Nozzle structure and secondary pneumatic-inertial focusing aerosol ink-jet printing method
By designing the first conical contraction channel, a constant diameter straight tube channel and a second conical contraction channel in the nozzle structure, the ink particles are pre-focused and actively converged at the center and terminals by using the sheath gas to prevent the ink particles from being focused and actively converged at the center and terminals, the problems of limited accuracy and over-spraying in the existing aerosol inkjet printing technology are solved, and aerosol inkjet printing with high precision and wide adaptability are achieved.
Patent Information
- Application Number
- CN202510639663.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-06-20
AI Technical Summary
The existing aerosol inkjet printing technology has limited ultimate accuracy and accuracy range, and there is a problem of over-spraying.
A nozzle structure is adopted, which includes a first conical contraction channel, a constant diameter straight tube channel and a second conical contraction channel, in which the ink particles are pre-focused and actively converged and end-bound, respectively, through the action of the sheath gas, thereby achieving high precision and wide adaptability of aerosol inkjet printing.
It significantly improves the ultimate accuracy and accuracy range of aerosol inkjet printing, reduces over-spraying, and achieves higher resolution and wider applicability.
Smart Images
Figure CN120171184A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of microfluid dynamics technology, and more specifically, to a nozzle structure and a secondary pneumatic-inertial focusing aerosol inkjet printing method. Background Art
[0002] With the rapid development of aerospace equipment towards high integration, intelligence and conformality, the configuration design of electronic systems also shows a trend of cross-generational evolution. In order to realize the integration of functional electronic devices on the surface of complex structures, conformal printing technology, as a manufacturing method that can adapt to curved surfaces and variable curvature substrates, has become an important direction for advanced equipment electronic manufacturing. Aerosol Jet Printing (AJP) technology has become one of the most reliable key means of conformal electronic manufacturing due to its advantages of non-contact, high resolution, and strong material compatibility. This technology atomizes functional ink into aerosol by pneumatic or ultrasonic means, transmits it to the nozzle with the help of inert carrier gas, and uses coaxial sheath gas for pneumatic focusing, so that it can be sprayed at high speed to the complex curved substrate under non-contact conditions to achieve patterned deposition. Finally, electronic devices with electrical functions are obtained by thermal sintering, photocuring, etc. Aerosol inkjet printing technology not only supports stable deposition on high-curvature and hyperbolic substrates at a spray distance of 1~5mm, but also can achieve a line width resolution of up to 10μm. It is compatible with a variety of conductive and dielectric ink materials with a particle size of less than 10~100nm and a viscosity range of 1~1000cP. It is currently the mainstream method for achieving high-performance conformal electronic manufacturing.
[0003] However, most of the existing pneumatic focusing nozzles rely only on sheath gas flow to form a single pneumatic focusing mechanism, and there are still the following technical bottlenecks and deficiencies: (1) The ultimate accuracy needs to be improved. The existing nozzle structure is limited by single-stage pneumatic focusing. Its particle beam stability is extremely sensitive to sheath gas velocity and carrier gas disturbance, which leads to particle scattering or focus outward shift when further compressing the focusing beam diameter to pursue higher resolution. It is difficult to break through the existing line width accuracy limit (20μm), limiting its application potential in higher-precision micro-nanoscale functional patterns. (2) The accuracy range needs to be expanded. The focusing ability of the existing nozzle varies significantly under different ink viscosities, particle sizes or flow rates. It lacks the ability to adjust the structure to adapt to multiple working conditions. Therefore, it is difficult to achieve flexible printing of line widths from tens of microns to hundreds of microns in the same nozzle structure, which restricts the versatility and adjustment freedom of the process. (3) Overspray needs to be suppressed. During high-speed spraying, the low-density area at the outer edge of the aerosol particle beam is prone to form an "overspray" effect due to lateral momentum diffusion, especially on multi-contour scanning and complex curvature substrates. It is more likely to cause pattern edge defects, which restricts the integration density of high-density arrays. The existing nozzle structure cannot effectively control particle alignment and boundary particle convergence, and lacks means to suppress spray diffusion at the source. Summary of the Invention
[0004] The object of the present invention is to provide a nozzle structure and a secondary pneumatic-inertial focusing aerosol inkjet printing method, which are used to solve the technical problems existing in the existing aerosol inkjet printing technology, such as limited ultimate precision and precision range, and overspray. In view of this, the present invention is realized through the following solutions.
[0005] In a first aspect, the present invention provides a nozzle structure that utilizes a sheath gas channel and an ink channel, and the sheath gas channel and the ink channel are connected. The nozzle structure includes: A first conical contraction channel, having a first expansion end and a first contraction end; A second conical contraction channel, having a second expansion end and a second contraction end with a nozzle opening; A constant-diameter straight tube channel, one end of which is connected to the first contraction end, the other end of which is connected to the second expansion end, and forms a passage from the first expansion end to the nozzle opening; The nozzle structure is connected to the outlet end of the ink channel through the first expansion end.
[0006] Compared with the prior art, the nozzle structure of the present invention is used for aerosol inkjet printing, specifically for secondary pneumatic-inertial focusing aerosol inkjet printing; by using the above nozzle structure, when using the ink particles to be printed, under the action of the sheath gas, the ink particles sequentially enter the first conical contraction channel, the constant-diameter straight tube channel and the second conical contraction channel, and finally are ejected onto the surface of the target substrate through the nozzle opening; further, based on the specific design of the above nozzle structure, the ink particles are pre-focused in the first conical contraction channel, actively centered in the constant-diameter straight tube channel, and terminally converged in the second conical contraction channel.
[0007] Specifically, on the first aspect, during the first-stage aerodynamic focusing (i.e., pre-focusing), based on the sheath flow compression mechanism induced by axial contraction, the high-speed inert sheath gas and the aerosol flow in the middle are guided to accelerate together in the axial direction through the structure of the first conical contraction channel, so that the sheath gas forms an obvious velocity difference and pressure gradient between the inlet and the center flow. According to the boundary layer superposition theory and the laminar shear focusing principle, the velocity distribution in this area presents a parabolic structure, with low velocity in the center and high velocity at the boundary, so that the aerosol particles close to the boundary are driven by the centripetal shear force to gather toward the center; in addition, since the aerosol particles (ink particles) have a certain inertia, and The Stokes number remains moderate in this area, and the particle trajectory is delayed from the flow-carrying streamline, so that it will not diffuse quickly along the edge, which helps to form a stable and uniform axial primary focusing core area. The main function of this stage is to suppress the early divergence and particle leakage from the nozzle outlet, and improve the initial symmetry of subsequent focusing; secondly, in the process of inertial focusing (i.e. active centering), its purpose is to achieve radial migration and active centering focusing; after the aerosol particle (ink particle) stream enters the above-mentioned constant diameter straight tube channel, since the flow field is close to the axisymmetric stable state, the shear velocity gradient gradually stabilizes along the radial direction, and the ink particles are controlled by the lateral inertial drift effect; at low Reynolds In the flow, the ink particles will migrate to a specific radial equilibrium position in the channel section due to inertia; this process makes the ink particles tend to be stably distributed at a certain distance from the axis and deviate from the wall, but there is still a centrifugal drift trend; because the sheath gas continues to form a shear zone in the channel, the particles are further induced by the radial velocity gradient, and their inertial response time controls their lateral drift path, and finally gradually aligns with the central axis; in this process, the channel length, flow rate and particle size jointly regulate the Stokes number of the ink particles, so that the ink particles just complete a complete centrifugal migration process in the inertial section; further, by calculating the optimal migration path and hysteresis The length of the constant diameter straight tube channel is designed so that all ink particles can complete lateral focusing before leaving this section; therefore, the constant diameter straight tube channel has the advantages of no external field drive, active centering, and strong anti-interference focusing, which significantly improves the symmetry and subsequent compression efficiency of the (ink particle) flow beam, and is the core of achieving multi-particle size adaptability and multi-condition stable focusing; thirdly, the second-stage pneumatic focusing (i.e., terminal convergence) process is the final convergence and emission forming stage of the entire focusing process. In this process, the above-mentioned second conical contraction channel is used. Unlike the first-stage pneumatic focusing, the (ink particle) flow beam has high centering and particle density at this time;At the second contraction end of the second conical contraction channel, which can also be considered as the nozzle, a strong axial negative pressure is formed, further accelerating the central aerosol main flow, increasing the outlet velocity and compressing the flow path, improving the collimation of the (ink particle) particle beam and reducing the jet divergence angle. During this process, the radial stress concentration mechanism can be as follows: a relatively high shear stress is formed on the contraction wall surface, which, combined with the compression of the central main flow, causes the (ink particles) to further concentrate in the axial region, forming a particle beam core with high density and low divergence. During this process, ink particles with a small Stokes number can also stably follow the flow during axial compression, avoiding dispersion near the nozzle (or outlet) due to insufficient inertia, effectively expanding the applicable particle size range. As a summary of the above description, the nozzle structure of the present invention is applicable to a specific aerosol inkjet printing method. By using the above nozzle structure, the specific aerosol inkjet printing method can perform the first-stage pneumatic focusing, inertial focusing, and second-stage pneumatic focusing in the first conical contraction channel, the constant-diameter straight tube channel, and the second conical contraction channel in sequence, thereby achieving the object of the present invention and solving the technical problems of limited ultimate accuracy and accuracy range and overspraying existing in the existing aerosol inkjet printing technology.
[0008] Further, in the nozzle structure of the present invention, the ratio of the inner diameter to the length of the constant-diameter straight tube channel is 1:(10 - 40).
[0009] Further, in the nozzle structure of the present invention, the ratio of the diameter of the first expansion end to the height of the first conical contraction channel is 1:(10 - 20); And / or, the ratio of the diameter of the second expansion end to the height of the second conical contraction channel is 1:(5 - 10).
[0010] In a second aspect, the present invention provides a secondary pneumatic-inertial focusing aerosol inkjet printing method. By using the above nozzle structure, under the action of sheath gas, ink particles perform the first-stage pneumatic focusing in the first conical contraction channel, inertial focusing in the constant-diameter straight tube channel, and second-stage pneumatic focusing in the second conical contraction channel, and then are ejected through the nozzle to the surface of the target substrate.
[0011] Compared with the prior art, the beneficial effects of the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention are the same as those of the nozzle structure described in the above technical solution, and will not be elaborated here.
[0012] Further, the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention includes the following steps: Step 1, atomizing liquid ink into suspended aerosol particles; Step 2, introducing the aerosol particles into the first conical contraction channel of the nozzle structure through the ink channel, and introducing inert sheath gas from a plurality of symmetrically arranged sheath gas channels; Step 3: The aerosol particles enter the constant-diameter straight tube channel from the first tapered contraction channel, and the aerosol particles undergo radial migration in the velocity gradient field induced by sheath gas shearing. Step 4: The aerosol particles enter the second tapered contraction channel from the constant-diameter straight tube channel, and the sheath gas performs pneumatic compression on the particle beam formed by the aerosol particles that have been inertially centered. Step 5: The aerosol particles after pneumatic compression in the second tapered contraction channel are ejected onto the surface of the target substrate.
[0013] Furthermore, in the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention, after the aerosol particles are ejected onto the surface of the target substrate, it further includes: Solidifying and forming the deposited layer of aerosol particles on the surface of the target substrate; the solidifying and forming methods include laser sintering, photocuring, and heat treatment; after solidifying and forming, a functional conformal electronic functional structure is formed on the surface of the target substrate.
[0014] Furthermore, in the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention, during the process of introducing the inert sheath gas from multiple symmetrically arranged sheath gas channels, the flow rate of the sheath gas is 5 - 120 sccm; and / or, the diameter of the nozzle is 300 - 500 μm; and / or, during the process of ejecting the aerosol particles onto the surface of the target substrate, the ejection speed of the aerosol particles is 10 - 100 m / s, and the distance from the nozzle to the surface of the target substrate is 1 - 5 mm.
[0015] Furthermore, in the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention, the atomization of the liquid ink into suspended aerosol particles includes: Converting the liquid ink containing conductive, dielectric, or functional nanomaterials into suspended aerosol particles by pneumatic atomization or ultrasonic atomization.
[0016] Furthermore, in the process of atomizing the liquid ink into suspended aerosol particles in the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention, the particle size of the ink is 10 - 100 nm, and a piezoelectric ultrasonic atomizer or a pneumatic atomizer is selected; an inert carrier gas is used to stably transport the atomized aerosol particles to the inlet of the nozzle mechanism.
[0017] In the third aspect, the present invention provides a secondary pneumatic-inertial focusing aerosol inkjet printing device, and the secondary pneumatic-inertial focusing aerosol inkjet printing device is provided with the above-mentioned nozzle structure.
[0018] Compared with the prior art, the beneficial effects of the secondary pneumatic-inertial focusing aerosol inkjet printing device of the present invention are the same as those of the nozzle structure described in the above technical solution, and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is a schematic connection diagram of the nozzle structure of the present invention with the sheath gas channel or the ink channel; Figure 2 is a schematic diagram of the arrangement of the sheath gas channel and the ink channel in the aerosol inkjet printing method of the present invention; Figure 3 is a schematic diagram of the first-stage pneumatic focusing in the aerosol inkjet printing using the nozzle structure of the present invention or the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention; Figure 4 is a schematic diagram of inertial focusing in the aerosol inkjet printing using the nozzle structure of the present invention or the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention; Figure 5 is a schematic diagram of the second-stage pneumatic focusing in the aerosol inkjet printing using the nozzle structure of the present invention or the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention; Figure 6 is a schematic connection diagram of a nozzle structure of the present invention with the ink channel; Figure 7 is a schematic connection diagram of another nozzle structure of the present invention with the ink channel; wherein: Figure 7 (a) is a perspective view, Figure 7 (b) is a front view; Figure 8 is a schematic diagram of various nozzle structures of the present invention; wherein: Figure 8 (a) is a schematic diagram of the first nozzle structure, Figure 8 (b) is a schematic diagram of the second nozzle structure, Figure 8 (c) is a schematic diagram of the third nozzle structure, Figure 8 (d) is a schematic diagram of the fourth nozzle structure.
[0020] REFERENCE SIGNS: 1. Sheath gas channel; 2. Ink channel; 3. Nozzle structure; 301. First tapered contraction channel; 302. Second tapered contraction channel; 303. Constant-diameter straight tube channel. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0022] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.
[0023] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined. "Several" means one or more unless otherwise specifically defined.
[0024] Most of the existing pneumatic focusing nozzles only rely on the sheath gas flow to form a single pneumatic focusing mechanism, and there are still the following technical bottlenecks and deficiencies: (1) The ultimate precision needs to be improved urgently. The existing nozzle structure is limited by the single-stage pneumatic focusing. The stability of its particle beam is extremely sensitive to the sheath gas velocity and carrier gas perturbation, resulting in particle scattering or focal point shift when further compressing the focused beam diameter to pursue higher resolution, and it is difficult to break through the existing line width precision limit (20 μm), which limits its application potential in higher-precision micro-nano scale functional patterns. (2) The precision range needs to be expanded urgently. The focusing ability of the existing nozzles varies significantly under different ink viscosities, particle sizes or flow rates, and lacks the structural adjustment ability for multi-condition adaptability. Therefore, it is very difficult to flexibly print line widths from tens of microns to hundreds of microns in the same nozzle structure, which restricts the universality and adjustment freedom of the process. (3) Overspray needs to be suppressed urgently. During the high-speed spraying process, the low-density region on the outer edge of the aerosol particle beam is prone to form an "overspray" effect due to lateral momentum diffusion, especially on multi-profile scans and complex curvature substrates, which is more likely to cause pattern edge defects, restricting the integration density of high-density arrays, making the existing nozzle structure unable to effectively control the particle alignment and the convergence of boundary particles, and lacking means to suppress spraying diffusion at the source.
[0025] Please refer to Figures 1 to 8 , to solve the above technical problems, in the first aspect, the present invention provides a nozzle structure 3, which utilizes a sheath gas channel 1 and an ink channel 2, and the sheath gas channel 1 and the ink channel 2 are connected. The nozzle structure 3 includes a first tapered contraction channel 301, a second tapered contraction channel 302 and a constant-diameter straight tube channel 303, wherein: The first conical contraction channel 301 has a first expansion end and a first contraction end; the second conical contraction channel 302 has a second expansion end and a second contraction end provided with a nozzle opening; one end of the constant-diameter straight tube channel 303 is connected to the first contraction end, the other end is connected to the second expansion end, and a path is formed from the first expansion end to the nozzle opening; the nozzle structure 3 is connected to the outlet end of the ink channel 2 through the first expansion end.
[0026] During specific implementation: by using the above nozzle structure 3 and using the ink particles to be printed, under the action of the sheath gas, the ink particles sequentially enter the first conical contraction channel 301, the constant-diameter straight tube channel 303, and the second conical contraction channel 302, and finally are ejected to the surface of the target substrate through the nozzle opening; based on the specific design of the above nozzle structure 3, the ink particles are pre-focused in the first conical contraction channel 301, actively centered in the constant-diameter straight tube channel 303, and terminally converged in the second conical contraction channel 302, and then are ejected to the surface of the target substrate through the nozzle opening.
[0027] Based on the composition and connection relationship of the above nozzle structure 3, and the above specific implementation process, it can be concluded that: The nozzle structure 3 of the present invention is used for aerosol inkjet printing, specifically for aerosol inkjet printing of secondary pneumatic-inertial focusing gas; by using the above nozzle structure 3 and the ink particles to be printed, under the action of the sheath gas, the ink particles sequentially enter the first conical contraction channel 301, the constant-diameter straight pipe channel 303, and the second conical contraction channel 302, and finally are ejected onto the surface of the target substrate through the nozzle; further, based on the specific design of the above nozzle structure 3, the ink particles are pre-focused in the first conical contraction channel 301, actively centered in the constant-diameter straight pipe channel 303, and terminally converged in the second conical contraction channel 302. Specifically, on the one hand, during the first-stage pneumatic focusing (i.e., pre-focusing) process, based on the sheath flow compression mechanism induced by axial contraction, through the structure of the above first conical contraction channel 301, the high-speed inert sheath gas and the intermediate aerosol flow are guided to accelerate together in the axial direction, so that there is an obvious velocity difference and pressure gradient between the sheath gas and the central flow at the inlet. According to the boundary layer superposition theory and the laminar shear focusing principle, the velocity distribution in this region presents a parabolic-like structure, with low velocity in the center and high velocity at the boundary, so that the aerosol particles near the boundary are driven by the centripetal shear force to gather towards the center; in addition, since the aerosol particles (ink particles) have a certain inertia and the Stokes number remains moderate in this region, the particle trajectory lags behind the carrier streamline, so that it will not quickly spread along the edge, which helps to form a stable and uniform axial primary focusing core area. The main function of this stage is to suppress early divergence and particle leakage at the nozzle outlet, and improve the initial symmetry of subsequent focusing; on the other hand, during the inertial focusing (i.e., active centering) process, its purpose is to achieve radial migration and active centering focusing; after the aerosol particle (ink particle) beam enters the above constant-diameter straight pipe channel 303, since the flow field is close to an axisymmetric steady state and the shear velocity gradient gradually stabilizes along the radial direction, the ink particles are controlled by the transverse inertial drift effect; in a low Reynolds number flow, the ink particles will migrate to a specific radial equilibrium position within the channel cross-section due to inertia; this process makes the ink particles tend to be stably distributed at a certain distance from the axis and deviate from the wall, but there is still a centrifugal drift trend; since the sheath gas continues to form a shear zone in the channel, the particles are further induced by the radial velocity gradient, and its inertial response time controls its transverse drift path, and finally gradually aligns with the central axis; in this process, the channel length, flow velocity and particle size jointly control the Stokes number of the ink particles, so that the ink particles just complete a complete centering migration process within the inertial section; further, by calculating the optimal migration path and the lag distance, the length of the constant-diameter straight pipe channel 303 is designed so that the ink particles complete lateral focusing before leaving this section; therefore, the constant-diameter straight pipe channel 303 has the focusing advantages of no external field drive, active centering, and strong anti-interference ability, significantly improving the symmetry of the (ink particle) beam and the subsequent compression efficiency, and is the core to achieve multi-particle size adaptability and multi-condition stable focusing;Thirdly, the second-stage pneumatic focusing (i.e., terminal convergence) process is the final convergence and emission forming stage of the entire focusing process. In this process, the above-mentioned second conical contraction channel 302 is adopted. Different from the first-stage pneumatic focusing, at this time, the (ink particle) beam already has high centricity and particle density; at the second contraction end of the second conical contraction channel 302, which can also be considered as the nozzle, a strong axial negative pressure is formed, further accelerating the central aerosol main flow, increasing the outlet velocity and compressing the flow path, so as to improve the collimation of the (ink particle) particle beam and reduce the jet divergence angle. In this process, the radial stress concentration mechanism can be: the contraction wall surface forms a relatively high shear stress, which cooperates with the central main flow compression, and the (ink particle) particles are further concentrated in the axial center region to form a high-density and low-divergence particle beam core. In this process, ink particles with a small Stokes number can also stably follow the flow during axial compression, avoiding dispersion near the nozzle (or outlet) due to insufficient inertia, effectively expanding the applicable particle size range. As a summary of the above description, the nozzle structure 3 of the present invention is applicable to a specific aerosol inkjet printing method. By using the above nozzle structure 3, the first-stage pneumatic focusing, inertial focusing and second-stage pneumatic focusing can be sequentially carried out in the first conical contraction channel 301, the constant-diameter straight pipe channel 303 and the second conical contraction channel 302 respectively, so as to achieve the purpose of the present invention and solve the technical problems existing in the existing aerosol inkjet printing technology, such as limited ultimate accuracy and accuracy range, and overspraying.;
[0028] As a possible implementation manner, in the nozzle structure 3 of the present invention, the ratio of the inner diameter to the length of the constant-diameter straight pipe channel 303 is 1:(10~40). In the case of adopting the above technical solution, based on the velocity gradient inside the flow field, through the coupling action of shear induction and inertial response, the ink particles are driven to migrate towards the central axis to achieve active centering focusing; specifically, by using the internal shear velocity difference, the ink particles at different radial positions are guided to spontaneously converge towards the center, improving the particle beam density and axial symmetry and enhancing the final focusing quality; further, the particle trajectories deviating from the main axis are effectively corrected, making the particle focusing more concentrated, which helps to eliminate the edge blur and satellite deposition phenomena caused by particle scattering and improve the pattern edge clarity; further, by designing a reasonable channel length and flow velocity range, the compatibility with the ink system and printing parameter fluctuations is enhanced; the shaping effect on the particle beam can provide a more concentrated and orderly input flow for the downstream pneumatic focusing section, significantly improving the subsequent convergence efficiency and helping to achieve ultra-high resolution and low-divergence beam output; for example, the ratio of the inner diameter to the length of the constant-diameter straight pipe channel 303 can be 1:10, 1:30 or 1:40.
[0029] As a possible implementation, in the nozzle structure 3 of the present invention, the ratio of the diameter of the first expansion end to the height of the first conical contraction channel 301 is 1:(10 - 20), and the ratio of the diameter of the second expansion end to the height of the second conical contraction channel 302 is 1:(5 - 10).
[0030] In the case of adopting the above technical solution, multi-level contraction control of the aerosol flow field can be achieved; specifically, in the first-stage pneumatic focusing process, an initial axial focusing environment is established. This process forms a wrapped compression through conical contraction and sheath gas injection, constructs a central acceleration region, and effectively prevents the initial divergence of aerosol particles; improves central symmetry, stabilizes the inlet flow field of the inertial section, creates conditions for subsequent inertial migration, and improves the consistency and repeatability of the overall focusing path; reduces early wall deposition, improves particle transport efficiency, and after pre-focusing, the particles are more concentrated on the main axis, reducing the probability of particle deviation and channel attachment; in the second-stage pneumatic focusing process, final particle beam compression can be achieved, reducing the divergence angle: the particle beam further converges at the outlet to form a printing jet with high collimation and extremely small divergence; it can also enhance the ejection speed, increase the deposition energy density, enhance the axial pressure difference, and improve the ejection speed and deposition stability; further, it can suppress overspray at the edge, improve the pattern boundary quality, effectively suppress the diffusion of particles outside the beam, and contribute to the formation of a clear and sharp pattern edge; for example, the ratio of the diameter of the first expansion end to the height of the first conical contraction channel 301 can be 1:10, 1:15 or 1:20; the ratio of the diameter of the second expansion end to the height of the second conical contraction channel 302 can be 1:5, 1:7 or 1:10.
[0031] In a second aspect, the present invention also provides a secondary pneumatic-inertial focusing aerosol inkjet printing method. This aerosol inkjet printing method uses the nozzle structure 3 of the above technical solution. Under the action of the sheath gas, ink particles are subjected to first-stage pneumatic focusing in the first conical contraction channel 301, inertial focusing in the constant-diameter straight pipe channel 303, and second-stage pneumatic focusing in the second conical contraction channel 302, and then are ejected onto the surface of the target substrate through the nozzle.
[0032] In the case of adopting the above technical solution, by using the nozzle structure 3 of the above technical solution and using the ink particles to be printed, under the action of the sheath gas, the ink particles sequentially enter the first conical contraction channel 301, the constant-diameter straight tube channel 303 and the second conical contraction channel 302, and finally are ejected onto the surface of the target substrate through the nozzle; further, based on the specific design of the above nozzle structure 3, the ink particles are pre-focused in the first conical contraction channel 301, actively centered in the constant-diameter straight tube channel 303, and finally converged at the terminal in the second conical contraction channel 302. Specifically, on the one hand, in the process of the first-stage pneumatic focusing (i.e., pre-focusing), based on the sheath flow compression mechanism induced by axial contraction, through the structure of the above first conical contraction channel 301, the high-speed inert sheath gas and the intermediate aerosol flow are guided to accelerate together in the axial direction, so that there is an obvious velocity difference and pressure gradient between the sheath gas and the central flow at the inlet. According to the boundary layer superposition theory and the laminar shear focusing principle, the velocity distribution in this region presents a parabolic-like structure, with low velocity in the center and high velocity at the boundary, so that the aerosol particles near the boundary are driven by the centripetal shear force to gather towards the center; in addition, since the aerosol particles (ink particles) have a certain inertia and the Stokes number remains moderate in this region, the particle trajectory lags behind the carrier streamline, so that it will not quickly spread along the edge, which helps to form a stable and uniform axial primary focusing core region. The main function of this stage is to suppress the early divergence and the leakage of particles at the nozzle outlet, and improve the initial symmetry of the subsequent focusing; on the other hand, in the process of inertial focusing (i.e., active centering), the purpose is to achieve radial migration and active centering focusing; after the aerosol particle (ink particle) beam enters the above constant-diameter straight tube channel 303, since the flow field is close to the axisymmetric steady state and the shear velocity gradient gradually stabilizes along the radial direction, the ink particles are controlled by the transverse inertial drift effect; in the low Reynolds number flow, the ink particles will migrate to a specific radial equilibrium position within the channel cross-section due to inertia; this process makes the ink particles tend to be stably distributed at a certain distance from the axis and deviate from the wall, but there is still a centrifugal drift trend; since the sheath gas continues to form a shear zone in the channel, the particles are further induced by the radial velocity gradient, and their inertial response time controls their transverse drift path, and finally gradually aligns towards the central axis; in this process, the channel length, flow velocity and particle diameter jointly regulate the Stokes number of the ink particles, so that the ink particles just complete a complete centering migration process within the inertial section; further, by calculating the optimal migration path and the lag distance, the length of the constant-diameter straight tube channel 303 is designed so that all the ink particles complete the transverse focusing before leaving this section; therefore, the constant-diameter straight tube channel 303 has the focusing advantages of being actively centered without external field drive and strong anti-interference ability, significantly improving the symmetry of the (ink particle) beam and the subsequent compression efficiency, and is the core to achieve multi-particle size adaptability and multi-condition stable focusing;Thirdly, the second-stage aerodynamic focusing (i.e., terminal focusing) process is the final focusing and emission forming stage of the entire focusing process. In this process, the second conical contraction channel 302 is used. Different from the first-stage aerodynamic focusing, the (ink particle) beam has high centrifugality and particle density at this time. The second contraction end of the second conical contraction channel 302 can also be considered as a strong axial negative pressure formed at the nozzle, which further accelerates the central aerosol mainstream, increases the outlet velocity and compresses the flow path, so that the (ink particle) particle beam collimation is improved and the jet divergence angle is reduced. In this process, the radial stress concentration mechanism can be: the contraction wall forms a higher shear stress, and with the compression of the central mainstream, the (ink particle) particles are further concentrated in the axial area to form a high-density, low-divergence particle beam core. In this process, ink particles with a smaller Stokes number can also stably follow the flow in the axial compression, avoiding dispersion near the nozzle (or outlet) due to insufficient inertia, and effectively expanding the applicable particle size range. ;
[0033] Furthermore, an embodiment of the present invention provides a specific secondary pneumatic-inertial focusing aerosol inkjet printing method, comprising the following steps: Step 1, atomizing the liquid ink into suspended aerosol particles; Step 2, introducing aerosol particles into the first tapered contraction channel 301 of the nozzle structure 3 through the ink channel 2, and introducing inert sheath gas from a plurality of symmetrically arranged sheath gas channels 1; Step 3, aerosol particles enter the constant diameter straight tube channel 303 from the first tapered contraction channel 301, and the aerosol particles migrate radially in the velocity gradient field induced by sheath gas shear; Step 4, the aerosol particles enter the second tapered contraction channel 302 from the constant diameter straight tube channel 303, and the sheath gas pneumatically compresses the particle beam formed by the aerosol particles that have been inertially centered; Step 5: The pneumatically compressed aerosol particles in the second conical contraction channel 302 are sprayed onto the target substrate surface.
[0034] In the case of adopting the above technical solution, in the secondary pneumatic-inertial focusing aerosol inkjet printing method of the present invention, the first-stage pneumatic focusing (i.e., pre-focusing) is performed in step 2, the inertial focusing (i.e., active centering) is performed in step 3, and the second-stage pneumatic focusing (i.e., terminal convergence) is performed in step 4; specifically, in step 2, the sheath gas forms an axially wrapped flow field, and the aerosol particles are compressed to the center of the channel by the boundary shear force. This process is mainly used to increase the axial velocity of the aerosol and suppress the initial particle divergence, and construct a preliminarily focused particle beam; in step 3, the aerosol particles enter a constant-diameter straight tube channel (inertial focusing section), and the aerosol particles undergo radial migration in the velocity gradient field induced by the sheath gas shear. Due to the density difference and fluid inertia of the aerosol particles, they will gather towards the central region with a lower velocity; this process strengthens the centering effect of the particles; by controlling the length-diameter ratio of the inertial section between 5 and 15, the inertial focusing path of different particle sizes can be adapted; in step 4, the second-stage sheath gas is introduced into the second conical contraction channel to further pneumatically compress the particle beam that has been inertially centered; this compression process has a stronger compression and wrapping effect, increases the particle beam density, converges the particle beam profile, and forms a jet with low divergence, high density, and stable output; more specifically, the detailed processes or principle explanations of the first-stage pneumatic focusing, inertial focusing, and second-stage pneumatic focusing have been specifically described in the foregoing technical solution, and will not be elaborated here.
[0035] Furthermore, another embodiment of the present invention provides a specific secondary pneumatic-inertial focusing aerosol inkjet printing method, including the following steps: S100, atomize the liquid ink into suspended aerosol particles; S200, introduce the aerosol particles into the first conical contraction channel 301 of the nozzle structure 3 through the ink channel 2, and introduce the inert sheath gas from a plurality of symmetrically arranged sheath gas channels 1; S300, the aerosol particles enter the constant-diameter straight tube channel 303 from the first conical contraction channel 301, and the aerosol particles undergo radial migration in the velocity gradient field induced by the sheath gas shear; S400, the aerosol particles enter the second conical contraction channel 302 from the constant-diameter straight tube channel 303, and the sheath gas pneumatically compresses the particle beam formed by the aerosol particles that have been inertially centered; S500, the aerosol particles pneumatically compressed in the second conical contraction channel 302 are ejected onto the surface of the target substrate; S600, cure and form the aerosol particle deposition layer on the surface of the target substrate; the curing and forming methods include laser sintering, photocuring, and heat treatment; after curing and forming, a functional conformal electronic functional structure is formed on the surface of the target substrate.
[0036] Furthermore, another embodiment of the present invention provides a specific secondary pneumatic-inertial focusing aerosol inkjet printing method, including the following steps: Step 1, atomize the liquid ink into suspended aerosol particles; Among them, atomizing the liquid ink into suspended aerosol particles includes: Convert the liquid ink containing conductive, dielectric or functional nanomaterials into suspended aerosol particles by pneumatic atomization or ultrasonic atomization; During the process of atomizing the liquid ink into suspended aerosol particles, the ink particle size is 10~100nm, and a piezoelectric ultrasonic atomizer or a pneumatic atomizer is selected; use an inert carrier gas to stably transport the atomized aerosol particles to the inlet of the nozzle mechanism; Step 2, introduce the aerosol particles into the first conical contraction channel 301 of the nozzle structure 3 through the ink channel 2, and introduce the inert sheath gas from the plurality of symmetrically arranged sheath gas channels 1; Among them, the flow rate of the sheath gas is 5~120 sccm, the diameter of the nozzle is 300~500μm, which can be adjusted according to the printing resolution requirements. During the process of the aerosol particles being ejected onto the target substrate surface, the ejection speed of the aerosol particles is 10~100m / s, and the distance from the nozzle to the target substrate surface is 1~5mm; Step 3, the aerosol particles enter the constant-diameter straight tube channel 303 from the first conical contraction channel 301, and the aerosol particles undergo radial migration in the velocity gradient field induced by the sheath gas shear; Step 4, the aerosol particles enter the second conical contraction channel 302 from the constant-diameter straight tube channel 303, and the sheath gas performs pneumatic compression on the particle beam formed by the aerosol particles that have been inertial-centered; Step 5, the pneumatically compressed aerosol particles in the second conical contraction channel 302 are ejected onto the target substrate surface; Step 6, cure and form the aerosol particle deposition layer on the target substrate surface; the curing and forming methods include laser sintering, photocuring and heat treatment; after curing and forming, a functional conformal electronic functional structure is formed on the target substrate surface.
[0037] In the above technical solution, various parameters can be adjusted according to the printing resolution requirements. For example, the flow rate of the sheath gas can be 5 sccm, 50 sccm, 100 sccm or 120 sccm, the diameter of the nozzle can be 300μm, 400μm or 500μm, the ejection speed of the aerosol particles can be 10m / s, 40m / s, 70m / s or 100m / s, and the distance from the nozzle to the target substrate surface can be 1mm, 3mm or 5mm; the target substrate surface can be a flat substrate or a complex curved substrate with double curvature or variable curvature.
[0038] In a third aspect, the present invention provides a secondary pneumatic-inertial focusing aerosol inkjet printing device, and the secondary pneumatic-inertial focusing aerosol inkjet printing device is provided with an upper nozzle structure 3.
[0039] In the case of adopting the above technical solution, the secondary pneumatic-inertial focusing aerosol inkjet printing device of the present invention is provided with the nozzle structure 3 of the above technical solution. Based on the nozzle structure 3, the secondary pneumatic-inertial focusing aerosol inkjet printing device of the present invention can utilize the above nozzle structure 3 to use the ink particles to be printed. Under the action of the sheath gas, the ink particles sequentially enter the first conical contraction channel 301, the constant-diameter straight pipe channel 303, and the second conical contraction channel 302, and finally are ejected onto the surface of the target substrate through the nozzle. Based on the specific design of the above nozzle structure 3, the ink particles are pre-focused in the first conical contraction channel 301, actively centered in the constant-diameter straight pipe channel 303, and finally converge at the end in the second conical contraction channel 302 and are ejected onto the surface of the target substrate through the nozzle. Specifically, the working principle of the secondary pneumatic-inertial focusing aerosol inkjet printing device of the present invention is the same as that of the nozzle structure 3 of the above technical solution, and is also the same as the principle of the secondary pneumatic-inertial focusing aerosol inkjet printing method described in the above technical solution, and will not be elaborated here.
[0040] In summary, in the foregoing technical solutions of the present invention, through the specific structures of the components in the nozzle structure 3, during the inertial focusing process, the velocity shear field in the constant-diameter straight pipe channel is utilized to drive the particles to migrate towards the central axis, significantly improving the particle aggregation density and the beam shaping ability. Furthermore, in combination with the fine compression effect of the second conical contraction channel, the divergence angle of the jet beam can be greatly reduced, and finally a printing focusing effect superior to the existing structure is achieved. In other embodiments of the present invention, through experiments, it is verified that the foregoing nozzle structure 3 can achieve stable and continuous printing with a line width of 10 μm, and the ultimate resolution is increased by more than 50%. Further, the present invention enhances the focusing robustness by introducing an inertial regulation mechanism, enabling high focusing efficiency to be maintained within a wider range of gas flow rates, particle sizes, and ink physical properties. It exhibits consistent focusing performance within the total flow rate range of 5 - 120 sccm, supports free switching of line widths from 10 - 200 μm, greatly expanding the process window and adaptability of aerosol inkjet printing. Further, since there are problems such as particle deviation from the main axis and scattered focusing beams in the existing single-stage pneumatic focusing structure under high-speed conditions, which often result in blurred pattern edges and severe overspray; the present invention effectively corrects the particle distribution position by realizing the active centripetal migration of particles in the inertial focusing section and achieves secondary pneumatic beam convergence in the terminal section, thereby forming a particle beam with high density and low divergence angle, ultimately reducing the overspray at the pattern boundary by more than 80%. Further, the focusing process of the present invention is completely realized by the coupling of the internal structure flow field and does not rely on external physical field auxiliary control devices, having the advantages of high system simplicity and easy engineering integration, and being convenient for deployment and application on various commercial printing platforms. Further, the present invention has no restrictive requirements on the physical and chemical properties of the aerosol jet printing ink material, is applicable to conductive and dielectric inks (particle size range 10 - 100 nm, ink viscosity 1 - 15 cP), and has no interference with the aerosol jet printing system and no destructive effect (including physical and chemical destructive effects) on the ink material for aerosol jet printing.
[0041] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in a suitable manner in any one or more embodiments or examples.
[0042] The above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims
1. A nozzle structure, using a sheath gas channel and an ink channel, wherein the sheath gas channel and the ink channel are connected, characterized in that: The nozzle structure includes: a first tapered converging passage having a first expanding end and a first converging end; A second conical contraction channel has a second expansion end and a second contraction end with a nozzle; a constant diameter straight pipe channel, one end of which is connected to the first contraction end, the other end of which is connected to the second expansion end, and a passage is formed from the first expansion end to the nozzle; The nozzle structure is connected to the outlet end of the ink channel through the first expansion end.
2. The nozzle structure according to claim 1, characterized in that: The ratio of the inner diameter to the length of the constant diameter straight tube channel is 1:(10-40).
3. The nozzle structure according to claim 2, characterized in that: The ratio of the diameter of the first expansion end to the height of the first tapered contraction channel is 1:(10-20); And / or, the ratio of the diameter of the second expansion end to the height of the second tapered contraction channel is 1:(5-10).
4. A secondary pneumatic-inertial focusing aerosol inkjet printing method, characterized in that: Utilizing the nozzle structure described in any one of claims 1 to 3, under the action of sheath gas, the ink particles are respectively subjected to first-stage pneumatic focusing in the first conical contraction channel, inertial focusing in the constant-diameter straight tube channel, and second-stage pneumatic focusing in the second conical contraction channel, and then are sprayed onto the target substrate surface through the nozzle.
5. The secondary pneumatic-inertial focusing aerosol inkjet printing method according to claim 4, characterized in that: The following steps are involved: Step 1, atomizing the liquid ink into suspended aerosol particles; Step 2, introducing the aerosol particles into the first conical contraction channel of the nozzle structure through the ink channel, and introducing inert sheath gas from a plurality of symmetrically arranged sheath gas channels; Step 3, the aerosol particles enter the constant diameter straight tube channel from the first tapered contraction channel, and the aerosol particles migrate radially in the velocity gradient field induced by sheath gas shear; Step 4, the aerosol particles enter the second tapered contraction channel from the constant diameter straight tube channel, and the sheath gas pneumatically compresses the particle beam formed by the aerosol particles that have been inertially centered; Step 5: The aerosol particles pneumatically compressed in the second conical contraction channel are sprayed onto the target substrate surface.
6. The secondary pneumatic-inertial focusing aerosol inkjet printing method according to claim 5, characterized in that: After the aerosol particles are sprayed onto the target substrate surface, the method further comprises: The aerosol particle deposition layer on the surface of the target substrate is solidified and formed; the solidification and forming method includes laser sintering, photocuring and heat treatment; after solidification and forming, the surface of the target substrate forms a functional conformal electronic functional structure.
7. The secondary pneumatic-inertial focusing aerosol inkjet printing method according to claim 6, characterized in that: In the process of introducing the inert sheath gas from the plurality of symmetrically arranged sheath gas channels, the flow rate of the sheath gas is 5-120 sccm; And / or, the diameter of the nozzle is 300-500 μm; And / or, during the process of spraying the aerosol particles onto the target substrate surface, the spraying speed of the aerosol particles is 10-100 m / s, and the distance from the nozzle to the target substrate surface is 1-5 mm.
8. The secondary pneumatic-inertial focusing aerosol inkjet printing method according to claim 7, characterized in that: The method of atomizing the liquid ink into suspended aerosol particles comprises: Liquid ink containing conductive, dielectric or functional nanomaterials is converted into suspended aerosol particles by pneumatic atomization or ultrasonic atomization.
9. The secondary pneumatic-inertial focusing aerosol inkjet printing method according to claim 8, characterized in that: In the process of atomizing the liquid ink into suspended aerosol particles, the ink particle size is 10-100 nm, and a piezoelectric ultrasonic atomizer or a pneumatic atomizer is selected; an inert carrier gas is used to stably transport the atomized aerosol particles to the inlet of the nozzle mechanism.
10. A secondary pneumatic-inertial focusing aerosol inkjet printing device, characterized in that: A nozzle structure according to any one of claims 1 to 3 is provided.