A droplet ejection device using a sector-shaped resonant cavity to focus acoustic waves

Abstract

The present invention discloses a droplet ejection device for focusing sound waves by a sector-shaped resonant cavity, which includes an ultrasonic generating device, a liquid supply device, a nozzle, a substrate and a resonant cavity assembly. The resonant cavity assembly includes a resonant cavity, a sound wave inlet channel and an aperture. The resonant cavity is provided with at least two layers of sector-shaped chambers, and each layer of sector-shaped chambers is at least connected to one of the sound wave inlet channels. The sound wave inlet channel is an arc coaxial with the sector-shaped chamber. The radii of the sector-shaped chamber and the arc-shaped sound wave inlet channel are both integer multiples of the sound wave wavelength, and the inlet of the sound wave inlet channel is directly opposite to the sound wave emitting end of the ultrasonic generator. The centers of the sector-shaped chambers communicate with each other to form the aperture. The nozzle is arranged in the aperture. In the multi-layer sector-shaped resonant cavity structure of the present invention, the sound wave enters the channel from the front and can form multi-order FP resonance, with better sound wave focusing effect, increasing the acoustic radiation force at the nozzle and reducing the diameter of the ejected droplets.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision electronic inkjet printing, and in particular to a droplet ejection device that focuses sound waves in a fan-shaped resonant cavity. Background Art

[0002] With the in-depth research of electronic inkjet printing by a wide range of scholars, a technique called acoustic levitation jet printing has emerged in recent years. This technique breaks through the limitations of traditional inkjet printing, which is only applicable to low-viscosity fluids, and electrohydrodynamic jet printing, which is only applicable to materials with specific electromagnetic properties. The acoustic levitation jet printing technique uses acoustic levitation force as an external force acting on droplets. Therefore, the electrical, chemical, magnetic and other properties of the printing ink do not need to be considered during the printing process.

[0003] According to the formula, since, where P is the sound pressure, it can be seen that during the acoustic levitation jet printing process, the sound pressure has a great influence on droplet formation. Therefore, many studies have applied acoustic focusing devices to acoustic levitation jet printing, among which typical representative printing devices include ring resonators and Fresnel acoustic lenses. Both have successfully ejected polyethylene glycol solutions with a viscosity range of 0 - 1000 mPa·s. However, due to the difference in the focusing effect of the two focusing devices, the sizes of the ejected droplets are slightly different, further verifying the influence of sound pressure on the droplet diameter.

[0004] A method and device for acoustic levitation compound flow focusing micro-nano printing disclosed in Chinese invention patent CN113978132B, and a ring resonator focusing micro-droplet printing device disclosed in Chinese utility model CN216153424U are both ring resonator focusing printing technologies. However, the existing focusing structures such as resonators have insufficiently obvious focusing effects and generate relatively small acoustic levitation forces, resulting in relatively large diameters of the ejected droplets. Therefore, it is necessary to further improve the acoustic levitation focusing structure in order to greatly increase the acoustic levitation force at the nozzle and reduce the size of the ejected droplets, and thus this case arises. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a droplet ejection device that focuses sound waves in a fan-shaped resonant cavity, which increases the acoustic levitation force at the nozzle and reduces the size of the ejected droplets by improving the focusing structure.

[0006] To solve the above technical problem, the technical solution of the present invention is:

[0007] A droplet ejection device using a sector-shaped resonant cavity to focus sound waves, comprising an ultrasonic generating device, a liquid supply device, a nozzle communicating with the liquid supply device, and a substrate arranged below the nozzle for receiving printed droplets. The ultrasonic generating device is provided with a sound wave emitting end; a resonant cavity assembly is also provided, and the resonant cavity assembly includes a resonant cavity, a sound wave inlet channel, and an aperture; the resonant cavity has at least two layers of sector-shaped chambers, and each layer of sector-shaped chamber is at least connected to one of the sound wave inlet channels. The sound wave inlet channel is an arc coaxial with the sector-shaped chamber, and the radii of the sector-shaped chamber and the arc-shaped sound wave inlet channel are both integer multiples of the sound wave wavelength, and the inlet of the sound wave inlet channel is facing the sound wave emitting end; the centers of each sector-shaped chamber communicate with each other to form the aperture; the nozzle is arranged within the aperture.

[0008] Preferably, there are multiple sound wave inlet channels, and each sector-shaped chamber is respectively connected to one sound wave inlet channel, and the sector-shaped chambers are not connected to each other.

[0009] Preferably, there are multiple sound wave inlet channels, and each sound wave inlet channel is respectively connected to one or more of the sector-shaped chambers. The sector-shaped chambers are not connected to each other or are connected to each other through the sound wave inlet channels.

[0010] Preferably, each layer of the sector-shaped chambers has different central angles or different radius lengths.

[0011] Preferably, on the surface of the body of the resonant cavity assembly on one side of the sound wave inlet channel, there is one or more grooves.

[0012] Preferably, the groove is an arc coaxial with the sector-shaped chamber.

[0013] Preferably, the resonant cavity has three layers of sector-shaped chambers, namely a first chamber, a second chamber, and a third chamber, and the three are sector-shaped chambers with different radii; there are three sound wave inlet channels, namely a first inlet channel, a second inlet channel, and a third inlet channel, and the three sound wave inlet channels are respectively located at positions of 4 times the sound wave wavelength, 3 times the sound wave wavelength, and 2 times the sound wave wavelength.

[0014] Preferably, the first inlet channel, the second inlet channel, and the third inlet channel communicate with the third chamber, the second chamber, and the first chamber respectively, and the three chambers are not connected to each other; or the first inlet channel simultaneously communicates with the second chamber and the third chamber, and the second inlet channel and the third inlet channel respectively communicate with the three chambers.

[0015] Preferably, the specific parameters of the resonant cavity assembly are as follows: the height of the fan-shaped chamber is 1-2 mm, or the difference between the aperture size and the outer diameter of the nozzle is 0.5-2 mm; or the number of grooves is 0-4, or the width of the groove is 2-4.5 mm; or the depth of the groove is 0.3-1.5 mm.

[0016] Preferably, the liquid supply device is connected to the nozzle through a hose, and a Luer connector is used to connect the hose and the nozzle; an outlet pipe is connected to the outer end of the aperture, and the outlet tip of the nozzle is located inside the outlet pipe; the nozzle is connected with an XYZ-axis fine adjustment device, and the position of the nozzle is fixed and adjusted through the XYZ-axis fine adjustment device.

[0017] After adopting the above scheme, the present invention forms a multi-sound wave channel composed of fan-shaped chambers, enabling the structure to generate multi-order Fabry-Perot resonance (FP resonance), which is easy to form a standing wave mode in the sub-wavelength structure, form local effective focusing, increase the sound pressure amplitude, greatly improve the performance of acoustic levitation spraying, and reduce the size of the sprayed liquid droplets.

[0018] Specifically, the present invention has at least the following beneficial effects:

[0019] The resonant cavity of the present invention is provided with multiple layers of fan-shaped chambers. The inlet of the sound wave entry channel of each layer of fan-shaped chamber is directly opposite to the sound wave emission end of the ultrasonic generating device, enabling the sound wave to enter the channel directly, allowing more sound waves to enter. Then, through the bending structure of the fan-shaped chamber, the FP resonance is shifted, realizing that the sound wave generation position and the focusing position are located at non-coaxial positions. The multiple layers of fan-shaped chambers of this structure can form multi-order Fabry-Perot resonance, with better sound wave focusing effect, increasing the acoustic levitation force at the nozzle, reducing the diameter of the sprayed liquid droplets. At the same time, the fan-shaped resonant cavity structure can greatly reduce the size of the resonant device.

[0020] Several grooves can also be provided on the surface of the resonant cavity assembly of the present invention, which can generate the coupling of the evanescent wave field and Fabry-Perot resonance, improve the effect of sub-wavelength acoustic wave focusing, generate a greater acoustic levitation force, and further reduce the diameter of the sprayed liquid droplets.

[0021] The present invention can be provided with multiple sound wave entry channels, and each sound wave entry channel is connected to multiple layers of fan-shaped chambers to form a mixed channel structure, which can further increase the sound pressure.

[0022] 4. The hose and the nozzle of the present invention can be connected by a Luer connector, preventing the hose from falling off when spraying high-viscosity liquids and affecting the solution delivery, and ensuring stable droplet spraying.

[0023] 5. The nozzle of the present invention can be connected with an XYZ-axis fine adjustment device, enabling the nozzle to move in three axes and easily placing the nozzle at the position with the best focusing effect. Description of the Drawings

[0024] Figure 1 is a schematic structural diagram of the present invention;

[0025] Figure 2 is a sectional view of the resonant cavity assembly of the present invention;

[0026] Figure 3 is a front view of the resonant cavity assembly of the present invention;

[0027] Figure 4 is a perspective view of the resonant cavity assembly of the present invention;

[0028] Figure 5 is the exploded structure of the resonant cavity assembly of the present invention Figure 1 ;

[0029] Figure 6 is the exploded structure of the resonant cavity assembly of the present invention Figure 2 ;

[0030] Figure 7 is a schematic structural diagram of the three-layer sector chamber of the resonant cavity of the present invention;

[0031] Figure 8 is a schematic diagram of the structural parameters of the resonant cavity of the present invention;

[0032] Figure 9 (a) is a schematic diagram of the LLL-type multi-channel structure of the resonant cavity assembly of the present invention;

[0033] Figure 9 (b) is a schematic diagram of the FLL-type multi-channel structure of the resonant cavity assembly of the present invention;

[0034] Figure 9 (c) is a schematic diagram of the hybrid multi-channel structure of the resonant cavity assembly of the present invention;

[0035] Figure 9 (d) is a schematic diagram of the improved hybrid multi-channel structure of the resonant cavity assembly of the present invention;

[0036] Figure 10 is Figure 9 the sound pressure result diagram of different multi-channel structures;

[0037] Figure 11 is the sound field distribution diagram in the aperture of the multi-channel sector resonant cavity structure of the present invention at a frequency of 20 kHz;

[0038] Figure 12 is the effect diagram of the channel width of the resonant cavity assembly of the present invention on the sound pressure amplitude;

[0039] Figure 13 is the effect diagram of the aperture size of the resonant cavity assembly of the present invention on the sound pressure amplitude around the nozzle;

[0040] Figure 14 It is the effect diagram of the influence of the number of grooves of the resonant cavity component described in the present invention on the sound pressure amplitude;

[0041] Figure 15 It is the effect diagram of the influence of the groove size of the resonant cavity component described in the present invention on the sound pressure amplitude. Specific embodiments

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0043] What the present invention discloses is a micro-droplet ejection device for focusing sound waves by a sector-shaped resonant cavity. As Figures 1 - 4 shown, it is a preferred embodiment of the present invention. The micro-droplet ejection device includes an ultrasonic generating device 1, a liquid supply device 2, a nozzle 3, a substrate 4, and a resonant cavity component 5. It may further include an XYZ-axis fine adjustment device 6 and a Luer connector 7. Among them:

[0044] The ultrasonic generating device 1 is used to generate ultrasonic waves and make the sound wave emitting end face the inlet of the subsequent resonant cavity component 5. The ultrasonic generating device 1 may include a pulse generating device 11, a power amplifier 12, and a sound wave emitting end 13. It emits a pulse signal through the pulse generating device 11, amplifies it through the power amplifier 12, and then emits ultrasonic waves through the sound wave emitting end 13.

[0045] The liquid supply device 2 is used to transport the ejection liquid into the nozzle 3. It is connected to the nozzle 3 through a hose. Further, the hose and the nozzle 3 can be connected by a Luer connector 7 to prevent the hose from falling off when ejecting high-viscosity liquid, which affects the solution transportation and ensures stable droplet ejection.

[0046] The nozzle 3 can be a glass nozzle, which is fixed in the aperture �3 of the subsequent resonant cavity component 5 and is located above the substrate 4.

[0047] The substrate 4 is arranged below the nozzle 3 and is used to receive the printed droplets. The substrate 4 can be placed on a moving platform, and the moving platform can perform three-axis movement to drive the substrate 4 to move.

[0048] The resonant cavity assembly 5 is provided with a resonant cavity 51, which is provided with at least two layers of fan-shaped chambers (in this embodiment, three layers are provided, namely a first chamber 511, a second chamber 512 and a third chamber 513). Each layer of the fan-shaped chamber is provided with at least one arc-shaped acoustic wave inlet channel 52 concentric with the fan-shaped chamber. The radius of both the fan-shaped chamber and the arc-shaped acoustic wave inlet channel 52 is an integer multiple of the acoustic wave wavelength, and the inlet of the acoustic wave inlet channel 52 faces the acoustic wave emitting end 13, that is to say, the size range of the acoustic wave emitting end 13 covers the inlet of the acoustic wave inlet channel 52. In addition, an aperture 53 is formed by communicating the centers of each of the fan-shaped chambers. The nozzle 3 is arranged in the aperture 53. The working principle of the present invention is as follows: The ultrasonic waves emitted by the ultrasonic generating device 1 enter each layer of the fan-shaped chambers of the resonant cavity 51 through the acoustic wave inlet channel 52, and finally converge into the aperture 53 to form a Fabry-Perot resonance, and sub-wavelength focusing is achieved at the outlet of the nozzle 3. A sound pressure is generated at the focused sound pressure focus to form a shear force on the droplets ejected from the nozzle 3, thereby generating droplets with a micron-sized dimension; finally, the droplets are deposited on the substrate 4 for patterning and forming. The sound pressure generated by the ultrasonic generating device 1 is much smaller than the sound pressure required for acoustic levitation printing. The resonant cavity 51 can focus the acoustic waves to increase the sound pressure so that the sound pressure reaches the sound pressure required for acoustic levitation printing. Each layer of the cavity of the resonant cavity 51 will form a first-order Fabry-Perot resonance at the aperture 53, and multiple layers of cavities can form multi-order Fabry-Perot resonances, realizing sub-wavelength acoustic wave focusing, and can increase the acoustic levitation force at the nozzle 3 and reduce the diameter of the ejected droplets.

[0049] Further, the fan-shaped chambers of each layer of the resonant cavity 51 may have different central angles, and the angle of the central angle should not be too large, preferably not more than 45 degrees. Theoretically, the larger the angle of the central angle of the fan-shaped chamber, the more acoustic waves enter and the greater the sound pressure. However, if the central angle is too large, it will cause the width of the fan-shaped chamber to be too wide, even wider than the size of the acoustic wave emitting end 13, so that the acoustic waves cannot enter the chamber directly, which is the reason why the central angle cannot be too large. In order to make the acoustic waves enter the resonant cavity 51 directly, if a larger central angle of the selected fan-shaped chamber is used, its two sides can be cut with parallel lines so that the width dimension of the fan-shaped chamber does not exceed the size of the acoustic wave emitting end 13. As Figure 7 shown in Figure 7 (a) is the structure of the first chamber 511, Figure 7 (b) is the structure of the second chamber 512, Figure 7 (c) is the structure of the third chamber 513, in which the two sides of the first and second chambers exceeding the size of the acoustic wave emitting end 13 are cut with parallel lines. In addition, the fan-shaped radius dimensions (i.e., the chamber lengths) of the fan-shaped chambers of each layer may also be different.

[0050] Specifically in this embodiment, the resonant cavity 51 is provided with three layers of fan-shaped chambers, namely a first chamber 511, a second chamber 512, and a third chamber 513. More specifically, the radius of the first chamber 511 is set to 3 times the wavelength of the sound wave, and the radii of the second chamber 512 and the third chamber 513 are set to 4 times the wavelength of the sound wave. The process of the ultrasonic wave entering the chamber of the resonant cavity 51 from the sound wave inlet channel 52 can be regarded as passing through a bending structure, so that the FP resonance is shifted, realizing that the sound wave generation position and the focusing position are not coaxial, that is, the ultrasonic wave generating device 1 and the nozzle 3 are not on the same axis. On the one hand, it can make the sound wave face the inlet of the resonant cavity 51 so that more sound waves can enter the resonant cavity, and on the other hand, it can reduce the size of the resonant device.

[0051] A plurality of sound wave inlet channels 52 may be provided. Each sound wave inlet channel 52 can be connected to multiple layers of fan-shaped chambers at the same time, but each layer of fan-shaped chamber must be connected to at least one sound wave inlet channel 52. In this embodiment, three sound wave inlet channels 52 are provided, namely a first inlet channel 521, a second inlet channel 522, and a third inlet channel 523. The first inlet channel 521 is simultaneously connected to the second chamber 512 and the third chamber 513, and the second inlet channel 522 and the third inlet channel 523 are respectively connected to the three chambers at the same time. The first inlet channel 521, the second inlet channel 522, and the third inlet channel 523 are all arc-shaped channels to ensure that the distances from the sound waves to the nozzle 3 at the aperture 53 are all integer multiples of the wavelength of the sound wave. Connecting the sound wave inlet channel 52 to multiple layers of chambers can further increase the sound pressure.

[0052] On the surface of the body of the resonant cavity assembly 5 on one side of the sound wave inlet channel 52, a plurality of grooves 56 may be provided. The grooves 56 can generate an evanescent wave field coupled with the Fabry - Perot resonance, improve the effect of sub-wavelength acoustic focusing, generate a greater acoustic streaming force, and further reduce the diameter of the ejected liquid droplets. The position or shape of the grooves 56 is theoretically not limited, but in order to avoid the sound wave inlet channel 52, the grooves 56 are arc-shaped grooves coaxial with the fan-shaped chambers. In addition, the number of the grooves 56 is preferably 1 - 4.

[0053] In addition, in order to arrange multiple layers of fan-shaped chambers inside the body of the resonant cavity assembly 5, various structures can be used to achieve this. Specifically in this embodiment, such as Figures 5 - 6As shown, the body of the resonant cavity assembly 5 includes a main body 546 and five mounting pieces, namely the first to the fifth mounting pieces. The main body 546 is provided with a mounting groove, and one side wall of the mounting groove is an arc-shaped side wall. Inside the mounting groove, the first mounting piece 541, the second mounting piece 542, and the third mounting piece 543 are sequentially installed outward. Near the arc-shaped side wall outside the mounting groove, the fourth mounting piece 544 and the fifth mounting piece 545 are also installed at intervals, and the fourth and fifth mounting pieces 544 and 545 are arc-shaped. Through holes 531 with opposite positions are respectively provided on the first, second, and third mounting pieces 541, 542, and 543, and each mounting piece is provided with a fan-shaped groove centered on its respective through hole 531 and opening towards its edge. The arc-shaped side of the fan-shaped groove is open, and the open side of the arc-shaped side of the fan-shaped groove of each mounting piece is also the corresponding arc. The first, second, and third mounting pieces 541, 542, and 543 face the main body 546 with the side of the fan-shaped groove and are sequentially installed in the mounting groove of the main body 546, so that a layer gap is formed between the first mounting piece 541 and the main body 546 and between adjacent two mounting pieces. This layer gap is the fan-shaped chamber of the resonant cavity 51 or a part of the fan-shaped chamber, while the fourth mounting piece 544 and the fifth mounting piece 545 compensate for the other part of the corresponding fan-shaped chamber. Specifically, the layer gap between the main body 546 and the first mounting piece 541 forms the third chamber 513; the layer gap between the first mounting piece 541 and the second and fourth mounting pieces 542 and 544 forms the second chamber 512; the layer gap between the second mounting piece 542 and the third and fifth mounting pieces 543 and 545 forms the first chamber 511. In order to enable the acoustic wave inlet channel 52 to connect multiple chambers, the fan-shaped groove of the second mounting piece 542 is provided with a first arc-shaped hole 542a corresponding to the arc-shaped side of the third mounting piece 543, and the fan-shaped grooves of the first mounting piece 541 are respectively provided with a second arc-shaped hole 541a and a third arc-shaped hole 541b corresponding to the arc-shaped sides of the second and third mounting pieces 542 and 543. A channel gap is left between the arc-shaped side of the first mounting piece 541 and the arc-shaped side wall of the mounting groove, and a channel interval is also left between the arc-shaped side wall of the mounting groove and the fourth mounting piece 544. The two channel gaps form the first inlet channel 521. The interval between the fourth and fifth mounting pieces 544 and 545 is set corresponding to the second arc-shaped hole 541a, thereby forming the second inlet channel 522. The interval between the fifth mounting piece 545 and the arc-shaped side of the third mounting piece 543 is set corresponding to the first arc-shaped hole 542a and the third arc-shaped hole 541b, thereby forming the third inlet channel 523. The main body 546 is also provided with a through hole 531 at the position corresponding to the through holes 531 of the first, second, and third mounting pieces 541, 542, and 543, and the four through holes 531 together form the aperture 53.An outlet pipe 55 is connected to the outer end of the through hole of the main body 546, and the connection method can be interference fit; the outlet pipe 55 can be an acrylic pipe; the outlet tip of the nozzle 3 is located inside the outlet pipe 55. A groove 56 is respectively provided on the outer side of the main body 546 close to the arc-shaped side wall, the fourth mounting piece 544, the fifth mounting piece 545 and the third mounting piece 543, and the groove 56 can be a corresponding arc shape. The main body 546 and the five mounting pieces can be connected to each other by a matching convex and concave structure, which makes the installation simple and can also avoid the shear force generated by bolt connection. In addition, it should be noted that the radii of the above-mentioned fan-shaped grooves and the arc radii involved are all integer multiples of the acoustic wavelength, and all are centered on the through hole 531. The radii of the fan-shaped grooves on the first, second and third mounting pieces 541, 542, 543 decrease in sequence, and the central angles also decrease in sequence.

[0054] The XYZ-axis fine adjustment device 6 is connected to the nozzle 3. On the one hand, it is used to fix the nozzle 3. On the other hand, through the adjustment of the XYZ-axis fine adjustment device 6, the nozzle 3 can be finely adjusted in the XYZ directions in the aperture 53, so that the outlet tip of the nozzle 3 can be located at the best acoustic focusing position to achieve the optimal state of acoustic levitation jetting. Among them, the best acoustic focusing position can be obtained by simulation analysis.

[0055] When the device of the present invention is working, the ultrasonic generating device 1 emits a pulse signal, which is transmitted to the piezoelectric ceramic at the acoustic wave transmitting end 13 through a wire to perform mechanical vibration, thereby generating ultrasonic waves. The ultrasonic waves are transmitted through the air, and the ultrasonic waves reaching the surface of the resonant cavity assembly 5 enter the channel 52. The ultrasonic waves enter the multi-layer fan-shaped chambers of the resonant cavity 51 in a vertically incident manner, that is, the chambers of the three fans in this embodiment, and then converge in the aperture 53 to form a multi-order Fabry-Perot resonance, realizing sub-wavelength acoustic focusing and increasing the sound pressure. The liquid supply device 2 transports the ink to be printed to the nozzle 3 through a hose. The position of the nozzle 3 can be finely adjusted in advance through the XYZ-axis fine adjustment device 6, and the tip of the nozzle 3 is adjusted to the best acoustic focusing position, where acoustic pressure shear force can be generated, thereby generating liquid droplets with micron-sized dimensions. Finally, by controlling the traveling speed of the liquid supply device 2 and the movement of the substrate 4, the generated liquid droplets are pattern-deposited. The multi-layer chambers of the resonant cavity 51 realize Fabry-Perot resonance and sub-wavelength acoustic focusing, further increasing the sound pressure, improving the acoustic levitation force at the nozzle 3, and reducing the diameter of the ejected liquid droplets. At the same time, the grooves 56 provided on the surface of the resonant cavity assembly 5 can generate an evanescent wave field coupled with the Fabry-Perot resonance, improving the effect of sub-wavelength acoustic focusing, generating a greater acoustic levitation force, and further reducing the diameter of the ejected liquid droplets.

[0056] The present invention can use Comsol finite element analysis software to perform acoustic field simulation modeling on the entire device to verify the effects and optimize the structure and parameters of the resonant cavity. During the fax process, the transmission medium in the fan-shaped chamber is selected as air, the acoustic wave generation frequency is 20 kHz, and the structural parameters of the resonant cavity assembly 5 are as Figure 8 shown. It is provided with three fan-shaped chambers, namely the first chamber 511, the second chamber 512, and the third chamber 513, and is provided with three acoustic wave entry channels 52, namely the first entry channel 521, the second entry channel 522, and the third entry channel 523, and the three acoustic wave entry channels 52 are respectively at the positions of 4λ, 3λ, and 2λ; in the figure: a is the height of the fan-shaped chamber, b is the diameter of the aperture 53, c is the width of the groove 56, d is the depth of the groove 56, and λ is the wavelength of the incident acoustic wave.

[0057] Based on the above basic structure, the present invention designs a variety of multi-channel (one channel is the path that the acoustic wave travels from one acoustic wave entry channel 52 into one fan-shaped chamber to reach the aperture 53) structures, such as Figure 9 shown as the cross-sectional views of 4 multi-channel structures. Among them: Figure 9 (a) is the LLL-type multi-channel structure, that is, one acoustic wave entry channel 52 corresponds to one fan-shaped chamber, and the three channels are not connected to each other; Figure 9 (b) is the FLL-type multi-channel structure, that is, the third acoustic wave entry channel 523 is connected to the first chamber 511, the second acoustic wave entry channel 522 is simultaneously connected to the first and second chambers 511 and 512, and the length of the first chamber 511 is extended to 3λ, and the third chamber 513 is connected through the first acoustic wave entry channel 521 and is not connected to the other two chambers; Figure 9 (c) is a hybrid multi-channel structure, and the three fan-shaped chambers are all connected to each other, where the second and third entry channels 522 and 523 are simultaneously connected to the three fan-shaped chambers, and the first entry channel 521 is simultaneously connected to the second and third chambers 512 and 513, and the length of the second chamber 512 is extended to 4λ, and the length of the first chamber 511 is extended to 3λ; Figure 9 (d) is an improved hybrid multi-channel structure, and its difference from the Figure 9 (c) hybrid multi-channel structure is that a plurality of grooves 56 are provided. The present invention simulates the above spraying device through software, and successively conducts simulation comparisons on the multi-channel structure, the channel width a (i.e., the height of the fan-shaped chamber), the size b of the aperture 53, the number of grooves, and the groove dimensions (c and d). The simulation comparison effects are as follows.

[0058] First, perform simulation analysis on the Figure 9 4 multi-channel structures described above, and take the sound pressure amplitude as a judgment of the quality of the structure to determine which multi-channel structure has the best effect. In order to facilitate observing the sound pressure amplitude around the glass nozzle 3, here intercept Figure 10The nozzle tip part in (a) shows the magnitude of the sound pressure around the nozzle as a drawing group. The coordinate corresponding to the nozzle tip is -396 mm. The sound pressure amplitude results of the final 4 multi-channel structures are as Figure 10 shown in (b). It can be seen from Figure 10 (b) that when changing from the LLL multi-channel structure to the FLL multi-channel structure, the sound pressure amplitude slightly increases. Inspired by this, the device is improved to obtain a hybrid multi-channel structure with a significant increase in the sound pressure amplitude. A groove is added to the hybrid multi-channel structure to obtain an improved multi-channel structure. It can be seen from the simulation results that the improved multi-channel structure has the best effect.

[0059] Figure 11 The spatial sound pressure level distributions of different lengths in the channel at a frequency of 20 kHz are given respectively. Among them: small L ( Figure 11 ABCL in Figure 11 ), medium L ( Figure 11 DFGL in

[0060] ), large L ( Figure 11 HIKL in

[0060] ). In these three channels with different lengths, a typical Fabry - Perot resonance sound field distribution appears, proving that Fabry - Perot resonance can occur simultaneously in channels with different lengths. Figure 12 Then, a simulation comparison of the change in the channel width is carried out. Figure 12 The change in the sound pressure amplitude around the nozzle when the channel width a is 1 mm, 1.5 mm, 2 mm, and 2.5 mm respectively is given. When the channel width increases from 1 mm to 2 mm, the sound pressure amplitude around the nozzle is significantly improved. Once the channel width increases to 2.5 mm, the absolute value of the sound pressure amplitude decreases instead. It can be determined that the channel width a is preferably 1 - 2 mm, and the best is 2 mm.

[0061] Regarding the influence of the aperture size b on the sound pressure amplitude around the nozzle, since the outer diameter of the glass nozzle is 1 mm, the aperture size b is taken as 1.5 mm, 2 mm, 2.5 mm, and 3 mm here. It can be seen from Figure 13 that as the aperture size increases, the sound pressure amplitude around the nozzle also increases. However, when the aperture size is 3 mm, the sound pressure amplitude around the nozzle not only does not increase, but instead slightly decreases. This is because the increase in the aperture can improve the transmission coefficient of sound waves. However, when the transmission coefficient is too high, it cannot be effectively coupled with the Fabry - Perot resonance, resulting in a slight decrease in the sound pressure result. Therefore, the aperture size is 1.5 - 3 mm, and the best is 2.5 mm. In practical applications, the size of the aperture is related to the outer diameter of the nozzle, and the difference between the two is preferably 0.5 - 2 mm.

[0062] In this invention, by adding arranged grooves on the surface of the multi-channel fan-shaped structure, it is used as an extension of the surface. Figure 14Figure (a) shows the magnitudes of the sound pressure around the glass nozzle when the number of grooves is 0, 1, 2, 3, and 4 respectively. It can be seen from this that the increase in the number of grooves is positively correlated with the sound pressure around the glass nozzle. Figure 14 Figure (b) shows the variation diagram of the sound pressure level at the nozzle with the number of grooves. According to Figure 14 the trend of the curve in Figure (b), it can be seen that the increase in the number of grooves helps to increase the sound pressure level around the glass nozzle, but this effect is not infinite. When the number of grooves increases to 4, the sound pressure level around the glass nozzle gradually levels off. This may be because when the incident sound wave is transmitted through the aperture to the output end, the evanescent wave excited by the grooves far from the sound wave inlet of the aperture has been greatly attenuated when passing through the aperture and cannot reach the aperture, so that an excessive number of grooves cannot significantly increase the sound pressure level around the glass nozzle.

[0063] Figure 15 Figure (a) shows the variation of the sound pressure amplitude around the nozzle with the groove width at 20 kHz. As the groove width c increases, the sound pressure amplitude around the nozzle also increases. Figure 15 Figure (b) shows the variation of the sound pressure amplitude at the nozzle tip with the groove width (the groove width varies from 2 - 4.5 mm). It can be seen from this that when the sound pressure at the nozzle increases to a certain value as the groove width increases, the increase rate of the sound pressure at the nozzle slows down. Figure 15 Figure (c) shows the variation of the sound pressure amplitude around the glass nozzle with the groove depth. As the groove depth d increases, the sound pressure amplitude around the nozzle also increases. When it increases to a certain extent, the increase in the groove depth will instead cause the sound pressure amplitude around the nozzle to decrease. The initial increase in the groove depth (from 0.3 mm to 1.5 mm) adjusts the effective surface period of the ASWs (acoustic surface waves), optimizes the interaction between the evanescent wave and the Fabry - Perot resonance, thus effectively increasing the sound pressure amplitude around the nozzle. However, as the groove depth further increases (from 1.5 mm to 1.8 mm), the effective surface period of the ASWs changes, and sufficient momentum compensation cannot be obtained in the designed structure and specific frequency, reducing the sound pressure gain effect, so the sound pressure amplitude around the nozzle decreases significantly. Both the groove depth d and the groove width c have a significant impact on the components of the evanescent wave. The influence of the groove size on the structure mainly explores the influence of the groove width c and the groove depth d on the sound pressure around the nozzle. As shown in Figure 15 Figure (a) and Figure 15 Figure (c), it can be seen that both the groove depth and the groove width have a greater impact on the structure.

[0064] The above description is only a preferred embodiment of the present invention and does not impose any limitation on the technical scope of the present invention. Therefore, any changes or modifications made in accordance with the claims and the description of the present invention shall fall within the scope covered by the patent of the present invention.

Claims

1. A droplet ejection device for focusing acoustic waves in a sector-shaped resonant cavity, comprising an ultrasonic generating device, a liquid supply device, a nozzle communicating with the liquid supply device, and a substrate disposed below the nozzle for receiving printed droplets, wherein the ultrasonic generating device is provided with an acoustic wave emitting end; characterized in that: A resonant cavity assembly is also provided. The resonant cavity assembly includes a resonant cavity, a sound wave inlet channel, and an aperture. The resonant cavity has at least two layers of sector chambers, and each layer of sector chambers is at least connected to one of the sound wave inlet channels. The sound wave inlet channel is an arc coaxial with the sector chamber. The radii of the sector chamber and the arc-shaped sound wave inlet channel are both integer multiples of the sound wave wavelength, and the inlet of the sound wave inlet channel faces the sound wave emitting end. The centers of the sector chambers communicate with each other to form the aperture, and the nozzle is arranged in the aperture.

2. The droplet ejection device using a sector-shaped resonant cavity to focus sound waves according to claim 1, wherein: There are multiple sound wave inlet channels, and each sector chamber is respectively connected to one sound wave inlet channel, and the sector chambers are not connected to each other.

3. The droplet ejection device using a sector-shaped resonant cavity to focus sound waves according to claim 1, wherein: There are multiple sound wave inlet channels, and each sound wave inlet channel is respectively connected to one or more of the sector chambers. The sector chambers are not connected to each other or are connected to each other through the sound wave inlet channels.

4. The droplet ejection device for focusing acoustic waves by a sector-shaped resonant cavity according to claim 1, characterized in that: Each layer of the sector chambers has different central angles or different radius lengths.

5. The droplet ejection device for focusing acoustic waves using a sector-shaped resonant cavity according to claim 1, wherein: On the surface of the body of the resonant cavity assembly on one side of the sound wave inlet channel, one or more grooves are provided.

6. The droplet ejection device using a sector-shaped resonant cavity to focus acoustic waves according to claim 5, wherein: The groove is an arc coaxial with the sector chamber.

7. A droplet ejection device using a sector-shaped resonant cavity to focus sound waves according to claim 1, characterized in that: The resonant cavity has three layers of sector chambers, namely a first chamber, a second chamber, and a third chamber, which are sector chambers with three different radii. There are three sound wave inlet channels, namely a first inlet channel, a second inlet channel, and a third inlet channel. The three sound wave inlet channels are respectively located at positions of 4 times the sound wave wavelength, 3 times the sound wave wavelength, and 2 times the sound wave wavelength.

8. A droplet ejection device using a sector-shaped resonant cavity to focus acoustic waves according to claim 7, characterized in that: The first inlet channel, the second inlet channel, and the third inlet channel communicate with the third chamber, the second chamber, and the first chamber respectively, and the three chambers are not connected to each other. Or the first inlet channel simultaneously communicates with the second chamber and the third chamber, and the second inlet channel and the third inlet channel respectively communicate with the three chambers.

9. The droplet ejection device for focusing acoustic waves by a sector-shaped resonant cavity according to claim 5, wherein: The specific parameters of the resonant cavity assembly are that the height of the sector chamber is 1-2 mm, or the difference between the size of the aperture and the outer diameter of the nozzle is 0.5-2 mm. Or the number of grooves is 0-4, or the width of the groove is 2-4.5 mm. Or the depth of the groove is 0.3-1.5 mm.

10. The droplet ejection device using a sector-shaped resonant cavity to focus sound waves according to claim 1, wherein: The liquid supply device is connected to the nozzle through a hose, and a Luer connector is used to connect the hose and the nozzle. An outlet pipe is connected to the outer end of the aperture, and the outlet tip of the nozzle is located in the outlet pipe. The nozzle is connected with an XYZ-axis fine adjustment device, and the position of the nozzle is fixed and adjusted through the XYZ-axis fine adjustment device.

Images