Three-dimensional porous piezoresistive sensor and melting 3D printing preparation method thereof

Abstract

The invention belongs to the technical field of piezoresistive sensors, and relates to a three-dimensional porous piezoresistive sensor and a fusion 3D printing preparation method thereof.The three-dimensional porous piezoresistive sensor is prepared through fusion 3D printing, and the number of printing layers is one; the three-dimensional porous piezoresistive sensor comprises a conductive material unit and a piezoresistive material unit, the conductive material unit is planar, and the piezoresistive material unit is in a shape formed by connecting a plurality of arched structures and is distributed on the surface of one side of the conductive material unit; the material A and the material B are extruded from the same nozzle of a fusion 3D printer and then printed on a bottom plate, and the three-dimensional porous piezoresistive sensor is obtained after cooling; the shrinkage rate of the material A is 3-6% higher than that of the material B, and the shrinkage rate of the material B is smaller than or equal to 0.6%; the material A is a piezoresistive material containing a foaming agent, and the material B is a conductive material; the nozzle temperature is higher than the foaming temperature of the foaming agent. According to the piezoresistive sensor, the response sensitivity to micro pressure can be improved; the preparation method is simple.

Description

Technical Field

[0001] This invention belongs to the field of fused 3D printing technology and relates to a three-dimensional porous piezoresistive sensor and its fused 3D printing preparation method. Background Technology

[0002] Fused 3D printing technology has the advantages of flexible design and rapid prototyping, and its use in fabricating piezoresistive sensors has become a research hotspot.

[0003] The working principle of a piezoresistive sensor is as follows: under the action of external force, the morphology of the conductive network inside the piezoresistive material changes, resulting in a corresponding change in resistance. By detecting this resistance signal, the magnitude of the force can be measured. The measurement accuracy of the sensor is affected by its sensitivity, which is closely related to the deformation of the device under pressure. Therefore, a structural design with excellent deformation capability helps to improve the sensitivity of the piezoresistive sensor. Porous structures, because they can undergo significant deformation under external pressure, can more sensitively sense pressure changes and are widely used in the design of piezoresistive sensors.

[0004] In recent years, piezoresistive sensors fabricated using melt printing technology have achieved porous structures. For example, patent CN202311323889.2 discloses a porous core-shell flexible piezoresistive sensor and its melt printing fabrication method. This sensor is internally composed of stacked wires with a porous core-shell structure, where the skin layer is a piezoresistive material containing micropores, and the core layer is a conductive material without micropores. However, the sensor fabricated by this method is still limited to a planar structure, and its deformation capability under pressure is limited, resulting in insufficient pressure response sensitivity and hindering further improvement in sensor performance.

[0005] Existing fused deposition modeling (FDM) technology produces planar (single-layer) products. To achieve multi-layer printing, it is necessary to stack layers to create a three-dimensional entity.

[0006] Therefore, it is of great significance to study a three-dimensional porous piezoresistive sensor and its fused 3D printing preparation method to solve the problems existing in the prior art. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide a three-dimensional porous piezoresistive sensor and its fused 3D printing preparation method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A three-dimensional porous piezoresistive sensor was prepared by melt 3D printing with a single printing layer.

[0010] The three-dimensional porous piezoresistive sensor includes a conductive material unit and a piezoresistive material unit. The conductive material unit is planar, while the piezoresistive material unit is a shape formed by multiple interconnected arched structures and is distributed on one side of the conductive material unit.

[0011] As a preferred technical solution:

[0012] The three-dimensional porous piezoresistive sensor described above is formed by cooling and solidifying a composite filament obtained by fused 3D printing. The micropore volume ratio in the composite filament is 10~40%, the micropores are spindle-shaped, and the equivalent circle diameter of the micropores is 10~150μm.

[0013] The three-dimensional porous piezoresistive sensor described above has an arch structure with a height of 0.25~0.35mm and a width of 0.75mm for each arch structure.

[0014] The three-dimensional porous piezoresistive sensor described above has a conductive material unit thickness of 1.2~1.25mm.

[0015] The three-dimensional porous piezoresistive sensor described above has a compression deformation of 0.2~0.3mm and a sensitivity of 3~5kPa. -1 Sensitivity = resistance change rate (ΔR / R0) / pressure (kPa), where ΔR is the resistance change value and R0 is the initial resistance.

[0016] Existing layered stacked structures are dense structures under external forces, resulting in very small deformation. Existing technologies also include three-dimensional structures such as frustum, pyramid, and hemispherical shapes. Compared to three-dimensional arched structures, these require more time to form, and under the same external force, the deformation of existing devices is smaller than that of this invention, resulting in lower sensitivity.

[0017] The present invention also provides a method for fabricating a three-dimensional porous piezoresistive sensor by fused 3D printing as described in any of the preceding claims, wherein material A and material B are extruded from the same nozzle of a fused 3D printer and printed onto a base plate, and the three-dimensional porous piezoresistive sensor is obtained after cooling.

[0018] Material A has a shrinkage rate 3-6% greater than material B (referring to the relative deviation, the percentage increase in shrinkage rate of material A relative to the shrinkage rate of material B), while the shrinkage rate of material B is ≤0.6%.

[0019] Material A is a piezoresistive material containing a foaming agent, and material B is a conductive material;

[0020] The nozzle temperature is higher than the foaming temperature of the foaming agent;

[0021] The nozzle comprises two spaced-apart channels, I and II. Channel I conveys material A, and channel II conveys material B. The outlets of channels I and II converge at an inverted frustum structure, and the melt is extruded from the smaller end of the frustum structure. The diameter of channel I is smaller than that of channel II. For the extruded composite filament, the cross-sectional diameter of material A must be smaller than that of material B because A needs to form an arch, and its shrinkage rate is greater than that of B. B needs to be slightly thicker to provide support. Otherwise, the arched shape of A would pull B away from the printing plate, making it impossible to obtain the piezoresistive device.

[0022] The printing speed is 1000~1500mm / min.

[0023] As a preferred technical solution:

[0024] In the above-described method for fabricating a three-dimensional porous piezoresistive sensor by fused deposition modeling, the temperature of the substrate is 80-120°C lower than T1, preferably 80-90°C lower than T1, where T1 is the lower of the viscous flow temperatures of materials A and B.

[0025] The above-described method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing comprises material A, a foaming agent, and a polymer matrix A. The conductive filler A and the foaming agent are uniformly distributed in the polymer matrix A, with the conductive filler A content being 0.3~3wt% and the foaming agent content being 1~10wt%.

[0026] The conductive filler A is carbon black, carbon nanotubes, graphene, expanded graphite, carbon fiber, or silver nanowires.

[0027] The foaming agent is AC foaming agent or thermally expanded microspheres, and the foaming temperature is 180~220℃;

[0028] The polymer matrix A is thermoplastic polyurethane (TPU) or thermoplastic elastomer (TPE).

[0029] The above-described method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing involves a material B composed of a conductive filler B and a polymer matrix B. The conductive filler B is uniformly distributed within the polymer matrix B, and its content is 0.5~10 wt%.

[0030] The conductive filler B is carbon black, carbon nanotubes, graphene, expanded graphite, carbon fiber, or silver nanowires.

[0031] The polymer matrix B is polylactic acid (PLA) or acrylonitrile-butadiene-styrene copolymer (ABS).

[0032] The above-described method for fabricating a three-dimensional porous piezoresistive sensor using fused 3D printing involves a wavy or straight filling path during printing, preferably a wavy one. A wavy printing path ensures better mechanical stability and is less prone to collapse. Furthermore, a wavy path has more contact units per unit area, making it more sensitive to changes in external forces.

[0033] Invention principle:

[0034] Existing technologies typically employ fused deposition modeling (FDM) to print planar structures, which are then stacked layer by layer to form a three-dimensional structure. In this invention, two materials are extruded through different channels of the same nozzle, strictly limiting the difference in shrinkage rates between the two materials. This ensures that part of the extruded composite filament arches into an arch shape, while the other part serves as a support, adhering to a base plate. Upon cooling and solidification, the composite filament forms a piezoresistive sensor with a three-dimensional arched structure. The arched portion of the composite filament is the piezoresistive material, also possessing a porous structure; the straight portion is the conductive material. Under external force, the arch is compressed and deformed (its height decreases), altering the internal conductive network and changing the resistance. If this invention also involved layer-by-layer stacking, the bottom composite filament would be subjected to compression from subsequent layers, leading to the loss of the arched structure.

[0035] Furthermore, in this invention, ensuring the synchronous extrusion of the two materials while forming a continuous three-dimensional arched structure makes the control of the printing speed crucial. If the printing speed exceeds 1500 mm / min, the extruded composite filament becomes thinner due to stretching force, reducing the contact area between the two materials and weakening the adhesion, which may prevent the formation of an arched structure due to the difference in shrinkage rates. If the printing speed is below 1000 mm / min, the two materials are fully bonded and foamed sufficiently, but an arched structure may still not be formed.

[0036] Beneficial effects:

[0037] (1) The three-dimensional porous piezoresistive sensor of the present invention can directly present a three-dimensional structure without post-processing, which expands the structure and shape of the piezoresistive sensor and is beneficial to improving the response sensitivity to small pressures.

[0038] (2) The present invention provides a fused 3D printing method for fabricating a three-dimensional porous piezoresistive sensor, which is simple and easy to operate. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the cross-section of the composite fuse before and after melt extrusion (foaming);

[0040] Figure 2 This is a schematic diagram of the printing path for a piezoresistive sensor.

[0041] Figure 3This is a schematic diagram of a three-dimensional porous piezoresistive sensor;

[0042] Figure 4 This is a schematic diagram showing the height (deformation) of a piezoresistive sensor before and after being subjected to an external force.

[0043] Figure 5 This is a schematic diagram of the nozzle of the 3D printer used in this invention;

[0044] Figure 6 The cross-sectional distribution of the composite filament extruded in Example 1;

[0045] Wherein, 1-conductive material B, 2-piezoresistive material A, and 3-foaming agent. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] The test methods involved in the performance indicators in the embodiments and comparative examples of this invention are as follows:

[0048] Shrinkage rate: Tested in accordance with GB / T 2951.13-2008.

[0049] Extrusion deformation: refers to the change in height of an arch bridge after being compressed under vertical pressure. Extrusion deformation is measured using a dial indicator (Mitutoyo 543-705B, Japan). The specific procedure is as follows: place the dial indicator probe against the top of the arch bridge, zero it, apply a compressive load of 5N, and the change in the dial indicator reading is the deformation.

[0050] Viscous flow temperature: tested using a rotational rheometer.

[0051] Example 1

[0052] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0053] (1) Preparation of piezoresistive material A: Carbon black (manufacturer: Adamas, grade: 01018339), AC foaming agent (manufacturer: Shanghai McLean Biochemical Technology Co., Ltd., grade: CAS: 123-77-3) and thermoplastic polyurethane (manufacturer: BASF Germany, grade: Elastollan® 1185A) constitute piezoresistive material A; carbon black and AC foaming agent are uniformly distributed in thermoplastic polyurethane, and the carbon black content is 0.3wt% and the AC foaming agent content is 1wt%; the foaming temperature of AC foaming agent is 180℃; the viscous flow temperature of piezoresistive material A is 170℃ and the shrinkage rate is 0.42%;

[0054] (2) Preparation of conductive material B: Carbon black (manufacturer: Adamas, grade: 01018339) and polylactic acid (brand: NatureWorks, model: Ingeo™ 3D850) are used to form conductive material B. The carbon black is uniformly distributed in the polylactic acid and the carbon black content is 0.5wt%. The viscous flow temperature of conductive material B is 160℃ and the shrinkage rate is 0.4%.

[0055] (3) such as Figure 1 , Figure 5 As shown, a piezoresistive material A1 (i.e., piezoresistive material containing foaming agent 3) and conductive material B2 with a mass ratio of 7:10 were extruded from the same nozzle of a fused 3D printer and printed onto a base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0056] The filling path during printing is wavy; the nozzle temperature is 200℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1500mm / min; and the substrate temperature is 80℃.

[0057] The micropore volume accounts for 10% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 10 μm.

[0058] like Figures 2-3 As shown, the final fabricated three-dimensional porous piezoresistive sensor has one printing layer. The sensor consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.25 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.2 mm. Figure 4 As shown, the extrusion deformation of the three-dimensional porous piezoresistive sensor is 0.2 mm, and its sensitivity is 3 kPa. -1 .

[0059] The cross-sectional distribution of the extruded composite fuse is as follows Figure 6 As shown, the left side is conductive material B (1.25mm), and the right side is piezoresistive material A (0.75mm).

[0060] Comparative Example 1

[0061] A method for fabricating a three-dimensional porous piezoresistive sensor by fused deposition modeling is basically the same as in Example 1, except that: in step (1), the shrinkage rate of piezoresistive material A is 2.4% greater than that of conductive material B, that is, the carbon black content in conductive material B is 0.3wt%, and the shrinkage rate of conductive material B is 0.41%.

[0062] The final fabricated three-dimensional porous piezoresistive sensor has an extrusion deformation of 0.15 mm and a sensitivity of 2.5 kPa. -1 .

[0063] Comparing Comparative Example 1 and Example 1, it can be found that the difference in shrinkage rate between the two is small, the extrusion deformation of the arch bridge is smaller, and the sensitivity of the device is reduced. This is because if the difference in shrinkage rate is too small, the arc of the arch structure formed by the material with a large shrinkage rate will be too small, the deformation of the arch during the pressing process will be small, and the sensitivity of the sensor device will be poor.

[0064] Comparative Example 2

[0065] A method for fabricating a three-dimensional porous piezoresistive sensor by fused 3D printing is basically the same as in Example 1, except that: in step (1), the shrinkage rate of piezoresistive material A is 7.5% greater than that of conductive material B, that is, the carbon black content in piezoresistive material A is 0.1wt%, and the shrinkage rate of piezoresistive material A is 0.43%.

[0066] The final fabricated three-dimensional porous piezoresistive sensor has an extrusion deformation of 0.23 mm and a sensitivity of 0.08 kPa. -1 .

[0067] Comparing Comparative Example 2 and Example 1, it can be found that the difference in shrinkage rate between the two is large, the extrusion deformation of the arch bridge is larger, and the sensitivity of the device is reduced. This is because the large difference in shrinkage rate will cause the arch structure formed by the material with a large shrinkage rate to have greater stress during the cooling process of the composite fuse. During the pressing process, the arch piezoresistive material will generate greater resistance, making the output performance of the sensor device unstable and shortening its service life.

[0068] Comparative Example 3

[0069] A method for fabricating a three-dimensional porous piezoresistive sensor by fused 3D printing is basically the same as in Example 1, except that the printing speed in step (1) is 900 mm / min.

[0070] Comparing Comparative Example 3 and Example 1, it can be found that the sensor device could not be fabricated. This is because the printing speed is less than 1000 mm / min, the two materials are fully bonded and the foaming is also very sufficient, making it impossible to form an arched structure.

[0071] Comparative Example 4

[0072] A method for fabricating a three-dimensional porous piezoresistive sensor by fused 3D printing is basically the same as in Example 1, except that the printing speed in step (1) is 1600 mm / min.

[0073] Comparing Comparative Example 4 and Example 1, it can be found that the sensor device cannot be fabricated. This is because the printing speed is higher than 1500 mm / min, and the extruded composite filament becomes thinner due to the stretching force. The contact area between the two materials is reduced, the adhesion is worse, and the arched structure cannot be formed due to the difference in shrinkage rate.

[0074] Example 2

[0075] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0076] (1) Preparation of piezoresistive material A: Piezoresistive material A is composed of carbon nanotubes (manufacturer: Saen Chemical Technology (Shanghai) Co., Ltd., grade: 308068-56-6), thermally expanded microspheres (manufacturer: American Boliken, grade: 220DU30) and thermoplastic elastomer (manufacturer: Korean SK Corporation, grade: S2008); carbon nanotubes and thermally expanded microspheres are uniformly distributed in thermoplastic elastomer, and the content of carbon nanotubes is 1wt% and the content of thermally expanded microspheres is 2wt%; the foaming temperature of thermally expanded microspheres is 190℃; the viscous flow temperature of piezoresistive material A is 190℃ and the shrinkage rate is 0.53%;

[0077] (2) Preparation of conductive material B: Carbon nanotubes (manufacturer: SABIC Chemical Technology (Shanghai) Co., Ltd., brand: 308068-56-6) and acrylonitrile-butadiene-styrene copolymer (brand: SABIC, model: CYCOLAC™ MG94) constitute conductive material B. The carbon nanotubes are uniformly distributed in the acrylonitrile-butadiene-styrene copolymer, and the carbon nanotube content is 5wt%. The viscous flow temperature of conductive material B is 200℃, and the shrinkage rate is 0.5%.

[0078] (3) Piezoresistive material A and conductive material B with a mass ratio of 4:5 were extruded from the same nozzle of the fused 3D printer and printed onto the base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0079] The filling path during printing is wavy; the nozzle temperature is 230℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1100mm / min; and the substrate temperature is 100℃.

[0080] The micropore volume accounts for 20% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 40 μm.

[0081] The final fabricated three-dimensional porous piezoresistive sensor has one printing layer. It consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.3 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.23 mm. The three-dimensional porous piezoresistive sensor has a compression deformation of 0.23 mm and a sensitivity of 3.5 kPa. -1 .

[0082] Example 3

[0083] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0084] (1) Preparation of piezoresistive material A: piezoresistive material A is composed of graphene (manufacturer: Saen Chemical Technology (Shanghai) Co., Ltd., grade: A60116), AC foaming agent (manufacturer: Shanghai McLean Biochemical Technology Co., Ltd., grade: CAS: 123-77-3) and thermoplastic polyurethane (manufacturer: BASF Germany, grade: Elastollan® 1185A); graphene and AC foaming agent are uniformly distributed in thermoplastic polyurethane, and the graphene content is 1.5wt% and the AC foaming agent content is 4wt%; the foaming temperature of AC foaming agent is 210℃; the viscous flow temperature of piezoresistive material A is 175℃ and the shrinkage rate is 0.31%;

[0085] (2) Preparation of conductive material B: Graphene (manufacturer: Saen Chemical Technology (Shanghai) Co., Ltd., brand: A60116) and polylactic acid (brand: NatureWorks, USA, model: Ingeo™ 3D850) constitute conductive material B. Graphene is uniformly distributed in polylactic acid, and the content of graphene is 2wt%. The viscous flow temperature of conductive material B is 165℃, and the shrinkage rate is 0.3%.

[0086] (3) Piezoresistive material A and conductive material B with a mass ratio of 3:4 were extruded from the same nozzle of the fused 3D printer and printed onto the base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0087] The filling path during printing is wavy; the nozzle temperature is 210℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1400mm / min; and the substrate temperature is 85℃.

[0088] The micropore volume accounts for 25% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 60 μm.

[0089] The final fabricated three-dimensional porous piezoresistive sensor has one printing layer. It consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.28 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.23 mm. The extrusion deformation of the three-dimensional porous piezoresistive sensor is 0.25 mm, and its sensitivity is 3.2 kPa. -1 .

[0090] Example 4

[0091] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0092] (1) Preparation of piezoresistive material A: Expanded graphite (manufacturer: Saen Chemical Technology (Shanghai) Co., Ltd., grade: A62064), thermally expanded microspheres (manufacturer: American Boliken, grade: 220DU30) and thermoplastic elastomer (manufacturer: Korean SK Corporation, grade: S2008) constitute piezoresistive material A; expanded graphite and thermally expanded microspheres are uniformly distributed in thermoplastic elastomer, and the content of expanded graphite is 3wt% and the content of thermally expanded microspheres is 5wt%; the foaming temperature of thermally expanded microspheres is 220℃; the viscous flow temperature of piezoresistive material A is 200℃, and the shrinkage rate is 0.63%;

[0093] (2) Preparation of conductive material B: Expanded graphite (manufacturer: SABIC Chemical Technology (Shanghai) Co., Ltd., brand: A62064) and acrylonitrile-butadiene-styrene copolymer (brand: SABIC, model: CYCOLAC™ MG94) constitute conductive material B. Expanded graphite is uniformly distributed in acrylonitrile-butadiene-styrene copolymer, and the content of expanded graphite is 10wt%. The viscous flow temperature of conductive material B is 220℃, and the shrinkage rate is 0.6%.

[0094] (3) Piezoresistive material A and conductive material B with a mass ratio of 5:6 were extruded from the same nozzle of the fused 3D printer and printed onto the base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0095] The filling path during printing is wavy; the nozzle temperature is 240℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1200mm / min; and the substrate temperature is 110℃.

[0096] The micropore volume accounts for 30% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 80 μm.

[0097] The final fabricated three-dimensional porous piezoresistive sensor has one printing layer. It consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.26 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.24 mm. The three-dimensional porous piezoresistive sensor has a compression deformation of 0.25 mm and a sensitivity of 4.5 kPa. -1 .

[0098] Example 5

[0099] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0100] (1) Preparation of piezoresistive material A: Piezoresistive material A is composed of carbon fiber (manufacturer: Zhongfu Shenying Carbon Fiber Co., Ltd., grade: 1K), AC foaming agent (manufacturer: Shanghai McLean Biochemical Technology Co., Ltd., grade: CAS: 123-77-3) and thermoplastic polyurethane (manufacturer: BASF Germany, grade: Elastollan® 1185A); carbon fiber and AC foaming agent are uniformly distributed in thermoplastic polyurethane, and the carbon fiber content is 0.8wt% and the AC foaming agent content is 6wt%; the foaming temperature of AC foaming agent is 195℃; the viscous flow temperature of piezoresistive material A is 180℃ and the shrinkage rate is 0.21%;

[0101] (2) Preparation of conductive material B: Conductive material B is composed of silver nanowires (manufacturer: Xianfeng Nano, grade: 102071) and polylactic acid. The silver nanowires are uniformly distributed in the polylactic acid, and the content of silver nanowires is 6wt%. The viscous flow temperature of conductive material B is 170℃ and the shrinkage rate is 0.2%.

[0102] (3) Piezoresistive material A and conductive material B with a mass ratio of 4:5 were extruded from the same nozzle of the fused 3D printer and printed onto the base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0103] The filling path during printing is wavy; the nozzle temperature is 220℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1300mm / min; and the substrate temperature is 90℃.

[0104] The micropore volume accounts for 35% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 120 μm.

[0105] The final fabricated three-dimensional porous piezoresistive sensor has one printing layer. It consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.32 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.21 mm. The extrusion deformation of the three-dimensional porous piezoresistive sensor is 0.28 mm, and its sensitivity is 4 kPa. -1 .

[0106] Example 6

[0107] A method for fabricating a three-dimensional porous piezoresistive sensor using melt 3D printing, comprising the following specific steps:

[0108] (1) Preparation of piezoresistive material A: Silver nanowires (manufacturer: Xianfeng Nano, grade: 102071), thermally expanded microspheres (manufacturer: American Boliken, grade: 220DU30) and thermoplastic elastomer (manufacturer: Korean SK Corporation, grade: S2008) constitute piezoresistive material A; the silver nanowires and thermally expanded microspheres are uniformly distributed in the thermoplastic elastomer, and the content of silver nanowires is 1wt% and the content of thermally expanded microspheres is 10wt%; the foaming temperature of thermally expanded microspheres is 200℃; the viscous flow temperature of piezoresistive material A is 205℃, and the shrinkage rate is 0.42%;

[0109] (2) Preparation of conductive material B: Conductive material B is composed of carbon fiber (manufacturer: Zhongfu Shenying Carbon Fiber Co., Ltd., grade: 1K) and acrylonitrile-butadiene-styrene copolymer (brand: SABIC, model: CYCOLAC™ MG94). The carbon fiber is uniformly distributed in the acrylonitrile-butadiene-styrene copolymer, and the carbon fiber content is 2wt%. The viscous flow temperature of conductive material B is 240℃, and the shrinkage rate is 0.4%.

[0110] (3) Piezoresistive material A and conductive material B with a mass ratio of 6:7 were extruded from the same nozzle of the fused 3D printer and printed onto the base plate. The resulting composite filament was cooled and solidified at 30°C to obtain a three-dimensional porous piezoresistive sensor.

[0111] The filling path during printing is wavy; the nozzle temperature is 250℃; the nozzle includes two spaced-apart channels I and II, channel I for conveying material A and channel II for conveying material B, and the outlets of channels I and II converge at an inverted frustum structure, with channel I having a diameter of 0.75mm and channel II having a diameter of 1.25mm; the printing speed is 1000mm / min; and the substrate temperature is 120℃.

[0112] The micropore volume accounts for 40% of the composite fuse, and the micropores are spindle-shaped with an equivalent circular diameter of 150 μm.

[0113] The final fabricated three-dimensional porous piezoresistive sensor has one printing layer. It consists of conductive material units and piezoresistive material units. The conductive material units are planar, while the piezoresistive material units are formed by multiple interconnected arched structures distributed on one side of the conductive material unit surface. Each arched structure has a height of 0.35 mm and a width of 0.75 mm. The conductive material unit has a thickness of 1.25 mm. The three-dimensional porous piezoresistive sensor has a compression deformation of 0.3 mm and a sensitivity of 5 kPa. -1 .

Claims

1. A three-dimensional porous piezoresistive sensor, fabricated by melt 3D printing, characterized in that: The number of printing layers is 1; The three-dimensional porous piezoresistive sensor includes a conductive material unit and a piezoresistive material unit. The conductive material unit is planar, while the piezoresistive material unit is a shape formed by multiple interconnected arched structures and is distributed on one side of the conductive material unit.

2. The three-dimensional porous piezoresistive sensor according to claim 1, characterized in that, The three-dimensional porous piezoresistive sensor is formed by cooling and solidifying a composite filament obtained by molten 3D printing. The micropore volume ratio in the composite filament is 10~40%, the micropores are spindle-shaped, and the equivalent circle diameter of the micropores is 10~150μm.

3. A three-dimensional porous piezoresistive sensor according to claim 1, characterized in that, Each arch structure has a height of 0.25~0.35mm and a width of 0.75mm.

4. A three-dimensional porous piezoresistive sensor according to claim 1, characterized in that, The thickness of the conductive material unit is 1.2~1.25mm.

5. A three-dimensional porous piezoresistive sensor according to claim 1, characterized in that, The extrusion deformation of the three-dimensional porous piezoresistive sensor is 0.2~0.3mm, and the sensitivity is 3~5kPa. -1 .

6. A method for fabricating a three-dimensional porous piezoresistive sensor by melt 3D printing as described in any one of claims 1 to 5, characterized in that: Material A and material B are extruded from the same nozzle of a fused 3D printer and printed onto a base plate. After cooling, a three-dimensional porous piezoresistive sensor is obtained. Material A has a shrinkage rate 3-6% greater than that of material B, while the shrinkage rate of material B is ≤0.6%. Material A is a piezoresistive material containing a foaming agent, and material B is a conductive material; The nozzle temperature is higher than the foaming temperature of the foaming agent; The nozzle includes two spaced-apart channels, I and II. Channel I is used to convey material A, and channel II is used to convey material B. The outlets of channels I and II converge at an inverted frustum structure. The diameter of channel I is smaller than that of channel II. The printing speed is 1000~1500mm / min.

7. The method for fabricating a three-dimensional porous piezoresistive sensor by melt 3D printing according to claim 6, characterized in that, The temperature of the bottom plate is 80~120℃ lower than T1, where T1 is the lower value of the viscous flow temperature of material A and material B.

8. The method for fabricating a three-dimensional porous piezoresistive sensor by melt 3D printing according to claim 6, characterized in that, Material A consists of conductive filler A, foaming agent, and polymer matrix A. The conductive filler A and foaming agent are uniformly distributed in the polymer matrix A, and the content of conductive filler A is 0.3~3wt%, and the content of foaming agent is 1~10wt%. The conductive filler A is carbon black, carbon nanotubes, graphene, expanded graphite, carbon fiber, or silver nanowires. The foaming agent is AC foaming agent or thermally expanded microspheres, and the foaming temperature is 180~220℃; The polymer matrix A is a thermoplastic polyurethane or a thermoplastic elastomer.

9. The method for fabricating a three-dimensional porous piezoresistive sensor by melt 3D printing according to claim 6, characterized in that, Material B consists of conductive filler B and polymer matrix B. The conductive filler B is uniformly distributed in the polymer matrix B, and the content of conductive filler B is 0.5~10 wt%. The conductive filler B is carbon black, carbon nanotubes, graphene, expanded graphite, carbon fiber, or silver nanowires. Polymer matrix B is polylactic acid or acrylonitrile-butadiene-styrene copolymer.

10. The method for fabricating a three-dimensional porous piezoresistive sensor by melt 3D printing according to claim 6, characterized in that, The fill path during printing can be either wavy or straight.

Images