CN113860254A - Method for manufacturing three-dimensional microstructure body by heterogeneous material filling reverse mould combined with reflux - Google Patents

Abstract

The invention discloses a method for manufacturing a three-dimensional microstructure body by heterogeneous material filling, reverse molding and reflux combination, which comprises the following steps: preparing a PDMS female die; pouring two or more than two kinds of mobile phase materials into a PDMS female mold step by step, curing, and demolding to obtain a heterogeneous male mold structure containing two or more than two kinds of materials; heating the obtained heterogeneous male mold structure and/or exposing the heterogeneous male mold structure in a steam environment, refluxing one or more materials in the heterogeneous male mold structure, and adjusting the deformation degree of each material to obtain the composite material; the vapor in the vapor environment is formed by volatilization of a solvent that dissolves one or more materials in the heteromale structure. The method can flexibly regulate and control the size, material characteristics and processing parameters of the die, and manufacture the 3D microstructure with high curvature, the curved surface-non-curved surface composite 3D microstructure and the multi-curvature complex curved surface microstructure, is beneficial to the development of novel micro-fluidic devices and micro-nano optical devices, and meets different application requirements.

Description

Method for manufacturing three-dimensional microstructure body by heterogeneous material filling reverse mould combined with reflux

Technical Field

The invention belongs to the technical field of micromachining, and particularly relates to a method for manufacturing a three-dimensional microstructure body by filling heterogeneous materials into a reverse mold and combining reflux.

Background

In recent years, with the development of micromachining technology, researchers have proposed various methods for forming microstructures, including mainly lithography (photolithography), laser micromachining (laser micromachining), hot embossing (hot embossing), injection molding (injection molding), 3D printing, and numerical control engraving, which can manufacture microstructures with high precision, but have a great limitation in the flexibility of microstructure manufacturing, and generally can only process microstructures with regular shapes, i.e., microstructures with regular and clear corners and regular 3D surfaces with rectangular or polyhedral shapes, and it is more and more important to manufacture microstructures or micro devices with complex three-dimensional curved surface features with further expansion of micromachining technology application. In order to realize the fabrication of microstructures with curved surface features, two main technologies have been developed in recent years: one is a gray scale photomask technology, which utilizes a photomask plate with gray scale gradient distribution to carry out exposure, so that photoresist is crosslinked or dissolved to different degrees under the action of ultraviolet light with different intensities, and a microstructure with curved surface characteristics is manufactured; the other is a photoresist reflux technology, which utilizes the mobility increase of some positive photoresists when the baking temperature is higher than the glass transition temperature to ensure that the microstructure with neat corners formed by photoetching development forms a microstructure with a smooth curved surface in a reflux mode. Recently, researchers further expand the conventional photoresist reflow technology, and an artificial compound eye device with a complex three-dimensional curved surface structure is manufactured by manufacturing a plurality of layers of positive photoresist microstructures and combining the photoresist reflow technology.

However, the two technologies have great limitations in practical application, and the gray scale photomask technology needs an expensive and high-resolution gray scale photomask, which is complex to process and has high cost; the photoresist reflow technology usually adopts a positive photoresist, the spin coating thickness of the positive photoresist is usually small (the thickness of single spin coating is less than 50 μm), the height of a prepared microstructure is limited, and the positive photoresist material is easily corroded by acid, alkali or organic reagents, so that the application range is limited. Particularly, the technology is not sufficient in the aspect of manufacturing high-complexity 3D microstructures, such as a high-curvature 3D microstructure (e.g., a spherical microstructure), a curved surface-non-curved surface composite 3D microstructure, a complex curved surface microstructure and the like. Therefore, a new process method is urgently needed to be developed to manufacture a novel device with a complex three-dimensional microstructure, such as a cell culture chip integrated with a spherical microcavity array, a spherical microlens, a bionic compound eye system and the like, so as to meet the development requirements of a micro-nano biological analysis technology and a micro-nano optical technology.

Disclosure of Invention

Aiming at the prior art, the invention provides a method for manufacturing a three-dimensional microstructure by combining heterogeneous material filling, reverse molding and reflux, so as to overcome the limitation that the traditional micro-machining technology cannot manufacture a complex three-dimensional microstructure with integrated curved surface characteristics.

In order to achieve the purpose, the invention adopts the technical scheme that: the method for manufacturing the three-dimensional microstructure body by filling heterogeneous materials into a reverse mold and combining reflux comprises the following steps:

(1) preparing a PDMS female die;

(2) pouring two or more than two kinds of mobile phase materials into a PDMS female die step by step, then carrying out curing treatment, and then demoulding to obtain a heterogeneous male die structure containing two or more than two kinds of materials;

(3) heating the obtained heterogeneous male mold structure and/or exposing the heterogeneous male mold structure in a steam environment, refluxing one or more materials in the heterogeneous male mold structure, and adjusting the deformation degree of each material to obtain the composite material; the steam in the steam environment is formed by volatilization of a solvent which can dissolve one or more materials in the heterogeneous male mold structure.

Heating the heterogeneous male mold structure or exposing the heterogeneous male mold structure to a solvent steam environment capable of dissolving one of the materials, controlling the heating temperature and time or controlling the saturated pressure and exposure time of the solvent steam to enable one or more of the structural materials to reflow, so that a local microstructure composed of the materials forms a curved surface shape due to the action of surface tension.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the PDMS female mold structure in the step (1) is prepared by the following method: and manufacturing a female die by adopting a photoetching technology, a laser processing technology, a 3D printing technology or a numerical control engraving technology, and then pouring and reversing the die to obtain the product.

Further, before pouring and filling in the step (2), the PDMS female mold is subjected to degassing treatment in a vacuum environment of 5-15 kPa for at least 20 minutes.

Further, the flowing phase material in the step (2) is photoresist solution and polystyrene solution and/or two-component epoxy glue, and the kinematic viscosity of the flowing phase material is less than 300 St.

Further, the glass transition temperature difference between two or more than two mobile phase materials in the step (2) is more than 10 ℃.

Further, the curing in the step (2) is heating crosslinking curing, room temperature crosslinking curing, light radiation crosslinking curing or heating volatilization-cooling curing.

Further, the heating temperature in the step (3) is not lower than 25 ℃.

Further, the steam environment in the step (3) is the saturated pressure environment of the solvent.

Further, the material reflux in the step (2) is repeated for a plurality of times.

The invention has the beneficial effects that: the 3D microstructure (such as a spherical microstructure), the curved surface-non-curved surface composite 3D microstructure and the multi-curvature complex curved surface microstructure with high curvature can be manufactured by flexibly regulating and controlling the size, the material characteristics and the processing parameters of the mold, so that the development of novel micro-fluidic devices and micro-nano optical devices is facilitated, different application requirements are met, and the development of micro-fluidic technologies and micro-nano optical technologies is expected to be promoted.

Drawings

FIG. 1 is a schematic flow chart of a method for manufacturing a spherical microlens structure;

FIG. 2 is a photomicrograph of a spherical micro-mirror structure prepared based on the method;

FIG. 3 is a schematic flow chart of a funnel-shaped micro-via array chip prepared according to the method;

fig. 4 is a schematic flow chart of the process for preparing the bionic compound eye structure based on the method.

Detailed Description

The following examples are provided to illustrate specific embodiments of the present invention.

Example 1

Filling and reflowing two heterogeneous materials, namely SU-8 and epoxy glue, to manufacture a spherical micro-lens structure (as shown in figure 1), and specifically comprises the following steps:

(1) preparing a female die: firstly, a master die is manufactured through a photoetching process, and the specific flow is as follows: spin-coating SU-83050 negative photoresist (500rpm, 12 s; 1000rpm, 40s) on a clean 4-inch silicon wafer, and standing for 2-3 h; and carrying out pre-baking (95 ℃, 30min), exposing (3min 0s), post-baking (93.5 ℃, 5min), naturally cooling, developing (PGEMA, 8min), hard baking (170 ℃, 30min), and cooling the silicon wafer to finish the manufacture of the master mold with the cylindrical structure.

(2) Preparing a PDMS female mold: the female die structure is manufactured by pouring and molding PDMS, and the concrete flow is as follows: mixing the PDMS prepolymer and a curing agent according to a mass ratio of 10:1, stirring uniformly, placing in a vacuum container, vacuumizing and removing bubbles for 1h, taking out the PDMS after removing the bubbles, pouring the PDMS on a master model, standing for 15min, moving to a hot plate, heating and curing for 2h at 80 ℃, cooling, peeling the cured PDMS from the model, and cutting off the excess PDMS by using a scalpel to obtain the PDMS female model structure with the cylindrical micro-cavity.

(3) Filling heterogeneous materials into a reverse mold: the heterogeneous male die structure is manufactured by two-step pouring and filling, and the specific process comprises the following steps: degassing the PDMS female mold prepared in the step (2) in a vacuum of 10kPa for 2h (figure 1a), pouring SU-8 photoresist (solute content is 70%) diluted by cyclopentanone on the PDMS female mold in a dark condition (figure 1b), standing for 30min, scraping the redundant SU-8 photoresist on the surface of the PDMS female mold by using a blade (figure 1c), transferring the PDMS female mold filled with the SU-8 photoresist on a hot plate, baking for 12h at 95 ℃, and depositing the SU-8 photoresist filled in the microcavity at the lower part of the microcavity due to solvent volatilization (figure 1 d); after cooling, pouring the mixed two-component epoxy glue on the surface of the PDMS female mold (shown in figure 1e), covering a glass slide, standing for 30min, transferring to a hot plate, and baking at 95 ℃ for 1h to further promote the crosslinking and curing of the epoxy glue (shown in figure 1 f); after cooling, the PDMS master mold (FIG. 1g) was peeled off to obtain a heterogeneous male mold structure composed of SU-8 and epoxy glue.

(4) And (3) heterogeneous male die structure reflow: the spherical micro-lens structure is formed by hot reflux SU-8, and the specific flow is as follows: placing the heterogeneous male die structure manufactured in the step (3) in an oven, and baking for 10min at 70 ℃ (note that the vitrification temperature of the non-crosslinked SU-8 photoresist is 55 ℃), wherein the viscosity of the non-crosslinked SU-8 photoresist is greatly reduced due to heating, the fluidity of the non-crosslinked SU-8 photoresist is increased, the SU-8 photoresist flowing under the action of surface tension forms a spherical shape based on the energy minimum principle, and the epoxy adhesive serving as a base structure keeps the original shape (figure 1 h); after cooling to room temperature (<30 ℃), SU-8 returns to a solid state (i.e., glassy state) and then uv-exposed and postbaked at 85 ℃ for 1 hour to complete the cross-linking of SU-8 (fig. 1i), yielding a spherical microlens structure with good physical and chemical stability (fig. 2).

Example 2

Filling, refluxing and reverse molding by using three heterogeneous materials including SU-8 photoresist, polystyrene and epoxy glue to manufacture a funnel-shaped micro through hole array filter membrane (as shown in figure 3), and specifically comprises the following steps:

(1) preparing a female die: firstly, a master die is manufactured through a photoetching process, and the specific flow is as follows: spin-coating SU-83050 negative photoresist (500rpm, 12 s; 3000rpm, 30s) on a clean 4-inch silicon wafer, and standing for 2-3 h; pre-baking (95 deg.C, 30min), exposing (3min40s), and post-baking (93.5 deg.C, 5 min); after natural cooling, a layer of SU-83050 negative photoresist (500rpm, 12 s; 3000rpm, 30s) is spin-coated on the first layer of photoresist again, and the mixture is kept stand for 2 to 3 hours; and carrying out pre-baking (95 ℃, 30min), exposing (3min40s), post-baking (93.5 ℃, 5min), developing (PGEMA, 8min), hard-baking (170 ℃, 30min), and cooling the silicon wafer to finish the manufacture of the master mold with the stepped cylindrical structure.

(2) Preparing a PDMS female mold: the female die structure is manufactured by pouring and molding PDMS, and the concrete flow is as follows: mixing the PDMS prepolymer and a curing agent according to a mass ratio of 10:1, stirring uniformly, placing in a vacuum container, vacuumizing and removing bubbles for 1h, taking out the PDMS after removing the bubbles, pouring the PDMS on a master model, standing for 15min, moving to a hot plate, heating and curing for 2h at 80 ℃, cooling, peeling the cured PDMS from the model, and cutting off the excess PDMS by using a scalpel to obtain the PDMS female model structure with the stepped cylindrical microcavity.

(3) Filling heterogeneous materials into a reverse mold: manufacturing a heterogeneous male die structure by three steps of pouring and filling, wherein the specific process is as follows: degassing the PDMS female mold prepared in the step (2) in a vacuum of 15kPa for 0.5h (figure 3a), pouring SU-8 photoresist (with the solute content of 10%) diluted by cyclopentanone on the PDMS female mold in a dark condition (figure 3b), standing for 30min, scraping the redundant SU-8 photoresist on the surface of the PDMS female mold by using a blade (figure 3c), transferring the PDMS female mold filled with the SU-8 photoresist on a hot plate, and baking for 24h at 95 ℃, wherein the SU-8 photoresist filled in the microcavity shrinks in volume due to the volatilization of the solvent and is deposited in a lower microcavity structure (figure 3 d); after cooling, ultraviolet exposure and baking at 85 ℃ for 1 hour to complete the crosslinking of SU-8; then, a polystyrene solution (25 wt%) prepared based on gamma butyrolactone solvent was poured onto the surface of the PDMS negative mold (fig. 3e), excess polystyrene solution on the surface of the PDMS negative mold was scraped with a blade, and the mold was transferred to a hot plate and the solvent was removed by two-step baking (4h @95 ℃, 12h @150 ℃) (fig. 3 f); naturally cooling to room temperature, pouring the mixed two-component epoxy glue on the surface of the PDMS female mold (figure 3g), covering a glass slide, standing for 30min, transferring to a hot plate, and baking at 95 ℃ for 1h to further promote the crosslinking and curing of the epoxy glue (figure 3 h); after cooling, the PDMS master mold was peeled off to obtain a heterogeneous male mold structure composed of SU-8, polystyrene and epoxy glue (FIG. 3 i).

(4) And (3) heterogeneous mold backflow: the method comprises the following steps of forming an integrated curved surface complex microstructure by dissolving and refluxing polystyrene, wherein the specific process comprises the following steps: placing the heterogeneous male die and the glass vessel filled with the gamma butyrolactone solvent, which are manufactured in the step (3), in a closed drying vessel, standing for 30min, wherein the mobility of the polystyrene microstructure is increased due to the fact that the volatile gamma butyrolactone dissolves the polystyrene, the polystyrene flowing under the action of surface tension forms a hemispherical curved surface structure based on the principle of minimum energy, and the cross-linked SU-8 and epoxy glue structure part keep the original shape (figure 3 j); and (3) volatilizing the gamma butyrolactone solvent after the die is transferred into the air, and recovering the polystyrene into a solid state to prepare the heterogeneous male die structure with the inverted funnel-shaped structure.

(5) Reverse molding to prepare a funnel-shaped micro through hole array filtering membrane: pouring and molding through PDMS to manufacture a funnel-shaped micro through hole array filter membrane, wherein the specific flow is as follows: mixing a PDMS prepolymer and a curing agent according to a mass ratio of 10:1, stirring uniformly, placing in a vacuum container, vacuumizing and removing bubbles for 1h, taking out the PDMS after removing the bubbles, pouring the PDMS on a heterogeneous male mold (figure 3k) with an inverted funnel-shaped structure manufactured in the step (4), covering a glass slide pasted with polyvinyl alcohol (PVA) on the PDMS, placing a 2kg weight on the glass slide, standing for 1h, moving to a hot plate, heating and curing for (80 ℃ and 2h) (figure 3l), cooling, removing the glass slide, peeling off the PDMS/PVA composite film from the mold (figure 3m), and removing a PVA supporting layer (figure 3n) by a water dissolving method, thereby preparing the filter membrane with the funnel-shaped micro through hole array (figure 3o), which can be applied to rapid and efficient enrichment of circulating tumor cells.

Example 3

The bionic compound eye structure is manufactured by filling and refluxing two heterogeneous materials of SU-8 and polystyrene (as shown in figure 3), and the specific steps are as follows:

(1) preparing a female die: firstly, a master die is manufactured through a photoetching process, and the specific flow is as follows: spin-coating SU-83050 negative photoresist (500rpm, 12 s; 1000rpm, 40s) on a clean 4-inch silicon wafer, and standing for 2-3 h; pre-baking (95 deg.C, 30min), exposing (3min40s), and post-baking (93.5 deg.C, 5 min); after natural cooling, a layer of SU-83010 negative photoresist (500rpm, 12 s; 3000rpm, 40s) is spin-coated on the first layer of photoresist again, and the mixture is kept stand for 2 to 3 hours; and (3) carrying out prebaking (95 ℃, 30min), exposing (3min40s), postbaking (93.5 ℃, 5min), developing (PGEMA, 8min), hard baking (170 ℃, 30min), and cooling the silicon wafer to finish the manufacture of the master mold with the multistage cylindrical array structure.

(2) Preparing a PDMS female mold: the female die structure is manufactured by pouring and molding PDMS, and the concrete flow is as follows: mixing the PDMS prepolymer and a curing agent according to a mass ratio of 10:1, stirring uniformly, placing in a vacuum container, vacuumizing and removing bubbles for 1h, taking out the PDMS after removing the bubbles, pouring the PDMS on a master model, standing for 15min, moving to a hot plate, heating and curing for 2h at 80 ℃, cooling, peeling the cured PDMS from the model, and cutting off the excess PDMS by using a scalpel to obtain the PDMS female model structure with the multistage cylindrical microcavity array.

(3) Filling heterogeneous materials into a reverse mold: the heterogeneous male mold structure is manufactured by two-step pouring and filling (as shown in figure 4), and the specific process is as follows: firstly, degassing the PDMS female mold prepared in the step (2) in a vacuum of 5kPa for 2h (figure 4a), then pouring SU-8 photoresist (solute content is 5%) diluted by cyclopentanone on the PDMS female mold under a dark condition (figure 4b), standing for 30min, transferring the PDMS female mold filled with the SU-8 photoresist on a hot plate, baking for 12h at 95 ℃, and as the solvent is volatilized, the SU-8 photoresist filled in the microcavity shrinks volumetrically and is deposited at the lower part of the microcavity (figure 4 c); after cooling, a frame-shaped PDMS sheet was reversibly bonded to the surface of the PDMS master mold to form a liquid storage enclosure, a polystyrene solution (25 wt%) prepared based on gamma butyrolactone solvent was poured into the enclosure (FIG. 4d), and the mold was transferred to a hot plate and the solvent was removed by two-step baking (4h @95 ℃, 12h @150 ℃) (FIG. 4 e); after natural cooling to room temperature, the PDMS rails and the female mold were peeled off to make a heterogeneous multi-stage cylindrical array male mold structure consisting of SU-8 and polystyrene (fig. 4 f).

(4) And (3) heterogeneous mold backflow: the bionic compound eye structure is formed by step-by-step hot reflux of SU-8 and polystyrene, and the specific process is as follows: adhering the heterogeneous male die manufactured in the step (3) on a glass slide, placing the glass slide in a baking oven, and baking the glass slide for 5min at 70 ℃, wherein the viscosity of the SU-8 photoresist which is not crosslinked at the upper layer is greatly reduced due to heating, fluidity is generated, the SU-8 photoresist which flows under the action of surface tension forms a hemispherical curved surface shape, and the polystyrene structure at the lower layer basically keeps the original shape (note: the vitrification temperature of polystyrene is 100 ℃) (figure 4 g); after cooling, ultraviolet exposure is carried out, and the heat baking is carried out for 1 hour at 110 ℃, so that on one hand, the cross-linking of SU-8 is completed (figure 4h), and on the other hand, the heat reflux of polystyrene is realized, so that the bottom polystyrene structure forms a spherical crown curved surface structure under the action of surface tension, and after cooling, the bionic compound eye with the multi-stage convex curved surface structure is prepared (figure 4 i).

While the present invention has been described in detail with reference to the embodiments, it should not be construed as limited to the scope of the patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.

Claims (9)

1. A method for manufacturing a three-dimensional microstructure body by heterogeneous material filling reverse mould and reflux is characterized by comprising the following steps:

(1) preparing a PDMS female die;

(2) pouring two or more than two kinds of mobile phase materials into a PDMS female die step by step, then carrying out curing treatment, and then demoulding to obtain a heterogeneous male die structure containing two or more than two kinds of materials;

(3) heating the obtained heterogeneous male mold structure and/or exposing the heterogeneous male mold structure in a steam environment, refluxing one or more materials in the heterogeneous male mold structure, and adjusting the deformation degree of each material to obtain the composite material; the steam in the steam environment is formed by volatilization of a solvent which can dissolve one or more materials in the heterogeneous male mold structure.

2. The method for fabricating a three-dimensional microstructure by heterogeneous material filling inverse mold combined with reflow according to claim 1, wherein the PDMS negative structure in step (1) is prepared by the following method: and manufacturing a female die by adopting a photoetching technology, a laser processing technology, a 3D printing technology or a numerical control engraving technology, and then pouring and reversing the die to obtain the product.

3. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: and (3) degassing the PDMS female mold for at least 20 minutes in a vacuum environment of 5-15 kPa before pouring and filling in the step (2).

4. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: the mobile phase material in the step (2) is photoresist solution and polystyrene solution and/or two-component epoxy glue, and the kinematic viscosity of the mobile phase material is less than 300 St.

5. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: the difference of the glass transition temperatures of the two or more than two mobile phase materials in the step (2) is more than 10 ℃.

6. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: and (3) the curing in the step (2) is heating crosslinking curing, room temperature crosslinking curing, light radiation crosslinking curing or heating volatilization-cooling curing.

7. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: the heating temperature in the step (3) is not lower than 25 ℃.

8. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: and (4) in the step (3), the steam environment is a saturated air pressure environment of the solvent.

9. The method for fabricating a three-dimensional microstructure according to claim 1, wherein the method comprises: and (4) refluxing the material in the step (3) for a plurality of times.

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