Method for manufacturing PMMA nanospray needle by heating stretching method and PMMA nanospray needle

Abstract

The invention discloses a method for manufacturing a PMMA nanospray needle by a heating and stretching method in the field of micro-electromechanical technology and a PMMA nanospray needle, wherein the method for manufacturing a PMMA nanospray needle by a heating and stretching method aims to solve the problems in the prior art that the size of the spray needle is too large, and the preparation method has high cost, low efficiency, and uncontrollability. The method comprises preparing a micron spray needle mold by using a photoresist as a micron mask and adopting a wet etching method. The PMMA microspray needle mold is used to perform hot embossing on a PMMA substrate to obtain a PMMA microspray needle. The PMMA microspray needle is subjected to a hot stretching treatment by a heating and stretching method, so that the microchannel of the PMMA microspray needle undergoes a necking phenomenon to generate a nanochannel, thereby obtaining an unbonded PMMA nanospray needle. The invention prepares the PMMA nanospray needle by a low-cost hot embossing method and a heating and stretching method, and the process is simple and the efficiency is high.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems, and relates to a method for manufacturing a PMMA nano-spray needle by a heating and stretching method and a polymer nano-spray needle. Background Art

[0002] Electro-hydraulic jet printing is referred to as electro-jet printing. Compared with traditional printing technology (thermal bubble method, piezoelectric method), the difference is that the traditional printing technology uses external force to "push" the droplets out, while electro-jet printing generates extremely fine jets from the nozzle in a "pulling" manner under the drive of electric field force. Under different conditions, three states of droplets, fibers and spray can be formed. Electro-jet printing can form a "Taylor cone" at the nozzle, thereby realizing micron and sub-micron scale printing.

[0003] Electro-hydraulic jet printing has a scale effect. By reducing the inner diameter of the needle, it is possible to obtain higher-resolution printing lines. How to manufacture nanochannels to further reduce the inner diameter of the needle is the key to solving the problem.

[0004] At present, there are many nano-manufacturing technologies, among which electron beam, proton beam, ion beam, laser direct writing and other methods have extremely high resolution and controllability, but the manufacturing cost is high and has the characteristics of serial time-consuming processing. The crack method is used to manufacture nano-channels. The method is simple and low-cost, but the nano-size is uncontrollable and the repeatability is low.

[0005] In summary, how to manufacture nanospray needles at low cost and with high controllability remains a difficult problem. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for manufacturing PMMA nanospray needles by a heating and stretching method and a PMMA nanospray needle. The PMMA nanospray needles are prepared by a low-cost hot embossing method and a heating and stretching method, with a simple process and high efficiency.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical scheme: a method for manufacturing PMMA nanospray needles by a heating and stretching method, comprising: step 1, preparing unbonded PMMA nanospray needles and PMMA nanospray needle cover plates;

[0008] The preparation steps of the unbonded PMMA nanospray needle include:

[0009] Step 1.1.1, prepare the micro-needle mold by wet etching.

[0010] The wet etching method comprises the following steps:

[0011] The oxidation furnace is heated up and oxygen is introduced, and the silicon wafer is placed on a quartz boat and pushed into the oxidation furnace for dry oxygen oxidation;

[0012] Nitrogen is introduced into the oxidation furnace, and the silicon wafer is taken out after annealing and cooling to obtain a silicon wafer with a silicon dioxide layer;

[0013] Spin-coat the photoresist on the surface of the silicon dioxide layer of the silicon wafer, and perform pre-baking, ultraviolet exposure, and development to obtain a photoresist micro-needle mold pattern;

[0014] The photoresist micro-needle mold pattern is placed in a hydrofluoric acid buffer solution to transfer the micro-needle pattern to the silicon dioxide layer, and then placed in an acetone solution for immersion to remove the photoresist to obtain a micro-needle mold;

[0015] Step 1.1.2, preparing PMMA micro-needles through a micro-needle mold by hot embossing,

[0016] The hot embossing method comprises the following steps:

[0017] The micron needle mold is placed in a drying tower;

[0018] The pattern on the micro-spray needle mold is transferred to the PMMA substrate by using a hot embossing method. After cooling to room temperature, the micro-spray needle mold is separated from the PMMA substrate to obtain a PMMA micro-spray needle.

[0019] Step 1.1.3, using a heating stretching method to heat-stretch the PMMA micro-needle to obtain an unbonded PMMA nano-needle;

[0020] The heating stretching method comprises the following steps:

[0021] A heating plate is attached to a part of the micron channel of the PMMA micron spray needle, and the micron channel of the PMMA micron spray needle is heated by the heating plate;

[0022] The PMMA micro-needle is stretched to obtain an unbonded PMMA nano-needle;

[0023] The preparation steps of the PMMA nanospray needle cover plate include:

[0024] Step 1.2.1, cutting the PMMA plate to obtain a PMMA nanospray needle cover plate;

[0025] Step 2, treating the unbonded PMMA nanospray needle and the PMMA nanospray needle cover plate with oxygen plasma;

[0026] Step 3, align and fix the PMMA nanospray needle cover plate processed in step 2 with the unbonded PMMA nanospray needle and apply pressure to obtain the PMMA nanospray needle through thermal bonding.

[0027] In a preferred embodiment of the present invention, in step 1.1.2, before heating the oxidation furnace, the step further includes cleaning the silicon wafer to obtain a cleaned silicon wafer;

[0028] The cleaning step comprises:

[0029] The silicon wafer is sequentially placed in acetone, ethanol and deionized water for ultrasonic cleaning for 5 to 10 minutes, and then the silicon wafer is sequentially placed in hydrofluoric acid buffer for 5 to 10 minutes, boiled concentrated sulfuric acid for 10 to 30 minutes, hydrofluoric acid buffer for 5 to 10 minutes, No. 1 cleaning solution for 5 to 10 minutes, hydrofluoric acid buffer for 5 to 10 minutes, No. 2 cleaning solution for 5 to 10 minutes, and hydrofluoric acid buffer for 5 to 10 minutes, and dried to obtain a cleaned silicon wafer;

[0030] The hydrofluoric acid buffer comprises hydrofluoric acid, ammonium fluoride and water, and HF:NH4F:H2O=2~4:5~7:8~10;

[0031] The first cleaning solution includes water, hydrogen peroxide and ammonia water, and the ratio of H2O:H2O2:NH4OH is 4-6:1-3:1-2;

[0032] The second cleaning solution includes water, hydrogen peroxide and hydrochloric acid, and H2O:H2O2:HCl=7~9:1~3:1~2.

[0033] In a preferred embodiment of the present invention, in the step 1.1.1, the temperature range of the oxidation furnace is 1000-1500° C., the ventilation time of the oxygen is maintained at 30-60 min, the dry oxygen oxidation time is 7-9 h, and the annealing time is 30-60 min;

[0034] And / or, in the step 1.1.1, the spin coating method is spin coating at a rotation speed of 500-800 rpm for 6-10 s, and spin coating at a rotation speed of 5000-7000 rpm for 30-40 s;

[0035] The pre-baking temperature is 60-90°C and the pre-baking time is 20-30min;

[0036] The UV exposure uses a needle mask, and the exposure time is 30 to 60 seconds.

[0037] The developing time is 40 to 60 seconds;

[0038] The photoresist micro-spray needle mold pattern is immersed in the hydrofluoric acid buffer solution and the acetone solution for 50-70 seconds and 30-60 minutes respectively.

[0039] In a preferred embodiment of the present invention, in step 1.1.2, the drying tower has a trimethylsiloxane atmosphere, and the micron needle mold is placed in the drying tower for 10 to 20 minutes;

[0040] The hot pressing parameters include: hot pressing temperature of 100-130° C., hot pressing time of 150-200 s, and pressing pressure of 1-2 MPa.

[0041] In a preferred embodiment of the present invention, in step 1.1.3, the heating temperature ranges from 100 to 130° C., and the heating time ranges from 150 to 200 s;

[0042] The stretching parameters include: a tension of 10-20N and a stretching time of 5-10s.

[0043] In a preferred embodiment of the present invention, in step 2, the oxygen plasma treatment parameters include: a treatment power of 15-25 W and a treatment time of 20-30 s.

[0044] In a preferred embodiment of the present invention, the thermal bonding parameters include: thermal bonding pressure of 0.1-0.2 MPa, thermal bonding temperature of 80-100° C., and thermal bonding time of 20-30 min.

[0045] In a preferred embodiment of the present invention, the excess length of the unbonded PMMA nanospray needle needs to be removed before thermal bonding with the PMMA nanospray needle cover plate, comprising the following steps:

[0046] A notch was made at 100 μm in the nanochannel of the unbonded PMMA nanospray needle;

[0047] Place the primary PMMA nanospray needle in a liquid nitrogen pot and let it stand for 5 to 10 minutes, then take it out and break the primary PMMA nanospray needle along the notch.

[0048] In a preferred embodiment of the present invention, a PMMA nanospray needle is prepared by a method for manufacturing a PMMA nanospray needle by a heating and stretching method.

[0049] In a preferred embodiment of the present invention, the PMMA is polymethyl methacrylate, which can be replaced by polyethylene terephthalate, polyethylene, polyimide, high-density polyethylene, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyether sulfone, polycarbonate, thermoplastic polyurethane elastomer, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, rigid polyvinyl chloride, polystyrene, styrene-acrylonitrile copolymer, hydroxypropyl propargyl ether, and polybutene.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention uses photoresist as a micron mask and adopts a wet etching method to obtain a micron needle mold. The micron needle mold can be prepared on a large area on a 4-inch silicon wafer, so that multiple PMMA micron needles can be manufactured by one hot pressing process. The micron needle mold can be reused many times, which greatly improves the production efficiency and is suitable for large-scale industrial production needs. It can be reused and reduces the production cost at the same time.

[0052] The present invention adopts a micron spray needle mold to perform hot embossing on a PMMA substrate to obtain a PMMA micron spray needle, and finally adopts a heating and stretching method to locally stretch the PMMA micron spray needle microchannel, so that the microchannel undergoes a necking phenomenon to generate a nanochannel, thereby obtaining a PMMA nano spray needle. The hot embossing method and the heating and stretching method have simple processes and low costs.

[0053] The prepared PMMA nanospray needle can reach nanometer size and fine structure, which provides a guarantee for obtaining higher resolution printing lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A schematic diagram of the preparation process of a micron spray needle mold in an embodiment of the present invention;

[0055] Figure 2 A schematic diagram of the preparation process of a PMMA micro-spray needle in one embodiment of the present invention;

[0056] Figure 3 A schematic diagram of the preparation process of a PMMA nanospray needle in one embodiment of the present invention;

[0057] Figure 4 This is a schematic diagram of the structure of a PMMA nanospray needle in an embodiment of the present invention;

[0058] Figure 5 A microscope image of a micro-spray needle mold in one embodiment of the present invention;

[0059] Figure 6 A microscope image of a PMMA micro-spray needle in one embodiment of the present invention;

[0060] Figure 7 This is a cross-sectional SEM image of a nanochannel of a PMMA nanospray needle in an embodiment of the present invention;

[0061] In the figure: 1-silicon wafer, 2-silicon dioxide layer, 3-photoresist, 4-needle mask, 5-ultraviolet light, 6-PMMA substrate, 7-heating plate, 8-laser, 9-oven. DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0063] It should be noted that if there are directional indications (such as up, down, bottom, top, etc.) involved in the embodiments of the present invention, the directional indication is only used to explain the relative position relationship, movement, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly. The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Unless otherwise clearly specified and defined, the terms "set", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Embodiment 1

[0064] The embodiment of the present invention provides a method for manufacturing PMMA nanospray needles by a heating and stretching method, comprising the following steps:

[0065] Step 1, preparing unbonded PMMA nanospray needles and PMMA nanospray needle cover plates;

[0066] The preparation steps of the unbonded PMMA nanospray needle include:

[0067] Step 1.1.1, prepare the micro-needle mold by wet etching.

[0068] The wet etching method comprises the following steps:

[0069] The oxidation furnace is heated up and oxygen is introduced, and the silicon wafer is placed on a quartz boat and pushed into the oxidation furnace for dry oxygen oxidation;

[0070] Nitrogen is introduced into the oxidation furnace, and the silicon wafer 1 is taken out after annealing and cooling to obtain a silicon wafer 1 with a silicon dioxide layer 2 (such as Figure 1 1a in Figure 1);

[0071] The photoresist 3 is spin-coated on the surface of the silicon dioxide layer 2 of the silicon wafer 1 (eg Figure 1 1b in the figure), and then pre-baking and UV exposure (as shown in the figure Figure 1 1c in), development (as shown in Figure 1 1d in the figure), and obtain the photoresist micro-needle mold pattern (as shown in Figure 1 1e in Figure 1);

[0072] The photoresist micro-needle mold pattern is placed in a hydrofluoric acid buffer solution to transfer the micro-needle pattern to the silicon dioxide layer, and then placed in an acetone solution for immersion to remove the photoresist to obtain a micro-needle mold (such as Figure 1 1f in Figure 1).

[0073] Specifically, Figure 1 As shown, the silicon wafer 1 is ultrasonically cleaned in acetone, ethanol, and deionized water for 5 to 10 minutes. Then it is placed in a hydrofluoric acid buffer (HF: NH4F: H2O = 2 to 4: 5 to 7: 8 to 10) for 5 to 10 minutes to remove the oxide layer on the surface of the silicon wafer 1. The silicon wafer 1 is placed in a boiling concentrated sulfuric acid solution for 10 to 30 minutes, and then placed in a hydrofluoric acid buffer for 5 to 10 minutes. The silicon wafer 1 is placed in a No. 1 cleaning solution (H2O: H2O2: NH4OH = 4 to 6: 1 to 3: 1 to 2) for cleaning for 5 to 10 minutes, and then placed in a hydrofluoric acid buffer for 5 to 10 minutes. The silicon wafer 1 is placed in a No. 2 cleaning solution (H2O: H2O2: HCl = 7 to 9: 1 to 3: 1) for cleaning for 5 to 10 minutes, and then placed in a hydrofluoric acid buffer for 5 to 10 minutes. Finally, place the wafer in a drying oven at 100-150°C for 30-50 minutes to complete the cleaning step of the silicon wafer 1.

[0074] Raise the oxidation furnace to 1000~1500℃, introduce oxygen to exhaust impurities, and maintain ventilation for 30~60min. Place silicon wafer 1 on a quartz boat and slowly push it into the oxidation furnace for oxidation for 7~9h. After dry oxygen oxidation, turn off the oxygen and introduce nitrogen, annealing for 30~60min. Then cool with the furnace in a nitrogen atmosphere, take out the silicon wafer, obtain a silicon wafer with a 600nm silicon dioxide layer 2, and complete the oxidation of silicon dioxide layer 2.

[0075] An AZ703 photoresist 3 is spin-coated on the silicon wafer 1 with the silicon dioxide layer 2, wherein the AZ703 photoresist 3 can be replaced by any one of AZ701, BP212, BN308, SU-8, AZ5214E, RFJ220, and RFJ210.

[0076] The low speed is 500~800rpm, the spin coating time is 6~10s, the high speed is 5000~7000rpm, and the spin coating time is 30~40s. After pre-baking on a 60~90℃ hot plate for 20~30min, the spray needle mask 4 is exposed to ultraviolet light for 30~60s, and developed for 40~60s to obtain the photoresist micron spray needle mold pattern. Place it in a hydrofluoric acid buffer for 50~70s to transfer the photoresist micron spray needle mold pattern to the silicon dioxide layer. Finally, place it in an acetone solution and soak it for 30~60min to remove the photoresist to obtain a micron spray needle mold, such as Figure 5 shown.

[0077] Step 1.1.2, preparing PMMA micro-needles through a micro-needle mold by hot embossing,

[0078] The hot embossing method comprises the following steps:

[0079] The micron needle mold is placed in a drying tower; the micron needle mold pattern is transferred to the PMMA substrate 6 (such as Figure 2 2a and 2b in FIG), after cooling to room temperature, the micro-spray needle mold is separated from the PMMA substrate 6 (as shown in FIG. Figure 2 As shown in 2c), a PMMA micron spray needle is obtained; Figure 6 shown.

[0080] Specifically, Figure 2 As shown, the micron needle mold is placed in a drying tower with a trimethylsiloxane atmosphere for 10 to 20 minutes, and then the micron needle mold pattern is transferred to the PMMA substrate 6 by hot pressing, wherein the hot pressing temperature is 100 to 130°C, the hot pressing time is 150 to 200 seconds, and the pressing pressure is 1 to 2 MPa.

[0081] Step 1.1.3, using a heating stretching method to heat-stretch the PMMA micro-needle to obtain an unbonded PMMA nano-needle;

[0082] The heating and stretching method comprises the following steps: attaching a heating plate to a part of the micron channel of the PMMA micron needle, heating the micron channel of the PMMA micron needle by using the heating plate; stretching the PMMA micron needle to obtain an unbonded PMMA nano needle. Specifically, Figure 3 As shown, a heating plate 7 (such as Figure 3 3a in the figure), the temperature is adjusted to 100-130°C, and after heating for 150-200s, the PMMA micro-spray needle is stretched using a tensile tester, wherein the tension is 10-20N, and the stretching is 5-10s. The size of the PMMA micro-spray needle micro-channel becomes longer and the depth and width are reduced to less than 100nm, and the PMMA nano-spray needle (as shown in FIG. Figure 3 3b in the figure). The length of the nanochannel is controlled to be about 100 mm, a notch is made at the length of 100 mm, the PMMA nanospray needle is placed in a liquid nitrogen pot, left to stand for 5-10 minutes, and then taken out to break off the excess length along the notch.

[0083] The preparation steps of the PMMA nanospray needle cover plate include:

[0084] Step 1.2.1, cut the PMMA plate to obtain the PMMA nanospray needle cover plate (such as Figure 3Specifically, another PMMA plate is cut by a laser cutting machine to manufacture a PMMA nanospray needle cover plate (as shown in 3d in FIG. Figure 3 3c in Figure 3), and make a reservoir (as shown in Figure 3c Figure 3 3d in Figure 3).

[0085] Step 2: treating the unbonded PMMA nanospray needles and the PMMA nanospray needle cover plate with oxygen plasma. Specifically, treating the PMMA nanospray needles and the PMMA nanospray needle cover plate with oxygen plasma, with a treatment power of 15-25 W and a treatment time of 20-30 seconds.

[0086] Step 3, align and fix the PMMA nanospray needle cover plate processed in step 2 with the unbonded PMMA nanospray needle and apply a pressure of 0.1-0.2 MPa, and place them in an oven 9 at 80-100° C. for thermal bonding (such as Figure 3 As shown in 3e in FIG), the thermal bonding parameters are thermal bonding pressure 0.1-0.2 MPa, thermal bonding temperature 80-100°C, thermal bonding time 20-30 min, and after cooling to room temperature, PMMA nanospray needles are obtained by thermal bonding, as shown in FIG. Figure 4 and Figure 7 shown.

[0087] Preparation principle:

[0088] The present invention uses photoresist as a micron mask and adopts a wet etching method to obtain a micron needle mold. The micron needle mold can be prepared on a large area on a 4-inch silicon wafer, so that multiple PMMA micron needles can be manufactured by one hot pressing process. The micron needle mold can be reused many times, which greatly improves the production efficiency and is suitable for large-scale industrial production needs. It can be reused and reduces the production cost at the same time.

[0089] The present invention adopts a micron spray needle mold to perform hot embossing on a PMMA substrate to obtain a PMMA micron spray needle, and finally adopts a heating and stretching method to locally stretch the PMMA micron spray needle microchannel, so that the microchannel undergoes a necking phenomenon to generate a nanochannel, thereby obtaining a PMMA nano spray needle. The hot embossing method and the heating and stretching method have simple processes and low costs.

[0090] The prepared PMMA nanospray needle can reach nanometer size and fine structure, which provides a guarantee for obtaining higher resolution printing lines. Embodiment 2

[0091] A PMMA nanospray needle is prepared by using a method for manufacturing a PMMA nanospray needle by a heating stretching method disclosed in Example 1, such as Figure 4 shown. Embodiment 3

[0092] Based on Example 1 or Example 2, the PMMA substrate is polymethyl methacrylate (PMMA), which can be replaced by one of polyethylene terephthalate, polyethylene, polyimide, high-density polyethylene, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyether sulfone, polycarbonate, thermoplastic polyurethane elastomer, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, rigid polyvinyl chloride, polystyrene, styrene-acrylonitrile copolymer, hydroxypropyl propargyl ether, and polybutylene.

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for manufacturing PMMA nanospray needles by heating and stretching, characterized in that: include: Step 1, preparing unbonded PMMA nanospray needles and PMMA nanospray needle cover plates; The preparation steps of the unbonded PMMA nanospray needle include: Step 1.1.1, prepare the micro-needle mold by wet etching. The wet etching method comprises the following steps: The oxidation furnace is heated up and oxygen is introduced, and the silicon wafer is placed on a quartz boat and pushed into the oxidation furnace for dry oxygen oxidation; Nitrogen is introduced into the oxidation furnace, and the silicon wafer is taken out after annealing and cooling to obtain a silicon wafer with a silicon dioxide layer; Spin-coat the photoresist on the surface of the silicon dioxide layer of the silicon wafer, and perform pre-baking, ultraviolet exposure, and development to obtain a photoresist micro-needle mold pattern; The photoresist micro-needle mold pattern is placed in a hydrofluoric acid buffer solution to transfer the micro-needle pattern to the silicon dioxide layer, and then placed in an acetone solution for immersion to remove the photoresist to obtain a micro-needle mold; Step 1.1.2, using hot embossing method to prepare PMMA micro-needle through micro-needle mold, The hot embossing method comprises the following steps: The micron needle mold is placed in a drying tower; The pattern on the micro-spray needle mold is transferred to the PMMA substrate by using a hot embossing method. After cooling to room temperature, the micro-spray needle mold is separated from the PMMA substrate to obtain a PMMA micro-spray needle. Step 1.1.3, using a heating stretching method to heat-stretch the PMMA micro-needle to obtain an unbonded PMMA nano-needle; The heating stretching method comprises the following steps: A heating plate is attached to a part of the micron channel of the PMMA micron spray needle, and the micron channel of the PMMA micron spray needle is heated by the heating plate; The PMMA micro-needle is stretched to obtain an unbonded PMMA nano-needle; The preparation steps of the PMMA nanospray needle cover plate include: Step 1.2.1, cutting the PMMA plate to obtain a PMMA nanospray needle cover plate; Step 2, treating the unbonded PMMA nanospray needle and the PMMA nanospray needle cover plate with oxygen plasma; Step 3, align and fix the PMMA nanospray needle cover plate processed in step 2 with the unbonded PMMA nanospray needle and apply pressure to obtain the PMMA nanospray needle through thermal bonding.

2. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 1, characterized in that: In step 1.1.2, before heating the oxidation furnace, the silicon wafer is cleaned to obtain a cleaned silicon wafer; The cleaning step comprises: The silicon wafer is sequentially placed in acetone, ethanol and deionized water for ultrasonic cleaning for 5 to 10 minutes, and then the silicon wafer is sequentially placed in hydrofluoric acid buffer for 5 to 10 minutes, boiled concentrated sulfuric acid for 10 to 30 minutes, hydrofluoric acid buffer for 5 to 10 minutes, No. 1 cleaning solution for 5 to 10 minutes, hydrofluoric acid buffer for 5 to 10 minutes, No. 2 cleaning solution for 5 to 10 minutes, and hydrofluoric acid buffer for 5 to 10 minutes, and dried to obtain a cleaned silicon wafer; The hydrofluoric acid buffer comprises hydrofluoric acid, ammonium fluoride and water, and HF:NH4F:H2O=2~4:5~7:8~10; The first cleaning solution includes water, hydrogen peroxide and ammonia water, and the ratio of H2O:H2O2:NH4OH is 4-6:1-3:1-2; The second cleaning solution includes water, hydrogen peroxide and hydrochloric acid, and H2O:H2O2:HCl=7~9:1~3:1~2.

3. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 2, characterized in that: In the step 1.1.1, the temperature range of the oxidation furnace is 1000-1500°C, the ventilation time of the oxygen is maintained at 30-60 minutes, the dry oxygen oxidation time is 7-9 hours, and the annealing time is 30-60 minutes; And / or, in the step 1.1.1, the spin coating method is spin coating at a rotation speed of 500-800 rpm for 6-10 s, and spin coating at a rotation speed of 5000-7000 rpm for 30-40 s; The pre-baking temperature is 60-90°C and the pre-baking time is 20-30min; The UV exposure uses a needle mask, and the exposure time is 30 to 60 seconds. The developing time is 40 to 60 seconds; The photoresist micro-spray needle mold pattern is immersed in the hydrofluoric acid buffer solution and the acetone solution for 50-70 seconds and 30-60 minutes respectively.

4. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 3, characterized in that: In the step 1.1.2, the drying tower has a trimethylsiloxane atmosphere, and the micron needle mold is placed in the drying tower for 10 to 20 minutes; The hot pressing parameters include: hot pressing temperature of 100-130° C., hot pressing time of 150-200 s, and pressing pressure of 1-2 MPa.

5. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 4, characterized in that: In the step 1.1.3, the heating temperature ranges from 100 to 130°C and the heating time ranges from 150 to 200 seconds; The stretching parameters include: a tension of 10-20N and a stretching time of 5-10s.

6. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 5, characterized in that: In step 2, the oxygen plasma treatment parameters include: treatment power of 15-25 W, and treatment time of 20-30 s.

7. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 1, characterized in that: In step 3, the thermal bonding parameters include: thermal bonding pressure of 0.1-0.2 MPa, thermal bonding temperature of 80-100° C., and thermal bonding time of 20-30 min.

8. The method for manufacturing PMMA nanospray needles by heating and stretching according to claim 1, characterized in that: Before thermal bonding of the unbonded PMMA nanospray needle and the PMMA nanospray needle cover plate, the excess length needs to be removed, including the following steps: A notch was made at 100 μm in the nanochannel of the unbonded PMMA nanospray needle; Place the primary PMMA nanospray needle in a liquid nitrogen pot and let it stand for 5 to 10 minutes, then take it out and break the primary PMMA nanospray needle along the notch.

9. A PMMA nanospray needle, characterized in that: The nano-spray needle is prepared by the method for manufacturing PMMA nano-spray needles by the heating stretching method described in any one of claims 1 to 8.

10. The PMMA nanospray needle according to claim 9, characterized in that: The PMMA is polymethyl methacrylate, which can be replaced by polyethylene terephthalate, polyethylene, polyimide, polypropylene, ethylene-vinyl acetate copolymer, polyether sulfone, polycarbonate, thermoplastic polyurethane elastomer, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polystyrene, styrene-acrylonitrile copolymer, hydroxypropyl propargyl ether, and polybutene.

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