CN110787361A - A hollow inclined metal microneedle array and its manufacturing method based on SU-8 mold - Google Patents

Abstract

The invention discloses a hollow inclined metal microneedle array and a manufacturing method based on a SU-8 mold, belonging to the field of micro-nano manufacturing technology. In the microneedle array, the metal material is electroplatable metal, the hollow inclined metal microneedles are inclined conical shape, the inclination angle is 50°～70°; the vertical height is 500μm～650μm; the hollow inclined metal microneedles have equal wall thickness from the bottom to the tip The structure has a wall thickness of 8 μm to 10 μm; the outer diameter of the bottom of the hollow inclined metal microneedle is 150 μm to 250 μm; the cone angle of the hollow inclined metal microneedle is 10° to 15°, and the top of the hollow inclined metal microneedle has a tip. The invention transfers the SU-8 mold mask pattern to the glass sheet, avoids the problem of air gaps in traditional contact exposure, improves the intensity of ultraviolet light reaching each layer of photoresist, and has stronger bonding force between the microneedle mold and the substrate. Making full use of OmniCoat improves the adhesion of the SU-8 mold to the glass sheet, while making it easier to remove the SU-8 mold later in the process. The tip of the inclined circular truncated microneedle was etched by RIE, and the tip structure of the metal microneedle was realized.

Description

A hollow inclined metal microneedle array and its manufacturing method based on SU-8 mold

technical field

The invention belongs to the field of micro-nano manufacturing technology, and more particularly relates to a hollow inclined metal micro-needle array and a manufacturing method based on a SU-8 mold.

Background technique

Micro-needle subcutaneous injection is an important development direction in the medical field. Micro-scale micro-needles can greatly reduce the pain of injection and the fear of needle injection, and bring great convenience to slow injection and quantitative drug injection. Microneedles, typically 100 to 1000 μm in length, penetrate the outer stratum corneum of the skin and directly inject the therapeutic material into the tissue layer. Controlling the length of the microneedles ensures a depth of penetration without affecting most of the nerve fibers and blood vessels located in the dermis. At present, microneedles mainly include solid microneedles, hollow microneedles, dissolvable microneedles, and hydrogel microneedles. The solid microneedle realizes drug injection by coating the drug on the surface of the microneedle, or by attaching the drug after pulling out the microneedle. Dissolvable microneedles and hydrogel microneedles require extremely high materials, and the material strength is difficult to control; hollow microneedles are more suitable for slow and continuous injection, and can deliver different types of pharmaceutical preparations, such as solutions, suspensions, emulsions, dry powders and gel, etc.

Microfabricated hollow microneedles can achieve controllable drug injection speed and dosage. In addition, hollow microneedles can not only provide therapy, but also extract biological fluids from the skin for analysis, monitoring, and biological response functions. The hollow microneedle needs to pierce the skin and enter the subcutaneous tissue to achieve drug release, so the head structure and strength of the microneedle have an important influence on the use of the microneedle.

At present, hollow microneedles are mainly divided into two categories: polymer microneedles and metal microneedles. In 2007, H HUANG et al. used back exposure technology to fabricate hollow hetero-planar microneedle arrays with dip angles (Huang H, Fu C. Different fabrication methods of out-of-plane polymer hollow needle arrays and their variations. Journal of Micromechanics and Microengineering, 2007). The method utilizes Fresnel diffraction effect and simultaneous exposure of multiple masks to prepare polymer microneedles with sharp corners. In 2007, Kabseog Kim et al. used back exposure and Fresnel diffraction effect to produce a vertical truncated SU-8 mold, and used the mold and electroplating process to make a hollow metal microneedle structure (Kim K, Lee J B. High aspect ratio tapered hollow metallicmicroneedle arrays with microfluidic interconnector. Microsystem Technologies, 2007). Analysis of the current hollow microneedle preparation process shows that: it is easier to use polymer materials to realize hollow microneedle arrays with tips, but the strength of polymer microneedles is not high; the SU-8 mold method can be used to prepare metal microneedles, but the top The tip is difficult to achieve, and the SU-8 mold is difficult to remove in the later demoulding process, which greatly limits the application of this method.

SUMMARY OF THE INVENTION

In view of the above shortcomings or improvement needs of the prior art, the present invention provides a hollow inclined metal microneedle array manufacturing method based on a SU-8 mold, which overcomes the difficulty of SU-8 molds in the current SU-8 molds for preparing hollow metal microneedles. It has the advantages of good structural consistency and strong adhesion between the microneedle mold and the substrate.

The invention provides a hollow inclined metal microneedle array, the metal material is electroplatable metal, the hollow inclined metal microneedle is in the shape of an oblique cone, the inclination angle is 50° to 70°, the vertical height is 500 μm to 650 μm; The bottom of the needle to the tip is of equal wall thickness, and the wall thickness is 8 μm to 10 μm; the outer diameter of the bottom of the hollow inclined metal microneedle is 150 μm to 250 μm; the cone angle of the hollow inclined metal microneedle is 10° to 15°, and the top of the hollow inclined metal microneedle is 10° to 15°. with tip.

The invention proposes a method for manufacturing a hollow inclined metal microneedle array based on SU-8 mold, which mainly includes micromachining processes such as photolithography, electroplating, and sputtering. It is obtained by etching and removing the SU-8 mold, and the specific preparation method includes the following steps:

Step 1: Preparation of SU-8 mold on glass substrate, including the following sub-steps:

1.1 Preparation of SU-8 mold mask pattern on glass substrate

Fully heat the glass sheet 1 with a thickness of 500 μm to 1000 μm or clean it with oxygen plasma to remove the organic matter on the surface of the substrate; then sputter a layer of metallic chromium on the surface of the glass sheet; spin-coat positive glue on the chromium metal layer, expose it after exposure and development Chromium that needs to be etched is etched in a metallic chromium etching solution to obtain the SU-8 mold mask pattern layer 4 .

1.2 Preparation of the sacrificial layer at the bottom of the SU-8 mold on the surface of the glass sheet

The sample was cleaned and fully heat-baked, and OmniCoat was spin-coated on the chromium-free side of the sample as the sacrificial layer 2 at the bottom of the SU-8 mold and fully heat-baked. OmniCoat, as a special SU-8 tackifying/debonding additive, helps to enhance the adhesion between SU-8 molds and glass substrates, and also helps to remove cured SU-8.

1.3 Back tilt exposure

Spin-coat the first layer of SU-8 photoresist 3 on the OmniCoat surface of the sample obtained in step 1.2, with a thickness of 1 μm to 2 μm, and then perform vertical maskless exposure on the front side (Figure 2a); spin-coat a second layer on the same side Layer SU-8 photoresist 5, the thickness is 500μm ~ 650μm, the thickness of the second layer of photoresist 5 determines the vertical height of the microneedles on the SU-8 mold and the vertical height H of the hollow inclined metal microneedles, the second layer of photoresist layer 5 After sufficient pre-baking, place the sample under the UV exposure lamp, with the SU-8 mold mask pattern layer 4 facing the UV lamp, and use the fixture to make the angle β between the sample and the UV light 40°~90° (Fig. 2c), the angle β between the sample and the ultraviolet light determines the inclination angle of the microneedles on the SU-8 mold and the inclination angle α of the hollow inclined metal microneedles, and then the SU-8 mold 6 is obtained after post-baking and development.

Due to the different refractive indices of UV light in different media, the tilt angle of the microneedles on the SU-8 mold is mainly determined by the incident angle, the refractive index of the SU-8 photoresist and the incident medium. The inclination angle of the microneedles on the -8 mold is 54° to 90°. Because the refractive index of ultraviolet light in glycerol and SU-8 photoresist is close, when the backside oblique exposure is performed in glycerol medium, the inclination angle of the microneedles on the SU-8 mold is 19°-90°. Therefore, when preparing a microneedle mold with an inclination angle of less than 54°, it is necessary to immerse the aforementioned sample in glycerol medium, and then perform oblique exposure on the back side (Fig. 2d).

A layer of OmniCoat was sprayed on the surface of the obtained SU-8 mold with a glue sprayer, and then placed in an incubator for thermal drying. The function of OmniCoat on the surface of the SU-8 mold microneedle is the same as that of the sacrificial layer at the bottom of the SU-8 mold structure in step (1.2), which is beneficial to remove the cured SU-8.

In back exposure, the photoresist in contact with the glass sheet can fully absorb ultraviolet light, which helps to improve the adhesion of the SU-8 mold to the glass substrate; the distance between the chrome pattern layer on the glass sheet and the bottom of the photoresist causes The Fresnel diffraction in lithography is enhanced, the SU-8 adhesive layer in contact with the glass sheet during exposure is outward, the diameter of the ultraviolet light distribution shrinks sharply, the ultraviolet light intensity decreases rapidly, and finally the microneedles on the SU-8 mold are inclined. Conesus-shaped; the SU-8 mold reticle pattern is copied to the glass sheet, eliminating the air gap that exists between the reticle and the glass sheet in contact exposure, improving the consistency of the SU-8 mold.

Step 2: Preparation of hollow inclined metal microneedles on the surface of the SU-8 mold; including the following sub-steps:

2.1 Sputter deposition of metal seed layer on the surface of SU-8 mold

On the SU-8 mold 6 obtained by spraying OmniCoat in step 1.3, sputter-deposit a metal seed layer 7 with a thickness of 100nm to 200nm. During sputtering, ensure that the angle between the sample and the metal deposition direction is 180°-α, SU-8 The microneedles on the mold were parallel to the metal deposition direction (Fig. 2e), ensuring that the outside of the microneedles on the SU-8 mold was completely wrapped by the deposited metal seed layer 7.

2.2 Electroplating a metal layer on the surface of the metal seed layer to form an inclined metal microneedle structure layer

The sample is placed in an electroplating metal electrolyte solution for electroplating, and the thickness of the electroplated metal layer is 8 μm to 10 μm to form an inclined metal microneedle structure layer 8 ( FIG. 2 f ).

Step 3: Prepare the top tip of the inclined metal microneedle, including the following sub-steps:

3.1 Preparation of SU-8 mold on the top tip mask of inclined metal microneedles

Coat the surface of the inclined metal microneedle structure layer 8 obtained in step 2.2 with SU-8 photoresist, and then place it on a hot plate to bake it to make the SU-8 adhesive layer sufficiently flat, and then place the sample under a microscope Observe the vertical distance d between the surface of the SU-8 photoresist and the top of the SU-8 mold microneedle, and repeat the aforementioned spin coating and thermal baking until the vertical distance d between the SU-8 photoresist surface and the top of the SU-8 mold microneedle is 50 μm～ 70 μm (Fig. 2g).

The glued surface of the sample is placed under an ultraviolet lamp for maskless vertical exposure, and the exposure amount is 1/4 to 1/3 of the standard exposure energy, and then normal heat baking is performed to obtain the microneedles on the .SU-8 mold. Top sloped tip mask 9. The temperature tolerance of the photoresist after exposure is improved, and insufficient exposure is beneficial to the removal of the mask 9 with the inclined tip on the top of the microneedle on the SU-8 mold.

3.2 Preparation of SU-8 molds on top of sloping metal microneedles with sloping tips

The sample processed in step 3.1 is subjected to the first RIE etching, the etching power is 80W ~ 120W, the oxygen flow rate is 10cm ³ /min ~ 40cm ³ /min, and the oxygen pressure is 0.5Pa ~ 15Pa. The included angle γ of the etching direction is 60°˜70°, and the SU-8 adhesive layer cured on the top of the inclined metal microneedle structure layer 8 is etched away.

Keep the angle between the sample and the etching direction unchanged, place the sample in a fluorine-containing gas (such as CF ₄ , O ₂ ) to perform a second RIE etching to remove the inclined metal on the top surface of the microneedle on the SU-8 mold Microneedle structure layer and electroplated metal layer until the SU-8 mold is exposed (Fig. 2h). Because the microneedles on the SU-8 mold are all inclined circular truncated truncated cones, during the second RIE etching, the inclined metal microneedle structure layer directly below the top of the microneedles on the SU-8 mold is blocked and cannot be etched. A tip structure was formed (Fig. 2h). The angle γ between the sample and the etching direction can increase the area of the shielding metal and adjust the topography of the microneedle tip.

Step 4: Remove the SU-8 mold

The sample obtained in step 3 was placed in the SU-8 special degumming solution, ultrasonic development for 30min-50min, ultrasonic power 30W-50W, temperature 50-80°C, to obtain a hollow inclined metal microneedle array with a tip (2i). ).

Compared with the prior art, the above technical solutions conceived by the present invention can achieve the following obvious progress.

1) The SU-8 mold mask pattern is transferred to the glass sheet, which avoids the problem of air gaps in traditional contact exposure, increases the intensity of ultraviolet light reaching each layer of photoresist, and strengthens the bonding force between the microneedle mold and the substrate.

2) The present invention makes full use of OmniCoat to improve the adhesion between the SU-8 mold and the glass sheet, and at the same time, it is easier to remove the SU-8 mold in the later stage of the process.

3) The tip of the inclined circular truncated microneedle is obtained by RIE etching, and the tip structure of the metal microneedle is realized.

The technical solutions of the present invention will be further described below with reference to the embodiments and drawings, but the technical solutions of the present invention are not limited.

Description of drawings

Figure 1: Schematic diagram of hollow inclined metal microneedle array

Figure 2a: Schematic diagram of the sacrificial layer at the bottom of the SU-8 mold, the mask pattern layer of the SU-8 mold, the distribution of the first layer of SU-8 photoresist on the glass sheet, and the front exposure of the first layer of SU-8 photoresist

Figure 2b: Schematic diagram of the second layer of SU-8 photoresist

Figure 2c: Schematic diagram of preparation of SU-8 mold by backside oblique exposure

Figure 2d: Schematic diagram of preparation of SU-8 mold by backside oblique exposure in glycerol

Figure 2e: Schematic diagram of sputter deposition of metal seed layer

Figure 2f: Schematic diagram of electroplated metal layer

Figure 2g: Schematic diagram of preparation of SU-8 mold on the top of the microneedle inclined tip mask

Figure 2h: Schematic diagram of the inclined tip on the top of the microneedle on the preparation of the SU-8 mold

Figure 2i: Schematic cross-section of a hollow inclined metal microneedle array with a tip

Reference number:

1. Glass sheet, 2. The sacrificial layer at the bottom of the SU-8 mold (the front is the structure), 3. The first layer of SU-8 photoresist, 4. The SU-8 mold mask pattern layer, 5. The second layer of SU- 8 photoresist, 6. SU-8 mold, 7. metal seed layer, 8. slanted metal microneedle structure layer, 9. slanted tip mask on top of microneedles on SU-8 mold, d. SU-8 photoresist The vertical distance between the surface and the top of the SU-8 mold microneedle, H. The vertical height of the hollow inclined metal microneedle, α. The inclination angle of the microneedle on the SU-8 mold and the inclination angle of the hollow inclined metal microneedle, β. The sample and UV light Included angle, 180°-α. The included angle between the sample and the metal deposition direction

γ. The angle between the etching direction and the sample

Detailed ways

The present invention will be further described below with reference to specific embodiments.

Example 1

Referring to FIG. 2 , the hollow inclined metal microneedle array in this embodiment has a vertical height H of the microneedles of 500 μm; the outer diameter of the bottom of the microneedles is 150 μm; the inclination angle α of the microneedles is 70°; The wall thickness is 8 μm; the taper angle of the microneedle is 10°.

The preparation process of the hollow inclined metal microneedle array of this embodiment is as follows:

Step 1: Preparation of SU-8 mold on glass substrate, including the following sub-steps:

1.1 Preparation of SU-8 mold mask pattern on glass substrate

The quartz glass sheet with a thickness of 500 μm is cleaned by oxygen plasma; then a layer of 60nm metal chromium is sputtered on the surface of the quartz glass sheet; After etching in liquid, the SU-8 mold mask pattern layer 4 was obtained.

1.2 Preparation of the sacrificial layer at the bottom of the SU-8 mold on the surface of the glass sheet

The sample was cleaned and fully thermally baked, and 3nm OmniCoat was spin-coated on the chromium-free side of the sample as the sacrificial layer 2 at the bottom of the SU-8 mold, and fully thermally baked.

1.3 Back tilt exposure

A first layer of SU-8 photoresist 3 was spin-coated on the OmniCoat side of step 1.2 with a thickness of 1 μm, followed by a front-side vertical maskless exposure (Fig. 2a) with an exposure dose of 70 mJ/cm2; spin-coat again on the same side The second layer of SU-8 photoresist 5 has a thickness of 500 μm. After the second layer of SU-8 photoresist 5 has been fully pre-baked, the sample is placed under the UV exposure lamp, the SU-8 mold mask pattern layer 4 is facing the UV lamp, and the sample is placed at an angle with the UV light by using a fixture β is 55° (Fig. 2c), the exposure dose is 200mJ/cm2, and SU-8 mold 6 is obtained after post-baking and development.

Spray a layer of OmniCoat on the surface of SU-8 mold 6 with a glue sprayer, put it on a spin coater and spin it at a speed of 3000 rpm, and then place it in an incubator at 200 °C for 1 minute.

Step 2: Preparation of hollow inclined metal microneedles on the surface of SU-8 mold, including the following sub-steps:

2.1 Sputter deposition of metal seed layer on the surface of SU-8 mold

On the SU-8 mold 6 obtained in step 1.3, the metal seed layer 7 is sputtered and deposited with a thickness of 100 nm. During sputtering, it is necessary to ensure that the angle between the sample and the metal deposition direction is 110°, and the microneedles on the SU-8 mold are Parallel to the metal deposition direction (Fig. 2e), ensure that the outside of the microneedles on the SU-8 mold is completely wrapped by the deposited metal seed layer 7.

2.2 Electroplating a metal layer on the surface of the metal seed layer to form an inclined metal microneedle structure layer

The sample was placed in an electrolyte solution of metallic nickel for electroplating, and the thickness of the electroplated metal layer was 8 μm to form an inclined metal microneedle structure layer 8 (FIG. 2f).

Step 3: Prepare the top tip of the inclined metal microneedle, including the following sub-steps:

3.1 Preparation of SU-8 mold on the top tip mask of inclined metal microneedles

The surface of the inclined metal microneedle structure layer 8 of the sample obtained in step 2.2 is coated with SU-8 photoresist, and then placed on a hot plate for thermal drying to make the SU-8 adhesive layer sufficiently flat, and then the sample is placed on the Observe the vertical distance d between the surface of the SU-8 photoresist and the top of the SU-8 mold microneedle under a microscope, and repeat the aforementioned spin coating and thermal baking until the vertical distance between the SU-8 photoresist surface and the top of the SU-8 mold microneedle is 50 μm (Fig. 2g).

The glue-coated surface of the sample is placed under an ultraviolet lamp for maskless vertical exposure, and the exposure amount is 200 mJ/cm 2 , and then normal thermal baking is performed to obtain a mask 9 for the top tip of the inclined metal microneedle.

3.2 Preparation of SU-8 molds on top of sloping metal microneedles with sloping tips

The sample processed in step 3.1 was subjected to the first RIE etching, the etching power was 80W, the oxygen flow rate was 10cm ³ /min, the oxygen pressure was 0.5Pa, and the included angle γ between the sample and the etching direction during the etching was 60° , and the SU-8 adhesive layer cured on the top of the inclined metal microneedle structure layer 8 is etched away.

Keep the angle between the sample and the etching direction unchanged, place the sample in a fluorine-containing gas (CF4, O2) for the second RIE etching to remove the inclined metal microneedle structure on the top surface of the microneedle on the SU-8 mold layer and plated metal layers until the SU-8 mold is exposed (Figure 2h).

4 Remove the SU-8 mold

The sample obtained in step 3 was placed in SU-8 special degumming solution, ultrasonic developed for 30 min, ultrasonic power 30 W, temperature 50 °C, and a hollow inclined metal microneedle array with a tip was obtained (Figure 2i).

Example 2

Referring to FIG. 2 , the hollow inclined metal microneedle array in this embodiment has a vertical height H of the microneedles of 650 μm; the outer diameter of the bottom of the microneedles is 250 μm; the inclination angle α of the microneedles is 50°; The wall thickness is 10 μm; the taper angle of the microneedle is 15°.

The preparation process of the hollow inclined metal microneedle array of this embodiment is as follows:

Step 1: Preparation of SU-8 mold on glass substrate

This step includes the following sub-steps:

1.1 Preparation of SU-8 mold mask pattern on glass substrate

The quartz glass sheet with a thickness of 1000 μm was cleaned by oxygen plasma; then a layer of 60nm metal chromium was sputtered on the surface of the quartz glass sheet; positive glue was spin-coated on the chromium metal layer, exposed and developed to expose the chromium to be corroded, and the chromium metal was corroded After etching in liquid, the SU-8 mold mask pattern layer 4 was obtained.

1.2 Preparation of the sacrificial layer at the bottom of the SU-8 mold on the surface of the glass sheet

The sample was cleaned and fully thermally baked, and 3nm OmniCoat was spin-coated on the chromium-free side of the sample as the sacrificial layer 2 at the bottom of the SU-8 mold, and fully thermally baked.

1.3 Back tilt exposure

Spin-coat the first layer of SU-8 photoresist 3 on the OmniCoat side of step 1.2 with a thickness of 2 μm, and then perform vertical maskless exposure on the front side (Fig. 2a) with an exposure dose of 80 mJ/cm ² ; spin again on the same side A second layer of SU-8 photoresist 5 was applied with a thickness of 650 μm. After the second layer of SU-8 photoresist 5 has been fully pre-baked, the sample is fixed in a quartz glass container and placed under an ultraviolet exposure lamp. The SU-8 mold mask pattern layer 4 faces the ultraviolet lamp. The angle β between the sample and the UV light is 48° (see Figure 2d). Add glycerol to the quartz glass container until the glycerol submerges the entire sample. Expose after the glycerol liquid level is still, and the exposure dose is 300mJ/cm ² . After post-baking and development, the SU-8 mold was obtained.

Spray a layer of OmniCoat on the surface of the SU-8 mold with a glue sprayer, spin the glue at a high speed of 3000 rpm on the spin coater, and then place it in an incubator at 200 °C for 1 minute.

Step 2: Preparation of hollow inclined metal microneedles on the surface of SU-8 mold, including the following sub-steps:

2.1 Sputter deposition of metal seed layer on the surface of SU-8 mold

On the SU-8 mold 6 obtained in step 1.3, the metal seed layer 7 is sputtered and deposited with a thickness of 200 nm. During sputtering, it is necessary to ensure that the angle between the sample and the metal deposition direction is 130°, and the microneedles on the SU-8 mold are Parallel to the metal deposition direction (Fig. 2e), ensure that the outside of the microneedles on the SU-8 mold is completely wrapped by the deposited metal seed layer 7.

2.2 Electroplating a metal layer on the surface of the metal seed layer to form an inclined metal microneedle structure layer

The sample is placed in an electrolytic solution of metallic nickel for electroplating, and the thickness of the electroplated metal layer is 10 μm to form the inclined metal microneedle structure layer 8 .

Step 3: Prepare the top tip of the inclined metal microneedle, including the following sub-steps:

3.1 Preparation of SU-8 mold on the top tip mask of inclined metal microneedles

The surface of the inclined metal microneedle structure layer 8 of the sample obtained in step 2.2 is coated with SU-8 photoresist, and then placed on a hot plate for thermal drying to make the SU-8 adhesive layer sufficiently flat, and then the sample is placed on the Observe the vertical distance d between the surface of the SU-8 photoresist and the top of the SU-8 mold microneedle under a microscope, and repeat the aforementioned spin coating and thermal baking until the vertical distance d between the SU-8 photoresist surface and the top of the SU-8 mold microneedle is 70μm.

The glued surface of the sample is placed under an ultraviolet lamp for maskless vertical exposure, and the exposure amount is 220 mJ/cm ² , and then normal thermal baking is performed to obtain a mask 9 on the top tip of the inclined metal microneedle.

3.2 Preparation of SU-8 molds on top of sloping metal microneedles with sloping tips

The sample processed in step 3.1 was subjected to the first RIE etching, the etching power was 120W, the oxygen flow rate was 40cm ³ /min, the oxygen pressure was 15Pa, and the included angle γ between the sample and the etching direction during the etching was 70°, The SU-8 adhesive layer cured on the top of the inclined metal microneedle structure layer 8 is etched away.

Keep the angle between the sample and the etching direction unchanged, place the sample in a fluorine-containing gas (CF4, O2) for the second RIE etching to remove the inclined metal microneedle structure on the top surface of the microneedle on the SU-8 mold layer and plated metal layers until the SU-8 mold is exposed (Figure 2h).

4. Remove the SU-8 mold

The sample obtained in step 3 was placed in SU-8 special degumming solution, and ultrasonic development was carried out for 50 minutes, ultrasonic power 50W, temperature 80 °C, and a hollow inclined metal microneedle array with a tip was obtained (see Figure 2i).

Claims (2)

1. A hollow inclined metal microneedle array is characterized in that a metal material is electroplatable metal, hollow inclined metal microneedles are in an inclined conical shape, and the inclination angle is 50-70 degrees; the vertical height is 500-650 mu m; the hollow inclined metal micro-needle has a structure with the same wall thickness from the bottom to the tip, and the wall thickness is 8-10 mu m; the outer diameter of the bottom of the hollow inclined metal micro-needle is 150-250 μm; the taper angle of the hollow inclined metal micro-needle is 10-15 degrees, and the top of the hollow inclined metal micro-needle is provided with a tip.

2. The method of manufacturing a hollow oblique metallic microneedle array as claimed in claim, comprising the steps of:

the method comprises the following steps: preparing an SU-8 mold on a glass substrate comprising the following substeps:

1.1 preparation of SU-8 mold mask pattern on glass substrate

Fully baking the glass sheet 1 by heat or cleaning the glass sheet by oxygen plasma to remove organic matters on the surface of the substrate; then sputtering a layer of metal chromium on the surface of the glass sheet; spin-coating positive photoresist on the chromium metal layer, exposing and developing to expose chromium to be corroded, and corroding in a metal chromium corrosion solution to obtain an SU-8 mold mask pattern layer 4;

1.2 preparing SU-8 mould bottom sacrificial layer on the surface of glass sheet

Cleaning and fully baking the sample piece, spin-coating Omnicoat on one surface of the sample piece without metal chromium as a SU-8 mold bottom sacrificial layer 2, and fully baking;

1.3 Back side oblique Exposure

Spin-coating a first layer of SU-8 photoresist 3 on the Omnicoat surface of the sample obtained in the step 1.2, and then performing vertical maskless exposure on the front surface, spin-coating a second layer of SU-8 photoresist 5 on the same surface, wherein the thickness of the second layer of photoresist 5 determines the vertical height of the microneedle on the SU-8 mold and the vertical height H of the hollow inclined metal microneedle, after the second layer of photoresist 5 is fully prebaked, placing the sample under an ultraviolet exposure lamp, enabling the mask pattern layer 4 of the SU-8 mold to face the ultraviolet lamp, making an included angle β between the sample and the ultraviolet light be 40-90 degrees by using a clamp, making an included angle β between the sample and the ultraviolet light determine the inclined angle α of the microneedle on the SU-8 mold, and then obtaining the SU-8 mold 6 through postbaking and developing;

spraying a layer of OmniCoat on the surface of the obtained SU-8 mould by using a glue sprayer, putting the mould on a spin coater for spin coating, and then putting the mould in a constant temperature box for hot drying;

step two: preparing hollow inclined metal microneedles on the surface of the SU-8 mould; the method comprises the following substeps:

2.1 sputtering and depositing a metal seed layer on the surface of the SU-8 mould

Sputtering and depositing a metal seed layer 7 on the SU-8 mould 6 sprayed with Omnicoat obtained in the step 1.3, wherein the included angle between the sample piece and the metal deposition direction is 180- α -8, and the microneedle on the mould is parallel to the metal deposition direction, so that the exterior of the microneedle on the SU-8 mould is completely wrapped by the deposited metal seed layer 7;

2.2 electroplating a metal layer on the surface of the metal seed layer to form an inclined metal micro-needle structure layer

Putting the sample piece into an electrolyte solution capable of plating metal for electroplating to form an inclined metal microneedle structure layer 8;

step three: preparing an inclined metallic microneedle tip comprising the following sub-steps:

3.1 preparation of tilted Metal microneedle tip mask on SU-8 mold

And (3) coating SU-8 photoresist on the surface of the inclined metal microneedle structure layer 8 obtained in the step 2.2, then placing the inclined metal microneedle structure layer on a hot plate for baking to ensure that an SU-8 adhesive layer is fully flat, then placing the sample under a microscope to observe the vertical distance d between the SU-8 photoresist surface and the top of the SU-8 mould microneedle, and repeating the spin coating and the baking until the vertical distance d between the SU-8 photoresist surface and the top of the SU-8 mould microneedle is 50-70 micrometers.

Placing the gluing surface of the sample piece under an ultraviolet lamp for maskless vertical exposure with the exposure amount being 1/4-1/3 of standard exposure energy, and then performing normal hot baking to obtain a microneedle top inclined tip mask 9 on the SU-8 mold;

3.2 preparation of inclined tips at tops of inclined metallic microneedles in SU-8 molds

Carrying out first RIE etching on the sample piece treated in the step 3.1, wherein the included angle gamma between the sample piece and the etching direction in the etching is 60-70 degrees, and etching off the solidified SU-8 adhesive layer at the top of the inclined metal microneedle structure layer 8;

keeping an included angle between the sample piece and the etching direction unchanged, placing the sample piece in fluorine-containing gas for second RIE etching, and removing the inclined metal microneedle structure layer and the electroplated metal layer on the top surface of the microneedle on the SU-8 mold until the SU-8 mold is exposed;

step four: removing the SU-8 mold;

and (4) placing the sample piece obtained in the step (3) into a special degumming solution for SU-8 to obtain the hollow inclined metal microneedle array with the tip.

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