Anti-adhesion treatment technology based on PDMS secondary reverse mold

Abstract

The invention discloses an anti-adhesion treatment technology based on PDMS (Polydimethylsiloxane) secondary mold reversing. The method specifically comprises the following steps: preparing a three-dimensional microstructure mother set by using a gray photoetching technology, pouring a PDMS mixing agent into the mother set, curing to obtain a first PDMS reverse mold, placing the first PDMS reverse mold on a glass slide, spin-coating a layer of thinner acetone film on the first PDMS reverse mold by using a spin coater, pouring a layer of PDMS mixing agent, heating and curing, soaking the whole structure in ethanol, and drying to obtain the three-dimensional microstructure. And separating the two layers of PDMS to obtain a second PDMS reverse mold, and cleaning the second PDMS reverse mold to obtain a PDMS copy reverse mold with a three-dimensional microstructure. In the method, the acetone film layer has an anti-adhesion effect, secondary demolding becomes easy after ethanol soaking, and the method is simple to operate and low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of soft lithography, and more particularly relates to an anti-adhesion treatment technology based on PDMS secondary molding. Background Art

[0002] Soft lithography is one of the technologies used in microstructure manufacturing. It is a technology that creates micro devices or three-dimensional structures by replicating and imprinting elastomers on molds. It has the advantages of simplicity, reliability and low cost. It mainly consists of three parts: a master mold, an elastomer mold and a secondary replication element.

[0003] The most commonly used elastic material for elastomeric molds in soft lithography is PDMS (polydimethylsiloxane). PDMS is a soft, physically compatible elastomer characterized by high thermal and chemical stability, low toxicity, transparency to UV and visible light, low cost, ease of molding, and mechanical flexibility and durability. In the PDMS secondary molding process, an elastomeric mold with the inverse microstructure of the master is first molded using PDMS. This is then used as a secondary master for a second mold, using PDMS to create the same structure as the initial master. However, adhesion between PDMS materials can lead to failure in the second demolding process, necessitating surface treatment of the PDMS prior to the second molding process.

[0004] Physical surface treatment methods for PDMS primarily involve forming an anti-adhesion layer on the PDMS surface. Currently, these layers are formed primarily by sputtering a metal layer onto the PDMS surface or by self-assembling 1H,1H,2H,2H-perfluorodecyltrichlorosilane vaporized onto the PDMS surface. Sputtering a metal layer can leave metal residue on the second molded PDMS replica and result in significant replication errors. The latter method also requires a long operation time. The surface modification method proposed in this paper offers the advantages of low cost and ease of use. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides an anti-adhesion treatment technology based on PDMS secondary molding.

[0006] The technical solution provided by the present invention comprises the following steps:

[0007] S1: The prepared PDMS mixture is degassed in a vacuum drying oven and then divided into two parts. One part is poured onto a three-dimensional microstructure master obtained by a photolithography process, and heated and cured to obtain a first PDMS mold;

[0008] S2: Place the first PDMS mold on a pretreated glass slide, fix it on a glue spreader, and use a dropper to drop acetone on the surface of the first PDMS mold. Use the glue spreader to evenly form a thin layer of acetone on the surface of the mold and let it stand for 1 to 2 minutes.

[0009] S3: pouring the second portion of the PDMS mixture onto the first PDMS mold with the acetone layer and heating and curing;

[0010] S4: Soaking the above assembly in ethanol for 15 to 20 minutes, separating the two PDMS layers to obtain a second PDMS mold;

[0011] S5: Pre-treating the second PDMS mold to obtain a clean three-dimensional microstructure PDMS replica mold.

[0012] Further:

[0013] The three-dimensional microstructure described in step S1 is a microlens array, and the surface morphology size is greater than 3 μm.

[0014] The master plate described in step S1 is obtained by grayscale photolithography on a thick resist, and exposure and development using a grayscale mask.

[0015] The PDMS mixture described in step S1 is made of PDMS and a curing agent in a mass ratio of 10:1.

[0016] The vacuum degree of the PDMS vacuum degassing treatment in step S1 is 0.1 Pa, and the time is 1 to 2 hours.

[0017] The temperature for heating and curing the PDMS in steps S1 and S3 is 100° C., and the curing time is 10 to 20 minutes.

[0018] The parameters of the glue spreader in step S2 are a rotation speed of 2000 rpm / min and a rotation time of 30 s.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] This invention provides an anti-adhesion treatment technology based on secondary PDMS molding. A layer of acetone is spin-coated on the first PDMS mold. Acetone dissolves PDMS polar groups or free chains and has a large contact angle with the PDMS surface, reducing surface energy and stickiness. After soaking in ethanol, demolding becomes easier. This method has the following advantages: 1) Acetone is volatile, resulting in a very thin adhesion layer that does not affect the accuracy of three-dimensional structure replication; 2) Residual acetone on the surface is easily cleaned, resulting in a clean replica component; 3) It is simple to operate and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of preparing a microlens array master based on DMD maskless lithography according to the present invention;

[0022] Figure 2Schematic diagram of obtaining a first PDMS mold using PDMS based on soft lithography technology in the present invention;

[0023] Figure 3 is a schematic diagram of forming an acetone anti-blocking layer according to the present invention;

[0024] Figure 4 It is a schematic diagram of a microlens array obtained by performing a second mold replication using the treated first PDMS mold of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions and advantages of the present invention more clear, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, taking a replicated microlens array as an example.

[0026] Example 1

[0027] S1: The prepared PDMS mixture is degassed in a vacuum drying oven and then divided into two parts. One part is poured onto a three-dimensional microstructure master obtained by a photolithography process, and heated and cured to obtain a first PDMS mold;

[0028] S2: Place the first PDMS mold on a pretreated glass slide, fix it on a glue spreader, and use a dropper to drop acetone on the surface of the first PDMS mold. Use the glue spreader to evenly form a thin layer of acetone on the surface of the mold and let it stand for 1 to 2 minutes.

[0029] S3: pouring the second portion of the PDMS mixture onto the first PDMS mold with the acetone layer and heating and curing;

[0030] S4: Soaking the above assembly in ethanol for 15 to 20 minutes, separating the two PDMS layers to obtain a second PDMS mold;

[0031] S5: Pre-treating the second PDMS mold to obtain a clean three-dimensional microstructure PDMS replica mold.

[0032] Figure 1 Schematic diagram of preparing a microlens array master based on DMD maskless lithography in Example 1. AZ4620 photoresist was spin-coated on a pretreated silicon wafer, pre-baked at 100°C for 5 minutes, and grayscale exposed and developed using DMD maskless lithography to obtain a microlens array master.

[0033] Figure 2This figure shows the process of obtaining the first PDMS mold using PDMS based on soft lithography in Example 1. PDMS and a curing agent were thoroughly mixed in a 10:1 mass ratio and placed in a vacuum dryer. The mixture was allowed to stand for 1-2 hours at a vacuum of 0.1 Pa for degassing. The prepared PDMS mixture was divided into two portions, one of which was cast onto a three-dimensional microstructure master obtained using a photolithography process. The mixture was then cured by heating at 100°C for 10-20 minutes to obtain the first PDMS mold.

[0034] Figure 3 Schematic diagram of forming an acetone anti-adhesive layer in Example 1. A first PDMS mold was placed on a pretreated glass slide and secured to a spin coater. Acetone was then dripped onto the surface of the first PDMS mold using a dropper. The spin coater was then spin-coated at 2000 rpm / min for 30 seconds to form a thin, even layer of acetone on the mold surface.

[0035] Figure 4 This diagram illustrates the microlens array obtained by performing a second mold replication using the treated first PDMS mold in Example 1. A second PDMS mixture was poured onto the first PDMS mold with the acetone layer and cured by heating. The removed second PDMS mold was then immersed in ethanol and deionized water for 2-3 minutes, followed by a nitrogen blowgun to remove most of the surface moisture. The second PDMS mold was then suspended with tweezers on a heating plate at 100°C to further dry the surface. This resulted in a clean PDMS replica mold for the microlens array.

[0036] The anti-adhesion treatment technology is not limited to the production of microlens arrays, and is also applicable when PDMS secondary molding is used in soft lithography.

[0037] The above embodiments of the present invention are merely examples for more clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An anti-adhesion treatment technology based on PDMS secondary molding, characterized in that: The steps include: S1: The prepared PDMS mixture is degassed in a vacuum drying oven and then divided into two parts. One part is poured onto a three-dimensional microstructure master obtained by a photolithography process, and heated and cured to obtain a first PDMS mold; S2: Place the first PDMS mold on a pretreated glass slide, fix it on a glue spreader, and use a dropper to drop acetone on the surface of the first PDMS mold. Use the glue spreader to evenly form a thin layer of acetone on the surface of the mold and let it stand for 1 to 2 minutes. S3: pouring the second portion of the PDMS mixture onto the first PDMS mold with the acetone layer and heating and curing; S4: Soaking the above assembly in ethanol for 15 to 20 minutes, separating the two PDMS layers to obtain a second PDMS mold; S5: Pre-treating the second PDMS mold to obtain a clean three-dimensional microstructure PDMS replica mold.

2. The method according to claim 1, characterized in that The three-dimensional microstructure is a microlens array, and the surface morphology size is above 3 μm.

3. The method according to claim 1, characterized in that The master is obtained by grayscale photolithography on a thick resist and exposure and development using a grayscale mask.

4. The method according to claim 1, wherein The PDMS mixture is prepared by pouring PDMS and a curing agent into a plastic beaker in a mass ratio of 10:1, stirring the mixture thoroughly, placing the mixture in a vacuum desiccator, and standing the mixture for 1 to 2 hours under a vacuum degree of 0.1 Pa for degassing.

5. The method according to claim 1, wherein The PDMS is heated and cured at a temperature of 100° C., and the curing time is 10 to 20 minutes.

6. The method according to claim 1, wherein The pretreatment step described in step S2 includes: placing the slide glass in a culture dish containing acetone, ethanol, and deionized water in sequence, and cleaning it in an ultrasonic cleaner for 2 to 3 minutes. After cleaning, use a nitrogen gun to blow dry the surface moisture.

7. The method according to claim 1, characterized in that The parameters of the glue spreader in step S2 are a rotation speed of 2000 rpm / min and a rotation time of 30 s.

8. The method according to claim 1, characterized in that The second PDMS mold pretreatment step described in step S5 includes: soaking the peeled second PDMS mold in ethanol and deionized water for 2 to 3 minutes, using a nitrogen gun to blow off most of the moisture on the surface, and using tweezers to hold the second PDMS mold suspended on a heating table at 100°C to further dry the surface.

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