A method for preparing a flexible pressure sensor based on FDM 3D printing

Abstract

The present invention relates to the technical field of flexible pressure sensor preparation, and specifically to a method for preparing a flexible pressure sensor based on FDM 3D printing, comprising the following steps: S1, obtaining a conical three-dimensional part by printing with an FDM 3D printer; S2, compressing the conical three-dimensional part into a two-dimensional planar part; S3, preparing a base material having a complex microstructure based on the two-dimensional planar part; S4, coating a conductive material on the surface layer of the complex microstructure; and S5, assembling different base materials with the surfaces facing each other to obtain a flexible pressure sensor. The flexible pressure sensor prepared by the flexible pressure sensor preparation method based on FDM 3D printing provided by the present invention has the advantages of high sensitivity, wide linear pressure range, good linearity, and long service life, and is highly practical.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible pressure sensor preparation, and in particular to a method for preparing a flexible pressure sensor based on FDM 3D printing. Background Art

[0002] Flexible pressure sensors are directly in contact with the skin and are installed on the human pulse or chest to detect blood pressure and heartbeat, playing an important role in human health monitoring. Flexible pressure sensors are generally divided into four types according to their working mechanism, including piezoresistive, capacitive, piezoelectric and triboelectric. Among them, the piezoresistive pressure sensor uses the change in contact area between electrodes to detect the change in resistance under applied pressure. It has the advantages of high sensitivity, simple device structure, and easy implementation of the readout circuit. It is the mainstream implementation method of flexible pressure sensors. Its preparation method can refer to the Chinese invention patent with application number 202010661459.1, entitled A flexible pressure sensor and its preparation method. Since the working mechanism of the piezoresistive pressure sensor is based on the change in contact resistance when pressure is applied, the shape of the contact area (i.e., the microstructure) is crucial to the sensitivity. Therefore, in order to improve the sensitivity, it is necessary to prepare a complex microstructure in the flexible pressure sensor. However, the current method of manufacturing complex microstructures in flexible pressure sensors is mainly photolithography and etching processes, which require a complex manufacturing process, high cost, long time and a clean room environment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an efficient and low-cost method for preparing a flexible pressure sensor based on FDM 3D printing, which can prepare the complex microstructure required for the flexible pressure sensor without the need for a clean room environment.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a flexible pressure sensor based on FDM 3D printing, comprising the following steps:

[0005] S1. Print a cone-shaped three-dimensional part using an FDM 3D printer;

[0006] S2, compressing the cone three-dimensional part into a two-dimensional plane part;

[0007] S3, preparation of matrix materials with complex microstructures based on two-dimensional planar parts;

[0008] S4, plating conductive materials on the surface of complex microstructures;

[0009] S5. Assemble different base materials in a manner where the surfaces are opposite to each other to obtain a flexible pressure sensor.

[0010] Furthermore, the S1 specifically includes:

[0011] Design and use FDM3D printing to produce hollow conical three-dimensional parts.

[0012] Furthermore, the step S2 specifically includes step S21:

[0013] The conical three-dimensional part is heated at an ambient temperature of 100 to 120° C. for 3 to 5 minutes, and a force is applied to the conical three-dimensional part for 50 to 70 seconds to obtain a two-dimensional plane part.

[0014] Furthermore, the step S2 specifically includes step S22:

[0015] The two-dimensional plane part is placed at room temperature to cool while keeping the applied force constant.

[0016] Furthermore, the step S3 specifically includes step S31:

[0017] PDMS and a curing agent are mixed in a mass ratio of 9 to 11:1, and the mixture is stirred at a rotation speed of 20 to 30 rpm for 30 to 40 minutes to obtain a mixture.

[0018] Furthermore, the step S3 specifically includes step S31:

[0019] The mixture is placed in a vacuum environment for 1 to 1.5 hours to obtain an electrode matrix material.

[0020] Furthermore, the step S3 specifically includes step S32:

[0021] The electrode matrix material is placed in a container so that the plane of the electrode matrix with a complex microstructure faces the sealing liquid in the container. The container is then placed in a thermostat at a temperature of 40-45°C for 24-30 hours. The solidified sealing liquid is peeled off to obtain a solidified matrix material.

[0022] Furthermore, the step S4 specifically includes step S41:

[0023] The conductive material is plated on the surface of the complex microstructure or smooth surface of different base materials by drop casting.

[0024] The beneficial effects of the present invention are: providing a method for preparing a flexible pressure sensor based on FDM 3D printing. FDM 3D printing, namely fused deposition 3D printing, has many advantages such as simple manufacturing process, low material and device cost, fast printing speed, and easy control of manufacturing parameters. Fused deposition 3D printing adopts layer-by-layer printing, which has the disadvantage of rough product surface, which is specifically reflected in the stratification of microstructures. The present invention can prepare the complex microstructure required for flexible pressure sensors in a low-cost manner by taking advantage of this disadvantage, thereby achieving low-cost, fast, simple manufacturing, and the preparation of flexible pressure sensors without a clean room environment, overcoming the shortcomings of existing flexible pressure sensor preparation methods such as complex manufacturing process, high cost, long time, and the need for a clean room environment. The flexible pressure sensor prepared by the flexible pressure sensor preparation method based on FDM 3D printing provided by the present invention has the advantages of high sensitivity, wide linear pressure range, good linearity, long service life, and good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a method for preparing a flexible pressure sensor based on FDM 3D printing according to the present invention.

[0026] Figure 2 This is a main view of a three-dimensional model of a hollow cone designed in the three-dimensional design software in an embodiment of the present invention;

[0027] Figure 3 A bottom view of a three-dimensional model of a hollow cone designed in the three-dimensional design software in an embodiment of the present invention;

[0028] Figure 4 This is a front view of a conical three-dimensional part in an embodiment of the present invention;

[0029] Figure 5 A bottom view of a conical three-dimensional part in an embodiment of the present invention;

[0030] Figure 6 A top view of a two-dimensional planar component in an embodiment of the present invention;

[0031] Figure 7 Schematic diagram of the structure of a base material with a complex microstructure in an embodiment of the present invention;

[0032] Figure 8 Schematic diagram of the structure of a base material with a smooth surface in an embodiment of the present invention;

[0033] Figure 9 is an assembly flow chart of the flexible pressure sensor in an embodiment of the present invention;

[0034] 1. Electrodes with complex surface microstructures; 2. Flat electrodes; 3. Conductive material coatings; 4. Silver-plated wires; 5. Circuits for testing resistance changes. DETAILED DESCRIPTION

[0035] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0036] The present invention provides a method for preparing a flexible pressure sensor based on FDM 3D printing, which is applied in the preparation of the flexible pressure sensor.

[0037] Please refer to Figures 1 to 2 A method for preparing a flexible pressure sensor based on FDM 3D printing comprises the following steps:

[0038] S1. Print a cone-shaped three-dimensional part using an FDM 3D printer;

[0039] S2, compressing the cone three-dimensional part into a two-dimensional plane part;

[0040] S3, preparation of matrix materials with complex microstructures based on two-dimensional planar parts;

[0041] S4, plating conductive materials on the surface of complex microstructures;

[0042] S5. Assemble different base materials in a manner where the surfaces are opposite to each other to obtain a flexible pressure sensor.

[0043] From the above description, it can be seen that the beneficial effects of the present invention are: providing a method for preparing a flexible pressure sensor based on FDM3D printing. FDM3D printing, namely fused deposition 3D printing, has many advantages such as simple manufacturing process, low material and device cost, fast printing speed, and easy control of manufacturing parameters. Fused deposition 3D printing adopts layer-by-layer printing, which has the disadvantage of rough product surface, which is specifically reflected in the stratification of microstructure. By taking advantage of this disadvantage, the present invention can prepare the complex microstructure required for flexible pressure sensors in a low-cost manner, achieving low-cost, fast, simple manufacturing, and no need for a clean room environment to prepare flexible pressure sensors, overcoming the shortcomings of existing flexible pressure sensor preparation methods such as complex manufacturing process, high cost, long time, and the need for a clean room environment. The flexible pressure sensor prepared by the flexible pressure sensor preparation method based on FDM3D printing provided by the present invention has the advantages of high sensitivity, wide linear pressure range, good linearity, long service life, and good practicality.

[0044] In an optional embodiment, the step S1 specifically includes step S11:

[0045] Design a 3D model of a hollow cone in 3D design software and save the 3D model in STL format.

[0046] In an optional embodiment, the step S1 specifically includes step S12:

[0047] Import the 3D model in STL format into the slicing software, preset the extrusion speed, nozzle movement speed, extrusion temperature, substrate temperature and layer height, and then use the slicing software to generate the G-code file.

[0048] From the above description, it can be seen that although the designed hollow cone 3D model is a hollow cone with a smooth surface, due to the layered characteristics of the microstructure in FDM 3D printing, the printed hollow cone 3D part is a hollow cone with layered surfaces, and the layer height is equal to the preset layer height.

[0049] In an optional embodiment, the step S1 specifically includes step S13:

[0050] The G-code file was imported into the FDM 3D printer, and 3D printing was performed using PLA filament with a diameter of 1.5 to 1.75 mm to obtain a hollow conical three-dimensional part.

[0051] From the above description, it can be seen that the extrusion speed is set to 30-40 mm / s, the nozzle movement speed is set to 40-50 mm / s, the extrusion temperature is set to 210-220°C, the substrate temperature is set to 30-40°C, and the layer height is set to 0.2-0.6 mm.

[0052] In an optional embodiment, the step S2 specifically includes step S21:

[0053] The conical three-dimensional part is heated at an ambient temperature of 100 to 120° C. for 3 to 5 minutes, and a force is applied to the conical three-dimensional part for 50 to 70 seconds to obtain a two-dimensional plane part.

[0054] As can be seen from the above description, the purpose of setting the temperature to 100-120°C is to heat the hollow conical 3D part to a temperature above the glass transition temperature (55-75°C) and below the melting temperature (165-180°C), so that the hollow conical 3D part can be compressed into a 2D planar part without melting the microstructure. Due to the direct compression of the complex microstructure of the hollow conical 3D part, the upper surface of the 2D planar part has a complex microstructure. Since the 2D planar part is compressed from the hollow conical 3D part, the outer contour of the 2D planar part is a very small cylinder.

[0055] In an optional embodiment, the step S2 specifically includes step S22:

[0056] The two-dimensional plane part is placed at room temperature to cool while keeping the applied force constant.

[0057] From the above description, it can be seen that the purpose of maintaining weight compression when the two-dimensional planar part is cooled at room temperature is to avoid deformation of the two-dimensional planar part during cooling.

[0058] In an optional embodiment, the step S3 specifically includes step S31:

[0059] PDMS and a curing agent are mixed in a mass ratio of 9 to 11:1, and the mixture is stirred at a rotation speed of 20 to 30 rpm for 30 to 40 minutes to obtain a mixture.

[0060] In an optional embodiment, the step S3 specifically includes step S31:

[0061] The mixture is placed in a vacuum environment for 1 to 1.5 hours to obtain an electrode matrix material.

[0062] As can be seen from the above description, after the stirring is completed, the mixture of PDMS and the curing agent is placed in a vacuum environment for 1 to 1.5 hours to remove bubbles to obtain the electrode base material.

[0063] In an optional embodiment, the step S3 specifically includes step S32:

[0064] The electrode matrix material is placed in a container so that the plane of the electrode matrix with a complex microstructure faces the sealing liquid in the container. The container is then placed in a thermostat at a temperature of 40-45°C for 24-30 hours. The solidified sealing liquid is peeled off to obtain a solidified matrix material.

[0065] As can be seen from the above description, the prepared electrode matrix material is poured into a cylindrical container, the inner diameter of the cylindrical container is equal to the outer diameter of the two-dimensional planar part, the liquid level is 3-4mm, and the plane of the two-dimensional planar part with a complex microstructure is facing the liquid surface to seal the liquid. Another prepared electrode matrix material is poured into another cylindrical container, the inner diameter of the cylindrical container is equal to the outer diameter of the two-dimensional planar part, the liquid level is 3-4mm, and a circular plate with a smooth surface and an outer diameter equal to the inner diameter of the cylindrical container is sealed with the liquid. The cylindrical container is placed in an incubator, the incubator temperature is set to 40-45°C, and the storage time is 24-30 hours to solidify the sealed liquid. After solidification, the seal is peeled off and the solidified matrix material is removed to obtain an electrode 1 matrix with a complex surface microstructure, and a flat electrode 2 matrix with a smooth surface.

[0066] In an optional embodiment, the step S4 specifically includes step S41:

[0067] The conductive material is plated on the surface of the complex microstructure or smooth surface of different base materials by drop casting.

[0068] As can be seen from the above description, the specific operation of the drop casting method is: drop the conductive material solution in the form of droplets on the surface to be coated, the number of droplets is 10-15 drops, and the volume of each droplet is 80-100 μL.

[0069] Please refer to Figures 1 to 2 , Embodiment 1 of the present invention is: a method for preparing a flexible pressure sensor based on FDM 3D printing, comprising the following steps:

[0070] S1. Print a cone-shaped three-dimensional part using an FDM 3D printer;

[0071] S2, compressing the cone three-dimensional part into a two-dimensional plane part;

[0072] S3, preparation of matrix materials with complex microstructures based on two-dimensional planar parts;

[0073] S4, plating conductive materials on the surface of complex microstructures;

[0074] S5. Assemble different base materials in a manner where the surfaces are opposite to each other to obtain a flexible pressure sensor.

[0075] Please refer to Figures 1 to 2 The difference between the second embodiment of the present invention and the first embodiment is that:

[0076] The specific operations of step S1 are:

[0077] S101. Design a three-dimensional model of a hollow cone in a three-dimensional design software. The model is a smooth hollow cone, and save the three-dimensional model in an STL format.

[0078] S102, importing the three-dimensional model in STL format obtained in step S101 into slicing software, setting process parameters, including: extrusion speed, nozzle movement speed, extrusion temperature, substrate temperature and layer height; and generating a G-code file using the slicing software;

[0079] The extrusion speed is set to 30-40 mm / s, the nozzle movement speed is set to 40-50 mm / s, the extrusion temperature is set to 210-220°C, the substrate temperature is set to 30-40°C, and the layer height is set to 0.2-0.6 mm;

[0080] S103, importing the G-code file obtained in step S102 into an FDM 3D printer for 3D printing, using PLA filament with a diameter of 1.5-1.75 mm as the material; printing to obtain a hollow conical three-dimensional part;

[0081] Preferably, although the hollow cone 3D model designed in step S101 is a hollow cone with a smooth surface, due to the layered characteristics of the microstructure in FDM 3D printing, the hollow cone 3D part obtained in step S103 is a hollow cone with layered surfaces, and the layer height is equal to the layer height set in step S102;

[0082] The specific operation of step S2 is as follows: placing the hollow conical three-dimensional part obtained in step S1 on a heating plate at 100-120°C for 3-5 minutes, compressing the hollow conical three-dimensional part with a weight of 2-4 kg for 50-70 seconds, and compressing the hollow conical three-dimensional part into a two-dimensional flat part; after the compression is completed, the temperature of the heating plate is turned off while maintaining the weight compression, and the two-dimensional flat part is cooled at room temperature;

[0083] Preferably, the temperature of the heating plate is set to 100-120°C in order to heat the hollow conical three-dimensional part to a temperature above the glass transition temperature (55-75°C) and below the melting temperature (165-180°C), so as to compress the hollow conical three-dimensional part into a two-dimensional planar part without melting the microstructure.

[0084] Preferably, the two-dimensional planar part needs to be kept under weight compression when cooling at room temperature in order to avoid deformation of the two-dimensional planar part during cooling;

[0085] Preferably, the upper surface of the two-dimensional planar part has a complex microstructure due to direct compression of the complex microstructure of the three-dimensional part of the hollow cone;

[0086] Preferably, since the two-dimensional planar part is obtained by compressing the hollow cone three-dimensional part, the outer contour of the two-dimensional planar part is a cylinder with a very small height;

[0087] The specific operations of step S3 are:

[0088] S301, preparing a matrix material for an electrode with a complex microstructure; mixing PDMS and a curing agent in a mass ratio of 11:1-9:1 and introducing the mixture into a stirrer and stirring at a speed of 20 rpm-30 rpm for 30 minutes-40 minutes. After stirring, placing the mixture of PDMS and the curing agent in a vacuum desiccator for 1-1.5 hours to remove bubbles to obtain the matrix material for the electrode;

[0089] Preferably, the brand of PDMS can be RTV-615 or Sylgard 184;

[0090] Preferably, the curing agent can be an organic peroxide or cyclohexane diisocyanate trimer;

[0091] S302, pouring the electrode matrix material prepared in step S301 into a cylindrical container, wherein the inner diameter of the cylindrical container is equal to the outer diameter of the two-dimensional planar component, the liquid level is 3-4 mm, and the plane of the two-dimensional planar component with the complex microstructure is facing the liquid surface to seal the liquid;

[0092] S303, pouring the electrode matrix material prepared in step S301 into another cylindrical container, wherein the inner diameter of the cylindrical container is equal to the outer diameter of the two-dimensional planar component, the liquid level is 3-4 mm, and a circular plate with a smooth surface and an outer diameter equal to the inner diameter of the cylindrical container is sealed with the liquid;

[0093] S304, placing the sealing liquids of S302 and S303 into an incubator at a temperature of 40-45° C. for 24-30 hours to solidify the sealing liquids. After solidification, peeling off the seals and removing the solidified matrix material. The material obtained from S302 is an electrode 1 matrix with a complex surface microstructure, and the material obtained from S303 is a flat plate electrode 2 matrix with a smooth surface.

[0094] Preferably, the oven temperature is set to 40-45°C to keep the temperature below the glass transition temperature of PLA to prevent deformation of two-dimensional planar parts;

[0095] Preferably, two-dimensional planar parts can be reused, which greatly reduces manufacturing costs and time;

[0096] The specific operation of step S4 is: using a drop casting method to plate the conductive material on the surface of the electrode 1 substrate with a complex surface microstructure and the smooth surface of the flat electrode 2 substrate;

[0097] Preferably, the specific operation of the drop casting method is: dropping the conductive material solution in the form of droplets on the surface to be coated, the number of droplets is 10-15 drops, and the volume of each droplet is 80-100 μL;

[0098] Preferably, the conductive material is poly (3,4-ethylenedioxythiophene): polystyrene sulfonate) (PEDOT:PSS), which has the advantages of high flexibility, stretchability and low cost compared to other types of conductive materials (such as Ag nanowires);

[0099] The specific operation of step S5 is: assembling the electrode 1 with a complex surface microstructure and the flat electrode 2 obtained in step S4 in a manner such that the conductive material coating 3 is opposite to each other, and connecting the conductive material coating surfaces of the two electrodes to the circuit 5 for testing resistance changes with silver-plated wires 4.

[0100] The working principle of the flexible pressure sensor prepared by the present invention is as follows: pressure changes cause changes in the contact area between the complex microstructure surface and the plane between the two electrodes, which ultimately causes a change in resistance. The resistance change is measured by the circuit 5 for testing the resistance change to obtain the pressure change;

[0101] In order to verify the effectiveness of the method proposed in the present invention, a flexible pressure sensor was prepared using the method of the present invention, and the prepared flexible pressure sensor was subjected to performance testing. The test results obtained were: sensitivity of 160kPa-1, linear pressure range of 0-0.577kPa, linearity of 0.978, and durability of 2000 times at 4.7kPa. It is proved that the flexible pressure sensor prepared using the method of the present invention has superior sensitivity, wide linear pressure range, good linearity and excellent service life, which proves the effectiveness and practicality of the present invention.

[0102] The flexible pressure sensor prepared by the method of the present invention is applied in the following scenarios: directly contacting the skin and being installed on the human pulse or chest to detect blood pressure and heartbeat, and used for human health monitoring.

[0103] In summary, the present invention provides a method for preparing a flexible pressure sensor based on FDM3D printing. FDM3D printing, namely fused deposition 3D printing, has many advantages such as simple manufacturing process, low material and device cost, fast printing speed, and easy control of manufacturing parameters. Fused deposition 3D printing adopts layer-by-layer printing, which has the disadvantage of rough product surface, which is specifically reflected in the stratification of microstructure. The present invention can prepare the complex microstructure required for the flexible pressure sensor in a low-cost manner by taking advantage of this disadvantage, thereby achieving low-cost, fast, simple manufacturing, and the preparation of flexible pressure sensors without a clean room environment, overcoming the shortcomings of the existing flexible pressure sensor preparation method, such as complex manufacturing process, high cost, long time, and the need for a clean room environment. The flexible pressure sensor prepared by the flexible pressure sensor preparation method based on FDM3D printing provided by the present invention has the advantages of high sensitivity, wide linear pressure range, good linearity, long service life, and good practicality.

[0104] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a flexible pressure sensor based on FDM 3D printing, characterized in that: The following steps are involved: S1. Print a cone-shaped three-dimensional part using an FDM 3D printer; S2, compressing the cone three-dimensional part into a two-dimensional plane part; S3, preparation of matrix materials with complex microstructures based on two-dimensional planar parts; S3 specifically includes step S31: mixing PDMS and a curing agent in a mass ratio of 9 to 11:1, and stirring at a speed of 20 to 30 rpm for 30 to 40 minutes to obtain a mixture; S3 specifically includes step S32: placing the mixture in a vacuum environment for 1 to 1.5 hours to obtain an electrode matrix material; S3 specifically includes step S33: placing the electrode matrix material in a container, sealing the liquid with the plane of the two-dimensional planar part having the complex microstructure facing the liquid surface, then placing the container in an incubator at a temperature of 40-45°C for 24-30 hours, peeling off the solidified sealing liquid to obtain a solidified matrix material; S4, plating conductive materials on the surface of complex microstructures; S5. Assemble different base materials in a manner where the surfaces are opposite to each other to obtain a flexible pressure sensor.

2. The method for preparing a flexible pressure sensor based on FDM 3D printing according to claim 1, characterized in that: Said S1 specifically includes: Design and use FDM3D printing to produce hollow conical three-dimensional parts.

3. The method for preparing a flexible pressure sensor based on FDM 3D printing according to claim 1, characterized in that: The step S2 specifically includes step S21: The conical three-dimensional part is heated at an ambient temperature of 100-120° C. for 3-5 minutes, and a force is applied to the conical three-dimensional part for 50-70 seconds to obtain a two-dimensional planar part.

4. The method for preparing a flexible pressure sensor based on FDM 3D printing according to claim 3, characterized in that: The step S2 specifically includes step S22: The two-dimensional plane part is placed at room temperature to cool while keeping the applied force constant.

5. The method for preparing a flexible pressure sensor based on FDM 3D printing according to claim 1, characterized in that: The step S4 specifically includes step S41: The conductive material is plated on the surface of the complex microstructure or smooth surface of different base materials by drop casting.

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