Droplet ejecting apparatus and method

Abstract

The liquid drop spraying device comprises a spraying plate with a spraying hole in the middle, the front face of the spraying plate is used for loading a stock solution to be sprayed, the back face of the spraying plate is fixedly connected with an annular vibration plate, and the annular vibration plate is made of a piezoelectric material; the spraying device further comprises an excitation main machine, and the excitation main machine is electrically connected with the annular vibration plate. According to the invention, the inverse piezoelectric effect of a piezoelectric material is utilized, an alternating current excitation electric signal is applied to an annular vibration plate to drive the annular vibration plate to regularly vibrate, the annular vibration plate transmits vibration to a rigid jet plate, and when the jet plate vibrates and acts on liquid, the liquid overcomes the action of surface tension, so that liquid drops are formed and escape from the bottom of a jet hole; by adjusting the output voltage and frequency of the excitation host, discontinuous and continuous picoliter droplet generation of different volumes of droplets can be flexibly controlled and realized, and the minimum droplet generation volume can reach 0.5 picoliter.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-droplet generation, and in particular to a droplet ejection device and method. Background Art

[0002] With the development of science and technology, researchers have higher and higher requirements for experimental systems and precision, and the reaction system has gradually become micro-scale. In the fields of biology, medicine, chemistry, and nanomaterials, trace reaction systems are becoming more and more normal for experimental analysis and measurement. Therefore, how to generate droplets with high throughput and precision has become one of the factors restricting the development of the industry.

[0003] Currently, the micro-droplet generation methods on the market are mainly based on the microfluidic micro-droplet generation system. This system can generally form droplets with uniform sizes based on a "T" structure and can be combined with downstream analysis to achieve high-throughput analysis downstream. However, the microfluidic droplet generation system still has many defects at present, including characteristics such as difficult adjustment of droplet size, high cost, and large operation difficulty, which restrict its application in the industry. In addition, for the microfluidic system, cross-contamination between different samples is also a factor affecting its application. Therefore, it is of great significance to develop a technology with low cost, high throughput, and capable of rapid droplet generation.

[0004] Currently, for picoliter droplet generation, most are by using the microfluidic method, and the volume is mostly several hundred picoliters. Moreover, for picoliter droplet generation, the smaller the volume, the higher the equipment requirements. In addition, the current droplet ejection technology based on surface acoustic waves usually requires a high generation power and a large vibration frequency, and during the ejection process, it is difficult to control the droplet size and it is difficult to perform continuous ejection. Summary of the Invention

[0005] The present invention provides a droplet ejection device and method based on surface acoustic waves, which solves the problems in the prior art such as difficult control of droplet size and large difficulty in continuous ejection.

[0006] The technical solution of the present invention is realized as follows:

[0007] In a first aspect, the present application provides a droplet ejection device, and the droplet ejection device includes:

[0008] An ejection plate, on which ejection holes are provided;

[0009] An annular vibration plate, which is arranged on the ejection plate, the ejection holes are located inside the annular vibration plate, and the annular vibration plate is made of a piezoelectric material;

[0010] An excitation host, which is electrically connected to the annular vibrating plate, is used to drive the annular vibrating plate to generate surface acoustic waves, and the surface acoustic waves are used to drive the ejection plate to vibrate to form droplets.

[0011] According to one aspect of the present invention, a droplet ejection device is provided, which includes an ejection plate with ejection holes in the middle. The front side of the ejection plate is used to load the stock solution to be ejected, and the back side of the ejection plate is fixedly connected with an annular vibrating plate made of piezoelectric material. The ejection device further includes an excitation host, which is electrically connected to the annular vibrating plate.

[0012] Piezoelectric material is a functional material, which is characterized by having the direct piezoelectric effect and the inverse piezoelectric effect. Under the action of mechanical force, the centers of positive and negative charges of the piezoelectric material will shift, resulting in polarization; while under the action of an electric field, the piezoelectric material will generate deformation. Based on this principle, when a regular voltage is applied, the piezoelectric material will generate a regular deformation motion, thus generating vibration. When the vibration propagates to the ejection plate, it will drive the vibration of the ejection plate. In this process, the sound waves generated by the piezoelectric material include surface acoustic waves and bulk acoustic waves, but for the vibration of the material, the surface acoustic waves play a key role. When the rigid material (ejection plate) vibrates and acts on the liquid, it enables the liquid to overcome the action of surface tension, thereby forming droplets and escaping from the bottom of the ejection holes. The present invention designs a low-cost pico-liter droplet generation device by utilizing the inverse piezoelectric effect of piezoelectric materials. By adjusting the output voltage and frequency of the excitation host, the intermittent and continuous pico-liter droplet generation of different volumes can be flexibly controlled and achieved, and the minimum droplet generation volume can reach 0.5 pico-liter.

[0013] As a preferred solution of the present invention, an inverted conical sampling hopper is hermetically connected to the front side of the ejection plate, and the bottom of the sampling hopper is communicated with the ejection holes. By installing the sampling hopper on the front side of the ejection plate, the present invention can accurately control the droplet ejection volume and ensure continuous ejection.

[0014] As a preferred solution of the present invention, the ejection holes are obtained by electric discharge machining. The ejection holes obtained by electric discharge piercing are uniform circles, the inner diameter sizes of the upper and lower ends of the holes are the same, there are no charred traces, and there is no attached material on the hole surface, which is more conducive to droplet ejection.

[0015] As a preferred solution of the present invention, the aperture of the ejection holes is 30 - 100 μm. In the specific implementation process, ejection holes with appropriate apertures can be processed according to actual requirements (the accuracy requirements of droplets).

[0016] As a preferred embodiment of the present invention, the excitation host includes a signal generator and a signal amplifier. The signal generator is used to generate an excitation electrical signal (alternating voltage signal), and the signal amplifier is used to amplify the excitation electrical signal. By adjusting parameters such as the frequency, voltage, number of cycles, and number of periods of the excitation electrical signal through the signal generator, the size, generation rate, etc. of the droplets can be adjusted.

[0017] As a preferred embodiment of the present invention, the frequency range of the excitation electrical signal is 1 - 200 kHz. In the specific implementation process, the appropriate operating frequency can be adjusted according to the actual situation.

[0018] As a preferred embodiment of the present invention, the voltage of the amplified excitation electrical signal is 200 - 300 V. In the specific implementation process, the appropriate operating voltage can be adjusted according to the actual situation.

[0019] As a preferred embodiment of the present invention, the ejection plate is a concave plate, and the ejection holes are located at the bottommost end of the concave plate. By designing the ejection plate as a concave plate in the present invention, on the one hand, the concave-shaped ejection plate can be directly used to hold the original liquid, eliminating the need for a sampling hopper, and all the vibrations generated by the annular vibrating plate can be transmitted to the original liquid through the ejection plate without the absorption of vibrations by the sampling hopper, resulting in higher droplet ejection efficiency. On the other hand, due to the concave shape of the ejection plate, the areas of its front and back surfaces are different. When the ejection plate vibrates, the deformation amounts of its front and back surfaces are different, which can increase the volume change amount inside the ejection holes, making it easier for the droplets inside the ejection holes to escape, thereby reducing the excitation voltage of the excitation electrical signal.

[0020] In a second aspect, the present application provides a droplet ejection method, which is applied to the droplet ejection device provided in any embodiment of the present application. The method includes:

[0021] Input an excitation electrical signal to the annular vibrating plate through the excitation host of the droplet ejection device to drive the annular vibrating plate to generate a surface acoustic wave, and the surface acoustic wave is used to drive the ejection plate to vibrate to form droplets;

[0022] Change the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets. According to another aspect of the present invention, a droplet ejection method is provided, including the following steps:

[0023] Load an appropriate amount of the original liquid onto the front surface of the ejection plate;

[0024] Input an alternating current excitation electrical signal to the annular vibrating plate through the excitation host, use the inverse piezoelectric effect to drive the annular vibrating plate to vibrate regularly, drive the ejection plate to vibrate, and use the surface acoustic wave generated by the vibration of the ejection plate to cause the micro-droplets in the original liquid to escape from the ejection holes after overcoming the surface tension;

[0025] By adjusting the frequency, voltage, and number of cycles of the alternating current excitation electrical signal output by the excitation host, micro-droplets that meet the requirements are obtained.

[0026] Advantageous Effects

[0027] Compared with the prior art, the advantageous effects of the present invention are as follows: The present invention utilizes the inverse piezoelectric effect of piezoelectric materials. By applying an alternating current excitation electrical signal to the annular vibrating plate, the annular vibrating plate is driven to vibrate regularly. The annular vibrating plate transfers the vibration to the rigid ejection plate. When the ejection plate vibrates and acts on the liquid, the liquid overcomes the action of surface tension, thereby forming droplets and escaping from the bottom of the ejection holes; by adjusting the output voltage and frequency of the excitation host, the intermittent and continuous picoliter droplet generation of different volumes of droplets can be flexibly controlled and achieved, and the minimum volume of the generated droplets can reach 0.5 picoliters; compared with the traditional methods of realizing picoliter liquid transfer using ultrasonic waves or microfluidics, the device and equipment of the present invention have a simple structure, low cost, and more convenient operation. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic structural diagram of a droplet ejection device according to Embodiment 1 of the present invention;

[0030] Figure 2 It is a schematic back structure diagram of the ejection plate in Embodiment 1 of the present invention;

[0031] Figure 3 It is a statistical chart of the size and number of ejected droplets at different working frequencies in Embodiment 1 of the present invention;

[0032] Figure 4 It is an effect diagram of the droplets ejected in Embodiment 1 of the present invention;

[0033] Figure 5 It is a schematic structural diagram of a droplet ejection device according to Embodiment 2 of the present invention;

[0034] Figure 6 It is a schematic structural diagram of another droplet ejection device according to Embodiment 1 of the present invention;

[0035] Figure 7 It is a schematic structural diagram of another droplet ejection device according to Embodiment 1 of the present invention;

[0036] Figure 8Another schematic diagram of the back structure of the ejection plate in Embodiment 1 of the present invention;

[0037] Figure 9 A schematic flow chart of the steps of a droplet ejection method provided by an embodiment of the present application;

[0038] Figure 10 A schematic diagram of the structure of another droplet ejection device in Embodiment 2 of the present invention.

[0039] In the figure: 1, ejection plate; 2, ejection hole; 3, annular vibration plate; 4, sample addition hopper; 5, excitation host. Detailed implementation manners

[0040] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Please refer to Figure 1 , Figure 2 and Figure 6 , Figure 1 A schematic diagram of the structure of a droplet ejection device in Embodiment 1 of the present invention, Figure 2 A schematic diagram of the back structure of the ejection plate in Embodiment 1 of the present invention, Figure 6 A schematic diagram of the structure of another droplet ejection device in Embodiment 1 of the present invention. The present application provides a droplet ejection device, which includes an ejection plate 1, an ejection hole 2, an annular vibration plate 3 and an excitation host 5. The ejection plate 1 is provided with the ejection hole 2, the annular vibration plate 3 is arranged on the ejection plate 1, the ejection hole 2 is located inside the annular vibration plate 3, and the annular vibration plate 3 is made of a piezoelectric material. The excitation host 5 is electrically connected to the annular vibration plate 3, and the excitation host 5 is used to drive the annular vibration plate 3 to generate a surface acoustic wave, and the surface acoustic wave is used to drive the ejection plate 1 to vibrate to form droplets.

[0042] Specifically, the droplet ejection device proposed in the present application is provided with an annular vibration plate 3 made of a piezoelectric material on the ejection plate 1. After the annular vibration plate 3 receives the electrical signal sent by the excitation host 5, due to the negative piezoelectric property of the piezoelectric material, it can generate a surface acoustic wave to drive the annular vibration plate 3 to vibrate, and then drive the ejection plate 1 to vibrate under the vibration of the annular vibration plate 3, so that the liquid on the ejection plate 1 overcomes the action of surface tension, thereby forming droplets and escaping from the bottom of the ejection hole 2.

[0043] Refer to Figure 1 , 2As shown in the figure, this embodiment provides a droplet ejection device, which includes an ejection plate 1 with an ejection hole 2 in the middle. The front side of the ejection plate 1 is used to load the stock solution to be ejected, and the back side of the ejection plate 1 is fixedly connected with an annular vibration plate 3 made of piezoelectric material. The ejection device further includes an excitation host, which is electrically connected to the annular vibration plate 3.

[0044] Exemplarily, the ejection plate 1 includes a first plate surface and a second plate surface. As the front side of the ejection plate 1 mentioned above is the first plate surface of the ejection plate 1, it is used to place the stock solution to be ejected.

[0045] It should be noted that in some embodiments, as Figure 1 shown, the annular vibration plate 3 is arranged on the first plate surface of the ejection plate 1. In some embodiments, as Figure 7 shown, the annular vibration plate 3 is arranged on the second plate surface of the ejection plate 1. Whether the annular vibration plate 3 is arranged on the first plate surface or the second plate surface, the excitation host 5 can drive the annular vibration plate 3 to generate surface acoustic waves, and then the annular vibration plate 3 vibrates to drive the ejection plate 1 to vibrate to form droplets.

[0046] Piezoelectric material is a functional material, which is characterized by having the direct piezoelectric effect and the inverse piezoelectric effect. Under the action of mechanical force, the centers of positive and negative charges of the piezoelectric material will shift, resulting in polarization; while under the action of an electric field, the piezoelectric material will generate deformation. Based on this principle, when a regular voltage is applied, the piezoelectric material will generate a regular deformation motion, thus generating vibration. When the vibration propagates to the ejection plate 1, it will drive the vibration of the ejection plate 1. In this process, the sound waves generated by the piezoelectric material include surface acoustic waves and bulk acoustic waves, but for the vibration of the material, the surface acoustic waves play a key role. When the rigid material (ejection plate) vibrates and acts on the liquid, it enables the liquid to overcome the action of surface tension, thereby forming droplets and escaping from the bottom of the ejection hole 2. The present invention designs a low-cost picoliter droplet generation device by using the inverse piezoelectric effect of piezoelectric materials. By adjusting the output voltage and frequency of the excitation host 5, it is possible to flexibly control and achieve the intermittent and continuous picoliter droplet generation of different volumes, and the minimum volume of droplet generation can reach 0.5 picoliter.

[0047] In order to ensure that the ejection plate 1 can vibrate continuously and stably, this embodiment uses a hard material to make the ejection plate 1. Common hard materials include hard metals, hard plastics, and glass, etc. When the surface acoustic waves causing vibration propagate on the surfaces of different materials, their attenuation has a large difference. During the test, we compared the ejection effects when hard metals, hard plastics, and glass were used as the ejection plates. Since hard plastics and glass have poor tolerance to vibration, hard metal was finally selected as the material for making the ejection plate.

[0048] Exemplarily, the hard metal includes any one of stainless steel, copper, and aluminum. Among them, since stainless steel has good vibration tolerance and good bendability, stainless steel is selected as the optimal material for fabricating the ejection plate 1.

[0049] To ensure the continuous and stable ejection of droplets, in this embodiment, three shapes of piezoelectric materials, namely square, cylindrical, and annular, are tested. It is found that when using an annular piezoelectric material pressed onto the ejection plate 1, continuous and stable ejection of droplets can be achieved; when an electric field is applied to the annular vibrating plate 3, the piezoelectric material will generate vibrations due to deformation. The main vibration form is the surface acoustic wave generated by the piezoelectric material, which drives the ejection plate 1 to vibrate, thereby pinching off the original liquid to form droplets. The annular vibrating plate 3 of this embodiment can be made of semiconductor piezoelectric materials such as CdS, CdSe, ZnO, ZnS, CdTe, ZnTe, etc., with more stable performance and long service life.

[0050] Exemplarily, the cross-sectional shape of the annular vibrating plate 3 is any one of circular ring shape, elliptical ring shape, square shape, and rhombus shape. Annular vibrating plates 3 with shapes such as circular ring shape, elliptical ring shape, square shape, and rhombus shape can all generate surface acoustic waves under the drive of the excitation host 5 and then drive the vibration of the ejection plate 1. For example, Figure 8 when the annular vibrating plate shown is a hollow square material, it can also achieve the drive of the vibration of the ejection plate 1. Considering the uniformity of the force on the ejection plate 1 when the annular vibrating plate 3 drives the ejection plate 1 to vibrate, in the embodiment of the present application, the cross-sectional shape of the annular vibrating plate 3 shown in Figure 2 is a circular ring shape as the optimal cross-sectional shape.

[0051] It should be noted that regardless of which one of the circular ring shape, elliptical ring shape, square shape, and rhombus shape the cross-sectional shape of the annular vibrating plate 3 is, its hollow shape needs to be set as a circular shape as shown in Figure 2 so that since the hollow shape of the annular vibrating plate 3 is the same as that of the ejection holes 2 and the ejection plate 1, the ejection plate 1 can receive more uniform force when the annular vibrating plate 3 vibrates, and droplets can be generated more uniformly and continuously and escape from the ejection holes 2.

[0052] As a preferred solution of the present invention, an inverted conical sampling hopper 4 is hermetically connected to the front surface of the ejection plate 1, and the bottom of the sampling hopper 4 is communicated with the ejection holes 2; in this embodiment, the top diameter of the sampling hopper 4 is 10 mm, and the aperture at the bottom is adjustable from 50 to 100 μm (the specific size can be adjusted according to the actual situation). The original liquid can be injected into the sampling hopper 4 through a pipette or an external sample injection device to achieve one-time pollution-free sampling; by installing the sampling hopper 4 on the front surface of the ejection plate 1, the present invention can accurately control the droplet ejection volume and the sample injection flow rate to ensure continuous ejection.

[0053] As a preferred solution of the present invention, the injection hole 2 is obtained by electric spark drilling; the injection hole 2 obtained by electric spark drilling is a uniform circle, the upper and lower ends of the inner diameter of the hole are consistent, there are no signs of burning, and there is no material attached to the surface of the hole, which is more conducive to the injection of droplets.

[0054] At present, the commonly used perforation technologies include laser perforation technology and electrospark perforation technology. Laser perforation technology uses tightly focused laser to melt the material under high heat. The main laser perforation technologies include pulse perforation and blasting perforation. Pulse perforation is a continuous perforation that uses intermittent laser irradiation to continuously melt the surface of the material and remove it; blasting perforation uses continuous laser irradiation of the material. Due to the continuous heat effect, it is quickly fused and forms a small hole. Laser perforation technology has a wide range of applications in the perforation field due to its low cost, fast speed and wide range of materials. Electrospark perforation technology uses a hollow copper rod as an electrode. When the electrode contacts the material, the instantaneous high temperature generated by the discharge between the copper rod and the material is used to achieve perforation. Electrospark perforation technology is suitable for perforating conductive materials. The processing aperture is smaller and the processing position can be accurately positioned.

[0055] In order to determine the optimal perforation technology, this embodiment compares the above two methods, and successfully obtains discs with 30μm, 50μm and 80μm small holes through laser perforation. Taking the 50μm small hole as an example, for laser perforation, it can be seen that the inside of the hole is burnt black, and the hole is characterized by being thicker at the upper end and thinner at the lower end, and there is a lot of melted material residue on the surface of the hole. Therefore, for laser perforation, the hole surface material needs to be cleared later. For electric spark perforation, it can be seen that the small hole is uniformly round, the inner diameter of the hole is consistent at the upper and lower ends, the hole has no signs of burning, and there is no material attached to the surface of the hole.

[0056] By comparison, it is found that electrospark perforation is the best solution. Small holes with uniform inner diameter can be obtained by electrospark drilling, which is more conducive to the injection of droplets. However, laser drilling obtains conical holes, and there are material residues around the holes, which hinder the normal injection of droplets and require subsequent processing for droplet injection. Therefore, this embodiment adopts the electrospark drilling method to prepare the injection hole 2.

[0057] As a preferred solution of the present invention, the excitation host includes a signal generator and a signal amplifier. The signal generator is used to generate an excitation electrical signal (AC voltage signal), and the signal amplifier is used to amplify the excitation electrical signal. The frequency, voltage, number of cycles, number of periods and other parameters of the excitation electrical signal can be adjusted by the signal generator to adjust the size of the droplets, the generation rate, etc.

[0058] Please refer to Figure 9 , Figure 9It is a schematic flow chart of the steps of a droplet ejection method provided by an embodiment of the present application. The provided method is applied to the droplet ejection device provided by any embodiment of the present application.

[0059] As Figure 9 shown, the provided droplet ejection method includes steps S101 to S102.

[0060] S101. An excitation host of the droplet ejection device inputs an excitation electrical signal to the annular vibration plate to drive the annular vibration plate to generate a surface acoustic wave, and the surface acoustic wave is used to drive the ejection plate to vibrate to form droplets.

[0061] Specifically, an excitation host of the droplet ejection device inputs an excitation electrical signal to the annular vibration plate. At this time, since the annular vibration plate is made of a piezoelectric material, under the action of the inverse piezoelectric effect, the annular vibration plate will generate a deformation motion and then generate vibration. Thus, the vibration of the annular vibration plate will be transmitted to the ejection plate of the droplet ejection device to drive the ejection plate to vibrate together. Furthermore, the undischarged stock solution carried on the ejection plate overcomes the action of surface tension, thereby forming droplets and escaping from the bottom of the ejection holes.

[0062] S102. Change the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets.

[0063] Since the parameter values of the excitation electrical signal directly affect the size and generation rate of the generated droplets, when it is determined that the generated droplets do not meet the requirements according to the size and generation rate of the droplets, for example, when the diameter of the droplets is not within 10 - 30 μm. By timely changing the parameters of the excitation electrical signal, it can be ensured that the provided method can maintain the generation of droplets that meet the requirements.

[0064] Corresponding to the above-mentioned ejection device, this embodiment also provides a droplet ejection method, including the following steps:

[0065] Load an appropriate amount of stock solution on the front surface of the ejection plate;

[0066] Input an alternating current excitation electrical signal to the annular vibration plate through the excitation host, use the inverse piezoelectric effect to drive the annular vibration plate to vibrate regularly, drive the ejection plate to vibrate, and use the surface acoustic wave generated by the vibration of the ejection plate to enable the micro-droplets in the stock solution to escape from the ejection holes after overcoming the surface tension; by adjusting the frequency, voltage, and number of cycles of the alternating current excitation electrical signal output by the excitation host, micro-droplets that meet the requirements are obtained.

[0067] As a preferred embodiment of the present invention, the frequency range of the excitation electrical signal is 1 - 200 kHz. To make the device work at the optimal working frequency and ensure that other experimental conditions remain unchanged, the frequency is adjusted, and the frequency range of 1 kHz - 200 kHz is divided into "low-frequency", "medium-frequency", and "high-frequency" range. Among them, the "low-frequency" range is 1 kHz - 30 kHz; the "medium-frequency" range is 30 kHz - 100 kHz; the "high-frequency" range is 100 kHz - 200 kHz. Several working frequencies are selected in the three range respectively, and the generated droplets are compared and analyzed. Since higher voltages are required to generate droplets in the "medium-frequency" and "high-frequency" ranges, the "low-frequency" band is selected in this device to adjust the optimal working frequency of the device.

[0068] To obtain accurate spraying data, within the low-frequency range, the number of droplets generated by one spraying and the diameter of a single droplet are analyzed, and the spraying conditions of materials within the pore diameter range of 30 - 80 μm are detected;

[0069] By analyzing the materials within the pore diameter range of 30 - 80 μm, it is found that the diameter range of the droplets ejected from the ejection hole 2 is 1 - 30 μm. Through simple modeling calculations, it can be obtained that the volume of the liquid ejected from the ejection hole 2 within the pore diameter range of 30 - 80 μm is approximately 0.5 - 14 pL respectively. Since the stability of liquid ejection from the ejection hole 2 with a relatively small or large pore diameter is poor, in this embodiment, a pore diameter in the middle range (such as 50 - 60 μm) is selected as the preferred pore diameter of the ejection hole 2.

[0070] In some embodiments, according to the remaining amount of the stock solution to be ejected on the ejection plate of the droplet ejection device and the pore diameter of the ejection hole, the parameters of the excitation electrical signal are changed to adjust the size and generation rate of the droplets to obtain the droplets meeting the requirements.

[0071] Since during the process of droplet generation on the ejection plate, the stock solution to be ejected carried by the ejection plate is also decreasing, when it is necessary to continuously generate droplets with sizes and preset rates meeting the requirements, it is necessary to adjust the parameters of the excitation electrical signal in real time according to the pore diameter of the ejection hole and the remaining amount of the stock solution to be ejected to ensure that both the size and generation rate of the droplets can be maintained within the required range. Exemplarily, according to the remaining amount of the stock solution to be ejected on the ejection plate of the droplet ejection device and the pore diameter of the ejection hole, changing the parameters of the excitation electrical signal includes: modeling the droplet ejection device according to the initial amount of the stock solution to be ejected on the ejection plate of the droplet ejection device and the pore diameter; obtaining the preset size range and preset generation rate range of the droplets meeting the requirements; setting the preset size range and preset generation rate range as boundary conditions, simulating the modeled droplet ejection device to obtain the correspondence between the remaining amount of the stock solution to be ejected and the parameters of the excitation electrical signal; changing the parameters of the excitation electrical signal according to the remaining amount of the stock solution to be ejected and the correspondence.

[0072] By modeling according to a droplet ejection device, for example, completing the modeling of the droplet ejection device based on information such as the shape, size, and manufacturing material parameters of the droplet ejection device. Among them, it is also necessary to set the initial amount of the stock solution to be ejected carried on the ejection plate of the droplet ejection device and the aperture diameter of the ejection holes, for example, 100 ml of the stock solution to be ejected and the aperture diameter of the ejection holes is 55 μm. Furthermore, by obtaining a preset size range and a preset generation rate range of droplets that meet the requirements, and using the preset size range and the preset generation rate range of droplets as boundary conditions, a simulation is performed on the modeled droplet ejection device, so that the droplets generated by driving the vibration of the ejection plate by the excitation electrical signal in the simulation process of the constructed droplet ejection device model all conform to the preset size range and the preset generation rate range.

[0073] By obtaining the correspondence relationship between the remaining amount of the stock solution to be ejected and the parameters of the excitation electrical signal during the simulation process, for example, through finite element simulation calculation. Furthermore, the method provided by the present application can, according to the correspondence relationship between the remaining amount of the stock solution to be ejected and the parameters of the excitation electrical signal obtained by the simulation, adjust the parameters of the excitation electrical signal in real time according to the remaining amount of the stock solution to be ejected, so as to ensure that the method provided can generate droplets that meet the requirements in real time. Using the simulation to obtain the correspondence relationship between the remaining amount of the stock solution to be ejected and the parameters of the excitation electrical signal can also greatly simplify the process of the excitation electrical signal and improve the efficiency of adjusting the excitation electrical signal. Exemplarily, in some embodiments, it is also possible to complete the construction of a mathematical model of the droplet ejection device based on information such as the shape, size, and manufacturing material parameters of the droplet ejection device, and then solve the correspondence relationship between the remaining amount of the stock solution to be ejected and the parameters of the excitation electrical signal through the method of mathematical model calculation, so as to change the parameters of the excitation electrical signal according to the remaining amount of the stock solution to be ejected and the correspondence relationship. Furthermore, it can greatly simplify the process of the excitation electrical signal.

[0074] Since during the process of droplet generation on the ejection plate, the stock solution to be ejected carried on the ejection plate is also decreasing, when it is necessary to continuously generate droplets whose size and preset rate both meet the requirements, it is necessary to adjust the parameters of the excitation electrical signal in real time according to the aperture diameter of the ejection holes and the remaining amount of the stock solution to be ejected, so as to ensure that the size and generation rate of the droplets can both be maintained within the required range.

[0075] Without changing other conditions, in the low-frequency range, the number of droplets generated by one ejection and the diameter of a single droplet are analyzed. For the ejection material with an aperture diameter in the middle range, droplets with a single diameter of about 10 - 30 μm can be stably generated, thereby achieving picoliter pipetting accuracy.

[0076] Keeping other experimental conditions unchanged, within the low-frequency range, adjust the voltage. For the injection material with an aperture in the middle range, within a specific voltage range (such as 220 - 300V), a single droplet can be stably generated. No droplet is generated below the critical voltage of 220V, and two droplets are generated above the critical voltage of 300V. In the actual process, this range can be adjusted according to the actual situation. To avoid damage to the device under high voltage, a relatively low voltage should be selected as much as possible.

[0077] Keeping other experimental conditions unchanged, within the low-frequency and specific voltage range, for the injection material with an aperture in the middle range, adjust the cycle number of the excitation wave. Under the condition of 1 cycle number, a single droplet can be stably generated. Increasing the cycle number so that the cycle number of the excitation wave is greater than 1, the number of generated droplets will increase accordingly, and multiple micro-droplets will be accompanied. From Figure 3 it can be seen that at low-frequency, the diameter of the droplet is the smallest (10 - 30μm), and a single droplet can be stably generated, as Figure 4 shown.

[0078] Example 2

[0079] In some embodiments, please refer to Figure 5 , the area of the first plate surface of the injection plate 1 is smaller than the area of the second plate surface. At this time, when the injection plate 1 vibrates, due to the smaller area of the first plate surface of the injection plate 1, when the surface acoustic wave is generated by the annular vibration plate 3, the volume change amount in the injection hole 2 can be increased, making the droplets in the injection hole 2 easier to escape, so that the excitation voltage of the excitation electrical signal can also be reduced under the condition of generating droplets of the same size and generation rate.

[0080] Exemplarily, the curvature of the first plate surface of the injection plate 1 is smaller than the curvature of the second plate surface. By restricting the curvatures of the first plate surface and the second plate surface of the injection plate 1, as Figure 5 shown, since the curvature of the first plate surface is smaller than the curvature of the second plate surface, at this time the area of the first plate surface is smaller, resulting in an increase in the volume change amount in the injection hole 2 when the surface acoustic wave is generated by the annular vibration plate 3, making the droplets in the injection hole 2 easier to escape.

[0081] As Figure 5As shown in the figure, this embodiment provides a droplet ejection device. The difference from the above-mentioned Embodiment 1 is that the ejection plate 1 is a concave plate, and the ejection hole 2 is located at the bottommost end of the concave plate. In this embodiment, by designing the ejection plate 1 as a concave plate, on the one hand, the concave-shaped ejection plate 1 can be directly used to hold the original liquid, eliminating the need for a sample addition hopper, and all the vibrations generated by the annular vibration plate 3 can be transmitted to the original liquid through the ejection plate 1 without the absorption of vibrations by the sample addition hopper, resulting in higher droplet ejection efficiency; on the other hand, since the ejection plate 1 is concave-shaped, the areas of its front and back surfaces are different, that is, the areas of the first plate surface and the second plate surface are different. When the ejection plate 1 vibrates, the deformation amounts of its front and back surfaces are different, thereby increasing the volume change amount in the ejection hole 2, making the droplets in the ejection hole 2 easier to escape, and thus reducing the excitation voltage of the excitation electrical signal.

[0082] Exemplarily, as Figure 10 shown, the front surface of the ejection plate 1 can be used as the first plate surface and made concave, while the second plate surface is not concave. Thus, when the annular vibration plate 3 generates surface acoustic waves, the volume change amount in the ejection hole 2 can be increased, making the droplets in the ejection hole 2 easier to escape. The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A droplet ejection device, characterized in that, The droplet ejection device includes: An ejection plate provided with ejection holes thereon; An annular vibrating plate disposed on the ejection plate, the ejection holes being located within the annular vibrating plate, and the annular vibrating plate being made of a piezoelectric material; An excitation main body electrically connected to the annular vibrating plate, the excitation main body being configured to drive the annular vibrating plate to generate a surface acoustic wave, and the surface acoustic wave being used to drive the ejection plate to vibrate to form droplets.

2. The droplet ejection device according to claim 1, wherein, The ejection plate includes a first plate surface and a second plate surface disposed opposite to the first plate surface. The first plate surface of the ejection plate is for placing the stock solution to be ejected, the ejection holes are located in the middle of the ejection plate, and the stock solution to be ejected forms droplets when the surface acoustic wave drives the ejection plate to vibrate.

3. The droplet ejection device according to claim 2, wherein The annular vibrating plate is disposed on the first plate surface or the second plate surface.

4. The droplet ejection device according to claim 2, characterized in that, The droplet ejection device further includes: A sampling hopper hermetically connected to the first plate surface of the ejection plate, and the bottom of the sampling hopper communicating with the ejection holes.

5. The droplet ejection device according to claim 4, characterized in that, The sampling hopper has an inverted conical shape.

6. The droplet ejection device according to claim 2, wherein, The area of the first plate surface of the ejection plate is larger than the area of the second plate surface.

7. The droplet ejection device according to claim 2, characterized in that, The shape of the first plate surface is a concave shape, or the shape of the ejection plate is a concave shape.

8. The droplet ejection device according to claim 2, wherein, The curvature of the first plate surface of the ejection plate is less than the curvature of the second plate surface.

9. The droplet ejection device according to claim 1, characterized in that, The piezoelectric material is any one or combination of CdS, CdSe, ZnO, ZnS, CdTe, and ZnTe.

10. The droplet ejection device according to claim 1, characterized in that, The ejection plate is made of a hard material.

11. The droplet ejection device according to claim 10, wherein, The hard material includes any one of hard metals, hard plastics, and glass.

12. The droplet ejection device according to claim 1, wherein, The cross-sectional shape of the annular vibrating plate is any one of a circular ring shape, an elliptical ring shape, a square shape, and a rhombus shape.

13. The droplet ejection device according to claim 1, wherein, The aperture diameter of the inlet to the outlet of the ejection hole is the same.

14. The droplet ejection device according to claim 1, characterized in that, The aperture diameter of the ejection hole is 30 - 80 μm.

15. The droplet ejection device according to claim 14, wherein, The aperture diameter of the ejection hole is 50 - 60 μm.

16. The droplet ejection device according to claim 1, wherein, The excitation main body includes a signal generator and a signal amplifier. The signal generator is configured to generate an excitation electrical signal, and the signal amplifier is configured to amplify the excitation electrical signal and then input it to the annular vibrating plate.

17. The droplet ejection device according to claim 16, characterized in that, The signal generator adjusts the size and generation rate of the droplets according to the frequency, voltage, number of cycles, and number of periods of the excitation electrical signal.

18. The droplet ejection device according to claim 1, characterized in that, The frequency range of the excitation electrical signal is 1 - 200 kHz; or the voltage of the excitation electrical signal is 220 - 300 V; or the number of cycles of the excitation wave of the excitation electrical signal is greater than or equal to 1.

19. The droplet ejection device according to claim 18, wherein, The frequency range of the excitation electrical signal is 1 - 30 kHz; or the voltage of the excitation electrical signal is 220 V; or the number of cycles of the excitation wave of the excitation electrical signal is 1.

20. A droplet ejection method, characterized in that, Applied to the droplet ejection device according to any one of claims 1 - 19; the method includes: Inputting an excitation electrical signal to the annular vibrating plate through the excitation main body of the droplet ejection device to drive the annular vibrating plate to generate a surface acoustic wave, and the surface acoustic wave being used to drive the ejection plate to vibrate to form droplets; Changing the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets.

21. The method according to claim 20, wherein The changing the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets includes: By changing one or more of the frequency, voltage, number of cycles, and number of periods of the excitation electrical signal, the size and generation rate of the droplets are adjusted.

22. The method according to claim 21, characterized in that, The frequency range of the excitation electrical signal is 1 to 200 kHz; alternatively, the voltage of the excitation electrical signal is 220 to 300 V; alternatively, the number of cycles of the excitation wave of the excitation electrical signal is greater than or equal to 1.

23. The method according to claim 22, wherein The frequency range of the excitation electrical signal is 1 to 30 kHz; alternatively, the voltage of the excitation electrical signal is 220 V; alternatively, the number of cycles of the excitation wave of the excitation electrical signal is 1.

24. The method according to claim 20, wherein Changing the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets includes: According to the remaining amount of the stock solution to be sprayed on the spraying plate of the droplet spraying device and the aperture of the spraying holes, changing the parameters of the excitation electrical signal to adjust the size and generation rate of the droplets, so as to obtain droplets meeting the requirements.

25. The method according to claim 24, wherein Changing the parameters of the excitation electrical signal according to the remaining amount of the stock solution to be sprayed on the spraying plate of the droplet spraying device and the aperture of the spraying holes includes: Modeling the droplet spraying device according to the initial amount of the stock solution to be sprayed on the spraying plate of the droplet spraying device and the aperture; Obtaining a preset size range and a preset generation rate range of the droplets meeting the requirements; Setting the preset size range and the preset generation rate range as boundary conditions, simulating the modeled droplet spraying device, and obtaining the corresponding relationship between the remaining amount of the stock solution to be sprayed and the parameters of the excitation electrical signal; Changing the parameters of the excitation electrical signal according to the remaining amount of the stock solution to be sprayed and the corresponding relationship.

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