Polymer micro-fluidic chip runner hydrophobic modification method and chip thereof

Abstract

The invention provides a hydrophobic modification method for a polymer micro-fluidic chip runner, which comprises the following steps: firstly, etching the surface of a micro-fluidic chip by adopting oxygen and carbon tetrafluoride plasmas to roughen the surface of the micro-fluidic chip, and then, treating the surface of the micro-fluidic chip by adopting octafluorocyclobutane plasmas to hydrophobize the surface of the micro-fluidic chip. The method provided by the invention solves the problems of difficulty in realizing uniform hydrophobicity of the inner and outer surfaces of the chip, easy attenuation of effect, complex operation and difficulty in batch production in the existing method.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and particularly to a method for hydrophobic modification of the flow channels of polymer microfluidic chips and the chip thereof. Background Technology

[0002] Microfluidics technology can integrate the entire experimental process and functions of conventional biochemical analysis, such as sampling, dilution, reagent addition, reaction, separation, and detection, onto a small solid material such as silicon, glass, plastic, or metal. This forms a microchip that includes multiple micro- and nano-channels and multiple micro- and nano-liter reaction chambers, allowing controllable fluid to flow through the entire system to achieve various functions of conventional chemical or biological laboratories.

[0003] Hydrophobic treatment of microfluidic chips is an important and necessary surface modification technology. For example, droplet chips require hydrophobic properties in the flow channels to effectively control the generation, movement, and fusion of droplets in the microfluidic chip. In the application of microfluidic chips for bioanalysis and medical diagnostics, hydrophobic modification can improve the biocompatibility of the chip surface, reduce non-specific adsorption, and thus improve the sensitivity and specificity of detection.

[0004] Existing hydrophobic modification technologies mainly fall into categories such as physical coating methods and surface microstructuring methods. These methods involve applying hydrophobic reagents to the surface of microfluidic chips through physical means such as spraying, spin coating, and immersion. However, the hydrophobic coatings obtained through these methods are prone to peeling off, exhibit poor uniformity, poor long-term stability, and poor biocompatibility. Furthermore, most methods require modification to be completed before chip bonding, as the bonding process may damage the already formed hydrophobic layer. After bonding, the sealed flow channels cannot access the modifying reagents, making uniform modification difficult to achieve. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for hydrophobic modification of the flow channels of a polymer microfluidic chip. The method first uses oxygen and carbon tetrafluoride plasma to etch the surface of the microfluidic chip to roughen it, and then uses octafluorocyclobutane plasma to treat the surface of the microfluidic chip to make it hydrophobic.

[0006] In one embodiment, the method includes the following steps: Step 1, placing the microfluidic chip into the reaction chamber of a plasma device, and sequentially setting the power, oxygen flow rate, carbon tetrafluoride flow rate, temperature, and time; Step 2, turning on the vacuum pump to evacuate the system, and then introducing oxygen and carbon tetrafluoride to perform plasma glow discharge to complete the roughening process; Step 3, after Step 2, introducing oxygen to perform plasma treatment to clean the surface of the microfluidic chip and form active groups; and Step 4, after Step 3, evacuating the system again, and introducing octafluorocyclobutane gas to perform plasma treatment to form a dense fluorinated hydrophobic coating on the chip surface to complete the hydrophobicization.

[0007] In one embodiment, in step 2, the volume ratio of oxygen to carbon tetrafluoride is 3:1 to 6:1.

[0008] In one embodiment, in step 1, the oxygen flow rate is 200 sccm, the carbon tetrafluoride flow rate is 50 sccm, the power is 500W, the time is 15min, and the temperature is 45℃.

[0009] In one implementation, the vacuum level in step 2 needs to reach below 100 mTorr.

[0010] In one embodiment, the oxygen flow rate in step 3 is 200 sccm, the power is 500 W, and the time is 1 min.

[0011] In one embodiment, the octafluorocyclobutane flow rate in step 4 is 50 sccm, the power is 400 W, and the time is 15 min.

[0012] In one embodiment, the polymer microfluidic chip material is any one of PC, PMMA, COC, and COP.

[0013] In one embodiment, the present invention provides a polymer microfluidic chip prepared by the above method.

[0014] This invention provides a method for hydrophobic modification of the flow channel of a polymer microfluidic chip, which solves the problems of existing methods that make it difficult to achieve uniform hydrophobicity on both the inner and outer surfaces of the chip at the same time, the effect is easy to decay, the operation is complicated and difficult to mass produce.

[0015] Meanwhile, this invention provides a method for hydrophobic modification of the flow channels of polymer microfluidic chips. The method first roughens the chip surface by etching with oxygen and carbon tetrafluoride plasma. However, due to application limitations of polymer microfluidic chips, such as precise fluid control, avoidance of specific adsorption, and bonding requirements, the chip surface roughness needs to be controlled below 200 nm. In the method of this invention, by controlling the oxygen:carbon tetrafluoride volume ratio in step 2, the chip surface roughness is controlled to below 200 nm, and the attenuation of the hydrophobic effect after hydrophobicating the chip surface with octafluorocyclobutane plasma is avoided. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a measurement of the water contact angle of the COC microfluidic chip before hydrophobic modification in Example 1. Figure 2 This is a measurement diagram of the water contact angle of the COC microfluidic chip after hydrophobic modification in Example 1; Figure 3 This is a water contact angle measurement diagram of the non-uniform COC microfluidic chip after hydrophobic modification in Example 1; Figure 4 This is a measurement diagram of the water contact angle of the COC microfluidic chip after hydrophobic modification and restoration in Example 2; Figure 5 This is a measurement diagram of the water contact angle of the COC microfluidic chip after hydrophobic modification in Example 3; Figure 6 This is a measurement chart of the water contact angle of the COC microfluidic chip after one week following hydrophobic modification in Example 3; Figure 7 This is a measurement diagram of the water contact angle of the COC microfluidic chip after hydrophobic modification in Example 4. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions in this application, the present invention will be further described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0019] Example 1

[0020] like Figure 1 As shown, Figure 1 This is a measurement chart of the water contact angle of the COC microfluidic chip before hydrophobic modification, and its hydrophobic angle measurement is 88°.

[0021] The hydrophobic modification method for microfluidic chip materials in this embodiment specifically includes the following steps: (1) Place the polymer microfluidic chip (material is COC) into the reaction chamber of the plasma device, close the chamber door, and evacuate the chamber to below 100 mtorr; (2) Open the oxygen valve and pass oxygen to perform plasma treatment, clean the chip surface (including the inner wall of the flow channel) and form active groups. Set the oxygen flow rate to 200 sccm, the power to 500W, and the treatment time to 1 min. (3) Close the oxygen valve, and the chamber will be automatically evacuated to below 100 mtorr; (4) Vacuum was drawn again, and octafluorocyclobutane was introduced for hydrophobic treatment to form a dense fluorine-containing hydrophobic coating on the chip surface. The octafluorocyclobutane gas flow rate was set to 50 sccm, the power to be 500W, and the treatment time to be 15min.

[0022] The hydrophobic properties of the modified microfluidic chip surface in this embodiment were characterized using a contact angle meter. The test results are as follows: Figure 2 As shown, the water contact angle on the chip surface is 105°, but the hydrophobic effect of the chip is not uniform, such as... Figure 3 As shown, some areas have a lower contact angle, with the measured contact angle being 65°.

[0023] Example 2.

[0024] The hydrophobic modification method for the polymer microfluidic chip in this embodiment specifically includes the following steps: (1) Place the microfluidic chip (material is COC) into the reaction chamber of the plasma device, and set the power to 500W, the carbon tetrafluoride flow rate to 50sccm, the temperature to 45℃, and the time to 15min; (2) Turn on the vacuum pump to evacuate to below 100 mtorr, and then introduce carbon tetrafluoride to perform plasma glow discharge to complete the roughening process; (3) In the second stage, oxygen is first introduced for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. The oxygen flow rate is 200 sccm, the power is 500W, the time is 1 min, and the oxygen purity is 99.9%.

[0025] (4) Vacuum was evacuated again to below 100 mtorr, and octafluorocyclobutane gas was introduced for plasma treatment to form a dense fluorine-containing hydrophobic coating on the chip surface to complete hydrophobization. The flow rate was 50 sccm, the power was 400 W, the time was 15 min, and the purity of octafluorocyclobutane was 99.9%.

[0026] The hydrophobic properties of the modified microfluidic chip surface in this embodiment were characterized using a contact angle meter. The test results are as follows: Figure 4 As shown, the water contact angle on the chip surface is 110°, and the hydrophobic effect of the chip is still uneven.

[0027] Example 3

[0028] The hydrophobic modification method for the polymer microfluidic chip in this embodiment specifically includes the following steps: (1) Place the microfluidic chip (material is COC) into the reaction chamber of the plasma device, and set the power to 500W, oxygen flow rate to 50sccm, carbon tetrafluoride flow rate to 50sccm, temperature to 45℃ and time to 15min in sequence. (2) Turn on the vacuum pump to evacuate to below 100 mtorr, and then introduce oxygen and carbon tetrafluoride to complete the roughening process by plasma glow discharge; (3) In the second stage, oxygen is first introduced for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. The oxygen flow rate is 200 sccm, the power is 500W, the time is 1 min, and the oxygen purity is 99.9%.

[0029] (4) Vacuum was evacuated again to below 100 mtorr, and octafluorocyclobutane gas was introduced for plasma treatment to form a dense fluorine-containing hydrophobic coating on the chip surface to complete hydrophobization. The flow rate was 50 sccm, the power was 400 W, the time was 15 min, and the purity of octafluorocyclobutane was 99.9%.

[0030] The hydrophobic properties of the modified microfluidic chip surface in this embodiment were characterized using a contact angle meter. The test results are as follows: Figure 5 As shown, the water contact angle on the chip surface is 110°, and the surface roughness Ra is 50 nm; furthermore, the hydrophobicity of the chip surface is uniform. To verify the long-term stability of the hydrophobicity, an aging test was conducted on the modified chip. During the first week of the test, the chip surface contact angle had already recovered to its pre-treatment state. Figure 6 As shown, the effectiveness of the octafluorocyclobutane hydrophobic treatment on the polymer chip surface is poor.

[0031] Example 4

[0032] The hydrophobic modification method for the polymer microfluidic chip in this embodiment specifically includes the following steps: (1) Place the microfluidic chip (material is COC) into the reaction chamber of the plasma device, and set the power to 500W, oxygen flow rate to 200sccm, carbon tetrafluoride flow rate to 50sccm, temperature to 45℃ and time to 15min in sequence; (2) Turn on the vacuum pump to evacuate to below 100 mtorr, and then introduce oxygen and carbon tetrafluoride to complete the roughening process by plasma glow discharge; (3) In the second stage, oxygen is first introduced for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. The oxygen flow rate is 200 sccm, the power is 500W, the time is 1 min, and the oxygen purity is 99.9%.

[0033] (4) Vacuum was evacuated again to below 100 mtorr, and octafluorocyclobutane gas was introduced for plasma treatment to form a dense fluorine-containing hydrophobic coating on the chip surface to complete hydrophobization. The flow rate was 50 sccm, the power was 400 W, the time was 15 min, and the purity of octafluorocyclobutane was 99.9%.

[0034] The hydrophobic properties of the chip surface modified by the method of this embodiment were characterized using a contact angle meter. The test results are as follows: Figure 7As shown, the water contact angle of the chip surface is 112°, the surface roughness Ra is 120nm, and the surface hydrophobicity is uniform. To verify the long-term stability of the hydrophobic performance, the modified chip was subjected to a 12-month aging test, with the test cycle being once a month. The specific data are shown in Table 1. The data shows that the hydrophobic effect of this embodiment is reliable, the performance is stable, and the aging effect is strong.

[0035] Table 1

[0036] Example 5

[0037] In Examples 3 and 4, this study found that during the roughening process of plasma glow discharge with oxygen and carbon tetrafluoride, the hydrophobic treatment of the polymer chip surface with octafluorocyclobutane had poor timeliness when the volume ratio of oxygen to carbon tetrafluoride was 1:1. However, when the volume ratio of oxygen to carbon tetrafluoride was 4:1, the hydrophobic effect was reliable, the performance was stable, and the timeliness was strong. That is, oxygen and carbon tetrafluoride must be present in a certain proportion to ensure that the subsequent treatment with octafluorocyclobutane can guarantee reliable hydrophobic effect, performance stability, and strong timeliness.

[0038] In this embodiment, based on the oxygen:carbon tetrafluoride volume ratios of 1:1 and 4:1 in Examples 3 and 4, the oxygen:carbon tetrafluoride volume ratios were adjusted to 2:1, 3:1, 4:1, 5:1, 6:1, and 8:1 to hydrophobically modify the polymer chip. The hydrophobic properties of the chip surface modified by this method were characterized using a contact angle meter. It was found that with the increase of the oxygen:carbon tetrafluoride volume ratio, the hydrophobic contact angle of the chip surface gradually increased slightly, successively to 110°, 112°, 115°, 120°, 123°, and 125°. Simultaneously, a 12-month aging test was conducted on the modified chip, with the test cycle being once a month. The data showed that the hydrophobic effect was reliable, the performance stable, and the aging effect strong. In addition, the surface roughness Ra also gradually increased, to 70nm, 90nm, 120nm, 150nm, 200nm, and 300nm, respectively. When the oxygen:carbon tetrafluoride volume ratio reaches 8:1, the chip surface roughness exceeds 200 nm. An increase in chip surface roughness beyond 200 nm is detrimental to subsequent chip microfabrication and applications.

[0039] Those skilled in the art will also recognize, or be able to identify, many equivalents of the specific embodiments of the invention described herein using no more than conventional experiments. These equivalents are also included in the appended claims.

Claims

1. A method for hydrophobic modification of the flow channel of a polymer microfluidic chip, characterized in that, The method first uses oxygen and carbon tetrafluoride plasma to etch the surface of the microfluidic chip to roughen it, and then uses octafluorocyclobutane plasma to treat the surface of the microfluidic chip to make it hydrophobic.

2. The method according to claim 1, characterized in that, The method includes the following steps: Step 1: Place the microfluidic chip into the reaction chamber of the plasma device, and set the power, oxygen flow rate, carbon tetrafluoride flow rate, temperature, and time in sequence. Step 2: After turning on the vacuum pump to draw a vacuum, oxygen and carbon tetrafluoride are then introduced to perform plasma glow discharge to complete the roughening process. Step 3: After step 2, oxygen is introduced for plasma treatment to clean the surface of the microfluidic chip and form active groups. Step 4: After step 3, vacuum is drawn again, and octafluorocyclobutane gas is introduced for plasma treatment to form a dense fluorine-containing hydrophobic coating on the chip surface to complete hydrophobization.

3. The method for hydrophobic modification of microfluidic chip channels according to claim 2, characterized in that, In step 2, the volume ratio of oxygen to carbon tetrafluoride is 3:1 to 6:

1.

4. The method according to claim 3, characterized in that, In step 1, the oxygen flow rate is 200 sccm, the carbon tetrafluoride flow rate is 50 sccm, the power is 500W, the time is 15min, and the temperature is 45℃.

5. The method according to claim 4, characterized in that, In step 2, the vacuum level needs to be below 100 mTorr.

6. The method according to claim 5, characterized in that, In step 3, the oxygen flow rate is 200 sccm, the power is 500W, and the time is 1 min.

7. The method according to claim 6, characterized in that, In step 4, the octafluorocyclobutane flow rate is 50 sccm, the power is 400 W, and the time is 15 min.

8. The method according to any one of claims 1-7, characterized in that, The polymer microfluidic chip is made of any one of PC, PMMA, COC, and COP.

9. A polymer microfluidic chip prepared by any one of the methods described in claims 1-7.

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