CN103920544B - Method for preparing polydimethylsiloxane (PDMS) micro-fluidic chip - Google Patents

Abstract

The invention discloses a method for preparing a PDMS microfluidic chip. The method comprises the following steps: preparing a paraffin positive mold of the PDMS microfluidic chip by using the droplet micro-injection method; preparing a negative mold of the PDMS microfluidic chip by using a molding method; bonding the negative mold of the PDMS microfluidic chip to the glass substrate by means of reversible bonding Together, the PDMS microfluidic chip is made. The preparation process of the paraffin positive mold of the PDMS microfluidic chip of the present invention only needs one step, the cost is low, no specific template is required, and the paraffin positive mold of the PDMS microfluidic chip with arbitrary graphics can be prepared.

Description

A kind of preparation method of PDMS microfluidic chip

technical field

The invention relates to a method for preparing a microfluidic chip, in particular to a method for preparing a PDMS microfluidic chip.

Background technique

A microfluidic chip refers to a chemical or biological laboratory built on a chip of a few square centimeters. It integrates the basic operation units involved in chemistry or biology, such as sample preparation, reaction, separation, detection, cell culture, sorting, lysis, etc., into a small chip, forming a network of micro-channels, with controllable fluid running through it. The whole system is used to realize various functions of conventional chemical or biological laboratory.

The materials commonly used to make microfluidic chips include single crystal silicon wafers, glass, quartz and various organic polymers. Silicon has good chemical inertness and thermal stability, but the disadvantages of silicon materials are that they are fragile and expensive , opacity, poor electrical insulation, and complex surface chemical properties, so it is limited in the application of microfluidic chips. Glass and quartz have good electroosmotic properties and optical properties, and standard etching processes can be used Processing, but the processing cost is higher and the sealing is more difficult. Among the organic polymers used to prepare microfluidic chips, polydimethylsiloxane (Polydimethylsiloxane, PDMS) has been widely used because of its good biocompatibility, excellent optical properties, and easy processing and packaging. Fabrication of microfluidic chips.

There are many methods for preparing microfluidic chips. The preparation process of microfluidic chips made of silicon wafers, glass and quartz generally goes through steps such as film deposition, photolithographic mask making, photolithography, corrosion, and degumming. The process is complicated. higher cost. The preparation methods of organic polymer microfluidic chips mainly include molding method, hot pressing method, injection molding method, laser ablation method, LIGA method and soft photolithography method. Simple, economical, and flexible have become the main preparation methods for organic polymer microfluidic chips. The first step in the preparation of microfluidic chips by soft lithography is to prepare the male mold required for the elastic mold seal. The traditional elastic mold seal male mold is generally made by traditional microfabrication technology and photolithography process. The preparation process is complicated and the equipment cost is relatively high. high. Some positive mold preparation methods developed in recent years include screen printing technology, local laser rapid prototyping, mask etching brass template, hot-pressed PMMA template to make ice crystal positive mold, dripping liquid mold method on paraffin pattern, etc., but these The method still has many limitations, and there are still problems such as cumbersome preparation process and high equipment cost. For example, in the brass printed mask etching method, the etching of copper or brass requires a mask, requires a toxic etchant, and requires additional etching and rinsing steps. The ice pattern in the ice crystal positive mold method using hot-pressed PMMA templates requires another PMMA mold, and evaporation and freezing measures are required. It is difficult to prepare microchannels with high aspect ratios in the liquid mold method.

Contents of the invention

In view of the disadvantages of the existing microfluidic chip preparation method described above, such as complex preparation process, high equipment requirements, and high cost, the purpose of the present invention is to provide a simple and high aspect ratio PDMS microfluidic chip preparation method.

The principle of the present invention is: use a droplet micro-injection technology to prepare the positive mold required for the PDMS microfluidic chip, use the droplet micro-injection method to micro-spray the paraffin wax onto the cleaned glass substrate to form a The PDMS microfluidic chip with a graphic structure requires a paraffin positive mold, and then deposits PDMS liquid on the paraffin positive mold of the microfluidic chip. After curing, the cured PDMS elastomer is separated from the glass sheet to obtain a PDMS microfluidic chip. Negative mold, after drilling and cleaning processes, the negative mold of the PDMS microfluidic chip is bonded to a clean glass substrate to obtain a PDMS microfluidic chip.

The present invention is achieved through the following technical solutions: a method for preparing a PDMS microfluidic chip, comprising the following steps:

The first step, the preparation of the paraffin positive mold of the PDMS microfluidic chip

1.1 Preparation of inner biconical glass micro-nozzles;

1.2 Clean the glass substrate;

1.3 Drive the internal biconical glass micro-nozzle to micro-spray the molten paraffin onto the clean glass substrate, thereby making the paraffin positive mold of the PDMS microfluidic chip;

The second step, the preparation of PDMS microfluidic chip

2.1 Evenly and slowly deposit PDMS liquid on the paraffin wax positive mold of the prepared PDMS microfluidic chip, form a negative mold after curing treatment, remove the negative mold of the PDMS microfluidic chip, and use the hollow tube cutting method to clean the PDMS microfluidic chip. The negative mold of the chip is punched to obtain the liquid inlet and outlet of the PDMS microfluidic chip;

2.2 Bond the negative mold of the PDMS microfluidic chip after punching to a clean glass substrate to prepare the PDMS microfluidic chip.

The outer diameter of the internal double-tapered glass micro-nozzle needle handle described in step 1.1 is 8 mm, the inner diameter is 6 mm, and the inner diameter of the micro-nozzle varies from 120 μm to 250 μm.

The glass substrate described in step 1.2 is cleaned with concentrated sulfuric acid, acetone and deionized water respectively.

The micro-injection described in step 1.3 is realized by cooperatively controlling the droplet micro-injection control parameters and the three-dimensional table motion parameters, wherein the droplet micro-injection control parameters include the driving voltage waveform and the driving voltage amplitude of the piezoelectric actuator. value and driving frequency, the driving voltage waveform of the piezoelectric actuator is a steep rise and slow fall waveform, the driving frequency is set to 6Hz, and the driving voltage amplitude range is 40-80V; The motion pattern of the workbench and the Z-axis deposition times of the 3D workbench, the droplet overlap ranges from 50% to 80%; the Z-axis deposition times of the 3D workbench ranges from 1 to 4.

The PDMS liquid described in step 2.1 is obtained by uniformly mixing PDMS elastomer and curing agent at a mass ratio of 10:1.

The bonding described in step 2.2 is to clean the negative mold of the PDMS microfluidic chip and the glass substrate, then bond the negative mold of the PDMS microfluidic chip to the glass substrate and clamp them tightly to form a closed PDMS microfluidic channel structure , placed in an oven and heated at 80°C for 10 minutes to obtain a bonded PDMS microfluidic chip.

Compared with prior art, the advantage of the present invention is:

(1) The preparation process of the paraffin positive mold of the PDMS microfluidic chip of the present invention only needs one step, the cost is low, no specific template is required, and the paraffin positive mold of the PDMS microfluidic chip with any graphics can be prepared.

(2) The present invention uses paraffin as the preparation material for the positive mold of the PDMS microfluidic chip, and micro-sprays the molten paraffin onto the clean glass substrate. After the paraffin is deposited on the glass substrate, it solidifies rapidly to form the paraffin positive mold of the PDMS microfluidic chip, and can Perform three-dimensional deposition, that is, use paraffin to make a paraffin positive model of a PDMS microfluidic chip with a high aspect ratio or a complex structure.

Description of drawings

Fig. 1 is a schematic diagram of the droplet micro-jet preparation of the paraffin positive mold of the PDMS microfluidic chip in the first step of the present invention.

Fig. 2 is a schematic diagram of the preparation process of the PDMS microfluidic chip in the second step of the present invention.

1. The first connecting piece; 2. The piezoelectric actuator; 3. The second connecting piece; 4. The holder for the biconical glass micronozzle; 5. The biconical glass micronozzle; 6. Melted paraffin; 7. Digital microscope; 8 heating ring; 9 three-dimensional workbench; 10 glass substrate; 11 PDMS microfluidic chip paraffin positive mold; 12 PDMS elastomer; 13 PDMS microfluidic chip negative mold; 14 PDMS microfluidic chip inlet and outlet; 15 PDMS microfluidic chip glass substrate

Detailed ways

In the present invention, the droplet micro-jet is driven by the pulse inertial force to overcome the internal biconical glass micro-nozzle (see doctoral thesis "Digital Droplet Micro-jet Technology and Its Application Research in Printed Electronics") The viscous force of the inner liquid is realized. The pulse inertial force can be produced in various ways. Since the piezoelectric device has the characteristics of good voltage-displacement dynamic response and high response frequency, it can be placed outside the micronozzle as an integral driver to generate the pulse inertial force. Therefore, the pulse inertial force of the present invention consists of Piezoelectric actuators are provided. Figure 1 shows a droplet micro-injection device. First, the piezoelectric actuator 2 and the required internal structure biconical glass micro-nozzle 5 are connected to the three-dimensional workbench 9 by the first connecting piece 1 and the second connecting piece 3. On the Z axis, the distance between the inner biconical glass micro-nozzle 5 and the glass substrate 10 is adjusted by controlling the Z-axis movement of the three-dimensional worktable. Adjust the magnification and focal length of the digital microscope 7 so that the built-in biconical glass micro-nozzle 5 and the glass substrate 10 can be clearly displayed on the computer screen. FIG. 2 is a schematic diagram of the preparation process of the PDMS microfluidic chip. Firstly, a paraffin positive mold 11 of the PDMS microfluidic chip is prepared on a cleaned glass substrate 10 by using droplet micro-injection technology. Then slowly and evenly deposit PDMS elastomer 12 on the paraffin wax positive mold 11 of the PDMS microfluidic chip. Chip inlet and outlet 14. Finally, the obtained negative mold of the PDMS microfluidic chip is bonded to the glass substrate 15 to obtain a PDMS microfluidic chip.

The internal biconical glass micro-fluidic devices 5 are made by cold and hot processing of glass, firstly using a self-developed glass micro-fluidic device (see the paper "Preparation of paper micro-fluidic devices used inbio-assay-based on drop- on-demand wax droplet generation"), the borosilicate glass capillary with an outer diameter of 8.0 mm and an inner diameter of 6 mm was broken into a microneedle, and then the microneedle was placed in a suitable place using a needle forging instrument (MF-900, Narishige, Japan). The size of the position is truncated and the outlet is forged into an internal double-cone shape. The micro-nozzle outlet diameter of the final preparation suitable for molten paraffin micro-injection is variable in the range of 120-250 μm; the internal double-conical glass micro-nozzle has a better Droplet micro-injection ability, compared with flat nozzles and other micro-nozzles, it can micro-inject solutions with greater viscosity.

Example 1

The preparation of the paraffin positive model 11 of the PDMS microfluidic chip, the specific steps are as follows:

Step 1 Preparation of the internally structured biconical glass micronozzle 5 : the internally structured biconically shaped glass micronozzle 5 was prepared by using the above described method for preparing the internally structured biconically shaped glass micronozzle.

Step 2 Cleaning of the glass substrate 10: Put the glass piece into a beaker, pour in an appropriate amount of concentrated sulfuric acid, heat it on a heating furnace for 10 minutes, then take it out and cool it for 10 minutes, and rinse the remaining concentrated sulfuric acid with deionized water. Dry it with a cotton ball, put it into a beaker containing acetone, put it into an ultrasonic cleaner and shake it for 10 minutes, take it out, rinse it with deionized water, and blow dry the surface moisture with nitrogen.

In step 3, the solid paraffin is melted and loaded into the inner double-conical glass micro-nozzle 5 .

Step 4 Set the driving voltage amplitude of the piezoelectric actuator 2 to 40V, the driving frequency to 2Hz, set the motion parameters of the three-dimensional table 9 so that the droplet overlap is 50%, the number of Z-axis depositions is 1, and the motion pattern of the table is selected Two-way micro-mixing patterns on a microfluidic chip. Drive the internal double-conical glass micro-nozzle 5, and at this moment, the internal double-conical glass micro-nozzle 5 is surrounded by a heating ring 8 to melt the paraffin in it. Micro-spray the molten paraffin wax 6 in the double-tapered glass micro-nozzle 5 with the inner structure onto the glass substrate 10 to obtain the paraffin wax male mold 11 of the PDMS microfluidic chip, and the obtained paraffin wax male mold 11 of the PDMS microfluidic chip has a height of 150 μm, and the width is 150 μm, as shown in Fig. 1, 2a, b.

Example 2

The preparation of the paraffin positive model 11 of the PDMS microfluidic chip, the specific steps are as follows:

Step 1 Preparation of the internally structured biconical glass micronozzle 5 : the internally structured biconically shaped glass micronozzle 5 was prepared with the internally structured biconically shaped glass micronozzle having an outlet inner diameter of 180 μm.

Steps 2 and 3 are identical to steps 2 and 3 described in Example 1

Step 4 Step 4 Set the driving voltage amplitude of the piezoelectric actuator 2 to 60V, the driving frequency to 2Hz, set the motion parameters of the three-dimensional workbench 9 so that the droplet overlap is 60%, the Z-axis deposition times are 2, and the workbench moves Pattern selection for dual-way micro-mixing patterns for microfluidic chips. Drive the internal double-conical glass micro-nozzle 3, and at this time, the internal double-conical glass micro-nozzle 5 is surrounded by a heating ring 8 to melt the paraffin in it. Micro-spray the molten paraffin wax 6 in the double-tapered glass micro-nozzle 5 onto the glass substrate 10 to obtain the paraffin wax positive mold 11 of the PDMS microfluidic chip, and the height of the prepared paraffin wax positive mold for the PDMS microfluidic chip is 510 μm , with a width of 330 μm as shown in Figures 1, 2a, and b.

Example 3

The preparation of the paraffin positive model 11 of the PDMS microfluidic chip, the specific steps are as follows:

Step 1 Preparation of the internally structured biconical glass micronozzle 5 : the internally structured biconically shaped glass micronozzle 5 was prepared by adopting the above described method for preparing the internally structured biconically shaped glass micronozzle.

Steps 2 and 3 are identical to steps 2 and 3 described in Example 1

Step 4 Set the driving voltage amplitude of the piezoelectric actuator 2 to 80V, the driving frequency to 2Hz, set the motion parameters of the three-dimensional table 9 so that the droplet overlap is 80%, the Z-axis deposition times are 6, and the motion pattern of the table is selected Two-way micro-mixing patterns on a microfluidic chip. Drive the internal double-conical glass micro-nozzle 5, and at this moment, the internal double-conical glass micro-nozzle 5 is surrounded by a heating ring 8 to melt the paraffin in it. Micro-spray the molten paraffin wax 6 in the double-tapered glass micro-nozzle 5 onto the glass substrate 10 to obtain the paraffin wax male mold 11 of the PDMS microfluidic chip, and the height of the prepared paraffin wax male mold of the PDMS microfluidic chip is 1390 μm , with a width of 450 μm as shown in Figures 1, 2a, and b.

Example 4

The preparation of the PDMS microfluidic chip, the specific steps are as follows:

Step 1: Take DC184SYLGARD PDMS elastomer and curing agent (special curing agent for PDMS elastomer) and mix according to the mass ratio of 10:1, stir on a magnetic stirrer for 20 minutes, and vacuum the fully mixed PDMS liquid to remove air bubbles in the liquid .

In step 2, slowly and evenly deposit the PDMS vacuumized liquid onto the paraffin wax positive mold 11 of the PDMS microfluidic chip prepared in Examples 1, 2, and 3, as shown in FIG. 2c. After evacuating again, put it in an oven and heat it at 30-40°C for 24 hours, peel off the cured PDMS, then insert a circular hollow tube into the part that needs to be punched, and take out the PDMS cylinder when pulling it out, and punch out the same The hole of the pipe joint is to make the negative mold 13 of the PDMS microfluidic chip, as shown in FIG. 2d.

Step 3: The cleaning treatment of the glass substrate 15 is the same as that of Step 2 in Embodiment 1.

Step 4 uses a reversible packaging process to bond the negative mold 13 of the PDMS microfluidic chip to the glass substrate 15 . First, the surface of each part used for packaging is repeatedly cleaned with deionized water and methanol, and then dried with clean nitrogen, and then the negative mold 13 of the PDMS microfluidic chip is directly bonded to the glass substrate 15, and the two pieces are tightly bonded. Clamp it tightly, put it in an oven at 80°C for about 10 minutes, and then make a PDMS microfluidic chip, as shown in Figure 2e. The obtained PDMS microfluidic chip can be torn apart by external force, that is to say, this process is reversible, and the advantage of the obtained chip is that it can be cleaned very conveniently. The PDMS microfluidic chip made by using the positive mold of the PDMS microfluidic chip made of paraffin has a higher aspect ratio. In the specific implementation process, the highest aspect ratio of the PDMS microfluidic chip is 3.1.

In the specific implementation process, the aspect ratio of the PDMS microfluidic chip and the microfluidic structure pattern of the microfluidic chip can be determined by the positive mold of the PDMS microfluidic chip.

Claims (8)

1. a PDMS micro-flow control chip preparation method, is characterized in that, comprises the following steps:

The preparation of the first step, PDMS micro-fluidic chip paraffin formpiston

Structure biconial glass micro-nozzle in 1.1 preparations;

1.2 pairs of substrate of glass carry out cleaning process;

1.3 drive interior structure biconial glass micro-nozzle, by melt paraffin micro-injection in the substrate of glass of cleaning, thus obtained PDMS micro-fluidic chip paraffin formpiston;

The preparation of second step, PDMS micro-fluidic chip

2.1 evenly, slowly deposit PDMS liquid on obtained PDMS micro-fluidic chip paraffin formpiston, negative norm is formed after solidification process, PDMS micro-fluidic chip negative norm is taken off, and adopt hollow pipe patterning method to punch to PDMS micro-fluidic chip negative norm, thus obtain the liquid in-out mouth of PDMS micro-fluidic chip;

PDMS micro-fluidic chip negative norm after punching and clean substrate of glass are carried out bonding by 2.2, i.e. obtained PDMS micro-fluidic chip.

2. PDMS micro-flow control chip preparation method according to claim 1, is characterized in that, the interior structure biconial glass micro-nozzle needle handle external diameter described in 1.1 steps is 8mm, and internal diameter is 6mm, and micro-nozzle internal diameter excursion is 120 μm-250 μm.

3. PDMS micro-flow control chip preparation method according to claim 1, is characterized in that, the substrate of glass described in 1.2 steps adopts the concentrated sulfuric acid, acetone and deionized water to carry out cleaning process respectively.

4. PDMS micro-flow control chip preparation method according to claim 1, is characterized in that, the micro-injection described in 1.3 steps is realized by Collaborative Control drop micro-injection controling parameters and three-dimensional working platform kinematic parameter.

5. the PDMS micro-flow control chip preparation method according to claim 1 or 4, it is characterized in that, drop micro-injection controling parameters comprises the driving voltage waveform of piezo-activator, driving voltage amplitude and driving frequency, the driving voltage waveform of piezo-activator slowly falls waveform for skyrocketing, driving frequency is set as 2Hz, and driving voltage amplitude scope is 40 ~ 80V.

6. PDMS micro-flow control chip preparation method according to claim 4, is characterized in that, three-dimensional working platform kinematic parameter comprises the degree of overlapping of drop, working table movement pattern and three-dimensional working platform Z axis frequency of depositing, and the degree of overlapping scope of drop is 50% ~ 80%; Three-dimensional working platform Z axis frequency of depositing scope is 1 ~ 6.

7. PDMS micro-flow control chip preparation method according to claim 1, is characterized in that, the PDMS liquid described in 2.1 steps to be mixed by 10:1 mass ratio by PDMS elastomer and curing agent and obtains.

8. PDMS micro-flow control chip preparation method according to claim 1, it is characterized in that, bonding described in 2.2 steps is by after PDMS micro-fluidic chip negative norm and substrate of glass cleaning process, PDMS micro-fluidic chip negative norm and substrate of glass bonded and tightly block the PDMS micro-channel structure being formed and close, at putting into 80 DEG C, baking oven, heating realized after 10 minutes.