Bridge embedded sensor and preparation method thereof

Abstract

The application discloses a bridge embedded sensor and a preparation method thereof. The sensor is a double-layer integrated structure, and the preparation method comprises the following steps: firstly, ZnO-Bi2O3 powder is coated with Al2O3-SiO2 nano to obtain functional ceramic powder A; the functional ceramic powder A is mixed with nano alumina and zirconia powder to prepare transition layer powder B; then, slurry of a dense functional layer and a porous anchoring layer with double templates for pore making is prepared and flow-casted into a blank; after water dissolving and lamination, a double-layer ceramic substrate is obtained through sintering; after laser etching of a microcavity, the slurry of the powder B and the powder A is filled in sequence, and the sensor unit is formed through co-sintering; Ni 80 Cr 20 alloy circuit, and an aluminum oxide film is deposited to package; the obtained sensor has a bonding strength with concrete of greater than or equal to 2.9 MPa, an electric resistance drift rate of less than or equal to 1.5% after aging for 500 hours, and high sensitivity, strong interface anchoring and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic sensor fabrication technology, and relates to a bridge-embedded sensor and its fabrication method. Background Technology

[0002] With the development of modern bridge engineering towards longer spans, heavier loads, and longer lifespans, there is an urgent need for long-term, in-situ, and reliable monitoring of the stress and strain state inside concrete structures. Traditional surface sensors are susceptible to environmental interference and lack durability, while existing embedded sensing elements often suffer from problems such as mismatched thermal expansion coefficients of materials and weak interface bonding, making it difficult to achieve long-term collaborative operation with concrete structures.

[0003] Achieving long-term compatibility between sensors and concrete hinges on resolving two key issues: material interface matching and internal sensing unit integration. Matching the coefficients of thermal expansion is fundamental to ensuring stable interfacial bonding. Research indicates that an alumina-zirconia composite ceramic system combined with a porous anchoring structure design can effectively regulate equivalent thermal expansion behavior and enhance mechanical interlocking. Once interface stability is ensured, the performance of the sensing unit becomes the dominant factor determining monitoring reliability. Its sensitivity, stability, and integration quality with the ceramic matrix directly impact the signal's authenticity and long-term consistency.

[0004] Therefore, developing an embedded intelligent sensor that combines thermal expansion matching characteristics with high-performance strain sensing capabilities and can be integrally molded using efficient processes has become an inevitable technical path to break through the technical bottleneck of long-term monitoring of the internal structure of bridges and realize intelligent early warning of structural health. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention aims to provide a bridge-embedded sensor and its fabrication method. The sensor has a dual-layer integrated structure. The fabrication method includes: firstly, Al2O3-SiO2 nano-coating of ZnO-Bi2O3 powder to obtain functional ceramic powder A; then, compounding functional ceramic powder A with nano-alumina and zirconium oxide powders to prepare a transition layer powder B; next, preparing a dense functional layer and a porous anchoring layer slurry with dual-template pore-forming and casting it into a blank; after water dissolution and lamination, sintering to obtain a dual-layer ceramic substrate; laser etching a microcavity followed by sequential filling with powder B and A slurry, and co-firing to form a sensing unit; and finally, fabricating Ni using mask-assisted magnetron sputtering. 80 Cr 20 Alloy circuitry, encapsulated with deposited alumina thin film; the resulting sensor has a bonding strength with concrete ≥2.9MPa, and a resistance drift rate <1.5% after 500 h of aging, combining high sensitivity, strong interface anchoring, and long-term stability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A bridge-embedded sensor, the sensor having a dual-layer integrated structure, including a gradient porous ceramic anchoring layer and a dense ceramic functional layer; the gradient porous ceramic anchoring layer has a macro-micro dual-scale pore structure, wherein the macroscopic through pores are formed by water-soluble removal of sodium sulfate crystal template, and the microscopic network pores are formed by sintering and decomposing PMMA microspheres. The surface of the dense ceramic functional layer is provided with embedded Ni 80 Cr 20 Alloy circuitry and a ZnO-Bi2O3-based piezoresistive sensing unit, wherein the ZnO-Bi2O3-based piezoresistive sensing unit is coated with an Al2O3-SiO2 composite nanoshell; the Ni 80 Cr 20 The alloy circuit electrically connects the piezoresistive sensing unit to the pad, and the circuit area of ​​the sensor is coated with a dense aluminum oxide encapsulation film.

[0007] This invention also provides a method for fabricating a bridge-embedded sensor, which is carried out in the following order: S1. Preparation of powders and slurries S11. Preparation of functional ceramic powder: ZnO-Bi2O3 functional ceramic powder was dispersed in anhydrous ethanol containing aluminum nitrate and tetraethyl orthosilicate, and stirred in a water bath at 60 °C for 4 h. After centrifugation, washing with ethanol and drying, functional ceramic powder A was obtained. S12. Preparation of transition layer powder: Nano alumina powder, zirconium oxide powder and the above-mentioned surface-modified functional ceramic powder A are mixed evenly to obtain a mixed powder; lead borosilicate glass powder is added to the mixed powder, and the mixture is ball-milled for 12 h using a planetary ball mill, followed by spray granulation to obtain transition layer powder B. S13. Preparation of functional layer green body: Alumina powder, zirconium oxide powder and magnesium oxide powder are mixed evenly at a mass ratio of 100:10:1.5 to obtain ceramic aggregate; organic carrier and solvent are added to ceramic aggregate, and after ball milling at 150 r / min for 12 h, the slurry is subjected to vacuum degassing treatment, and after casting and drying, a functional layer green body with a thickness of 260 μm is obtained. S14. Preparation of anchoring layer green body: Alumina powder, zirconium oxide powder and magnesium oxide powder are mixed evenly at a mass ratio of 100:10:1.5 to obtain ceramic aggregate; organic carrier, solvent, sodium sulfate crystals with a particle size of 100 μm and PMMA microspheres with a particle size of 20 μm are added to the ceramic aggregate, and after ball milling at 150 r / min for 12 h, the slurry is subjected to vacuum degassing treatment, and after casting and drying, an anchoring layer green body with a thickness of 260 μm is obtained. S2, Green embryo stacking and sintering The anchoring layer green body is repeatedly immersed in deionized water to dissolve the sodium sulfate crystal template, then dried at 50-60 ℃ for 2-3 h, and then precisely aligned and stacked with the functional layer green body, and isostatically laminated and sintered to obtain a double-layer ceramic substrate with one side being dense and the other side having a gradient porous structure. S3, sensor unit integration The dense surface of the ceramic substrate is laser-etched with interconnected wire pre-reserved areas, piezoresistive sensing unit pre-reserved areas, and pad areas; the transition layer powder B and functional ceramic powder A are respectively prepared into slurries and sequentially filled into the piezoresistive sensing unit pre-reserved areas. After drying at 80-100 ℃ for 1-2 h, the substrate is placed in a muffle furnace and heated to 1100 ℃ at 2-3 ℃ / min, held for 50 min, and then cooled with the furnace to complete co-firing; after co-firing, the substrate is treated with oxygen plasma for 5-10 min to clean the surface of the wires and pad trenches. S4. Circuit wiring and packaging Ni is deposited in the wire pre-reserved area and pad area using high-power pulsed magnetron sputtering technology with the assistance of a precision metal mask. 80 Cr 20 An alloy thin film is used to form an embedded circuit. After the wire connection is completed, an alumina thin film is deposited and encapsulated using atomic layer deposition technology to obtain an embedded ceramic stress-strain sensor for health monitoring of bridge concrete structures.

[0008] As a limitation of the preparation method of the present invention, in step S11, the mass of aluminum nitrate is 4-6 wt.% of the mass of functional ceramic powder, the mass of tetraethyl orthosilicate is 9-11 wt.% of the mass of functional ceramic powder, and the mass of anhydrous ethanol is 142-174 wt.% of the mass of functional ceramic powder.

[0009] As another limitation of the preparation method of the present invention, in step S12, the mass ratio between the nano alumina powder, zirconium oxide powder and functional ceramic powder A is 5:3:2; the mass of the lead borosilicate glass powder is 4-6 wt.% of the total mass of the mixed powder.

[0010] As a third limitation of the preparation method of the present invention, in steps S13 and S14, the organic carrier is polyvinyl butyral (PVB), dioctyl phthalate, triethyl phosphate (DOP), and polyvinyl butyral (TEP), wherein: the mass of polyvinyl butyral is 6-8 wt.% of the ceramic aggregate, the mass of dioctyl phthalate is 3-5 wt.% of the ceramic aggregate, and the mass of triethyl phosphate is 0.8-1.2 wt.% of the ceramic aggregate; the solvent is anhydrous ethanol, and the mass of anhydrous ethanol is 20-40 wt.% of the ceramic aggregate.

[0011] As a fourth limitation of the preparation method of the present invention, in step S14, the mass of the sodium sulfate crystals is 15-25 wt.% of the mass of the ceramic aggregate, and the mass of the PMMA microspheres is 10-15 wt.% of the mass of the ceramic aggregate.

[0012] As a fifth limitation of the preparation method of the present invention, in step S2, the sintering is carried out according to the following procedure: (a) In the first heating stage, the temperature was increased from room temperature to 450℃ at a rate of 0.5℃ / min and held for 1 h. Then, the temperature was increased to 600℃ at the same rate and held for another 1 h. (b) In the second heating stage, the temperature is increased from 600 ℃ to 1100 ℃ at a heating rate of 1 ℃ / min, and held for 1-1.5 h; (c) In the third heating stage, the temperature is increased from 1100 ℃ to 1600 ℃ at a heating rate of 2 ℃ / min, and held for 2-3 hours; (d) During the cooling stage, the temperature is first reduced from 1600 ℃ to 800 ℃ at a cooling rate of 3 ℃ / min, and then cooled to room temperature along with the furnace.

[0013] The sintering stage of this invention affects the densification process, phase evolution, and microstructure evolution of the ceramic matrix. In the first heating stage, when the temperature is increased from room temperature to 450 ℃ at a heating rate of 0.5 ℃ / min, the organic additives (including binders, plasticizers, and dispersants) slowly undergo thermal decomposition and initial volatilization. Then, at the same heating rate, when the temperature is increased from 450 ℃ to 600 ℃, the pore-forming agent PMMA microspheres will completely decompose and the residual organic matter will be completely eliminated. Holding the temperature for 1 h in each stage is to ensure that the organic components are fully and completely eliminated, avoiding defects such as green body cracking and delamination caused by rapid gas generation, and at the same time laying the foundation for the formation of the subsequent porous structure. In the second heating stage, when the temperature is increased from 600 °C to 1100 °C at a heating rate of 1 °C / min, the initial sintering necks between ceramic particles form and grow, and the glass phase in the transition layer powder B softens and flows. Holding for 1-1.5 h promotes the full wetting of the glass phase and its penetration into the interfacial micropores, achieving initial chemical bonding and interfacial strengthening between the transition layer, functional layer, and substrate. In the third heating stage, when the temperature is increased from 1100 °C to 1600 °C at a heating rate of 2 °C / min, the main crystal phase densification sintering of the alumina-zirconia ceramic matrix occurs, including grain boundary migration, pore removal, and grain growth. Holding for 2-3 h achieves complete densification of the functional layer and anchoring layer, obtaining a high-strength ceramic matrix, while stabilizing the gradient pore structure of the porous anchoring layer. During cooling, the temperature is first reduced from 1600 °C to 800 °C at a cooling rate of 3 °C / min. The temperature is set at ℃ to control the cooling rate, prevent the ceramic matrix from cracking due to excessive thermal stress, suppress the brittle precipitation of grain boundary phases, and stabilize the mechanical and electrical properties of the ceramic. The ceramic is then cooled to room temperature in the furnace.

[0014] As a sixth limitation of the preparation method of the present invention, in step S3, the depth of the laser etching is 50 μm; the reserved area of ​​the piezoresistive sensing unit is a square area with a side length of 2 mm, the width of the reserved area of ​​the conductor is 150 μm, the pad area is a square area with a side length of 1 mm; and the filling thickness of the transition layer powder B slurry is 40%-60% of the trench depth of the reserved area of ​​the piezoresistive sensing unit.

[0015] As a seventh limitation of the preparation method of the present invention, in step S3, the preparation process of the slurry of the transition layer powder B and the functional ceramic powder A is as follows: the transition layer powder B and the functional ceramic powder A are respectively mixed with α-terpineol at a mass ratio of 3:1, and ethyl cellulose accounting for 1 wt.% of the powder mass is added to each as a binder, and then ground to form a slurry.

[0016] As an eighth limitation of the preparation method of the present invention, in step S4, the high-power pulsed magnetron sputtering is performed under an argon atmosphere with a working pressure of 0.3-0.8 Pa and a high-pulse peak power of 1-2 kW / cm². 2The pulse frequency is 200 Hz, the duty cycle is 20%, and the deposited Ni 80 Cr 20 The alloy film thickness is 1-2 μm; the alumina film thickness of the atomic layer deposition is 50-200 nm.

[0017] This invention modifies the surface of ZnO-Bi2O3 functional ceramic powder by nano-coating, constructing an amorphous Al2O3-SiO2 composite shell on its surface. During sintering, this shell acts as a diffusion barrier, regulating the surface activity of the powder and inhibiting abnormal grain growth. Furthermore, its amorphous structure, similar to the alumina matrix, significantly reduces interfacial energy, promoting neck formation and grain boundary diffusion in the early stages of sintering. This fundamentally improves the sintering compatibility and interfacial bonding strength between the functional ceramic and the alumina substrate, laying a solid foundation for subsequent heterogeneous integration.

[0018] To achieve high-strength mechanical anchoring and long-term stress matching between the sensor and concrete, this invention employs a dual-template pore-forming technique to prepare a gradient porous anchoring layer: 100 μm water-soluble sodium sulfate crystals serve as the macroscopic pore-forming template, forming a pervasive macroscopic pore network after water-soluble treatment during the greening stage, providing channels for cement paste penetration; 20 μm PMMA microspheres serve as the microscopic pore-forming template, forming a connected microscopic network of pores throughout the ceramic skeleton after decomposition during the sintering and binder removal stage. This macro-micro dual-scale gradient porous structure achieves high-strength microscopic mechanical engagement with cement hydration products through the high specific surface area of ​​the micron-sized pores, while effectively buffering the interfacial stress caused by the slight difference in thermal expansion coefficients between the sensor and concrete, achieving adaptive thermal matching and multi-level mechanical interlocking, fundamentally ensuring the stability of the interfacial structure after long-term sensor embedding.

[0019] In the construction of the core sensing functional unit, a picosecond laser is used to etch a high-precision embedded microcavity on the surface of a dense ceramic substrate. Then, through precision 3D printing technology, transition layer powder B slurry and functional layer powder A slurry are sequentially and precisely filled into the microcavity. During the subsequent co-firing process, the lead borosilicate glass phase in the transition layer undergoes controllable softening and flow. This not only fully fills the microscopic gaps between heterogeneous materials and achieves a strong chemical bond at the interface, but its viscoelastic properties also act as a "stress buffer," uniformly dispersing external stress and local stress concentration caused by internal sintering shrinkage. This ensures that the external stress signal is efficiently and linearly transmitted to the piezoresistive functional ceramic, significantly improving the stress-strain response sensitivity and signal-to-noise ratio of the sensing unit.

[0020] Finally, to address the challenge of highly reliable integration of micron-level embedded circuits, a precision mask and high-power pulsed magnetron sputtering technology were employed. The high peak power generates a highly ionized plasma, which imparts extremely high energy to metal particles, producing an "atomic forging" effect during deposition. This allows for the direct formation of high-density, low-stress, and strongly adherent Ni within complex three-dimensional trenches at low temperatures. 80 Cr 20 An alloy thin film constructs a highly reliable conductive path. After the circuit is connected, a dense, pinhole-free Al2O3 thin film is built on the device surface using atomic layer deposition. This film, with its conformal covering ability and the inherent chemical inertness of ceramics, completely encapsulates the internal circuitry and sensing unit, effectively blocking moisture and OH radicals from the concrete environment. - and Cl - The penetration and corrosion of ions provide ultimate environmental protection that matches the lifespan of the bridge, with almost no impact on stress and strain transmission.

[0021] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0022] The above technical solution has the following advantages or beneficial effects: 1. This invention achieves adaptive thermal matching and multi-level mechanical interlocking between the sensor and concrete by modifying Al2O3-SiO2 composite nanoshell powder and using a macro-micro dual-scale gradient porous structure design with dual template pore formation. This significantly improves the interfacial bonding strength and solves the industry problem of thermal expansion mismatch and interfacial bonding failure from the root, ensuring the structural stability of the sensor after long-term embedding. 2. This invention utilizes high-power pulsed magnetron sputtering to prepare high-density Ni. 80 Cr 20 The alloy circuit has high conductivity and reliability. Combined with the dense Al2O3 nano-encapsulation film without pinholes deposited by atomic layer deposition, it can completely block the penetration of water vapor and corrosive ions in the concrete environment. Without affecting the transmission of stress and strain, it can achieve full-cycle protection that matches the design life of the sensor and the bridge, and significantly reduce the signal drift rate of long-term monitoring. 3. The bridge embedded sensor prepared by this invention has excellent stress-strain response sensitivity, high-strength anchoring performance with concrete matrix and excellent long-term environmental stability.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0024] Figure 1 This is a diagram of the stacked structure of the sensor obtained in Embodiment 1 of the present invention, wherein: 1 is the anchoring layer and 2 is the functional layer; Figure 2 This is a simplified circuit diagram of the sensor obtained in Embodiment 1 of the present invention, wherein: 3 is a solder pad, 4 is a wire, and 5 is a piezoresistive unit; Figure 3 This is a SEM image of the functional ceramic powder A prepared in Example 1 of the present invention; Figure 4 This is a physical image of the sensor obtained in Embodiment 1 of the present invention, wherein: 3 is a solder pad, 4 is a wire, and 5 is a piezoresistive unit. Detailed Implementation

[0025] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified. Example 1

[0027] This embodiment describes the fabrication of a bridge-embedded sensor, and the fabrication process and steps are as follows: S1. Preparation of powders and slurries S11. Preparation of functional ceramic powder: Weigh 100.0 g of ZnO-Bi2O3 functional ceramic powder and disperse it in 200 mL of anhydrous ethanol containing 5.0 g of aluminum nitrate and 10.0 g of tetraethyl orthosilicate. Stir and react in a water bath at 60 °C for 4 h. After the reaction, centrifuge, wash with ethanol and dry to obtain functional ceramic powder A with an Al2O3-SiO2 nanoshell on the surface. S12. Preparation of transition layer powder: Weigh 50 g of nano alumina powder, 30 g of zirconium oxide powder and 20 g of functional ceramic powder A, add 5.0 g of lead borosilicate glass powder, mix by planetary ball milling for 12 h and then spray granulation. The inlet temperature of spray granulation is 200 ℃ and the outlet temperature is 80 ℃ to obtain transition layer powder B. S13. Preparation of functional layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 7.0 wt.% PVB (7.8 g), 4.0 wt.% DOP (4.5 g), 1.0 wt.% TEP (1.1 g) and 30 wt.% anhydrous ethanol (33.4 g) as aggregates, ball mill at 150 r / min for 12 h to obtain functional layer slurry, and after casting and drying, obtain a functional layer green body with a thickness of 260 μm; S14. Preparation of anchoring layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 7.0 wt.% PVB (7.8 g), 4.0 wt.% DOP (4.5 g), 1.0 wt.% TEP (1.1 g), 30 wt.% anhydrous ethanol (33.4 g), 20 wt.% 100 μm sodium sulfate crystals (22.3 g) and 12.5 wt.% 20 μm PMMA microspheres (13.9 g) according to the aggregate mass, ball mill at 150 r / min for 12 h to obtain anchoring layer slurry, and after casting and drying, obtain an anchoring layer green body with a thickness of 260 μm; S2, Green embryo stacking and sintering S21. Green embryo stacking: The anchoring layer green embryo is repeatedly immersed in deionized water to dissolve the sodium sulfate crystal template, then dried at 55 ℃ for 2.5 h, and then precisely aligned and stacked with the functional layer green embryo, and isostatically laminated at 100 MPa for 15 min to obtain the green embryo stack. S22. The green wafers are stacked in a muffle furnace. First, the temperature is increased from room temperature to 450℃ at a heating rate of 0.5℃ / min and held for 1 h. Then, the temperature is increased from 450℃ to 600℃ at a heating rate of 0.5℃ / min and held for 1 h. Next, the temperature is increased from 600℃ to 1100℃ at a heating rate of 1℃ / min and held for 1 h. Then, the temperature is increased from 1100℃ to 1600℃ at a heating rate of 2℃ / min and held for 2 h. Finally, the temperature is decreased from 1600℃ to 800℃ at a cooling rate of 3℃ / min and then cooled to room temperature with the furnace to obtain a double-layer ceramic substrate with one side being dense and the other side having a gradient porous structure. S3, sensor unit integration S31. A picosecond laser is used to etch a wire reservation area with a depth of 50 μm and a width of 150 μm on the dense surface of the substrate; a square piezoresistive sensing unit reservation area with a side length of 2 mm and a depth of 50 μm; and a square pad area with a side length of 1 mm and a depth of 50 μm. The wire reservation area, the square piezoresistive sensing unit reservation area, and the square pad area are connected. S32. The transition layer powder B and functional ceramic powder A are mixed with α-terpineol at a ratio of 3:1, and 1 wt.% of ethyl cellulose by weight of the powder is added to prepare a slurry. Using precision 3D printing, the transition layer powder B slurry is first filled into the reserved area of ​​the square piezoresistive sensing unit, with a filling depth of 50% (25 μm) of the reserved area depth. Then, the functional ceramic powder A slurry is filled until level. After drying at 90 ℃ for 1.5 h, it is placed in a muffle furnace and heated to 1100 ℃ at a heating rate of 2.5 ℃ / min. It is held for 50 min and then cooled in the furnace to complete co-firing. After co-firing, the substrate is treated with oxygen plasma for 7.5 min to clean the surface of the wires and pad trenches. S4. Circuit wiring and packaging S41. Use a precision metal mask that is completely consistent with the area where the alloy circuit needs to be deposited (i.e., the hollowed-out wire reserved area and the pad area), align the metal mask with the laser etched trench pattern on the substrate obtained in step S3, and fix them tightly. S42, using Ni 80 Cr 20 The target material was deposited by high-power pulsed magnetron sputtering in an argon atmosphere (pressure 0.55 Pa): peak power 1.5 kW / cm². 2 An alloy thin film with a frequency of 200 Hz, a duty cycle of 20%, and a deposition thickness of 1.5 μm was deposited. S43. Remove the mask and vacuum dry the substrate at 100 °C for 1 h. S44. A gold-plated nickel wire with an outer diameter of 100 μm is welded to the alloy pad using laser micro-welding technology. Finally, a dense Al2O3 film with a thickness of approximately 100 nm is deposited using atomic layer deposition technology for encapsulation, resulting in a bridge-embedded sensor. Its stacked structure, circuit schematic diagram, and physical object are shown below. Figure 1 , Figure 2 and Figure 4 As shown. Furthermore, from Figure 3 The SEM images show that the surface of functional ceramic powder A particles exhibits uniform contrast and clear, rounded outlines, with no obvious uncoated areas or agglomerates. This indicates that the Al2O3-SiO2 composite nanoshell has been continuously and uniformly coated on the surface of ZnO-Bi2O3-based ceramic powder. Example 2

[0028] This embodiment describes the fabrication of a bridge-embedded sensor, and the fabrication process and steps are as follows: S1. Preparation of powders and slurries S11. Preparation of functional ceramic powder: Weigh 100.0 g of ZnO-Bi2O3 functional ceramic powder and disperse it in 180 mL of anhydrous ethanol containing 4.0 g of aluminum nitrate and 11.0 g of tetraethyl orthosilicate. Stir and react in a water bath at 60 °C for 4 h. After the reaction, centrifuge, wash with ethanol and dry to obtain functional ceramic powder A with an Al2O3-SiO2 nanoshell on the surface. S12. Preparation of transition layer powder: Weigh 50 g of nano alumina powder, 30 g of zirconium oxide powder and 20 g of functional ceramic powder A, add 4.0 g of lead borosilicate glass powder, mix by planetary ball milling for 12 h and then spray granulation. The inlet temperature of spray granulation is 200 ℃ and the outlet temperature is 80 ℃ to obtain transition layer powder B. S13. Preparation of functional layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 6.0 wt.% PVB (6.7 g), 5.0 wt.% DOP (5.6 g), 0.8 wt.% TEP (0.9 g), and 20 wt.% anhydrous ethanol (22.3 g) as aggregates, ball mill at 150 r / min for 12 h to obtain functional layer slurry, and after casting and drying, obtain a functional layer green body with a thickness of 260 μm; S14. Preparation of anchoring layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 6.0 wt.% PVB (6.7 g), 5.0 wt.% DOP (5.6 g), 0.8 wt.% TEP (0.9 g), 20 wt.% anhydrous ethanol (22.3 g), 15 wt.% 100 μm sodium sulfate crystals (16.7 g) and 10 wt.% 20 μm PMMA microspheres (11.1 g) as aggregates, ball mill at 150 r / min for 12 h to obtain anchoring layer slurry, and after casting and drying, obtain an anchoring layer green body with a thickness of 260 μm; S2, Green embryo stacking and sintering S21. Green embryo stacking: The anchoring layer green embryo is repeatedly immersed in deionized water to dissolve the sodium sulfate crystal template, then dried at 50 ℃ for 3 h, and then precisely aligned and stacked with the functional layer green embryo, and isostatically laminated at 80 MPa for 20 min to obtain the green embryo stack. S22. The green wafers are stacked in a muffle furnace. First, the temperature is increased from room temperature to 450℃ at a heating rate of 0.5℃ / min and held for 1 h. Then, the temperature is increased from 450℃ to 600℃ at a heating rate of 0.5℃ / min and held for 1 h. Next, the temperature is increased from 600℃ to 1100℃ at a heating rate of 1℃ / min and held for 1.2 h. Then, the temperature is increased from 1100℃ to 1600℃ at a heating rate of 2℃ / min and held for 2.5 h. Finally, the temperature is decreased from 1600℃ to 800℃ at a cooling rate of 3℃ / min and then cooled to room temperature with the furnace to obtain a double-layer ceramic substrate with one side being dense and the other side having a gradient porous structure. S3, sensor unit integration S31. A picosecond laser is used to etch a wire reservation area with a depth of 50 μm and a width of 150 μm on the dense surface of the substrate; a square piezoresistive sensing unit reservation area with a side length of 2 mm and a depth of 50 μm; and a square pad area with a side length of 1 mm and a depth of 50 μm. The wire reservation area, the square piezoresistive sensing unit reservation area, and the square pad area are connected. S32. The transition layer powder B and functional ceramic powder A are mixed with α-terpineol at a ratio of 3:1, and 1 wt.% of ethyl cellulose is added to prepare a slurry. Using precision 3D printing, the transition layer powder B slurry is first filled into the reserved area of ​​the square piezoresistive sensing unit to a depth of 40% (20 μm) of the reserved area depth. Then, the functional ceramic powder A slurry is filled until level. After drying at 80 ℃ for 2 h, it is placed in a muffle furnace and heated to 1100 ℃ at a heating rate of 2 ℃ / min. It is held for 50 min and then cooled in the furnace to complete the co-firing. After co-firing, the substrate is treated with oxygen plasma for 5 min to clean the surface of the wires and pad trenches. S4. Circuit wiring and packaging S41. Use a precision metal mask that is completely consistent with the area where the alloy circuit needs to be deposited (i.e., the hollowed-out wire reserved area and the pad area), align the metal mask with the laser etched trench pattern on the substrate obtained in step S3, and fix them tightly. S42, using Ni 80 Cr 20 The target material was deposited by high-power pulsed magnetron sputtering in an argon atmosphere (pressure 0.3 Pa): peak power 1 kW / cm². 2 , frequency 200 Hz, duty cycle 20%, deposited alloy thin film with a thickness of 1 μm; S43. Remove the mask and vacuum dry the substrate at 100 °C for 1 h. S44. A gold-plated nickel wire with an outer diameter of 100 μm is welded at the alloy pad using laser micro-welding technology. Finally, a dense Al2O3 film with a thickness of about 50 nm is deposited by atomic layer deposition technology for encapsulation to obtain a bridge embedded sensor.

[0029] The sensor fabricated in this embodiment combines high sensitivity, strong interface anchoring, and long-term stability, making it suitable for monitoring internal stress and strain in bridge concrete structures. Example 3

[0030] This embodiment describes the fabrication of a bridge-embedded sensor, and the fabrication process and steps are as follows: S1. Preparation of powders and slurries S11. Preparation of functional ceramic powder: Weigh 100.0 g of ZnO-Bi2O3 functional ceramic powder and disperse it in 220 mL of anhydrous ethanol containing 6.0 g of aluminum nitrate and 9.0 g of tetraethyl orthosilicate. Stir and react in a water bath at 60 °C for 4 h. After the reaction, centrifuge, wash with ethanol and dry to obtain functional ceramic powder A with an Al2O3-SiO2 nanoshell on the surface. S12. Preparation of transition layer powder: Weigh 50 g of nano alumina powder, 30 g of zirconium oxide powder and 20 g of functional ceramic powder A, add 6.0 g of lead borosilicate glass powder, mix by planetary ball milling for 12 h and then spray granulation. The inlet temperature of spray granulation is 200 ℃ and the outlet temperature is 80 ℃ to obtain transition layer powder B. S13. Preparation of functional layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 8.0 wt.% PVB (8.9 g), 3.0 wt.% DOP (3.3 g), 1.2 wt.% TEP (1.3 g), and 40 wt.% anhydrous ethanol (44.6 g) as aggregates, ball mill at 150 r / min for 12 h to obtain functional layer slurry, and after casting and drying, obtain a functional layer green body with a thickness of 260 μm; S14. Preparation of anchoring layer slurry: Weigh 100.0 g of alumina powder, 10.0 g of zirconium oxide powder and 1.5 g of magnesium oxide powder as ceramic aggregates, add 8.0 wt.% PVB (8.9 g), 3.0 wt.% DOP (3.3 g), 1.2 wt.% TEP (1.3 g), 40 wt.% anhydrous ethanol (44.6 g), 25 wt.% 100 μm sodium sulfate crystals (27.9 g) and 15 wt.% 20 μm PMMA microspheres (16.7 g) as aggregates, ball mill at 150 r / min for 12 h to obtain anchoring layer slurry, and after casting and drying, obtain an anchoring layer green body with a thickness of 260 μm; S2, Green embryo stacking and sintering S21. Green embryo stacking: The anchoring layer green embryo is repeatedly immersed in deionized water to dissolve the sodium sulfate crystal template, then dried at 60 ℃ for 2 h, and then precisely aligned and stacked with the functional layer green embryo, and isostatically laminated at 120 MPa for 10 min to obtain the green embryo stack. S22. The green wafers are stacked in a muffle furnace. First, the temperature is increased from room temperature to 450℃ at a heating rate of 0.5℃ / min and held for 1 h. Then, the temperature is increased from 450℃ to 600℃ at a heating rate of 0.5℃ / min and held for 1 h. Next, the temperature is increased from 600℃ to 1100℃ at a heating rate of 1℃ / min and held for 1.5 h. Then, the temperature is increased from 1100℃ to 1600℃ at a heating rate of 2℃ / min and held for 3 h. Finally, the temperature is decreased from 1600℃ to 800℃ at a cooling rate of 3℃ / min and then cooled to room temperature with the furnace to obtain a double-layer ceramic substrate with one side being dense and the other side having a gradient porous structure. S3, sensor unit integration S31. A picosecond laser is used to etch a wire reservation area with a depth of 50 μm and a width of 150 μm on the dense surface of the substrate; a square piezoresistive sensing unit reservation area with a side length of 2 mm and a depth of 50 μm; and a square pad area with a side length of 1 mm and a depth of 50 μm. The wire reservation area, the square piezoresistive sensing unit reservation area, and the square pad area are connected. S32. The transition layer powder B and functional ceramic powder A are mixed with α-terpineol at a ratio of 3:1, and 1 wt.% of ethyl cellulose is added to prepare a slurry. Using precision 3D printing, the transition layer powder B slurry is first filled into the reserved area of ​​the square piezoresistive sensing unit to a depth of 60% (30 μm) of the reserved area depth, and then the functional ceramic powder A slurry is filled until level. After drying at 100 ℃ for 1 h, it is placed in a muffle furnace and heated to 1100 ℃ at a heating rate of 3 ℃ / min, held for 50 min, and then cooled with the furnace to complete co-firing. After co-firing, the substrate is treated with oxygen plasma for 10 min to clean the surface of the wires and pad trenches. S4. Circuit wiring and packaging S41. Use a precision metal mask that is completely consistent with the area where the alloy circuit needs to be deposited (i.e., the hollowed-out wire reserved area and the pad area), align the metal mask with the laser etched trench pattern on the substrate obtained in step S3, and fix them tightly. S42, using Ni 80 Cr 20 The target material was deposited by high-power pulsed magnetron sputtering in an argon atmosphere (pressure 0.8 Pa): peak power 2 kW / cm². 2An alloy thin film with a frequency of 200 Hz, a duty cycle of 20%, and a deposition thickness of 2 μm was formed. S43. Remove the mask and vacuum dry the substrate at 100 °C for 1 h. S44. A gold-plated nickel wire with an outer diameter of 100 μm is welded at the alloy pad using laser micro-welding technology. Finally, a dense Al2O3 film with a thickness of about 200 nm is deposited by atomic layer deposition technology for encapsulation to obtain a bridge embedded sensor.

[0031] The sensor fabricated in this embodiment combines high sensitivity, strong interface anchoring, and long-term stability, making it suitable for monitoring internal stress and strain in bridge concrete structures.

[0032] Comparative Example To investigate the impact of differences in different steps during the preparation process of this invention on the performance of the product, the following comparative experiments were conducted. Different bridge-embedded sensors were prepared in the following comparative examples: Comparative Example 1 This comparative example prepares a bridge embedded sensor. The preparation process is similar to that of Example 1, except that in step S32, the transition layer powder B slurry is not filled, that is, the reserved area of ​​the square piezoresistive sensing unit is filled with functional ceramic powder A slurry.

[0033] Comparative Example 2 This comparative example prepares a bridge-embedded sensor. The preparation process is similar to that of Example 1, except that in step S42, ordinary DC magnetron sputtering technology is used instead of high-power pulsed magnetron sputtering for deposition, and the sputtering conditions are the same as in Example 1.

[0034] Comparative Example 3 This comparative example prepares a bridge-embedded sensor. The preparation process is similar to that of Example 1, except that in step S44, a room temperature curing silicone rubber with a coating thickness of about 20 μm is used to replace the atomic layer deposition alumina film for encapsulation. The bridge embedded sensors prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention were subjected to a series of tests at 25 °C. The specific test results are shown in Tables 1-3. Table 1. Performance test results of Examples 1-3 and Comparative Examples 1-3 at 25°C

[0035] Table 2. Stress-output voltage response characteristics of the sensor in Example 1 at 25°C.

[0036] Note: Driven by a constant voltage source of 5V, the sensor and the concrete test block are loaded together. Table 3. Strain-output voltage response characteristics of the sensor in Example 1 at 25°C.

[0037] Note: Driven by a constant voltage source of 5V, the sensor is attached to the surface of a standard concrete beam for four-point bending loading.

[0038] As shown in Table 1, removing the transition layer, replacing the high-power pulsed magnetron sputtering process, or changing the atomic layer deposition (ALD) encapsulation method all lead to severe degradation or even failure of the device's key performance characteristics. This is because the transition layer acts as a gradient buffer interface, ensuring the mechanical compatibility and electrical stability between heterogeneous materials; high-power pulsed magnetron sputtering is crucial for forming low-defect, high-adhesion alloy wires, ensuring the conductivity reliability of micron-level circuits under long-term stress; and the ultra-thin, dense ceramic encapsulation layer prepared by ALD is a necessary barrier to resist the erosion of the alkaline environment of concrete and achieve full-lifecycle protection for the device. Table 2 illustrates a good linear relationship between the sensor's output voltage and the applied stress, with a stress sensitivity of approximately 8.22 mV / MPa, which can be used for quantitative monitoring of internal pressure in concrete structures. Table 3 illustrates a good linear relationship between the sensor's output voltage and the applied strain, with a strain sensitivity of approximately 19.5 mV / 1000 με, which can be used for quantitative monitoring of deformation (strain) in concrete structures. This fully demonstrates that the process system constructed in this invention is necessary and efficient for realizing a high-reliability embedded stress-strain monitoring device.

[0039] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A bridge-embedded sensor, characterized in that, The sensor has a dual-layer integrated structure, including a gradient porous ceramic anchoring layer and a dense ceramic functional layer; the gradient porous ceramic anchoring layer has a macro-micro dual-scale pore structure. The surface of the dense ceramic functional layer is provided with embedded Ni 80 Cr 20 Alloy circuitry and a ZnO-Bi2O3-based piezoresistive sensing unit; the ZnO-Bi2O3-based piezoresistive sensing unit is coated with an Al2O3-SiO2 composite nanoshell, and the Ni 80 Cr 20 The alloy circuit electrically connects the piezoresistive sensing unit to the pads, and the circuit area of ​​the sensor is coated with a dense aluminum oxide encapsulation film.

2. The method for fabricating a bridge-embedded sensor according to claim 1, characterized in that, Follow these steps in sequence: S1. Preparation of powders and slurries S11. Preparation of functional ceramic powder: ZnO-Bi2O3 functional ceramic powder was dispersed in anhydrous ethanol containing aluminum nitrate and tetraethyl orthosilicate, and stirred in a water bath at 60 °C for 4 h. After centrifugation, washing with ethanol and drying, functional ceramic powder A was obtained. S12. Preparation of transition layer powder: Nano alumina powder, zirconium oxide powder and functional ceramic powder A are mixed evenly to obtain a mixed powder; lead borosilicate glass powder is added to the mixed powder, and the mixture is ball-milled for 12 h using a planetary ball mill, followed by spray granulation to obtain transition layer powder B. S13. Preparation of functional layer green body: Alumina powder, zirconium oxide powder and magnesium oxide powder are mixed evenly at a mass ratio of 100:10:1.5 to obtain ceramic aggregate; organic carrier and solvent are added to ceramic aggregate, and after ball milling at 150 r / min for 12 h, the slurry is subjected to vacuum degassing treatment, and after casting and drying, a functional layer green body with a thickness of 260 μm is obtained. S14. Preparation of anchoring layer green body: Alumina powder, zirconium oxide powder and magnesium oxide powder are mixed evenly at a mass ratio of 100:10:1.5 to obtain ceramic aggregate; organic carrier, solvent, sodium sulfate crystals with a particle size of 100 μm and PMMA microspheres with a particle size of 20 μm are added to the ceramic aggregate, and after ball milling at 150 r / min for 12 h, the slurry is subjected to vacuum degassing treatment, and after casting and drying, an anchoring layer green body with a thickness of 260 μm is obtained. S2, Green embryo stacking and sintering The anchoring layer green body is repeatedly immersed in deionized water to dissolve the sodium sulfate crystal template, dried at 50-60 ℃ for 2-3 h, and then precisely aligned and stacked with the functional layer green body, and isostatically laminated and sintered to obtain a double-layer ceramic substrate with one side being dense and the other side having a gradient porous structure. S3, sensor unit integration The dense surface of the ceramic substrate is laser-etched with interconnected wire pre-reserved areas, piezoresistive sensing unit pre-reserved areas, and pad areas; transition layer powder B and functional ceramic powder A are respectively prepared into slurries and sequentially filled into the piezoresistive sensing unit pre-reserved areas. After drying at 80-100 ℃ for 1-2 h, the substrate is placed in a muffle furnace and heated to 1100 ℃ at 2-3 ℃ / min, held for 50 min, and then cooled with the furnace to complete co-firing; after co-firing, the substrate is treated with oxygen plasma for 5-10 min to clean the surface of the wires and pad trenches. S4. Circuit wiring and packaging Ni is deposited in the wire pre-reserved area and pad area using high-power pulsed magnetron sputtering technology with the assistance of a precision metal mask. 80 Cr 20 An alloy thin film is used to form an embedded circuit. After the wire connection is completed, an aluminum oxide thin film is deposited and encapsulated using atomic layer deposition technology to obtain a bridge embedded sensor.

3. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S11, the mass of aluminum nitrate is 4-6 wt.% of the mass of the functional ceramic powder, the mass of tetraethyl orthosilicate is 9-11 wt.% of the mass of the functional ceramic powder, and the mass of anhydrous ethanol is 142-174 wt.% of the mass of the functional ceramic powder.

4. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S12, the mass ratio of the nano-alumina powder, zirconium oxide powder, and functional ceramic powder A is 5:3:2; the mass of the lead borosilicate glass powder is 4-6 wt.% of the total mass of the mixed powder.

5. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In steps S13 and S14, the organic carriers are all polyvinyl butyral, dioctyl phthalate, and triethyl phosphate, wherein: the mass of polyvinyl butyral is 6-8 wt.% of the ceramic aggregate, the mass of dioctyl phthalate is 3-5 wt.% of the ceramic aggregate, and the mass of triethyl phosphate is 0.8-1.2 wt.% of the ceramic aggregate; the solvents are all anhydrous ethanol, and the mass of anhydrous ethanol is 20-40 wt.% of the ceramic aggregate.

6. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S14, the mass of the sodium sulfate crystals is 15-25 wt.% of the ceramic aggregate, and the mass of the PMMA microspheres is 10-15 wt.% of the ceramic aggregate.

7. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S2, the sintering is performed according to the following procedure: (a) In the first heating stage, the temperature was increased from room temperature to 450℃ at a rate of 0.5℃ / min and held for 1 h. Then, the temperature was increased to 600℃ at the same rate and held for another 1 h. (b) In the second heating stage, the temperature is increased from 600 ℃ to 1100 ℃ at a heating rate of 1 ℃ / min, and held for 1-1.5 h; (c) In the third heating stage, the temperature is increased from 1100 ℃ to 1600 ℃ at a heating rate of 2 ℃ / min, and held for 2-3 h; (d) During the cooling stage, the temperature is first reduced from 1600 ℃ to 800 ℃ at a cooling rate of 3 ℃ / min, and then cooled to room temperature along with the furnace.

8. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S3, the depth of the laser etching is 50 μm; the reserved area of ​​the piezoresistive sensing unit is a square area with a side length of 2 mm; the width of the wire reserved area is 150 μm; and the pad area is a square area with a side length of 1 mm. The filling thickness of the transition layer powder B slurry is 40%-60% of the groove depth of the reserved area of ​​the piezoresistive sensing unit.

9. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S3, the preparation process of the transition layer powder B and functional ceramic powder A slurry is as follows: the transition layer powder B and functional ceramic powder A are mixed with α-terpineol at a mass ratio of 3:1, and ethyl cellulose accounting for 1 wt.% of the powder mass is added to each as a binder, and then ground to form a slurry.

10. The method for fabricating a bridge-embedded sensor according to claim 2, characterized in that, In step S4, the high-power pulsed magnetron sputtering is performed under an argon atmosphere with a working pressure of 0.3-0.8 Pa and a high-pulse peak power of 1-2 kW / cm². 2 The pulse frequency is 200 Hz, the duty cycle is 20%, and the deposited Ni 80 Cr 20 The alloy film thickness is 1-2 μm; the alumina film thickness of the atomic layer deposition is 50-200 nm.

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