Metal micro-fluidic chip surface hydrophobic modification method and chip thereof

Abstract

The invention discloses a metal micro-fluidic chip surface hydrophobic modification method and a chip thereof, and the method comprises the following steps: roughening the surface of a metal micro-fluidic chip by adopting pulse electroforming, and then hydrophobizing the metal surface by adopting octafluorocyclobutane plasma treatment. The water contact angle of the modified metal surface obtained through the method reaches 110 degrees or above, an accelerated aging experiment verifies that the hydrophobic effect is uniform and consistent, long-term stability is achieved, complex pretreatment is not needed, cost is low, and batch production is easy.

Description

Technical Field

[0001] This invention relates to the field of microfluidic chip technology, specifically to a method for hydrophobic modification of the surface of a metal microfluidic chip and the chip thereof. Background Technology

[0002] Metals can serve as substrate materials for microfluidic chips, and their unique physicochemical properties offer advantages over traditional materials such as glass and polymers in specific applications. The core value of metal microfluidic chips lies in their high thermal conductivity, high mechanical strength, and good chemical stability, making them primarily suitable for applications requiring extreme conditions (such as high temperature, high pressure, and strong corrosion) or specific functions (such as rapid temperature control and electromagnetic induction).

[0003] Hydrophobic treatment of metal microfluidic chips is also an important surface modification technology. For example, in metal inkjet printheads, one side of the metal needs to remain hydrophilic, while the other side needs to be hydrophobic. This allows for precise control of the ink flow path and jet pattern, while simultaneously addressing ink leakage and printhead contamination issues, ensuring printing stability and accuracy. During hydrophobic modification, the surface roughness of the metal microfluidic chip must be maintained between 200-500 nm. A roughness exceeding 500 nm can easily render the metal inkjet printhead unusable. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for hydrophobic modification of the surface of a metal microfluidic chip. The method first roughens the surface of the metal microfluidic chip using pulsed electroforming, and then hydrophobizes the metal surface using octafluorocyclobutane plasma treatment.

[0005] In one embodiment, the method includes the following steps: Step 1, placing the metal microfluidic chip in an electroforming tank, performing pulse electroforming on the surface of the metal microfluidic chip, and cleaning the surface of the metal microfluidic chip with alcohol and pure water in sequence after electroforming; Step 2, placing the cleaned metal microfluidic chip into a plasma equipment chamber, evacuating the vacuum, and then introducing oxygen for plasma treatment to clean the metal surface and form active groups; and Step 3, evacuating the vacuum again, introducing octafluorocyclobutane gas for plasma treatment, and forming a dense fluorinated hydrophobic coating on the surface of the metal microfluidic chip to complete hydrophobication.

[0006] In one embodiment, step 1 uses positive and negative pulses for pulse electroforming, with a positive-to-negative pulse ratio of 2:3 to 3:2.

[0007] In one embodiment, in step 1, the current is 2A, the frequency is 1000Hz, the number of negative pulses is 3, and the number of positive pulses is 2.

[0008] In one embodiment, in step 1, the current is 2A, the frequency is 1000Hz, the number of negative pulses is 2, and the number of positive pulses is 3.

[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 metal is any one of nickel, copper, and aluminum.

[0013] In one embodiment, the present invention provides a metal microfluidic chip, which is prepared by the method described above.

[0014] This invention provides a method for hydrophobic modification of the surface of a metal microfluidic chip, which solves the problems existing in the prior art and can achieve long-term stable and effective hydrophobicity of the metal surface.

[0015] This invention provides a method for hydrophobic modification of the surface of a metal microfluidic chip. The first step involves roughening the metal surface using positive and negative current pulse electroforming. Under the action of an electric field, the anolyte metal dissolves into ions, which migrate to the cathode for deposition, creating micro-pits on the metal surface and providing an excellent substrate for the subsequent hydrophobic layer. The second step involves treating the surface with octafluorocyclobutane plasma, where the decomposed fluorine-containing fragments bond with the active groups on the metal surface to form a uniform and dense fluorine-containing hydrophobic coating. Through the synergistic effect of the two processes, the uniformity and stability of the hydrophobicity of the metal surface are improved.

[0016] The water contact angle of the metal surface modified by the present invention is over 110°. Aging test verifies that the hydrophobic effect is uniform, stable over a long period of time, requires no complicated pretreatment, is low in cost and easy to mass-produce.

[0017] In this invention, by controlling the ratio of positive to negative pulses in step 1, on the one hand, the water contact angle of the modified metal surface reaches more than 110°, and the hydrophobic effect is uniform, consistent and stable over a long period of time; on the other hand, it ensures that the surface roughness of the metal chip is below 500nm, which is suitable for the assembly of metal chips. Attached Figure Description

[0018] Figure 1 This is a measurement diagram of the water contact angle on the surface of the nickel chip before hydrophobic modification in Example 1; Figure 2 This is a measurement diagram of the water contact angle on the surface of the nickel chip after hydrophobic modification in Example 1; Figure 3 This is a measurement diagram of the water contact angle on the surface of the nickel chip after hydrophobic modification in Example 2; Figure 4 This is a measurement diagram of the water contact angle on the surface of the nickel chip after hydrophobic modification in Example 3; Figure 5 This is a measurement diagram of the water contact angle on the surface of the nickel chip after hydrophobic modification in Example 4; Figure 6 This is a measurement diagram of the water contact angle on the surface of the nickel chip after hydrophobic modification in Example 5. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto. Example 1

[0020] The method for hydrophobic modification of the surface of the metal microfluidic chip in this embodiment specifically includes the following steps: (1) Place the nickel chip into the plasma equipment chamber, close the chamber door, and evacuate the chamber to below 100 mtorr; (2) Set the oxygen flow rate to 200 sccm, the power to 500W, and the processing time to 1 min. Open the oxygen valve and introduce oxygen for plasma treatment to clean the chip surface and form active groups. (3) Evacuate again to below 100 mtorr, set the octafluorocyclobutane gas flow rate to 50 sccm, the power to 500 W, and the processing time to 15 min, and introduce octafluorocyclobutane gas for plasma treatment to form a dense fluorinated hydrophobic coating on the metal surface to complete hydrophobization.

[0021] The hydrophobic properties of the microfluidic chip surface before and after hydrophobic modification in this embodiment were characterized using a contact angle meter. The contact angle image before modification is shown below. Figure 1 As shown, the water contact angle on the chip surface is 45°. The image of the contact angle after modification is shown below. Figure 2 As shown, the water contact angle on the chip surface is 110°, but the hydrophobic effect of the chip is uneven, with some areas still having a lower contact angle. To verify the long-term stability of the hydrophobic performance, an aging test was conducted on the modified chip. In the first week of the test, the contact angle on the chip surface had already recovered to its previous state, indicating that the aging effect of the octafluorocyclobutane hydrophobic treatment on the metal surface is poor. Example 2

[0022] The method for hydrophobic modification of the surface of the metal microfluidic chip in this embodiment specifically includes the following steps: (1) Place the surface of the metal microfluidic chip (material is nickel) into the electroforming tank, set the current to 2A and the frequency to 1000Hz, and perform DC electroforming on the surface of the metal microfluidic chip. After the electroforming is completed, clean the surface of the metal microfluidic chip with alcohol and pure water in sequence. (2) Place the surface of the metal microfluidic chip (material is nickel) into the plasma device cavity, close the chamber door, and evacuate the chamber to below 100 mtorr; (3) Set the oxygen flow rate to 200 sccm, the power to 500W, and the processing time to 1 min. Open the oxygen valve and introduce oxygen for plasma treatment to clean the chip surface and form active groups. (4) Evacuate again to below 100 mtorr, set the octafluorocyclobutane gas flow rate to 50 sccm, the power to 500 W, and the processing time to 15 min, and introduce octafluorocyclobutane gas for plasma treatment to form a dense fluorinated hydrophobic coating on the metal surface to complete the hydrophobicity.

[0023] The hydrophobic properties of the microfluidic chip surface modified by the method of this invention were characterized using a contact angle meter. The contact angle images are shown below. Figure 3 As shown, the surface water contact angle is 130° and the chip surface roughness is 600nm, indicating excellent initial hydrophobicity. However, the large surface roughness is not conducive to chip assembly and use. In this embodiment, since only reverse DC current is used, that is, only the metal dissolution process is involved. This process results in a large surface roughness, which is too large to be assembled and used when used as an inkjet printhead chip. Example 3

[0024] The method for hydrophobic modification of the surface of the metal microfluidic chip in this embodiment specifically includes the following steps: (1) Place the surface of the metal microfluidic chip (material is nickel) into the electroforming tank, set the current to 2A, the frequency to 1000Hz, the number of positive pulses to 2, and the number of negative pulses to 3, and perform pulse electroforming on the surface of the metal microfluidic chip. After the electroforming is completed, clean the surface of the metal microfluidic chip with alcohol and pure water in sequence. (2) Place the surface of the metal microfluidic chip (material is nickel) into the plasma device cavity, close the chamber door, and evacuate the chamber to below 100 mtorr; (3) Set the oxygen flow rate to 200 sccm, the power to 500W, and the processing time to 1 min. Open the oxygen valve and introduce oxygen for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. (4) Evacuate again to below 100 mtorr, set the octafluorocyclobutane gas flow rate to 50 sccm, the power to 500 W, and the processing time to 15 min, and introduce octafluorocyclobutane gas for plasma treatment to form a dense fluorinated hydrophobic coating on the metal surface to complete the hydrophobicity.

[0025] Pulse electroforming was employed, alternating between periods of negative and positive current to dissolve and deposit portions of the material. The hydrophobic properties of the microfluidic chip surface modified using this method were characterized using a contact angle meter. Contact angle images are shown below. Figure 4 As shown, the surface water contact angle is 125°, indicating excellent initial hydrophobicity, and the chip surface roughness is 350nm. To verify the long-term stability of the hydrophobic performance, a 12-month aging test was conducted on the modified chip, with the test cycle being once a month. The specific data are shown in Table 1. The data proves that the surface hydrophobic effect of the chip in this embodiment is reliable, the performance is stable, and the aging effect is strong.

[0026] Table 1

[0027] Example 4

[0028] The method for hydrophobic modification of the surface of the metal microfluidic chip in this embodiment specifically includes the following steps: (1) Place the surface of the metal microfluidic chip (material is nickel) into the electroforming tank, set the current to 2A, the frequency to 1000Hz, the number of positive pulses to 3, and the number of negative pulses to 2, and perform pulse electroforming on the surface of the metal microfluidic chip. After the electroforming is completed, clean the surface of the metal microfluidic chip with alcohol and pure water in sequence. (2) Place the surface of the metal microfluidic chip (material is nickel) into the plasma device cavity, close the chamber door, and evacuate the chamber to below 100 mtorr; (3) Set the oxygen flow rate to 200 sccm, the power to 500W, and the processing time to 1 min. Open the oxygen valve and introduce oxygen for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. (4) Evacuate again to below 100 mtorr, set the octafluorocyclobutane gas flow rate to 50 sccm, the power to 500 W, and the processing time to 15 min, and introduce octafluorocyclobutane gas for plasma treatment to form a dense fluorinated hydrophobic coating on the metal surface to complete the hydrophobicity.

[0029] The positive / negative pulse ratio is 3:2, resulting in more deposition than dissolution, lower surface roughness, and little improvement in hydrophobicity. The hydrophobic properties of the microfluidic chip surface modified by the method of this invention were characterized using a contact angle meter. The water contact angle of the chip surface is as follows: Figure 5As shown, the contact angle is 110°, and the surface roughness of the chip is measured to be 450nm. Similar to Example 3, this example verifies the long-term stability of the hydrophobic performance. The modified chip is subjected to a 12-month aging test, with the test cycle being once a month. The test proves that the hydrophobic effect of the chip surface in this example is reliable, the performance is stable, and the aging effect is strong. Example 5

[0030] The method for hydrophobic modification of the surface of the metal microfluidic chip in this embodiment specifically includes the following steps: (1) Place the surface of the metal microfluidic chip (material is nickel) into the electroforming tank, set the current to 2A, the frequency to 1000Hz, the number of positive pulses to 2, and the number of negative pulses to 4, and perform pulse electroforming on the surface of the metal microfluidic chip. After the electroforming is completed, clean the surface of the metal microfluidic chip with alcohol and pure water in sequence. (2) Place the surface of the metal microfluidic chip (material is nickel) into the plasma device cavity, close the chamber door, and evacuate the chamber to below 100 mtorr; (3) Set the oxygen flow rate to 200 sccm, the power to 500W, and the processing time to 1 min. Open the oxygen valve and introduce oxygen for plasma treatment to clean the chip surface (including the inner wall of the flow channel) and form active groups. (4) Evacuate again to below 100 mtorr, set the octafluorocyclobutane gas flow rate to 50 sccm, the power to 500 W, and the processing time to 15 min, and introduce octafluorocyclobutane gas for plasma treatment to form a dense fluorinated hydrophobic coating on the metal surface to complete the hydrophobicity.

[0031] The hydrophobic properties of the microfluidic chip surface modified by the method of this invention were characterized using a contact angle meter. The contact angle images are shown below. Figure 6 As shown, the water contact angle on the chip surface is 130°, indicating that its initial hydrophobic effect is excellent, but the measured surface roughness of the chip is 650nm.

[0032] 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 surface of a metal microfluidic chip, characterized in that, The method first roughens the surface of the metal microfluidic chip by pulse electroforming, and then hydrophobizes the metal surface by octafluorocyclobutane plasma treatment.

2. The method according to claim 1, characterized in that, The method includes the following steps: Step 1: Place the metal microfluidic chip into an electroforming tank, perform pulse electroforming on the surface of the metal microfluidic chip, and then clean the surface of the metal microfluidic chip with alcohol and pure water in sequence after electroforming. Step 2: Place the cleaned metal microfluidic chip into the plasma equipment chamber, evacuate the vacuum, and then pass oxygen through for plasma treatment to clean the metal surface and form active groups. Step 3: Vacuum is drawn again, and octafluorocyclobutane gas is introduced for plasma treatment to form a dense fluorinated hydrophobic coating on the surface of the metal microfluidic chip, thus completing the hydrophobicization process.

3. The method according to claim 2, characterized in that, In step 1, positive and negative pulses are used for pulse electroforming, with a positive-to-negative pulse ratio of 2:3 to 3:

2.

4. The method according to claim 3, characterized in that, In step 1, the current is 2A, the frequency is 1000Hz, the number of negative pulses is 3, and the number of positive pulses is 2.

5. The method according to claim 3, characterized in that, In step 1, the current is 2A, the frequency is 1000Hz, the number of negative pulses is 2, and the number of positive pulses is 3.

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

7. The method according to claim 2, characterized in that, In step 3, the oxygen flow rate is 200 sccm, the power is 500W, and the time is 1 min.

8. The method according to claim 2, characterized in that, In step 4, the octafluorocyclobutane flow rate is 50 sccm, the power is 400 W, and the time is 15 min.

9. The method according to any one of claims 1-8, characterized in that, The metal is any one of nickel, copper, and aluminum.

10. A metal microfluidic chip, which is prepared by the method according to any one of claims 1-8.

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