CN102980930B - Preparation method of electric wettability electrode - Google Patents

Abstract

A method for preparing an electrowetting electrode, the steps are: 1) load conductive silver ink, and use a printer to print a silver electrode on a polyethylene terephthalate (PET) film; 2) after printing, the printed The electrode is sintered at a temperature of 120-200°C, and the time is 3min-30min; 3) UV/ozone treatment: 20-40mW/cm ² , time 3-10min, then double-distilled water cleaning, nitrogen drying; 4) The obtained in step 3 The electrode is placed in a 1-3mM ethanol solution of 1H,1H,2H,2H-perfluorodecanethiol, shaken for 1.5-5 hours, taken out, washed with ethanol, and dried with nitrogen to obtain an electrowetting electrode. The electrowetting electrode prepared by the invention has the characteristics of convenient manufacture, low cost, and long-term maintenance of hydrophilicity, can be used to manufacture electronically controlled valves in microfluidic devices, and has a positive effect on the popularization and use of convenient microfluidic analysis methods.

Description

A kind of preparation method of electrowetting electrode

technical field

The invention relates to the field of analysis and testing, in particular to a method for preparing an electrowetting electrode used in a portable microflow analysis device.

Background technique

Bioanalytical devices based on microfluidics have the advantages of strong specificity and high sensitivity, so they are becoming more and more popular. At present, microfluidics used for clinical disease diagnosis have disadvantages such as complex structure and high price, and are not suitable for mobile use, so they are not suitable for use in farms and other places that require on-site testing. The flow of liquid in microfluidics requires special devices to drive, usually using external pumps (such as micro injection pumps, peristaltic pumps and or pneumatic pumps) to provide power. Due to the use of the pump, the volume of the detection equipment is greatly increased. Therefore, researchers have been engaged in the design and development of pumpless microfluidics.

Using electroosmotic drive is one way to solve the problem. However, the voltage required for electroosmotic flow is very high, so this method has rarely been adopted in portable, low-cost mobile detection devices.

The use of capillary flow in microfluidics has many advantages, the most prominent of which is the ability of liquids to flow without pumps, which is very conducive to the simplification and miniaturization of the system. This is also an important reason why direction finding flow analysis methods can be widely used in detection and diagnosis. Capillary fluid flow in microfluidic devices is influenced by several factors, including the design of the tubing, liquid viscosity, and solid-liquid contact angle. Usually the liquid used in the analysis process is hydrophilic, while the polymer material used to make microfluidic devices is hydrophobic. How to apply surface modification technology to reduce the contact angle between the two is one of the research hotspots in this field. Coating the surface is the most commonly used method to obtain hydrophilicity, for example, coating the surface of polyvinyl chloride with cellulose acetate can increase capillary flow.

In addition, enhancing the hydrophobicity of some areas in the channel can slow down the flow of liquid and increase the incubation (such as the combination of antigen and antibody) time. Currently, increasing channel surface hydrophobicity has been used for sample mixing in microfluidic channels.

Electrowetting on Dielectric (EWOD) is a special phenomenon in which the polarity of a hydrophobic medium is changed when a voltage is applied. PTFE is a kind of hydrophobic medium, when it is electrified, it can change its polarity and convert it into hydrophilic, which shows that the contact angle becomes smaller. The flow of liquid in the capillary is not only affected by its own properties, but also affected by the contact angle of the inner surface of the pipe. So the hydrophobic PTFE gate in the tube can block the flow of liquid in the capillary. If the PTFE is converted to hydrophilic, capillary liquid flow resumes. Therefore, this electrowetting PTFE can be made into an electrically controlled valve without the need for moving parts. Some scholars have shown that the electrowetting phenomenon can be used to make valves for controlling liquids driven by capillary siphons. In the experiment, when the elastic polydimethylsiloxane on the glass was induced to be hydrophilic, the liquid in the capillary could flow. However, this surface modification is not suitable for preparation of commercial materials.

Accordingly, the invention discloses an electro-wetting valve and a preparation method thereof. Compared with elastic polydimethylsiloxane, the method has the characteristics of easy preparation, low cost and high benefit, and can maintain hydrophilicity for a long time.

Contents of the invention

Technical problem to be solved: the purpose of this invention is to prepare an electrowetting electrode suitable for use on a microfluidic device. After the voltage is applied, the polarity of the electrode changes from hydrophobic to hydrophilic, so as to control the flow and resistance of the liquid in the microfluidic device. broken.

Technical solution: A method for preparing an electrowetting electrode, the steps are: 1). Load conductive silver ink, and use a printer to print a silver electrode on a polyethylene terephthalate (PET) film; 2). 10-90 minutes after printing, sinter the printed electrode at a temperature of 120-200°C for 3-30 minutes; 3). Treat with UV/ozone: 20-40mW/cm ² for 3-10 minutes, then wash with double distilled water , dry with nitrogen; 4). Place the electrode obtained in step 3 in an ethanol solution of 1-3mM 1H,1H,2H,2H-perfluorodecanethiol, oscillate for 1.5-5 hours, take it out, wash with ethanol, and dry with nitrogen to obtain Electrowetting electrodes.

Beneficial effects: the existing microfluidic devices usually adopt mechanical valves, which are large in volume, difficult to carry, and inconvenient for on-the-spot detection. The electrowetting electrode prepared by the invention has the characteristics of convenient manufacture, low cost, and long-term maintenance of hydrophilicity, can be used to manufacture electronically controlled valves in microfluidic devices, and has a positive effect on the popularization and use of convenient microfluidic analysis methods.

Description of drawings

Figure 1 is a silver electrode printed on a PET film;

Fig. 2 is a schematic diagram of the electric control valve prepared by using the electrode prepared by the present invention. In the figure, A is the capillary flow in the microfluid, B is the common silver electrode, and C is the electrowetting electrode.

Detailed ways

The performance of the electrowetting electrode prepared by the present invention was evaluated by measuring the contact angle.

Contact angle of the electrode: The contact angle between the electrode and pure water is detected on a goniometer.

Electrode contact angle under electrowetting: The liquid used is 3 μL 1M KCl solution, a 25 μm diameter gold wire is placed in the KCl droplet, and a 4V voltage is applied to measure the relationship between the contact angle and time.

The following specific embodiments do not limit the technical solutions of the present invention in any form, and all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Example 1

Using HP Photosmart C-4580 inkjet printer, remove the ink in the ink cartridge, clean it and dry it. Conductive silver ink ((Sigma-Aldrich Corp., St.Louis, MO, USA) was loaded into the ink cartridge. AutoCAD software was used to design the electrodes and print. Before printing, 70%wt ethanol was sprayed onto PET (3M, St. Paul, MN, USA) film, then washed with double distilled water, and dried with nitrogen. Printed with high quality (1200Dpi), the silver electrode was obtained, as shown in Figure 1.

Example 2

1) After the electrode printed in Example 1 was printed for 10 minutes, the printed electrode was sintered at a temperature of 190°C for 3 minutes;

2) UV/ozone treatment: 20mW/cm ² for 5min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in a 3mM ethanol solution of 1H,1H,2H,2H-perfluorodecanethiol, shake for 4 hours, take it out, and wash it with ethanol. Nitrogen dry.

The obtained electrode had a contact angle of 140° with respect to pure water. The contact angle to KCl is 106°, and after 4V voltage is applied, the contact angle is 28° after 15s, and 22° after 60s.

Example 3

1) After printing the electrode in Example 1 for 15 minutes, sinter the printed electrode at a temperature of 175°C for 5 minutes;

2) UV/ozone treatment: 28mW/cm ² for 6min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in an ethanol solution of 2mM 1H,1H,2H,2H-perfluorodecanethiol, shake for 3 hours, take it out, and wash it with ethanol. Nitrogen dry.

The contact angle of the obtained electrode with respect to pure water was 148°. The contact angle to KCl is 112°, and after 4V voltage is applied, the contact angle is 29° after 15s, and 23° after 60s.

Example 4

1) After the electrode printed in Example 1 was printed for 90 minutes, the printed electrode was sintered at a temperature of 150°C for 30 minutes;

2) UV/ozone treatment: 40mW/cm ² for 10min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in an ethanol solution of 2mM 1H,1H,2H,2H-perfluorodecanethiol, shake for 1.5h, take it out, and wash it with ethanol. Nitrogen dry.

The contact angle of the obtained electrode to pure water was 142°. The contact angle to KCl is 108°, and after 4V voltage is applied, the contact angle is 26° after 15s, and 21° after 60s.

Example 5

1) After the electrode printed in Example 1 was printed for 75 minutes, the printed electrode was sintered at a temperature of 160°C for 20 minutes;

2) UV/ozone treatment: 28mW/cm ² , time 4min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in an ethanol solution of 4mM 1H,1H,2H,2H-perfluorodecanethiol, shake for 2 hours, take it out, and wash it with ethanol. Nitrogen dry.

The contact angle of the obtained electrode with respect to pure water was 139°. The contact angle to KCl is 105°, and 4V voltage is applied. After 15s, the contact angle is 27°, and after 60s, the contact angle is 25°.

Example 6

1) After the electrode printed in Example 1 was printed for 30 minutes, the printed electrode was sintered at a temperature of 120°C for 5 minutes;

2) UV/ozone treatment: 28mW/cm ² for 7min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in a 2.5mM ethanol solution of 1H,1H,2H,2H-perfluorodecanethiol, shake for 5h, take it out, and wash it with ethanol. Nitrogen dry.

The obtained electrode had a contact angle of 145° with respect to pure water. The contact angle to KCl is 111°, and after 4V voltage is applied, the contact angle is 26° after 15s, and 22° after 60s.

Example 7

1) After the electrode printed in Example 1 was printed for 60 minutes, the printed electrode was sintered at a temperature of 130°C for 10 minutes;

2) UV/ozone treatment: 20mW/cm ² , time 3min. Then double-distilled water cleaning, nitrogen drying;

3) Place the electrode in an ethanol solution of 1.5mM 1H,1H,2H,2H-perfluorodecanethiol, shake for 3 hours, take it out, and wash it with ethanol. Nitrogen dry.

The obtained electrode had a contact angle of 150° with respect to pure water. The contact angle to KCl is 115°, and 4V voltage is applied. After 15s, the contact angle is 29°, and after 60s, the contact angle is 23°.

The obtained electrode is used to prepare an electric control valve, which is used in a microfluidic analysis device, and the flow and blocking of the capillary can be realized by changing the voltage. as shown in picture 2. The microfluidic device has two silver electrodes, the left side (upper layer) is a common silver electrode, which is hydrophilic, and the right side (lower layer) is an electrowetting electrode prepared by the present invention. When no voltage is applied, the liquid in the capillary is blocked. When the voltage of 4V is applied, the liquid flow in the microfluidic pipeline is smooth.

Claims (1)

1. a preparation method for electric wetting state electrode, is characterized in that step is: adopt HP Photosmart C-4580 ink-jet printer, remove the ink in print cartridge, clean up, be dried; Conductive silver ink is put into print cartridge; Adopt AutoCAD Software for Design electrode, and print; Before printing, with the ethanol of 70wt%, be sprayed on PET film, then with distilled water, clean nitrogen drying; Adopt 1200Dpi high-quality to print, obtain silver electrode; By after printed electrode 75 min, by printed electrode sintering, 160 ℃ of temperature, time 20min; By UV/ozone, process: 28 mW/cm ², times 4 min; Then distilled water cleans, nitrogen drying; Electrode is placed in to 4 mM 1H, 1H, 2H, the ethanolic solution of 2H-perfluor decyl mercaptan, vibration 2h, takes out, and ethanol cleans, and obtains electric wetting state electrode after nitrogen drying.