Photocuring composition, conductive flexible film layer and flexible pressure sensor

Abstract

The invention provides a photocuring composition, a conductive flexible film layer and a flexible pressure sensor, and the conductive flexible film layer and the flexible pressure sensor are prepared from the photocuring composition comprising flexible photosensitive resin, a photoinitiator and modified carbon nanotubes by using a 3D printing technology. The conductive flexible film layer can still maintain the conductivity even after being greatly bent, and in the flexible pressure sensor prepared by the invention, each sensing unit in the pressure sensor array has obvious response to a slight load less than 1kPa and a load more than 150kPa. The flexible pressure sensor has a wide pressure detection range, and has a wide application prospect in the fields of flexible electronics, intelligent wearable equipment, medical health monitoring and the like.

Description

Technical Field

[0001] The invention relates to the technical field of photocurable resins and nanomaterials, and in particular to a photocurable composition, a conductive flexible film layer and a flexible pressure sensor. Background Art

[0002] As medical and health technology evolves towards intelligence, the performance requirements for pressure sensors for flexible medical catheters, surgical intervention tools, and personal health monitoring devices are becoming increasingly higher. In existing technologies, a new generation of wearable biosensors and medical devices has been developed by combining flexible electronic materials with 3D printing technology. However, currently commercialized photocurable 3D printing resins generally lack conductivity, which limits the potential of these devices in achieving conductive functions.

[0003] The prior art discloses a photocurable resin composition, a method for preparing a photocurable material, and an application (CN118108900A), wherein the photocurable resin composition comprises: by weight percentage, 10%-80% unsaturated polymer, 10%-80% reactive monomer, 0.5%-5% photoinitiator, 1%-30% modified conductive filler, and 0.1%-2% filler. The conductive material is introduced on the basis of the traditional photocurable resin, and it can be widely used in the 3D component printing of photocurable resin materials in scenes with high power consumption. However, the disadvantages are as follows: its flexibility and conductivity cannot meet the requirements of pressure sensors.

[0004] Therefore, there is an urgent need for a photocurable composition and a conductive flexible film layer that can maintain its excellent conductive properties under large bending conditions. Summary of the invention

[0005] In view of the above problems, the present invention provides a photocurable composition, a conductive flexible film layer and a flexible pressure sensor to solve at least one problem existing in the prior art.

[0006] To achieve the above objectives, in a first aspect, the present invention protects a 3D printable photocurable composition, comprising a flexible photosensitive resin, a photoinitiator and a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent.

[0007] Further, preferably, the mass components of the photocurable composition are: 1-10 parts of photoinitiator, 1000 parts of flexible photosensitive resin, and 5-50 parts of conductive filler.

[0008] Further, preferably, the flexible photosensitive resin is at least one of acrylic photosensitive resin, epoxy photosensitive resin or polyurethane photosensitive resin.

[0009] Furthermore, preferably, the photoinitiator is a benzoin ether photoinitiator or an acrylate photoinitiator.

[0010] In a second aspect, the present invention protects a conductive flexible film layer, which is prepared by using the above-mentioned 3D printable photocurable composition through a photocuring 3D printer.

[0011] In a third aspect, the present invention protects a flexible pressure-sensitive layer, which is prepared by using the above-mentioned 3D printable photocurable composition through a photocurable 3D printer.

[0012] Further, preferably, the flexible pressure-sensitive layer has a microstructure; the microstructure is any one of a pyramid shape, a cone shape or an N-pyramid shape.

[0013] In a fourth aspect, the present invention protects a flexible pressure sensor having the above-mentioned flexible pressure-sensitive layer.

[0014] In a fifth aspect, the present invention protects a method for preparing a conductive flexible film layer, the method comprising:

[0015] The photosensitive resin, the photoinitiator and the conductive filler are mixed by ball milling process; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent;

[0016] The uniformly mixed raw materials are printed using a light-curing 3D printer, and after secondary curing in a curing box, a conductive flexible film layer is obtained.

[0017] Further, preferably, the conditions for printing the mixed raw materials using a light-curing 3D printer are that the exposure intensity of each layer ranges from 20 to 80 mW / cm 2 , exposure time is 1-10 seconds;

[0018] The time for secondary curing using a curing box is 3-6 seconds.

[0019] Further, preferably, the method of mixing the photosensitive resin, the photoinitiator and the conductive filler by ball milling process further comprises adding the photosensitive resin, the photoinitiator and the conductive filler into a homogenizer and mixing them according to the following steps;

[0020] Run at a speed of 600 to 800 r / min for 20 to 40 seconds;

[0021] Run at a speed of 1000 to 1500 r / min for 40 to 70 seconds;

[0022] Run at a speed of 800 to 1000 r / min for 20 to 40 seconds.

[0023] In a sixth aspect, the present invention protects a method for preparing a flexible pressure sensor.

[0024] Using a mask plate to grow interdigitated electrodes on a flexible substrate by electron evaporation;

[0025] The pre-prepared flexible pressure-sensitive layer is cut according to the area of ​​the interdigital electrodes and attached to the interdigital electrodes; wherein the preparation method of the flexible pressure-sensitive layer comprises mixing a photosensitive resin, a photoinitiator and a carbon nanotube modified by a silane coupling agent by a ball milling process; printing the uniformly mixed raw materials by a photocuring 3D printer, and performing secondary curing in a curing box to obtain a conductive flexible film layer with a microstructure as the flexible pressure-sensitive layer;

[0026] The flexible pressure-sensitive layer is packaged to complete the preparation of the flexible pressure sensor.

[0027] Further, preferably, in the process of growing interdigitated electrodes on a flexible substrate using a mask plate by electron evaporation, the conditions of electron evaporation are: evaporation current of 270 mA, background vacuum of 1×10^-4 Pa, vacuum in the evaporation chamber of 3×10^-3 Pa, and evaporation rate of 1 A / s.

[0028] Further, preferably, the interdigitated electrodes have a finger length of 6 to 20 mm, a finger width of 0.1 to 0.5 mm, and a finger spacing of 0.1 to 0.5 mm.

[0029] The photocurable composition, conductive flexible film layer and flexible pressure sensor provided by the present invention, the conductive flexible film layer prepared by the prepared 3D printable photocurable composition has good conductivity and resilience. Even after undergoing a large bending, it can still maintain its conductive properties, which makes it suitable for occasions that require frequent bending or maintain function in a dynamic environment. The flexible pressure sensor prepared by the present invention not only has good bending performance, but also has excellent biocompatibility. This means that the sensor can be attached to a curved surface such as the skin and maintain stable sensing performance under various bending conditions. In addition, the sensor exhibits high sensitivity and a wide measurement range, and its sensing performance is almost not attenuated even after more than 500 cycles, showing excellent durability. In the flexible pressure sensor prepared by the present invention, each sensing unit in the pressure sensor array has consistent sensing performance. There is a significant response to a slight load of less than 1kPa and a load of more than 150kPa; this shows that the flexible pressure sensor of the present invention has a wide pressure detection range and has broad application prospects in the fields of flexible electronics, smart wearable devices, medical health monitoring, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A comparison diagram of the sedimentation of a flexible photosensitive resin provided in one embodiment of the present invention.

[0031] Figure 2 It is a cross-sectional view of the conductive flexible film layer of each preparation example provided in one embodiment of the present invention obtained under a scanning electron microscope at a low magnification.

[0032] Figure 3 is a structural diagram of a flexible pressure sensor provided in one embodiment of the present invention.

[0033] Figure 4 is the response time of the sensor unit of the flexible pressure sensor provided by an embodiment of the present invention.

[0034] Figure 5 A pressure response curve of a sensor unit of a flexible pressure sensor provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described in more detail with reference to the following examples. However, the protection scope of the present invention is not limited to the following examples.

[0036] Among the various experimental supplies mentioned in this article (including but not limited to: chemical reagents, biological products, cells, organisms, instruments, etc.), for those that are special or difficult to obtain, the manufacturers, references or detailed preparation methods have been indicated in the article; those not otherwise specified are conventional experimental supplies and can be easily obtained by various means (such as purchase, self-preparation, etc.) before the date of this application.

[0037] Photocuring refers to the curing process of monomers, oligomers or polymer matrices under light induction, which is generally used in the film forming process.

[0038] 3D printing is an advanced technology for manufacturing three-dimensional objects. The working principle of a 3D printer is to cut a digital model into thin slices, then print these slices layer by layer, stack them layer by layer, and finally form a complete physical object. In the present invention, a light-curing 3D printer is used. Specifically, the printing process of the light-curing 3D printer is itself a curing process; in addition, a curing box is used for secondary curing; the curing box is a device that irradiates ultraviolet light at 360°. The purpose of the secondary curing for 3-6 seconds is to increase the surface curing degree of the printed part, so that the device is not easily worn or damaged.

[0039] DLP (Digital Light Processing) 3D printing is an advanced additive manufacturing technology that uses a digital light projector (rather than a laser) to cure photosensitive resin by flashing a single image of each layer simultaneously on the resin, building up three-dimensional objects layer by layer.

[0040] Preparation Example 1

[0041] A 3D printable photocurable composition comprises 1 part of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 5 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is an acrylic photosensitive resin, and the photoinitiator is a benzoin ether photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 1.

[0042] Among them, the specific method of modifying the carbon nanotubes modified by silane coupling agent includes: selecting a suitable carbon nanotube raw material, which can be at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, hydroxylated carbon nanotubes or carboxylated carbon nanotubes. Select a silane coupling agent, which can be at least one of KH550, KH560, KH570, KH171, KH792, KBM403, and SI69. Prepare the instruments required for the co-thermal reaction, including a magnetic stirrer, an oil bath, a temperature sensor, a magnetic stirrer, a round-bottomed flask, a condenser and a reflux tube. Install the equipment from bottom to top in the order of a magnetic stirrer, an oil bath, a round-bottomed flask, a condenser, and a reflux tube. Put the magnetic stirrer into the round-bottomed flask so that its bottom contacts the bottom of the oil bath. Insert the temperature sensor into the oil bath in the air to ensure that it does not contact any glass wall. Set the speed of the magnetic stirrer to 500 to 800 revolutions per minute (rpm). Set the temperature of the oil bath to 60 to 90 degrees Celsius. Maintain the heating time for 8 to 12 hours. After the modification reaction is completed, wash the product with deionized water. Use a centrifuge to separate the solid product and the liquid solvent, and repeat this process 3 to 5 times to obtain a clean sample. The modified sample is dried from the ethanol solution. The methods that can be used include at least one of vacuum drying, vacuum freeze drying, spray drying, hot air drying, film drying, radiation drying or adsorption drying. Through the above steps, a conductive filler with good compatibility with the photosensitive resin, i.e., the modified carbon nanotubes, can be obtained.

[0043] The photocurable composition 1 is printed by using a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 1 .

[0044] Preparation Example 2

[0045] A 3D printable photocurable composition comprises 5 parts of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 6 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is a polyurethane photosensitive resin. The photoinitiator is an acrylate photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 2.

[0046] The photocurable composition 2 is printed by using a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 2 .

[0047] Preparation Example 3

[0048] A 3D printable photocurable composition comprises 5 parts of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 7 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is a polyurethane photosensitive resin. The photoinitiator is an acrylate photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 3.

[0049] The photocurable composition 2 is printed by a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 3 .

[0050] Preparation Example 4

[0051] A 3D printable photocurable composition comprises 5 parts of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 7 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is a polyurethane photosensitive resin. The photoinitiator is an acrylate photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 4.

[0052] The photocurable composition 2 is printed by a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 4 .

[0053] Preparation Example 5

[0054] A 3D printable photocurable composition comprises 5 parts of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 50 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is a polyurethane photosensitive resin. The photoinitiator is an acrylate photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 5.

[0055] The photocurable composition 2 is printed by a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 5 .

[0056] Preparation Example 6

[0057] A 3D printable photocurable composition comprises 3 parts of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 35 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is an epoxy photosensitive resin. The photoinitiator is an acrylate photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 6.

[0058] The photocurable composition 3 is printed by a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 6 .

[0059] Comparative Example 1

[0060] A 3D printable photocurable composition comprises 1 part of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 5 parts of a conductive filler; wherein the conductive filler is a carbon nanotube. The flexible photosensitive resin is an acrylic photosensitive resin, and the photoinitiator is a benzoin ether photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 7.

[0061] The precipitation of the flexible photosensitive resin in the photocurable composition 7 and the photocurable composition 1 was compared. Figure 1 As shown. By observing Figure 1 By uniformly mixing the modified carbon nanotubes with the flexible photosensitive resin, good dispersion was achieved, and this dispersion state could be maintained for at least a week, avoiding the occurrence of sedimentation. This improvement not only improves the stability of the material, but also helps to maintain the performance consistency of the photocurable conductive resin.

[0062] Comparative Example 2

[0063] A 3D printable photocurable composition comprises 1 part of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 4 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is an acrylic photosensitive resin, and the photoinitiator is a benzoin ether photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 8.

[0064] The photocurable composition 5 is printed by a 3D printer and subjected to secondary curing in a curing box to obtain a conductive flexible film layer 8 .

[0065] The resistivity of conductive flexible film layer 1, conductive flexible film layer 2, conductive flexible film layer 3, conductive flexible film layer 4, conductive flexible film layer 5 and conductive flexible film layer 6 were tested, and it was found that by controlling the doping amount at 0.5-5wt.%, a conductive flexible film layer with a resistivity meeting the requirements can be obtained by 3D printing.

[0066] Among them, when 0.4wt.% doping, the resistivity is 66kΩ·cm. When 0.5wt.% doping, the resistivity is 10kΩ·cm. When 0.6wt.% doping, the resistivity is 3.0kΩ·cm. When 0.7wt.% doping, the resistivity is 1.2kΩ·cm. It can be seen from the observation that when the doping of the conductive filler is less than 0.5wt.%, the resistivity is too large.

[0067] The cross-sectional images of the conductive flexible film layer 1, the conductive flexible film layer 2, the conductive flexible film layer 3 and the conductive flexible film layer 8 were obtained by scanning electron microscopy at low magnification. Figure 2 As shown. By observing Figure 2 It can be found that the bright parts of the surfaces of the conductive flexible film layer 1, the conductive flexible film layer 2, and the conductive flexible film layer 3 are carbon nanotubes with good conductivity. However, the bright part of the surface of the conductive flexible film layer 8 of the comparative example 1 is poor.

[0068] Comparative Example 3

[0069] A 3D printable photocurable composition comprises 1 part of a photoinitiator, 1000 parts of a flexible photosensitive resin, and 60 parts of a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent. The flexible photosensitive resin is an acrylic photosensitive resin, and the photoinitiator is a benzoin ether photoinitiator; the photosensitive resin, the photoinitiator, and the conductive filler are uniformly mixed by a ball milling process to obtain a photocurable composition 6.

[0070] The light penetration depth of the photocurable composition 6 is less than 25 μm, and thus it cannot be printed using a 3D printer.

[0071] By observation Figure 2 , it can be found that the bright part of the surface is the carbon nanotube with good conductivity. By controlling the doping amount to 0.5-5wt.%, a conductive flexible film layer with a resistivity that meets the requirements can be obtained by 3D printing.

[0072] Example 1

[0073] The carbon nanotubes modified by using a silane coupling agent are prepared.

[0074] The selected multi-walled carbon nanotubes and silane coupling agents are placed in a round-bottom flask in the order of addition and mixed to obtain a mixed solution. The mixed solution is heated to a set temperature of 80°C by a mixer. Set up a condensation reflux and oil bath device, set a suitable stirring rate of 700rpm and a stirring time of 10 hours. Take out the liquid and wash it with deionized water, centrifuge to take the precipitate, and repeat the washing operation 3-5 times. Take the last precipitate and rinse it with deionized water, ultrasonically disperse it and put it in a refrigerator at -20°C for standby use. Transfer the frozen raw material to a vacuum freeze dryer and vacuum freeze-dry it at -40°C for 4 days to obtain a dry and fluffy modified carbon nanotube raw material.

[0075] Mix the modified carbon nanotubes with the photosensitive resin. Mix the dry and fluffy modified carbon nanotube raw materials with the photosensitive resin in a vacuum degassing mixing tank, ready for the subsequent 3D printing process.

[0076] The flexible pressure-sensitive layer is prepared based on the above-mentioned photocurable composition, and is prepared by using the above-mentioned 3D printable photocurable composition through a 3D printer. The specific steps include:

[0077] The multi-walled carbon nanotubes and acrylic photosensitive resin were mixed in a mass ratio of 100:0.8, and the mixed material was homogenized using a homogenizer with the parameter set at 800 r / min for 120 seconds to ensure the uniformity of the mixed material.

[0078] The homogenized mixed resin material is used for 3D printing, and the conductive and flexible pressure-sensitive layer is printed through the above-mentioned printing parameters and scraper technology. The microstructure of the pressure-sensitive layer is designed using 3D modeling software, specifically in the shape of a stepped pyramid. The designed 3D model is sliced ​​using printer slicing software to facilitate 3D printer printing layer by layer. The 3D printing parameters are set, and the exposure power is 15mW / mm 2 , the exposure time is 5 seconds. During the printing process, the scraper technique is used to ensure the uniform distribution of the resin and the flatness between layers. Acrylic light-curing resin is selected as the printing material because of its good light-curing characteristics and physical properties.

[0079] Example 2

[0080] A flexible pressure sensor is prepared based on the flexible pressure-sensitive layer of Example 1. The structure of the flexible pressure sensor is as follows: Figure 3As shown. It includes a flexible substrate 1, a forked electrode 2 and a 3D printed conductive flexible pressure-sensitive layer 3, the forked electrode 2 is grown on the flexible substrate 1 by electron beam evaporation, and the 3D printed conductive flexible pressure-sensitive layer 3 is cut and attached to the corresponding forked electrode 2. In the specific implementation process, the flexible substrate can be selected from at least one of PET film, PI film, plastic film, PVA, PDMS, silicone, Ecoflex, SBS elastomer, POE elastomer, rubber, resin, styrene block copolymer, PVC, polyethylene terephthalate plastic, and thermoplastic elastomer. The material of the forked electrode 2 can be selected from one of gold, silver, copper, platinum or laser-induced graphene.

[0081] A method for preparing a flexible pressure sensor based on the flexible pressure-sensitive layer of Example 1 comprises the following steps.

[0082] S110, directly forming an interdigital electrode pattern on the flexible substrate by laser induction, wherein the flexible substrate 1 is EM+23 photocurable resin.

[0083] S120, cutting the pre-prepared flexible pressure-sensitive layer according to the area of ​​the interdigital electrodes, and attaching the interdigital electrodes to the interdigital electrodes. The interdigital electrodes have a finger length of 6 mm, a finger width of 0.1 mm, and a finger spacing of 0.1 mm.

[0084] S130, encapsulating the flexible pressure-sensitive layer to complete the preparation of the flexible pressure sensor.

[0085] Example 3

[0086] A method for preparing a flexible pressure sensor based on the flexible pressure-sensitive layer of Example 1 comprises the following steps.

[0087] S110, using a mask plate to grow interdigital electrodes on a flexible substrate by electron evaporation. The flexible substrate 1 is a commercial flexible PET film, and the interdigital electrodes 2 are made by electron beam evaporation, and the thickness of the evaporated conductive material is 100nm Au. In the process of growing interdigital electrodes on a flexible substrate by electron evaporation using a mask plate, the conditions of electron evaporation are: evaporation current of 270mA, background vacuum of 1×10^-4Pa, vacuum in the evaporation chamber of 3×10^-3Pa, and evaporation rate of 1A / s.

[0088] S120, cutting the pre-prepared flexible pressure-sensitive layer according to the area of ​​the interdigital electrodes, and attaching the interdigital electrodes to the interdigital electrodes. The interdigital electrodes have a finger length of 20 mm, a finger width of 0.5 mm, and a finger spacing of 0.5 mm.

[0089] S130, encapsulating the flexible pressure-sensitive layer to complete the preparation of the flexible pressure sensor.

[0090] The flexible pressure sensor obtained in Example 3 was installed on a stretching machine for pressure testing. The response time of the sensor unit of the flexible pressure sensor was as follows: Figure 4 As shown in Figure 1, the response times of the sensor unit are 110 milliseconds and 143 milliseconds respectively. This means that after the pressure is applied, the sensor unit is able to quickly detect the change and generate an output signal, with the fastest response time being 110 milliseconds and the slower response time being 143 milliseconds. The pressure response curve of the sensor unit of the flexible pressure sensor is shown in Figure 1. Figure 5 As shown: When the compressive stress is 0.73kPa, the R 2 The value is 0.97, indicating that the sensor response under this pressure has a good linear relationship and high fit. When the compressive stress is 0.33 kPa, the R 2 The value is 0.96, which also shows a high degree of fit and good linear response. This shows that the sensor can maintain high sensitivity and stability (R 2 The value is close to 1, which means that there is a good linear relationship between the sensor's response and the pressure change. The conductive sensitive structure of the flexible pressure sensor (i.e., flexible resistive micro-nano force sensor) is formed using DLP (digital light processing) 3D printing technology, thereby achieving high-precision manufacturing of complex structures at an extremely small scale. This technology effectively solves the problem that existing technologies cannot manufacture micro-nano force sensors at the micron scale.

[0091] In summary, the present invention provides a photocurable composition, a conductive flexible film layer and a flexible pressure sensor. The conductive flexible film layer prepared by the 3D printable photocurable composition prepared by the present invention has good conductivity and resilience. Even after a large bending, it can still maintain its conductive properties, which makes it suitable for occasions that require frequent bending or maintain function in a dynamic environment. The flexible pressure sensor prepared by the present invention not only has good bending performance, but also has excellent biocompatibility. This means that the sensor can be attached to a curved surface such as the skin and maintain stable sensing performance under various bending conditions. In addition, the sensor exhibits high sensitivity and a wide measurement range, and its sensing performance is almost not attenuated even after more than 500 cycles, showing excellent durability. In the flexible pressure sensor prepared by the present invention, each sensing unit in the pressure sensor array has consistent sensing performance. There is a significant response to a slight load of less than 1kPa and a load of more than 150kPa; this shows that the flexible pressure sensor of the present invention has a wide pressure detection range and has broad application prospects in the fields of flexible electronics, smart wearable devices, medical health monitoring, etc.

[0092] Although the present invention has been described in detail above by general description, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications and improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A 3D printable photocurable composition, characterized in that: The invention comprises a flexible photosensitive resin, a photoinitiator and a conductive filler; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent.

2. The 3D printable photocurable composition according to claim 1, characterized in that: The mass components of the photocurable composition are: 1-10 parts of photoinitiator, 1000 parts of flexible photosensitive resin, and 5-50 parts of conductive filler.

3. The 3D printable photocurable composition according to claim 2, characterized in that: The flexible photosensitive resin is at least one of acrylic photosensitive resin, epoxy photosensitive resin or polyurethane photosensitive resin.

4. The 3D printable photocurable composition according to claim 1, characterized in that: The photoinitiator is a benzoin ether photoinitiator or an acrylate photoinitiator.

5. A conductive flexible film layer, characterized in that: The 3D printable photocurable composition according to claim 1 is prepared by a 3D printer.

6. A flexible pressure-sensitive layer, characterized in that: The 3D printable photocurable composition according to claim 1 is prepared by a 3D printer.

7. The flexible pressure-sensitive layer according to claim 6, characterized in that: The flexible pressure-sensitive layer has a microstructure; the microstructure is any one of a pyramid shape, a cone shape or an N-pyramid shape.

8. A flexible pressure sensor, characterized in that: A flexible pressure-sensitive layer as claimed in claim 6.

9. A method for preparing a conductive flexible film layer, characterized in that: Methods include, The photosensitive resin, the photoinitiator and the conductive filler are mixed by ball milling process; wherein the conductive filler is a carbon nanotube modified by a silane coupling agent; The uniformly mixed raw materials are printed using a light-curing 3D printer, and after secondary curing in a curing box, a conductive flexible film layer is obtained.

10. The method for preparing a conductive flexible film layer according to claim 9, characterized in that: The mixed raw materials are printed using a light-curing 3D printer under the following conditions: the exposure intensity of each layer ranges from 20 to 80 mW / cm 2 , exposure time is 1-10 seconds; The time for secondary curing using a curing box is 3-6 seconds.

11. The method for preparing a conductive flexible film layer according to claim 9, characterized in that: The method for mixing the photosensitive resin, the photoinitiator and the conductive filler by ball milling process also includes adding the photosensitive resin, the photoinitiator and the conductive filler into a homogenizer and mixing them according to the following steps; Run at a speed of 600 to 800 r / min for 20 to 40 seconds; Run at a speed of 1000 to 1500 r / min for 40 to 70 seconds; Run at a speed of 800 to 1000 r / min for 20 to 40 seconds.

12. A method for preparing a flexible pressure sensor, characterized in that: Using a mask plate to grow interdigitated electrodes on a flexible substrate by electron evaporation; The pre-prepared flexible pressure-sensitive layer is cut according to the area of ​​the interdigital electrodes and attached to the interdigital electrodes; wherein the preparation method of the flexible pressure-sensitive layer comprises mixing a photosensitive resin, a photoinitiator and a carbon nanotube modified by a silane coupling agent by a ball milling process; printing the uniformly mixed raw materials by a photocuring 3D printer, and performing secondary curing in a curing box to obtain a conductive flexible film layer with a microstructure as the flexible pressure-sensitive layer; The flexible pressure-sensitive layer is packaged to complete the preparation of the flexible pressure sensor.

13. The method for preparing the flexible pressure sensor according to claim 12, characterized in that: In the process of growing interdigital electrodes on a flexible substrate using a mask plate by electron evaporation, the conditions of electron evaporation are: evaporation current of 270 mA, background vacuum of 1×10^-4 Pa, vacuum in the evaporation chamber of 3×10^-3 Pa, and evaporation rate of 1 A / s.

14. The method for preparing the flexible pressure sensor according to claim 12, characterized in that: The interdigital electrodes have a finger length of 6 to 20 mm, a finger width of 0.1 to 0.5 mm, and a finger spacing of 0.1 to 0.5 mm.

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