hour of healing is as follows: (1) Three standard sensitivity strips were prepared by cutting the flexible sensing substrate to be tested. Rectangular electrodes with dimensions of 20 mm in length and 5 mm in width were prepared on the surface of both ends of the strips using conductive silver paste. After drying for 2 hours to ensure the electrodes were conductive, the initial resistance R0 was measured. For example, the length, width and thickness of the standard sensitivity strips were 20 mm, 20 mm and 150 μm, respectively.

[0054] (2) Fix each sensitivity sample on the pressure test bench, then connect the electrode to the resistance tester, apply a gradient pressure of 0→10→20→50→80→100kPa, hold each pressure point for 30s, and record the resistance R under the corresponding pressure P; calculate the relative change rate of resistance ΔR / R0 at each pressure point as (R-R0) / R0×100%; plot the curve with ΔR / R0 as the vertical axis and P as the horizontal axis, calculate each initial sensitivity Δ(ΔR / R0) / ΔP by linear fitting method, and take the average value as the initial sensitivity S0 of the flexible sensing substrate to be tested.

[0055] (3) Three sensitivity samples after healing were obtained by using the same cutting and healing process as the 1h self-healing efficiency.

[0056] (4) Using the method of (2), the three post-healing sensitivities were calculated based on the three post-healing sensitivities splines in (3), and the average value was taken as the 1-hour post-healing sensitivities S1.

[0057] (5) Calculate the piezoresistive sensitivity recovery rate ζ after 1 hour of healing ζ = (sensitivity after healing S1 / initial sensitivity S0) × 100%. R0, R, S0, S1 and ζ are all rounded to two decimal places.

[0058] The damping coefficient is characterized by the loss factor tanδ, reflecting the material's energy dissipation capacity. Calculating the ratio of tanδ before and after healing determines the damping coefficient recovery rate after healing. tanδ = E'' / E', where E'' represents the loss modulus and E' represents the storage modulus. The damping coefficient recovery rate test process after 1 hour of healing is as follows: (1) Three DMA three-point bending standard strips were prepared by cutting the flexible sensing substrate to be tested. For example, the length, width and thickness of the DMA three-point bending standard strips are 50 mm, 100 mm and 150 μm, respectively.

[0059] (2) Dynamic mechanical analysis DMA settings: The test mode is three-point bending, the frequency is 1Hz, and the strain amplitude is 0.1%; by scanning each DMA three-point bending standard specimen to obtain its own storage modulus E' and loss modulus E'', the initial damping coefficient tanδ0=E'' / E' is calculated; then the average value of the initial damping coefficients of the three DMA three-point bending standard specimens is taken as the initial damping coefficient of the flexible sensing substrate to be tested.

[0060] (3) Three DMA three-point bending splines after healing were obtained by using the same cutting and healing process as the 1h self-healing efficiency.

[0061] (4) Using the method of (2), the three post-healing DMA three-point bending splines of (3) were used to calculate the three post-healing damping coefficients. The average value was taken as the tanδ1 of the 1h post-healing damping coefficient.

[0062] (5) Calculate the recovery rate of the damping coefficient after 1 hour of healing: θ = (damping coefficient after healing tanδ1 / initial damping coefficient tanδ0) × 100%. E', E'', tanδ0, tanδ1 and θ are all rounded to two decimal places.

[0063] By simulating the fatigue process of materials during long-term use through 5000 cycles of tensile testing at room temperature, and comparing the tensile strength at break before and after the cycles, the retention rate can be calculated to reflect the durability of the flexible sensing substrate under test. The tensile strength retention rate test process after 5000 cycles is as follows: (1) Prepare three standard tensile specimens, three standard sensitivity specimens and three DMA three-point bending standard specimens. Use a universal testing machine to test the initial tensile strength of each tensile specimen and take the average as the initial tensile strength of the flexible sensing substrate to be tested.

[0064] (2) All parallel samples from (1) were subjected to 5000 tensile cycles using a fatigue testing machine. The fatigue testing machine was set to: tensile mode, stress range from 0 to initial fracture tensile strength, frequency 1Hz, and number of cycles 5000. During the cycle, each sample was monitored in real time for cracks. If a sample broke, it was discarded and a parallel sample was retested.

[0065] (3) The tensile strength at break of all specimens after 5000 tensile cycles was tested using a universal testing machine and the average was taken as the tensile strength at break of the flexible sensing substrate after 5000 tensile cycles. (4) Tensile strength retention rate after 5000 cycles of stretching = (tensile strength at break after 5000 cycles / initial tensile strength at break) × 100%.

[0066] By simulating the bending scenario of materials in flexible devices through 1000 reciprocating bends at room temperature, the rate of change of resistance was calculated by comparing the initial resistance before and after bending. The rate of change of resistance reflects the electrical stability of the flexible sensing substrate; the smaller the change in resistance, the better the stability. The test process for the rate of change of resistance after 1000 bends is as follows: (1) Cut the flexible sensing substrate to be tested to prepare three standard resistance change rate test strips. For example, the length, width and thickness of the standard resistance change rate test strips are 100 mm, 10 mm and 150 μm respectively.

[0067] (2) Prepare circular electrodes with a diameter of 3 mm using conductive silver paste at 10 mm from the end of each standard resistance change rate test strip along the length direction. After drying for 2 hours, measure the resistance of each strip in a flat state and take the average to obtain the initial resistance of the flexible sensing substrate to be tested.

[0068] (3) Fix both ends of the sample to the fixture of the bending tester, ensuring that the bending center is located at the midpoint of the sample. The bending tester performs 1000 bending cycles on all the samples in (2). Bending tester settings: bending mode is reciprocating 90° bending, bending radius R=3mm, bending frequency 1 time / s, 1000 cycles; (4) After completing 1000 bends, restore the sample to a flat state and let it stand for 10 minutes to eliminate bending stress.

[0069] (5) The resistance of each sample after 1000 bends is measured by the same resistance tester and the average is taken to obtain the resistance of the flexible sensing substrate after 1000 bends.

[0070] (6) Calculate the resistance change rate after 1000 bends = |resistance after 1000 bends - initial resistance| / initial resistance × 100%. Keep two decimal places for each data. If the resistance change rate after 1000 bends is less than or equal to 5%, the flexible sensing substrate under test is judged to have excellent electrical stability.

[0071] The results of the various performance tests are shown in Table 1.

[0072] Table 1. Test results of different performance characteristics of flexible sensing substrates As shown in Table 1, the high-durability self-healing polyimide-based flexible sensing substrate of the present invention exhibits better performance than the conventional flexible sensing substrate of the comparative example. At room temperature, the high-durability self-healing polyimide-based flexible sensing substrate shows a microcrack self-healing efficiency ≥90% after 1 hour, a piezoresistive sensitivity recovery rate ≥91% after 1 hour of healing, and a damping coefficient recovery rate ≥88% after 1 hour of healing, demonstrating excellent self-healing performance. Furthermore, after 5000 cycles of tensile stretching, the tensile strength retention rate is ≥86%, and after 1000 cycles of bending, the resistance change rate is ≤5%, indicating strong durability.

[0073] Furthermore, the high-durability self-healing polyimide-based flexible sensing substrate of the present invention can achieve a large degree of healing in a short period of time at room temperature, making it suitable for human skin contact scenarios and applicable to the medical rehabilitation field; it also has high piezoresistive sensitivity, which can meet the sensor and buffering needs of multiple scenarios.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A highly durable, self-healing polyimide-based flexible sensing substrate, characterized in that, By weight, it contains the following components: 80-90 parts of dynamically modified polyimide matrix, silane coupling agent KH-580 modified Ti3C2T x MXene 5-10 parts, self-healing microcapsules 4-8 parts, polycaprolactone-polyethylene glycol block copolymer 1-3 parts; The dynamically modified polyimide matrix is ​​prepared by copolymerization of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 4,4'-diaminodiphenyl disulfide and dimercaptopropionic acid. The silane coupling agent KH-580 modified Ti3C2T x MXene is made from Ti3C2T x MXene has a quality rating of Ti3C2T x MXene is obtained by surface modification with 3-5% by mass of silane coupling agent KH-580; The core material of the self-healing microcapsule is an isocyanate-polyol prepolymer, and the wall material is urea-formaldehyde resin.

2. The high-durability self-healing polyimide-based flexible sensing substrate according to claim 1, characterized in that, The content of dimercaptopropionic acid in the dynamically modified polyimide matrix is ​​8-15 wt%, and the molar ratio of 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-diaminodiphenyl disulfide is 1:

1.

3. The high-durability self-healing polyimide-based flexible sensing substrate according to claim 2, characterized in that, The silane coupling agent KH-580 modified Ti3C2T x MXene has a sheet thickness of 1-5 nm and a lateral dimension of 0.5-2 μm.

4. The high-durability self-healing polyimide-based flexible sensing substrate according to claim 3, characterized in that, The self-healing microcapsules have a particle size of 1-5 μm and a wall material thickness of 150-250 nm. The mass ratio of isocyanate to polyol in the core material of the self-healing microcapsule is 1:1.2-1.

5.

5. The high-durability self-healing polyimide-based flexible sensing substrate according to claim 2, characterized in that, The content of dimercaptopropionic acid in the dynamically modified polyimide matrix is ​​10-12 wt%.

6. The high-durability self-healing polyimide-based flexible sensing substrate according to claim 3, characterized in that, The silane coupling agent KH-580 modified Ti3C2T x The weight of MXene is 7-9 parts, and the thickness of the sheet is 2-3 nm.

7. A method for preparing a high-durability self-healing polyimide-based flexible sensing substrate, used to prepare the high-durability self-healing polyimide-based flexible sensing substrate as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Add 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 4,4'-diaminodiphenyl disulfide and dimercaptopropionic acid to dimethylacetamide, and stir at 60-80℃ for 3-5 hours to obtain a dynamic polyamic acid solution; the dynamic polyamic acid solution contains 85wt% dimethylacetamide; Step 2: Modify Ti3C2T with silane coupling agent KH-580 x MXene was added to dimethylacetamide and ultrasonically dispersed for 40-60 min to obtain an MXene dispersion; the MXene dispersion contained 85 wt% dimethylacetamide. Step 3: Add the self-healing microcapsules and polycaprolactone-polyethylene glycol block copolymer to the MXene dispersion and mechanically stir for 2-3 hours to obtain the composite filler solution; Step 4: Add the composite filler liquid to the dynamic polyamic acid solution and stir at 70-90℃ for 4-6 hours to form a slurry; Step 5: Coat the slurry onto the substrate and subject it to heat treatment at 100℃ / 1.5h, 200℃ / 1h, and 300℃ / 1h in sequence. After cooling, peel it off to obtain a high-durability self-healing polyimide-based flexible sensing substrate.

8. The method for preparing the high-durability self-healing polyimide-based flexible sensing substrate according to claim 7, characterized in that, In step 5, the substrate is made of PET or polytetrafluoroethylene.

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