CN114749222B - Integrated piezoelectric type multi-column uniform liquid drop generator - Google Patents

Abstract

The invention discloses an integrated piezoelectric type multi-column uniform liquid drop generator, relates to the technical field of liquid micro-flow control, and aims to solve the problems that the uniformity of liquid drops dispersed by the existing liquid drop generator is poor, the precision is low, and the micro-flow control precision is seriously affected; meanwhile, the existing generator has the problems of high price, high use cost and the like; the invention comprises a connecting disc, a fluid cavity, piezoelectric ceramics, a piezoelectric ceramic groove, an annular sealing ring, a jet flow sheet, a screw cap, an injection pump connecting port and a BNC interface; the whole piezoelectric ceramic device is made of stainless steel, the piezoelectric ceramic device is ensured to safely operate through the design of the insulating layer, the electric shock condition of a user can not occur, and the safety is good. The method has wide application in the field of micro-flow control, and a user can determine proper crushing frequency according to a table so as to achieve the optimal effect. The generation of the multi-column uniform liquid drop generator can greatly improve the application efficiency and widen the application scene of a single column, and has important effects in the field of quick bio-pharmaceuticals.

Description

Integrated piezoelectric multi-column uniform droplet generator

technical field

The invention relates to the technical field of liquid microfluidics, in particular to an integrated piezoelectric multi-column uniform droplet generator.

Background technique

Microfluidics refers to the precise control and manipulation of micro-scale fluids. Since the application scenario is a micro-nano structure, and the fluid in this structure displays and produces special properties different from those of the macro-scale, it is necessary to analyze its unique physical and chemical properties. For the preparation of uniform micro-droplets, high-precision, regular monodisperse droplet strings have great application prospects in the fields of chemical industry, food, inkjet printing, and medical treatment. In such application scenarios, how to Precise control of the flow of high-speed droplets and regular droplet strings has always been a difficult problem to be solved. And with the deepening of the application, how to efficiently and quickly complete the preparation of micro-droplets with different needs has become the direction of current attention.

At present, the general piezoelectric droplet generator in China is separated by placing the fluid chamber, nozzle, piezoelectric module and BNC connection port to form experimental conditions through mechanical means, and then produces continuous monodisperse droplets. Since the main components are not integrated, Therefore, it is cumbersome to use and less commercially available.

In addition to the above-mentioned piezoelectric droplet generators, there are also pneumatic droplet generators and the preparation of droplets through microchannels. Although these two methods can generate continuous droplets through a fixed device, they also have certain disadvantages. Although the pneumatic droplet generator can produce dispersed droplets, its uniformity is poor; droplets prepared through microchannels will also undergo certain deformation in the channel, and this method is mostly used for two kinds of substances mix of , mostly closed environments.

At the same time, the above-mentioned droplet generator also has problems such as poor use effect and low precision. This is also a difficulty of the droplet generator. It will interfere with the flow of the droplet string, and each droplet may be uneven, which will seriously affect the precision of microfluidics. And the practicability of many droplet generators has not been verified. Although there are formed droplet generators in foreign countries, the price is relatively expensive, and the single continuous droplet and multiple groups of droplet jets are switched by switching the entire nozzle, which is cumbersome and costly.

On the basis of the original single-column droplet, the present invention is improved into a replaceable nozzle-type multi-column droplet. The generation of multi-column uniform droplet generator can greatly improve the application efficiency and broaden the application scenarios of a single column, which plays an important role in the field of rapid biopharmaceuticals.

Contents of the invention

The present invention solves the problem of poor uniformity and low precision of dispersed droplets in the existing droplet generator, which further seriously affects the precision of microfluidic control; at the same time, there are problems such as high price and high use cost; it provides an integrated press Electric multi-column uniform droplet generator.

Integrated piezoelectric multi-column uniform droplet generator, including connecting plate, fluid chamber, piezoelectric ceramics, piezoelectric ceramic tank, annular sealing ring, jet sheet, screw cap, syringe pump connection port and BNC interface;

One end of the fluid chamber is fixed with a connection plate, and communicates with the connection port of the syringe pump through the connection plate, and the connection port of the syringe pump introduces the fluid into the fluid chamber through the delivery hose;

The other end of the fluid chamber is equipped with an annular sealing ring, a jet sheet and a screw cap, and the jet sheet is fixed in the groove of the screw cap by the stress of the annular sealing ring and the screw cap;

A groove is provided outside the cavity of the fluid chamber as a piezoelectric ceramic groove, and an insulating layer and piezoelectric ceramic are arranged in the piezoelectric ceramic groove, and are fixed by cable ties;

The BNC interface is installed on the connecting plate, and serves as the electrical signal input terminal of the piezoelectric ceramic, and transmits the square wave or sinusoidal control signal amplified by the power amplifier to the piezoelectric ceramic to generate micron-level vibration;

Multiple rows of jet holes are arranged on the jet sheet, and the distance between adjacent jet holes is the same; the thickness of the jet sheet is 0.5mm-1mm.

Beneficial effects of the present invention: the integrated piezoelectric multi-column uniform droplet generator described in the present invention has the following advantages:

1. In the droplet generator of the present invention, each column of jet droplets runs more stably and has a better crushing effect. Compared with pneumatic droplet generators, the application range is wider and the effect is better.

2. Compared with TSI and other manufacturers, the droplet generator of the present invention is cheaper and has a wider range of applications. In the present invention, by using the jet sheet instead of the nozzle, it does not need to replace the fixed nozzle many times, and the operation is relatively simple , lower cost and wider adaptability.

3. The droplet generator of the present invention is a droplet generator that integrates piezoelectric ceramics, BNC connection ports, fluid chambers, jet holes, and integration. The whole is made of stainless steel and the safety of piezoelectric ceramics is ensured by designing an insulating layer. Running, there will be no electric shock for the user, and the safety is better.

4. Through repeated verifications such as experiments and simulation calculations, the best piezoelectric ceramic physical parameters and various parameters such as strength, output, resonance frequency and driving voltage are obtained and verified, and the relationship between voltage and amplitude is given. Finally, it can achieve an optimal crushing effect by cooperating with the designed droplet generator. The crushing effect has been verified by shooting with a high-speed camera. Under the condition of ensuring the crushing condition, the present invention has passed the accuracy test and can achieve the number of broken droplets of about Equal to the set frequency, the error is not more than 0.5% of the set frequency. There are a wide range of application scenarios in the field of microfluidics.

5. In the design process of the entire fluid chamber, the optimal piezoelectric ceramic groove depth and wall thickness are given through repeated simulations, which ensures the effective amplitude of the piezoelectric ceramic. The selection range of the thickness of the jet sheet The present invention has obtained the optimum thickness range through experimental verification.

6. The present invention also provides the frequency ranges used under different flow rates (the present invention takes 100um as an example), and users can determine the appropriate crushing frequency according to the table to achieve the optimal effect. And the diameter of the droplet outlet can be determined according to the flow rate and the outlet aperture through the empirical formula, and the aperture size can be customized according to needs.

Description of drawings

Fig. 1 is the structural representation of integrated piezoelectric multi-column uniform droplet generator of the present invention;

Fig. 2 is the explosion diagram of integrated piezoelectric multi-column uniform droplet generator of the present invention;

Fig. 3 is the main, side and top three views of the piezoelectric ceramic sheet;

Fig. 4 is the relationship diagram of the driving voltage and the displacement of the piezoelectric ceramic sheet;

Fig. 5 is the schematic diagram of the integrated piezoelectric uniform droplet generator of the present invention;

Fig. 6 is an effect diagram of continuous droplets generated by the integrated piezoelectric uniform droplet generator using a high-speed camera;

Figure 7 is a schematic diagram of a jet hole radius of 100um and a 5*5 jet sheet;

Figure 8 is a schematic diagram of a 7*7 jet sheet with a jet hole radius of 71um;

Fig. 9 is a schematic diagram of a 10*10 jet sheet with a jet hole radius of 50um.

In the figure: 1. Power amplifier, 2. Signal generator, 3. Syringe pump, 4. Droplet generator, 4-1. Connection plate, 4-2. Fluid cavity, 4-3. Piezoelectric ceramics, 4- 4. Piezoelectric ceramic tank, 4-5, annular sealing ring, 4-6, jet sheet, 4-7, screw cap, 4-8, injection pump connection port, 4-9, BNC interface.

Detailed ways

This embodiment is described in conjunction with Fig. 1 to Fig. 9. The integrated piezoelectric multi-column uniform droplet generator includes a connection plate 4-1, a fluid chamber 4-2, a piezoelectric ceramic 4-3, and a piezoelectric ceramic groove 4-4 , ring sealing ring 4-5, jet sheet 4-6, screw cap 4-7, syringe pump connection port 4-8 and BNC port 4-9;

The left end of the connection port of the injection pump 3 is connected with the external thread of the fluid chamber 4-2 by a threaded port, and the right end is connected with a water delivery pipe by a smooth cylindrical interface. The connection port is a fluid inlet, and the fluid is introduced into the fluid cavity through the transport hose. The left side of the BNC interface is fixed with the card slot of the connecting plate 4-1 with strong fixing glue, which is convenient for replacement. The connection port is an electrical signal input port of piezoelectric ceramics, which transmits the square wave or sinusoidal control signal amplified by the power amplifier 1 to the stacked piezoelectric ceramics 4-3, thereby generating micron-level vibrations.

The connection plate is connected to the fluid cavity 4-2 through an internal thread, and the entire connection plate 4-1 is stuck on the outer boss of the fluid cavity 4-2. The main function of the connecting plate 4-1 is to connect the fluid chamber 4-2 with the other two interfaces, and play the role of connecting the entire generator.

There is an insulating coating between the piezoelectric ceramic 4-3 and the groove of the fluid chamber, and the piezoelectric ceramic sheet is fixed in the center of the groove of the fluid chamber after the insulating coating is produced during manufacture, and fixed with a cable tie.

Piezoelectric ceramics, one of the core components of this embodiment, are determined and processed through continuous testing and calculations during the design process, as shown in Table 1, piezoelectric ceramic parameters.

Table 1

The polarization direction is set as shown in Figure 3, and the external silver is used as the electrode in the height direction, and the welding wire method adopts two-sided welding perpendicular to the height, which is convenient for lead wires. When the stacked ceramics reaches the resonance frequency, the displacement is about 3.3um. Before reaching the resonance frequency, the displacement relationship is mainly related to the frequency range of the present invention, which is about 10000hz, and the amplitude is about 2um. When piezoelectric ceramics are used, preload must be added to prevent the internal ceramic sheets from being damaged due to tensile stress. The method of adding preload can be through cable ties, steel hoops, etc. Figure 4 shows the variation curve of piezoelectric ceramic amplitude with voltage. The test curve below is the relationship between voltage and displacement when the piezoelectric ceramic voltage is applied from 0. The curve above is the curve of the voltage dropping from 150v to 0v. Because it is capacitive impedance, residual voltage displacement will occur. will not be 0.

The left end of the fluid cavity 4-2 is connected with the screw cap 4-7 through an external thread, and the right side is connected with the connecting plate 4-1 through an external thread. The internal fluid fills the fluid cavity, and the outer part of the fluid cavity is a groove for placing stacked piezoelectric ceramics and covering the insulating layer to prevent users from getting an electric shock. The thickness of the middle part is designed to maximize the vibration efficiency of the piezoelectric ceramics.

The piezoelectric ceramic groove 4-4 is processed by turning on the outside of the fluid chamber. The design of the piezoelectric ceramic groove is also a key to this embodiment. Through multiple simulation results, it is concluded that the wall thickness of the piezoelectric ceramic groove must be 0.5 -1.5mm is the best, too thick will greatly reduce the displacement of the piezoelectric ceramic sheet, and too thin will cause the fluid cavity to deform under high pressure.

The annular sealing ring 4-5 is turned into a card groove in the rotary cap 4-7, which plays a role in fixing the annular sealing ring 4-5, and the right end of the annular sealing ring 4-5 is squeezed by the fluid chamber to fix it on the screw cap inside the cap slot. A cross-section rectangular sealing ring is used for sealing, which can achieve an optimal sealing effect. The annular sealing ring compresses the jet sheet 4-6 in the inner groove of the screw cap 4-7 through the compressive stress of the fluid cavity 4-2 and itself.

The jet sheet 4-6 can be obtained through fine processing, and the jet sheet 4-6 is fixed in the groove of the screw cap 4-7 through the compressive stress of the annular sealing ring 4-5 and the screw cap 4-7. The jet holes on the jet sheets 4-6 can be obtained by laser technology, and need to be polished with 10,000-mesh sandpaper after processing to eliminate burrs. Through continuous testing, it is found that thicker jet sheets 4-6 will lead to serious inclination of the jet outlet, and thinner ones will lead to insufficient strength of the jet sheet at high flow rates, resulting in bending of the jet sheet. Finally, it is obtained that the thickness of the jet sheet 4-6 is preferably between 0.5mm-1mm. By customizing the size of the hole on the chip according to different pore diameters and flow rates, the jet hole is also the only outlet for the fluid.

The screw cap 4-7 is connected with the external thread of the fluid cavity 4-2 through an internal thread. The internal groove of the screw cap 4-7 plays a role of fixing the jet sheet 4-6, and the screw cap 4-7 also plays a role of packaging and sealing the entire fluid cavity 4-2.

This embodiment is described in conjunction with FIG. 5 and FIG. 6. The working principle of the integrated piezoelectric uniform droplet generator described in this embodiment is:

The signal generator 5v square wave or sine signal is amplified by the power amplifier 1 (the multiple of the power amplifier is determined as 50), as shown in Figure 5, the electrical signal is acted on the piezoelectric ceramic 4-3 by connecting the BNC interface 4-9. Piezoelectric ceramics 4-3 exhibit capacitive impedance, which can convert electrical energy into regular mechanical vibration. Then the continuous fluid is disturbed regularly, so that the continuous fluid is broken into uniform circular drops. The specific process is as follows:

1. Adjust the 3 parameters of the syringe pump, and set the required liquid flow and flow rate. The syringe pump 3 pressurizes the liquid to push the liquid through the rotation of the screw to push the syringe. The flow rate and flow rate can be adjusted by adjusting the parameters of the syringe pump 3. The stable flow rate is roughly above 3m/s, and the approximate experimental range is 3m/s. -30m/s. Since the design stability of the structure is also better than before, this flow rate range is larger than the previous domestic flow rate range.

2. The signal generator 2 for driving piezoelectric ceramics can be set as sine wave or square wave, and the peak voltage is 5v. The square wave effect may be better, and the output impedance is determined to be 5 ohms (consistent with the power amplifier impedance). The sensitivity to the phase is not high, and the initial phase can be selected from 0. The selection of the frequency is based on the empirical formula:

In the formula, u is the fluid velocity, and d is the diameter of the nozzle, which can be obtained. Multi-column is the same as single-column. Taking 100um aperture as an example, here are the frequency ranges corresponding to different flow rates, the flow rate and the diameter of the droplets after they flow out. . By calculating the minimum wavelength under this working condition to satisfy the minimum wavelength formula: λ≥πd, the stability of this droplet generator can be ensured. Table 2, droplet parameter table under 100um aperture;

Table 2

Nozzle Straight Code flow(ml/h) Droplet Velocity(m/s) Excitation frequency (min hz) Excitation frequency (max hz) median frequency Droplet diameter (um) Minimum wavelength(um) 100 100 3.539 3380.80 10142.40 6761.60 198.7501 348.931 100 105 3.715 3549.84 10649.52 7099.68 198.7332 348.842 100 110 3.892 3718.88 11156.64 7437.76 198.7348 348.851 100 115 4.069 3887.92 11663.76 7775.84 198.7363 348.858 100 120 4.246 4056.96 12170.88 8113.92 198.7377 348.865 100 125 4.423 4226.00 12678.00 8452.00 198.7389 348.872 100 130 4.600 4395.04 13185.12 8790.08 198.7401 348.878 100 135 4.777 4564.08 13692.24 9128.16 198.7411 348.884 100 140 4.954 4733.12 14199.36 9466.24 198.7421 348.889 100 145 5.131 4902.16 14706.48 9804.32 198.7430 348.894 100 150 5.308 5071.20 15213.60 10142.40 198.7439 348.898 100 155 5.485 5240.24 15720.72 10480.48 198.7447 348.903 100 160 5.662 5409.28 16227.84 10818.56 198.7455 348.907 100 165 5.839 5578.32 16734.96 11156.64 198.7462 348.910 100 170 6.016 5747.36 17242.08 11494.72 198.7468 348.914 100 175 6.192 5916.40 17749.20 11832.80 198.7368 348.861 100 180 6.369 6085.44 18256.32 12170.88 198.7377 348.865 100 185 6.546 6254.48 18763.44 12508.96 198.7385 348.870 100 190 6.723 6423.52 19270.56 12847.04 198.7393 348.874 100 195 6.900 6592.56 19777.68 13185.12 198.7401 348.878 100 200 7.077 6761.60 20284.80 13523.20 198.7408 348.882 100 205 7.254 6930.64 20791.92 13861.28 198.7415 348.886 100 210 7.431 7099.68 21299.04 14199.36 198.7421 348.889 100 215 7.608 7268.72 21806.16 14537.44 198.7427 348.892 100 220 7.785 7437.76 22313.28 14875.52 198.7433 348.895

3. After adjusting the signal generator 2, continue to adjust the power amplifier 1. After the power amplifier 1 is turned on, the impedance of the power amplifier is 5 ohms, and the voltage magnification starts from the lower 2 times, so as to avoid damage to the power amplifier due to short circuit due to wiring errors.

4. Put the piezoelectric ceramic slot 4-4 into the side wall insulation pit and securely fix it with plastic insulating cable ties to increase the pre-tightening force (if the pre-tightening force is not applied to the ceramic sheet, the stacked ceramic will be broken), and the The piezoelectric ceramic is connected to the BNC adapter cable, and then connected to the power amplifier 1. Ensure that the entire wiring line is insulated.

5. Press the start button of the syringe pump 3, click the output button of the signal generator; press the output button of the power amplifier; after hearing the buzzing sound of the piezoelectric ceramics, gradually adjust the multiple from 2 to 50, and finally through the observation equipment such as a high-speed camera Check the droplet quality of the droplet generator; then further confirm the frequency through the signal generator 2, adjust it in units of 1khz at first, adjust it in units of 100hz after finding the best frequency, and finally adjust it in units of 10hz and 1hz The unit performs final fine-tuning to find the best fragmentation phenomenon and finally achieve the best effect.

As shown in Figure 6, the continuous droplet image observed by the high-speed camera, the speed is about 6m/s, the set frequency is 4400hz, and about 4400±20 drops are produced per second. The error is about 0.05%, which has reached the forefront of international technology.

Figure 7 to Figure 9 respectively show the number of holes of 5*5; 7*7; 10*10 in the area of 10mm*10mm in the case of constant flow, and the hole radii are 100um, 71um, and 50um respectively. Because under equal flow conditions, as the number of holes increases, the droplet radius of each column will decrease, and the flow rate will not decrease. The equal-area design method can use different density holes for fixed objects to obtain multi-row droplet strings of different sizes and different numbers but with a certain total flow rate. The error of the number of droplets produced by a single column is basically between 0.5% and 0.8% of the set frequency.

Since the generation of multiple columns of droplets will cause the interference of each column of droplets, it is found through repeated tests that the optimal hole spacing of this device is 5 times or more than the droplet diameter. If the distance is less than five times, the two columns of droplets may stick and interact with each other.

The integrated piezoelectric multi-column uniform droplet generator described in this embodiment guarantees a good droplet breaking effect and cleverly connects the parts of the generator through mechanical design to form a product that can be directly applied. Its accuracy is verified by high-speed cameras. The successfully processed droplet generator has passed a large number of experiments, and has been repeatedly verified with high-speed cameras and other equipment, and the data reliability is high.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (4)

1. An integrated piezoelectric type multi-column uniform liquid drop generator is characterized in that: the liquid drop generator comprises a connecting disc (4-1), a fluid cavity (4-2), piezoelectric ceramics (4-3), an annular sealing ring (4-5), a jet flow sheet (4-6), a rotary cap (4-7), a syringe pump connecting port (4-8) and a BNC interface (4-9);

one end of the fluid cavity (4-2) is fixed with a connecting disc (4-1), the connecting disc (4-1) is communicated with a connecting port (4-8) of the injection pump, and the connecting port (4-8) of the injection pump introduces fluid into the fluid cavity (4-2) through a conveying hose;

the other end of the fluid cavity (4-2) is provided with an annular sealing ring (4-5), a jet flow sheet (4-6) and a rotary cap (4-7), and the jet flow sheet (4-6) is fixed in a groove of the rotary cap (4-7) through stress of the annular sealing ring (4-5) and the rotary cap (4-7);

a groove is formed in the outer portion of the fluid cavity (4-2) and used as a piezoelectric ceramic groove (4-4), an insulating layer and piezoelectric ceramic are arranged in the piezoelectric ceramic groove (4-4), and the piezoelectric ceramic groove is fixed by adopting a binding belt;

the BNC interface (4-9) is arranged on the connecting disc (4-1) and is used as an electric signal input end of the piezoelectric ceramic, and square waves or sine control signals amplified by the power amplifier are transmitted to the piezoelectric ceramic (4-3) to generate micron-sized vibration;

the frequency is selected according to the empirical formula:

where u is the fluid velocity and d is the nozzle diameter;

a plurality of rows of jet holes are arranged on the jet sheet (4-6), and the distances between adjacent jet holes are the same; the thickness of the jet sheet (4-6) is 0.5mm-1mm;

the length, width and height of the piezoelectric ceramic (4-3) are respectively 7mm, 7mm and 5mm, the electrostatic capacity is 300-500nf, the output is 2000-3000N, the driving voltage is 150V, the displacement range is 3um, and the resonance frequency is 200-300khz.

2. The integrated piezoelectric multi-column uniform droplet generator of claim 1, wherein: the wall thickness of the piezoelectric ceramic groove (4-4) is 0.5-1.5mm.

3. The integrated piezoelectric multi-column uniform droplet generator of claim 1, wherein: the jet flow sheets (4-6) are used for setting the sizes of jet flow holes according to different apertures and flow rates, and the jet flow holes are used as fluid outlets.

4. The integrated piezoelectric multi-column uniform droplet generator of claim 1, wherein: the optimal jet hole spacing is 5 times the droplet diameter.

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