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

Abstract

The application discloses a preparation method of a conical array flexible pressure sensor based on 3D printing. First, a 3D model of a required mold is made through modeling software, and the required model is printed by using a light-curing 3D printing technology. Then, a flexible organic matter is prepared, the flexible organic matter is added into the mold, and the mold is placed into a vacuum box to eliminate bubbles. Subsequently, the mold is placed on a 70 DEG C baking machine to solidify for 5 hours, and then the mold is demolded. Finally, the sample is immersed into a carbon nanotube (CNT) solution, and the CNT uniformly coated conical array flexible pressure sensor with a surface wrinkle microstructure is obtained after stirring. The light-curing 3D printing is used to realize the micron-level wrinkle microstructure of the conical array flexible pressure sensor, and the preparation method is simple, has high use repetition rate, short cycle and is easy to control.

Description

Technical Field

[0001] This invention relates to the field of electronic component manufacturing technology, specifically to a method for fabricating a flexible pressure sensor with a conical array based on 3D printing. Background Technology

[0002] As a novel sensor technology, flexible pressure sensors are primarily used in biomedicine, robotics, and smart home applications. Compared to traditional silicon-based pressure sensors, flexible pressure sensors offer advantages such as flexibility, lightweight design, low cost, and ease of molding. In smart homes, flexible pressure sensors can be used in furniture such as mattresses and sofas for intelligent detection and adjustment. In human-computer interaction technology, flexible sensors can improve the flexibility and comfort of wearable devices. In the medical field, applying flexible pressure sensors to surgical instruments can not only improve treatment outcomes but also reduce medical risks.

[0003] Parameters used to evaluate the performance of pressure sensors include sensitivity, pressure range, response time, and repeatability. Since piezoresistive pressure sensors operate on the principle of changing the resistance of the contact surface when pressure is applied, improving the overall performance of flexible sensors can involve altering their surface geometry and hierarchical structure to reduce internal resistance and increase compressibility. Many researchers have attempted to create microstructures such as pyramids, domes, or cylinders and replicate these microstructures using polydimethyloxane (PDMS). However, introducing such microstructures requires complex processes, is time-consuming, and costly, making it difficult to achieve both a wide pressure sensing range and high sensitivity.

[0004] Therefore, a cost-effective and simple fabrication process is needed to create high-sensitivity surface microstructures for flexible pressure sensors. To achieve this, some researchers have turned to 3D printing technology, which is inexpensive and easy to operate. While some have attempted to fabricate microstructures using fused deposition modeling (FDM) or ink-writing (DIW) 3D printing techniques, these methods offer relatively low precision. Creating more complex and precise microstructures and achieving high sensitivity and wide pressure range sensing in microstructured pressure sensors using simple fabrication processes remains a key research challenge in the field of flexible pressure sensors and a crucial foundation for their industrialization. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by proposing a 3D-printed, cone-shaped array flexible pressure sensor and its fabrication method. This sensor achieves highly sensitive force-to-electrical signal conversion over a wide pressure range, exhibiting fast response speed and good repeatability. Furthermore, it boasts high repeatability and low fabrication cost using 3D modeling molds.

[0006] Technical solution

[0007] The object of the present invention is to provide a preparation method of a conical array flexible pressure sensor based on 3D printing, including the following steps:

[0008] S1. Design the 3D model of the conical hole array mold

[0009] Use modeling software to design a groove mold, and a closely arranged conical small hole array is provided in the groove mold.

[0010] Based on the designed groove mold model, use a light-curing printer to fix the printing platform of the light-curing printer at a preset angle, and perform layer-by-layer printing on the printing platform to obtain a groove mold;

[0011] The conical small holes on the groove mold all have a wrinkled microstructure formed by layer-by-layer printing of the light-curing printer.

[0012] S2. Preparation of the conical array PDMS

[0013] Mix the PDMS main agent and the curing agent and pour them into the groove mold. After curing, demold from the groove mold to obtain the conical array PDMS.

[0014] S3. Conductive integration on the surface of the conical array PDMS

[0015] Prepare a CNT and deionized water mixture according to a mass ratio of 1:10. Immerse the conical array PDMS in the above mixture, take it out after magnetic stirring, and place it in an oven at 70-90 °C for drying to obtain a conical array CNT / PDMS conductive functional layer uniformly coated with CNT.

[0016] S4. Preparation of the flexible pressure sensor with a conical array microstructure

[0017] Place the upper electrode and the lower electrode parallel to the upper and lower sides of the conical array CNT / PDMS conductive functional layer respectively to obtain a flexible pressure sensor with a conical array microstructure.

[0018] As a preference, in the step S1, when modeling, set the spacing in the sketch design, the interval between two cones is 0.1-0.3 mm, and set the printing accuracy to 0.1-0.3 mm according to the interval of the model during printing;

[0019] The light-curing printer uses a high-temperature resistant photosensitive resin.

[0020] Let the preset angle be a, and the range of a is as follows:

[0021] Let the optimal printing angle of the printing platform of the light-curing printer be b, 0.99b < a < b, or b < a < 1.01b

[0022] The optimal printing angle b is calculated as follows:

[0023] b = arctan(c / d)

[0024] Where c is the layer height parameter set on the light curing printer, and d is the pixel width parameter set on the light curing printer h;

[0025] The aforementioned folded microstructure refers to the following: Due to the principle of photopolymerization layer-by-layer printing, the model to be printed is first divided into horizontal layers. The photopolymerization printer projects the shape of the previous layer onto the photosensitive resin for photopolymerization. After the previous layer is formed, the model rises slightly, and then the shape of the next layer is printed. This process is repeated to create the required mold. After printing, a folded structure is left on the entire surface of the mold. On the conical surface of the conical part of the mold, the folded microstructure is arranged in a spiral pattern from top to bottom, while the folded microstructure on the planar part of the mold is arranged in a parallel stripe pattern. The spacing between the stripes in the folded microstructure is 50–100 micrometers; the spacing between the threads in the folded microstructure is 50–100 micrometers.

[0026] Preferably, in step S2, the diameter of the bottom circle of each cone of the prepared conical array PDMS is about 1 to 3 mm, the height of the cone is about 0.5 to 3 mm, and the thickness of the PDMS block is about 1 to 2 mm.

[0027] Preferably, in step S2, the main agent is polydimethyl-methylvinylsiloxane and the curing agent is polydimethyl-methylhydrosiloxane.

[0028] Preferably, both the upper and lower electrodes are conductive copper foils. The flexible pressure sensor with the conical array microstructure obtained in step S4 has a response time of 15 ms and a recovery time of 13 ms, respectively; and a sensitivity of 32.24 kPa in the pressure range of 0-0.11 kPa. -1 .

[0029] This invention has the following characteristics and beneficial effects:

[0030] Using the above technical solution, polydimethylsiloxane (PDMS) is used as a flexible substrate. A densely packed conical array is constructed on the mold surface using photopolymerization 3D printing technology. Each conical array and the substrate contain uniformly distributed folded microstructures of approximately 50–100 micrometers. After demolding, carbon nanotubes are impregnated onto the PDMS surface of the microstructure to serve as the conductive functional layer. The 3D modeling mold used to introduce the microstructure is inexpensive, reusable, allows for manual adjustment of structural parameters, and has a high reusability rate, ensuring the production efficiency of this flexible sensor.

[0031] A flexible piezoresistive pressure sensor is constructed by sandwiching a microstructure conductive functional layer with two copper foil electrodes. This enables highly sensitive sensing of force signals to electrical signals over a wide pressure range, with fast response speed and good repeatability of the response signal.

[0032] Furthermore, the manufacturing process is simple and inexpensive, the molds are reusable, and the mold parameters can be manually adjusted, greatly reducing manufacturing costs. The raw materials used for the molds are inexpensive, non-toxic, non-polluting, and environmentally friendly, making them suitable for mass production.

[0033] Its overall structure is thin, light and flexible, making it suitable for new wearable devices and possessing extremely high market value and industrialization potential. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the cone array CNT / PDMS model and structure in an embodiment of the present invention. The schematic diagram shows the cone array PDMS prepared in step S2, which includes: a PDMS block and conical protrusions located on the upper surface of the PDMS block, where d is the spacing between the conical protrusions, h1 is the height of the cone, and h2 is the thickness of the PDMS block.

[0036] Figure 2 The schematic diagram of sensor performance testing prepared according to an embodiment of the present invention consists of a stepper motor, a controller, a precision balance computer, and a digital source instrument.

[0037] Figure 3 The pressure-current step response curve of the sensor in this embodiment of the invention records the current feedback of the sensor under four different pressures.

[0038] Figure 4 This is a pressure-current response / recovery time curve of the sensor in an embodiment of the present invention. The left side is the response time after applying pressure, and the right side is the recovery time after releasing pressure.

[0039] Figure 5 The graph shows the relationship between pressure and current of the sensor fabricated by the CNT / PDMS conductive functional layer in this embodiment of the invention. The sensor exhibits better sensitivity in the low-pressure region (sensitivity is the slope of the current-pressure curve in the graph). Detailed Implementation

[0040] This invention provides a 3D-printed conical array flexible pressure sensor and its fabrication method, comprising the following steps:

[0041] S1. Design a 3D model of a conical hole array mold.

[0042] The groove mold is designed using modeling software, and a dense array of conical holes is designed inside the groove. After printing layer by layer with a photopolymerization printer, the wrinkled microstructure of the conical surface is obtained.

[0043] Unlike common fused deposition modeling (FDM) printing, S1 uses stereolithography (SLA) to construct 3D solids by irradiating photosensitive resin with ultraviolet light. First, a 3D structural design model to be printed is created using Solidworks modeling software. The photosensitive resin is then introduced into the printer's print chamber, and the printing platform is fixed using positioning jigs, adjusting its position and angle. Because stereolithography printing has extremely high precision, a suitable angle results in a smooth, wrinkle-free print surface. The arctan(layer height / pixel width) of the printing angle needs to be controlled within 1% of 45°, excluding the optimal 45° printing angle. At this angle, the printed model will have a jagged structure. In S2, this jagged structure is molded using PDMS, and only then does the mold achieve a wrinkled structure.

[0044] Once everything is set up, start the printer and focus the ultraviolet light on the designated area. When the ultraviolet light shines on the surface of the photosensitive resin, it causes a polymerization reaction, curing each cross-section of the printed object layer by layer. As printing progresses, the printer will gradually raise the printing platform from the slot to continue printing the next layer of structure until the entire model is printed.

[0045] S2, Preparation of cone-shaped array PDMS (polydimethylsiloxane)

[0046] Mix the main agent and curing agent in a petri dish at a mass ratio of 10:1 until homogeneous. Place the dish in a vacuum chamber to remove air bubbles and pour the mixture into a 3D printed mold. Then place the mold on a 70-90℃ baking machine. After curing, demold the PDMS block from the mold and cut the cured PDMS block into small rectangular pieces.

[0047] S3, Conductive Integration on the Surface of a Conical Array PDMS

[0048] A CNT and deionized water mixture was prepared at a mass ratio of 1:10. The conical array PDMS was immersed in the mixture, magnetically stirred, and then placed in an oven to dry for several hours to obtain a CNT / PDMS conductive functional layer uniformly coated with CNTs.

[0049] S4. Fabrication of a flexible pressure sensor with a conical array microstructure.

[0050] Conductive copper foils are placed parallel to each other on the upper and lower sides of the conical array CNT / PDMS conductive functional layer to form the upper and lower electrodes, and wires are led out from the upper and lower electrodes.

[0051] This invention also discloses a flexible pressure sensor based on a conical array fabricated using 3D printing, such as... Figure 1 As shown, the flexible pressure sensor with a conical array fabricated by 3D printing was prepared using the method provided in the above embodiment.

[0052] This embodiment tests the performance of the fabricated pressure sensor, and the test data is used to further illustrate its performance:

[0053] During testing, such as Figure 2 As shown, the upper electrode is fixed on a vertically displaced electrically controlled displacement platform, and the lower electrode is placed on the surface of a precision balance. The upper and lower electrodes are connected to a digital source meter by copper foil. The electrically controlled displacement platform is driven by a stepper motor to apply pressure to the upper electrode of the conical array flexible pressure sensor. The change of current signal with different pressures is measured by the digital source meter.

[0054] Based on the test results, such as Figure 3 As shown, the conical array microstructure flexible pressure sensor prepared by this invention can respond quickly to different pressures and has good repeatability of the response signal. Figure 4 This indicates that the flexible pressure sensor with a conical array microstructure prepared in this invention has rapid response and recovery capabilities to pressure, with response and recovery times of 15 ms and 13 ms, respectively. Furthermore, as... Figure 5 As shown, the honeycomb microstructure flexible pressure sensor prepared by this invention can achieve highly sensitive sensing of force signals to electrical signals over a wide pressure range, with a sensitivity as high as 32.24 kPa. -1 .

[0055] In summary, the test results show that the technical solution provided by the embodiments of the present invention not only simplifies the process and reduces costs, but also significantly improves the performance of the resulting flexible pressure sensor.

[0056] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments, including components, without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for fabricating a flexible pressure sensor with a conical array based on 3D printing, characterized in that, Includes the following steps: S1. Design a 3D model of a conical hole array mold. A groove mold was designed using modeling software. The groove mold has a closely spaced array of conical holes inside. Based on the designed groove mold model, a UV-curing printer is used to fix the printing platform of the UV-curing printer at a preset angle, and the printing is performed layer by layer on the printing platform to obtain the groove mold. The conical holes on the groove mold all have folded microstructures formed by layer-by-layer printing by the photopolymer printer; Let the preset angle be 'a', and the range of 'a' is as follows: Let the optimal printing angle of the printing platform of the aforementioned photopolymer printer be b, where 0.99b < a < b, or b < a < 1.01b. The optimal printing angle b is calculated as follows: b = arctan(c / d) Where c is the layer height parameter set on the light-curing printer, and d is the pixel width parameter set on the light-curing printer h; The aforementioned wrinkled microstructure refers to the following: Due to the principle of layer-by-layer photopolymerization printing, the model to be printed is first divided into horizontal layers. The photopolymerization printer projects the shape of the previous layer onto the photosensitive resin for photopolymerization. After the previous layer is formed, the model rises slightly, and then the shape of the next layer is printed. This process of layering is repeated to print the required mold. After printing, a wrinkled structure is left on the entire surface of the mold. On the conical surface of the conical part of the mold, the wrinkled microstructure is arranged in a spiral pattern from top to bottom, while the wrinkled microstructure on the planar part of the mold is arranged in a parallel stripe pattern. The spacing between the stripes in the wrinkled microstructure is 50-100 micrometers; the spacing between the threads in the wrinkled microstructure is 50-100 micrometers. S2, Fabrication of cone-shaped PDMS array The PDMS main agent and curing agent are mixed and poured into the groove mold. After curing, the mixture is demolded from the groove mold to obtain a cone-shaped array of PDMS. S3, Conductive Integration on the Surface of a Conical Array PDMS A CNT and deionized water mixture was prepared at a mass ratio of 1:

10. The conical array PDMS was immersed in the mixture, magnetically stirred, and then placed in an oven at 70~90℃ to dry, thus obtaining a CNT uniformly coated conical array CNT / PDMS conductive functional layer. S4. Fabrication of a flexible pressure sensor with a conical array microstructure. The upper and lower electrodes are placed parallel to each other on the upper and lower sides of the cone array CNT / PDMS conductive functional layer, respectively, to obtain a flexible pressure sensor with a cone array microstructure.

2. The method for fabricating a flexible pressure sensor based on a 3D-printed conical array according to claim 1, characterized in that, In step S1, when modeling, the spacing is set in the sketch design, with the spacing between any two cones being 0.1-0.3mm. When printing, the printing accuracy is set to 0.1-0.3mm according to the spacing of the model. The photopolymer printer uses a high-temperature resistant photosensitive resin.

3. The method for fabricating a flexible pressure sensor based on a 3D-printed conical array according to claim 1, characterized in that, In step S2, the diameter of the bottom circle of each cone of the prepared conical array PDMS is 1~3mm, the height of the cone is 0.5~3mm, and the thickness of the PDMS block is 1~2mm.

4. The method for fabricating a flexible pressure sensor based on a 3D-printed conical array according to claim 1, characterized in that, In step S2, the main agent is polydimethyl-methylvinylsiloxane.

5. The method for fabricating a flexible pressure sensor based on a 3D-printed conical array according to claim 1, characterized in that, In step S2, the curing agent is polydimethyl-methylhydrosiloxane.

6. The method for fabricating a flexible pressure sensor based on a 3D-printed conical array according to claim 1, characterized in that, Both the upper and lower electrodes are conductive copper foils.

7. The method for fabricating a 3D-printed conical array flexible pressure sensor as described in claim 6, characterized in that, The flexible pressure sensor with the conical array microstructure obtained in step S4 has a response time of 15 ms and a recovery time of 13 ms; its sensitivity reaches 32.24 kPa in the pressure range of 0-0.11 kPa. -1 .

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