Superhydrophobic needle and method, device for making same, and microdroplet generation device and method

Abstract

The application discloses a super-hydrophobic needle and a preparation method and device thereof, and a micro-droplet generating device and method, and relates to the technical field of micro-fluids; specifically, in the application, the injection needle is modified by a laser light filament to obtain a modified needle, and then the modified needle is subjected to heat treatment to obtain a super-hydrophobic needle. The injection needle is modified by the laser light filament, the characteristics of the laser light filament are utilized, the inner surface of the injection needle is rapidly modified, the inner surface of the injection needle is converted into a super-hydrophobic surface by cooperating with a heat treatment method, the adhesion force acting on the liquid droplets flowing out of the injection needle is greatly reduced, and only a physical treatment method is adopted, so that the processing is simple and quick while avoiding the introduction of any chemical substances. Further, the size of the injection needle and the flow rate of the liquid can be selected to control the volume and generation frequency of the micro-droplets.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and in particular to a superhydrophobic needle and its preparation method and apparatus, as well as a microdroplet generation device and method. Background Technology

[0002] Methods for generating micro / nanolithic droplets have attracted widespread attention in various technological fields, including chemical analysis, inkjet printing, additive manufacturing, and liquid fuel combustion. Currently, many methods exist for generating microdroplets, which can be broadly categorized into active and passive methods based on the presence or absence of external force. Active methods require external electric fields, magnetic fields, temperature gradients, etc., necessitating additional devices and involving complex technologies, as well as issues of space and energy waste. Passive methods, on the other hand, primarily utilize the hydrodynamic effects of a flow field to generate droplets, thus requiring no additional devices.

[0003] In passive methods, one approach is to prepare a superhydrophobic needle by altering the wettability of the needle tip, thereby reducing the adhesion of the fluid and enabling the generation of micro / nanolitical droplets. This method is simple, quick, and can reduce needle droplet residue, producing microdroplets with precise volume.

[0004] Existing methods for preparing superhydrophobic needles mainly fall into two categories: laser modification and chemical treatment. Laser-modified needles, due to the limited focusing of conventional laser processing, can only alter the wettability at the needle's cross-section. The modified area is too small, resulting in insufficient reduction in adhesion, and the generated droplets are typically not small enough, potentially limiting their use in certain high-precision applications. While chemical treatment can modify the curved inner wall of the needle tip, enabling the preparation of superhydrophobic needles to produce extremely small droplets, the introduction of chemicals poses a potential risk of contamination.

[0005] It is evident that existing methods for preparing superhydrophobic needles either have too small a modification area, resulting in insufficient reduction of adhesion, or introduce chemical substances that pose a potential risk of contamination. Therefore, there is an urgent need to provide a new method for preparing superhydrophobic needles to solve the aforementioned problems in the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a superhydrophobic needle and its preparation method, apparatus, and microdroplet generation device and method to solve the problems existing in the prior art. It can greatly reduce the adhesive force on the droplets when they flow out of the injection needle and avoid the introduction of chemical substances, thereby avoiding potential pollution risks.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a method for preparing a superhydrophobic needle, comprising the following steps:

[0009] S1. Modify the injection needle using a laser filament to obtain a modified needle;

[0010] S2. The modified needle is subjected to heat treatment to obtain a superhydrophobic needle.

[0011] Preferably, before step S1, the method further includes the following step:

[0012] S01. Clean the surface of the injection needle;

[0013] Step S01 includes:

[0014] The injection needle was sequentially placed in acetone, ethanol, and deionized water for ultrasonic cleaning, and the cleaning time of the injection needle in acetone, ethanol, and deionized water was 10-20 minutes.

[0015] Preferably, in step S1, modifying the injection needle using a laser filament includes:

[0016] The injection needle is fixed on a displacement platform with its bevel facing outwards. The injection needle is then scanned by the laser filament to achieve modification.

[0017] The laser filament scans the injection needle at a speed of 1–5 mm / s and at a scanning interval of 100 μm.

[0018] Preferably, the laser filament in step S1 is a filament generated by a femtosecond laser passing through a lens;

[0019] The lens has a focal length of 50–120 cm, the femtosecond laser is generated by a femtosecond laser amplifier with an oscillator, the center wavelength of the femtosecond laser is 260–1200 nm, the pulse width is 45–1000 fs, the repetition frequency is 0.1–10 kHz, and the single pulse energy is greater than the laser filamentation threshold.

[0020] Preferably, the heat treatment of the modified needle in step S2 includes:

[0021] The modified needle was placed in a heating chamber and heated at 110–130°C for 3–5 hours.

[0022] The present invention also provides a superhydrophobic needle preparation apparatus for implementing the superhydrophobic needle preparation method described above, comprising:

[0023] A laser assembly for generating a laser filament to modify the injection needle;

[0024] A heat treatment apparatus for heat treating the modified needle.

[0025] The present invention also provides a superhydrophobic needle, which is prepared by the superhydrophobic needle preparation method described above.

[0026] The present invention also provides a microdroplet generating device, including an injection needle tube, a pushing device, and a superhydrophobic needle as described above. The superhydrophobic needle is mounted on the injection needle tube, and the piston of the injection needle tube is connected to the pushing device. The pushing device can drive the piston to reciprocate along the axial direction of the injection needle tube. The injection needle tube is used to store liquid. When the pushing device pushes the piston, it can push the liquid in the injection needle tube out through the superhydrophobic needle to form microdroplets.

[0027] Preferred options also include:

[0028] A fixed bracket is provided, on which the injection needle is mounted;

[0029] A control device, electrically connected to the pushing device, is used to control the pushing device to move the piston and control the piston's moving speed; wherein the piston's moving distance ranges from 50 to 400 mm, the displacement accuracy is 2.5 μm, the superhydrophobic needle is any size from 4 to 50, and the injection syringe has a volume of 25 μL to 20 mL; and

[0030] A data acquisition device is used to collect information on the formation of the microdroplets, wherein the data acquisition device is a high-speed camera, and the high-speed camera is positioned directly in front of the superhydrophobic needle.

[0031] The present invention also provides a method for generating microdroplets, implemented using the microdroplet generating device described above, comprising the following steps:

[0032] The superhydrophobic needle is mounted on the injection needle tube, and the piston is pushed by the pushing device to push the liquid in the injection needle tube out through the superhydrophobic needle to form microdroplets.

[0033] The present invention achieves the following technical effects compared to the prior art:

[0034] This invention modifies the injection needle using a laser filament. The laser filament is a plasma channel with constant internal intensity clamping formed by the combined action of various nonlinear effects when a strong femtosecond laser propagates nonlinearly in a medium. Utilizing its intensity clamping characteristic over a certain distance, the inner surface of the injection needle can be rapidly modified, and the entire curved inner wall of the injection needle can be processed in a single scan. Combined with heat treatment, the inner surface of the injection needle is transformed into a superhydrophobic surface, which greatly reduces the adhesive force on the droplets when they flow out of the injection needle, thereby enabling the generation of very small droplets.

[0035] Moreover, the treatment of the injection needle in this invention is limited to physical treatment methods such as laser filament processing and heat treatment, which avoids the introduction of any chemical substances and is simple and quick to process.

[0036] Furthermore, the present invention can also regulate the volume and generation frequency of microdroplets by selecting the size of the injection needle and controlling the flow rate of the liquid. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the microdroplet generation device in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the generation of microdroplets by superhydrophobic needles No. 4, 6, 8, and 10 in an embodiment of the present invention;

[0040] Figure 3 This is a graph showing the diameter curves of microdroplets generated by superhydrophobic needles No. 4, 6, 8, and 10 in the embodiments of the present invention and the oblique tip needle in the blank control.

[0041] Figure 4 This is a schematic diagram of microdroplets generated by the No. 4 superhydrophobic needle at different flow rates in an embodiment of the present invention;

[0042] Figure 5 This is a frequency curve of microdroplets generated by the No. 4 superhydrophobic needle in the embodiment of the present invention at different flow rates.

[0043] In the diagram: 1-Superhydrophobic needle, 2-Injection needle tube, 3-Fixed bracket, 4-One-dimensional electrically controlled displacement platform, 5-Control computer, 6-High-speed camera. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The purpose of this invention is to provide a superhydrophobic needle and its preparation method, apparatus, and microdroplet generation device and method to solve the problems existing in the prior art. It can greatly reduce the adhesive force on the droplets when they flow out of the injection needle and avoid the introduction of chemical substances, thereby avoiding potential pollution risks.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Example 1

[0048] This embodiment provides a method for preparing a superhydrophobic needle, which mainly includes the following steps:

[0049] S1. Modify the injection needle using a laser filament to obtain a modified needle;

[0050] S2. The modified needle is subjected to heat treatment to obtain superhydrophobic needle 1.

[0051] In this embodiment, the injection needle is modified by using a laser filament. The laser filament is a plasma channel with constant internal intensity clamping formed by the combined action of multiple nonlinear effects when a strong femtosecond laser propagates nonlinearly in a medium. Utilizing its intensity clamping characteristic over a certain distance, the inner surface of the injection needle can be rapidly modified, and the entire curved inner wall of the injection needle can be processed in a single scan. Combined with heat treatment, the inner surface of the injection needle is transformed into a superhydrophobic surface, which greatly reduces the adhesive force on the droplets when they flow out of the injection needle, thereby enabling the generation of very small droplets.

[0052] Moreover, the treatment of the injection needle in this invention is limited to physical treatment methods such as laser filament processing and heat treatment, which avoids the introduction of any chemical substances and is simple and quick to process.

[0053] In this embodiment, before step S1, the following step is also included:

[0054] S01. Clean the surface of the injection needle;

[0055] The surface cleaning of the injection needle in step S01 mainly includes:

[0056] The injection needle is sequentially placed in acetone, ethanol, and deionized water for ultrasonic cleaning, with each cleaning time in these solutions being 10–20 minutes. This process yields a clean injection needle.

[0057] In this embodiment, the modification of the injection needle by laser filament in step S1 mainly includes: fixing the injection needle on a displacement platform, wherein the injection needle is usually a beveled needle with a beveled end, so that the bevel of the injection needle faces outward, and scanning the injection needle by laser filament to achieve modification;

[0058] The displacement platform can be selected according to specific work needs, preferably a two-dimensional electrically controlled displacement platform. The two-dimensional electrically controlled displacement platform is used to continuously change the interaction position between the laser filament and the surface of the injection needle to achieve full-coverage scanning of the surface of the injection needle.

[0059] Furthermore, the scanning speed of the laser filament scanning the injection needle is preferably 1 to 5 mm / s, and the scanning interval is preferably 100 μm.

[0060] In this embodiment, the laser filament in step S1 is a filament generated by a femtosecond laser through a lens, and the focal length of the lens is preferably 50-120cm; while the femtosecond laser is generated by a femtosecond laser amplifier with an oscillator, and the center wavelength of the femtosecond laser is preferably 260-1200nm, the pulse width is preferably 45-1000fs, the repetition frequency is preferably 0.1-10kHz, and the single pulse energy is greater than the laser filamentation threshold.

[0061] In this embodiment, the heat treatment of the modified needle in step S2 mainly includes:

[0062] The modified needle was placed in a heating chamber and heated at 110–130°C for 3–5 hours.

[0063] Example 2

[0064] This embodiment discloses the specific steps for preparing a superhydrophobic needle 1 from injection needles of different types, mainly including the following steps:

[0065] 1. Cleaning the needle surface

[0066] Angled injection needles of sizes 4, 6, 8, and 10 were used, with outer diameters of 0.42, 0.62, 0.81, and 1.02 mm, and inner diameters of 0.2, 0.32, 0.51, and 0.7 mm, respectively. The injection needles were then subjected to ultrasonic cleaning in acetone, ethanol, and deionized water, respectively, for 15 minutes in each liquid. This process yielded surface-cleaned angled injection needles.

[0067] 2. Surface modification of injection needles

[0068] A laser filament formed by an ultrafast laser with a center wavelength of 790–810 nm, a pulse width of 45 fs, a repetition frequency of 500 Hz, and a single pulse energy of 1.5 mJ was used to modify a surface-cleaned beveled injection needle. A two-dimensional electrically controlled displacement platform was used to continuously change the interaction position between the laser filament and the surface of the beveled injection needle, achieving a full-coverage scan of the beveled injection needle surface. The scanning speed was 2 mm / s and the scanning interval was 0.1 mm, thereby obtaining a modified needle with a femtosecond laser filament surface.

[0069] 3. Heat treatment of needle tip

[0070] The modified needle, whose surface has been modified by femtosecond laser filament, was placed in a heating chamber and heated at 120°C for 4 hours to obtain a superhydrophobic needle 1.

[0071] Example 3

[0072] This embodiment provides a superhydrophobic needle preparation apparatus for implementing the superhydrophobic needle preparation methods described in Embodiments 1 and 2, mainly including:

[0073] A laser assembly for generating a laser filament to modify the injection needle;

[0074] A heat treatment apparatus for heat treating the modified needle.

[0075] In this embodiment, the laser component and the heat treatment device can be selected according to specific working needs. As a preferred embodiment, the laser component mainly includes a femtosecond laser amplifier and a lens. The femtosecond laser amplifier has an oscillator and can generate a femtosecond laser with a center wavelength preferably of 260-1200nm, a pulse width preferably of 45-1000fs, a repetition frequency preferably of 0.1-10kHz, and a single pulse energy greater than the laser filamentation threshold. This femtosecond laser generates a laser filament through the lens. The heat treatment device can be a heating chamber, which is a mature existing technology in the field and will not be described in detail in this embodiment.

[0076] In this embodiment, the superhydrophobic needle preparation device may further include a displacement platform, which drives the injection needle to move; wherein, the displacement platform is preferably a two-dimensional electrically controlled displacement platform, which continuously changes the interaction position between the laser filament and the surface of the injection needle to achieve full-coverage scanning of the surface of the injection needle.

[0077] Example 4

[0078] This embodiment provides a superhydrophobic needle 1, which is prepared using the superhydrophobic needle preparation method described in Embodiment 1.

[0079] Example 5

[0080] This embodiment provides a microdroplet generating device, such as... Figure 1 As shown, it mainly includes an injection needle tube 2, a pushing device, and a superhydrophobic needle 1 as described in Embodiment 4. The injection needle tube 2 is used to store liquid. The superhydrophobic needle 1 is installed on the injection needle tube 2. The piston of the injection needle tube 2 is connected to the pushing device. The pushing device can drive the piston to reciprocate along the axial direction of the injection needle tube 2, thereby drawing or expelling liquid. When the pushing device pushes the piston, it can push the liquid in the injection needle tube 2 out through the superhydrophobic needle 1 to form microdroplets.

[0081] In this embodiment, a superhydrophobic needle 1 is used instead of a regular needle, which greatly reduces the manufacturing difficulty and preparation cost of the microdroplet generation device. It is simple, flexible, and has good scalability.

[0082] In this embodiment, the microdroplet generating device further includes a fixing bracket 3, and the injection needle tube 2 is vertically clamped on the fixing bracket 3.

[0083] Furthermore, it also includes a control device. The pushing device is preferably a one-dimensional electrically controlled displacement platform 4. The control device is electrically connected to the one-dimensional electrically controlled displacement platform 4 and is used to control the one-dimensional electrically controlled displacement platform 4 to drive the piston up and down and control the movement speed of the piston, thereby controlling the liquid flow rate in the injection needle tube 2. The control device is preferably a control computer 5. The piston's movement distance is preferably 50–400 mm, the displacement accuracy is preferably 2.5 μm, the superhydrophobic needle 1 can be any size from 4 to 50 (i.e., the injection needle used to prepare the superhydrophobic needle 1 can be any size from 4 to 50), and the volume of the injection needle tube 2 is preferably 25 μL–20 mL. In this embodiment, by selecting different sizes of superhydrophobic needles 1 and controlling the liquid flow rate, the volume and generation frequency of microdroplets can be adjusted.

[0084] In summary, the microdroplet generation device in this embodiment has the advantages of simple processing, no pollution, high efficiency, and controllable microdroplet volume and generation frequency.

[0085] In this embodiment, the microdroplet generating device further includes a data acquisition device, which is used to collect information on the formation of the microdroplets. The data acquisition device can be selected according to specific working needs. As a preferred embodiment, the data acquisition device can be a high-speed camera 6, which is positioned facing the superhydrophobic needle 1 and can observe the volume and generation frequency of the droplets at the superhydrophobic needle 1.

[0086] Example 6

[0087] This embodiment provides a method for generating microdroplets, implemented using the microdroplet generating device described in Embodiment 5, and mainly includes the following steps:

[0088] The superhydrophobic needle 1 is mounted on the injection needle tube 2. The piston connected to it is controlled by the one-dimensional electronically controlled displacement platform 4. By pushing the piston downward, the liquid in the injection needle tube 2 is pushed out by the superhydrophobic needle 1 to form microdroplets.

[0089] Example 7

[0090] This embodiment tests the performance of the microdroplet generating device in Example 5, specifically testing the volume and frequency of microdroplets generated by the superhydrophobic needle 1 in the microdroplet generating device. In this embodiment, an unmodified angled injection needle is used as a blank control; the blank control sample is cleaned only according to the pretreatment method before surface modification in Example 1. The specific testing steps include the following:

[0091] (1) Droplet volume test

[0092] like Figure 2 As shown, these are microdroplets generated by different types (4, 6, 8, 10) of superhydrophobic needles 1 obtained in Example 2; Figure 3 As shown, the average diameters of the corresponding microdroplets (the average of three microdroplets) are 0.55, 0.62, 1.32, and 1.68 mm, with corresponding volumes of 87, 125, 1204, and 2482 nL. The average droplet diameters of the blank control samples are 2.30, 2.79, 3.01, and 3.24 mm, with volumes of 51, 91, 114, and 142 μL, respectively.

[0093] The above results show that the superhydrophobic needle 1 obtained in Examples 1 and 2 can generate droplets on the order of nanoliters, which is much smaller than the injection needle of the blank control group.

[0094] (2) Droplet generation frequency test

[0095] like Figure 4 As shown, these are the microdroplets generated by the No. 4 superhydrophobic needle 1 obtained in Example 2 at flow rates of 2.5, 15, 30, 45, 60, and 75 μL / s; Figure 5 As shown, the corresponding microdroplet repetition frequencies (the number of microdroplets generated per second) are 15, 21, 58, 69, 88, and 105 Hz, respectively.

[0096] The above results show that the superhydrophobic needle 1 obtained in Examples 1 and 2 can generate microdroplets with controllable frequency.

[0097] As can be seen from the above test examples, the microdroplet generation device provided by the present invention can generate nanoliter droplets with controllable volume and frequency. Moreover, it is simple to prepare and easy to operate, and has great application potential and broad development prospects in the field of microfluidics.

[0098] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for preparing a superhydrophobic needle, characterized in that: Includes the following steps: S1. Modify the injection needle by using a laser filament to obtain a modified needle; wherein, the laser filament is a plasma channel with constant internal intensity clamped by multiple nonlinear effects when a strong femtosecond laser propagates nonlinearly in a medium, which can rapidly modify the inner surface of the injection needle and complete the processing of the entire curved inner wall of the injection needle in one scan. In step S1, the laser filament is a filament generated by a femtosecond laser passing through a lens; The focal length of the lens is 50-120cm, the femtosecond laser is generated by a femtosecond laser amplifier with an oscillator, the center wavelength of the femtosecond laser is 260-1200nm, the pulse width is 45-1000 fs, the repetition frequency is 0.1-10kHz, and the single pulse energy is greater than the laser filamentation threshold. S2. The modified needle is subjected to heat treatment to obtain a superhydrophobic needle.

2. The method for preparing a superhydrophobic needle according to claim 1, characterized in that: Before step S1, the following step is also included: S01. Clean the surface of the injection needle; Step S01 includes: The injection needle was sequentially placed in acetone, ethanol, and deionized water for ultrasonic cleaning, and the cleaning time of the injection needle in acetone, ethanol, and deionized water was 10-20 minutes.

3. The method for preparing a superhydrophobic needle according to claim 1, characterized in that: Step S1 involves modifying the injection needle using a laser filament, including: The injection needle is fixed on a displacement platform with its bevel facing outwards. The injection needle is then scanned by the laser filament to achieve modification. The laser filament scans the injection needle at a speed of 1-5 mm / s and at a scanning interval of 100 μm.

4. The method for preparing a superhydrophobic needle according to claim 1, characterized in that: The modified needle undergoes heat treatment in step S2, including: The modified needle was placed in a heating chamber and heated at 110-130°C for 3-5 hours.

5. A device for preparing superhydrophobic needles, characterized in that: The method for preparing a superhydrophobic needle as described in any one of claims 1 to 4 includes: A laser assembly for generating a laser filament to modify the injection needle; A heat treatment apparatus for heat treating the modified needle.

6. A superhydrophobic needle, characterized in that: It is prepared by the superhydrophobic needle preparation method as described in any one of claims 1 to 4.

7. A microdroplet generating device, characterized in that: The device includes an injection needle, a pushing device, and a superhydrophobic needle as described in claim 6. The superhydrophobic needle is mounted on the injection needle, and the piston of the injection needle is connected to the pushing device. The pushing device can drive the piston to reciprocate along the axial direction of the injection needle. The injection needle contains liquid, and when the pushing device pushes the piston, it can push the liquid in the injection needle out through the superhydrophobic needle to form microdroplets.

8. The microdroplet generating device according to claim 7, characterized in that: Also includes: A fixed bracket is provided, on which the injection needle is mounted; A control device, electrically connected to the pushing device, is used to control the pushing device to move the piston and control the piston's moving speed; wherein the piston's moving distance ranges from 50 to 400 mm, the displacement accuracy is 2.5 μm, the superhydrophobic needle is any size from 4 to 50, and the injection syringe has a volume of 25 μL to 20 mL; and A data acquisition device is used to collect information on the formation of the microdroplets, wherein the data acquisition device is a high-speed camera, and the high-speed camera is positioned directly in front of the superhydrophobic needle.

9. A method for generating microdroplets, characterized in that: The implementation using the microdroplet generation device as described in claim 7 or 8 includes the following steps: The superhydrophobic needle is mounted on the injection needle tube, and the piston is pushed by the pushing device to push the liquid in the injection needle tube out through the superhydrophobic needle to form microdroplets.

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