Cross response type screen printing paper-based micro-fluidic chip as well as preparation method and application thereof

Abstract

The invention relates to a cross response type silk-screen printing paper-based micro-fluidic chip and a preparation method and application thereof, and the preparation method comprises the following steps: S1, printing a hydrophobic agent on a non-pattern area on the surface of a paper base through a silk-screen printing technology, and cooling to obtain a first modified paper base; or soaking the paper base in the hydrophobic agent solution to obtain a hydrophobic paper base, and then printing the hydrophilic auxiliary agent on the pattern area on the surface of the hydrophobic paper base through the silk-screen printing technology to obtain a second modified paper base; s2, the pattern area of the first modified paper base or the pattern area of the second modified paper base are coated with a series of sensitive indicator printing ink, the sensitive indicator printing ink contains hydroxyethyl cellulose, and the paper-based micro-fluidic chip is obtained after drying. The modified paper base with the hydrophilic array pattern and the hydrophobic non-pattern area is prepared through a one-step method or a two-step method, so that free diffusion of a hydrophilic indicator is avoided, it is guaranteed that the pattern is clear, and the modified paper base can be applied to detection of gas and solution specific substrates.

Description

Technical Field

[0001] This invention relates to the field of detection, specifically to a cross-responsive screen-printed paper-based microfluidic chip, its preparation method, and its application. Background Technology

[0002] Microfluidic analysis is a technology that integrates the functions of an analytical platform onto small analytical instruments or even micron-sized microfluidic chips. Microfluidic chip technology integrates sample processing, separation, and reaction processes related to analysis, offering advantages such as low sample consumption, short sample processing time, and high detection sensitivity and resolution, significantly improving analytical efficiency. As a liquid transport platform at the microscale, it allows for quantitative and stable control of liquid flow, enabling multiple functions such as biochemical analysis, DNA sequencing, protein screening, microdroplet manipulation, cell separation, and even material synthesis. Compared to traditional laboratory analytical techniques, microfluidic chips offer advantages such as small size, portability, rapid response, low sample requirements, and multifunctional integration. Because of these advantages, microfluidic chip technology is an ideal platform for realizing the concept of rapid, real-time on-site detection, possessing significant research and application value.

[0003] There are many technologies for realizing microfluidic chips, among which screen printing involves applying pressure to a screen using a squeegee. Ink can be transferred through the mesh openings in the image areas of the screen, while ink cannot pass through the non-image areas because they are sealed by photosensitive emulsion. This process ultimately forms a pattern on the substrate. Screen printing technology uses flexible screens, requires relatively low pressure during printing, and has relatively low requirements for ink properties, making it widely applicable to various types of substrates.

[0004] Among various printing substrates, paper-based substrates have the advantages of being lightweight, biocompatible, and environmentally friendly. However, the natural hydrophilicity of cellulose and the large number of pores in its fiber structure make it easy for hydrophilic sensitive indicators to penetrate and diffuse freely, resulting in unclear patterns on paper-based microfluidic chips and making it impossible to effectively achieve the detection purpose. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a cross-responsive screen-printed paper-based microfluidic chip, its preparation method, and its application, thereby solving the technical problem of unclear patterns in existing paper-based microfluidic chips.

[0006] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: In a first aspect, the present invention provides a method for preparing a cross-responsive screen-printed paper-based microfluidic chip, comprising the following steps: S1, printing a hydrophobic agent on a non-patterned area of ​​a paper substrate using screen printing technology, and cooling to obtain a first modified paper substrate; or, immersing the paper substrate in a hydrophobic agent solution to obtain a hydrophobic paper substrate, and then printing a hydrophilic additive on a patterned area of ​​the hydrophobic paper substrate surface using screen printing technology to obtain a second modified paper substrate; S2, coating a series of sensitive indicator inks, wherein the sensitive indicator inks contain hydroxyethyl cellulose, and drying to obtain a paper-based microfluidic chip.

[0007] Secondly, the present invention provides a paper-based microfluidic chip prepared by the above-described preparation method.

[0008] Thirdly, the present invention provides an application of the above-mentioned paper-based microfluidic chip in the preparation of paper-based colorimetric sensor array tags.

[0009] Fourthly, the present invention provides an application of the above-mentioned paper-based microfluidic chip in gas cross-response or solution detection.

[0010] Compared with the prior art, the beneficial effects of the present invention include: This invention prepares a modified paper substrate with a hydrophilic array pattern and hydrophobic non-patterned regions using a one-step or two-step method. A series of sensitive indicator inks are then coated onto the patterned regions of the first or second modified paper substrate. The hydrophobic boundary prevents the free diffusion of the hydrophilic indicator, ensuring a clear pattern. Furthermore, the addition of hydroxyethyl cellulose as a binder to the sensitive indicator ink effectively strengthens the bond between the indicator ink and the modified paper substrate. The resulting paper-based microfluidic chip exhibits good consistency, high reliability, and is flexible and foldable. It can achieve clear patterns on the paper substrate surface, enabling applications in the detection of specific substrates in gases and solutions. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the one-step preparation process of the modified paper base in Embodiment 1 of the present invention; Figure 2 This is a physical image of the modified paper base prepared by the one-step method in Example 1 of the present invention; Figure 3 This is a schematic diagram showing the changes in the paper-based microfluidic chip obtained in Embodiment 1 of the present invention when applied as a colorimetric sensor array tag for ammonia detection; wherein, (a) before response, (b) after response, and (c) response "fingerprint spectrum"; Figure 4 This invention illustrates the application of the paper-based microfluidic chip obtained in Example 2 as a colorimetric sensor array tag in protein concentration detection; wherein, (a) before detection, and (b) after detection; Figure 5This is a schematic diagram of the two-step process for preparing the modified paper base in Example 3 of the present invention: Figure 6 This is a physical image of the modified paper base prepared by the two-step method in Example 3 of the present invention; Figure 7 This is a schematic diagram showing the changes in the paper-based microfluidic chip obtained in Embodiment 3 of the present invention when used as a colorimetric sensor array tag for acetic acid detection; wherein, (a) before response, (b) after response, and (c) response "fingerprint spectrum"; Figure 8 This is a schematic diagram showing the changes in the paper-based microfluidic chip obtained in Embodiment 4 of the present invention when used as a colorimetric sensor array tag for the detection of hydrochloric acid; wherein, (a) before detection, (b) after detection. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0013] To address the issue of unclear patterns in paper-based microfluidic chips, the hydrophilic and hydrophobic properties of the paper substrate need to be controlled. This invention uses alkyl ketene dimer (AKD) as a hydrophobic additive. It is insoluble in water but readily soluble in organic solvents such as n-hexane. The AKD molecule contains a reactive four-membered lactone ring and two long hydrocarbon chains (C16-C20). Under heating conditions, the lactone ring opens and undergoes an esterification reaction with the hydroxyl groups in cellulose, thereby fixing it to the fiber surface. The two hydrocarbon chains impart hydrophobicity to the fiber surface.

[0014] In a first aspect, the present invention provides a method for preparing a cross-responsive screen-printed paper-based microfluidic chip, comprising the following steps: S1, using screen printing technology, a hydrophobic agent is printed on the non-patterned area of ​​the paper base surface, and then cooled to obtain the first modified paper base; or, the paper base is immersed in a hydrophobic agent solution to obtain a hydrophobic paper base, and then a hydrophilic additive is printed on the patterned area of ​​the hydrophobic paper base surface using screen printing technology to obtain the second modified paper base. S2, a series of sensitive indicator inks containing hydroxyethyl cellulose are coated on the patterned areas of the first modified paper base or the second modified paper base, and dried to obtain a paper-based microfluidic chip.

[0015] In this invention, the non-patterned areas of the first modified paper substrate are directly printed with a hydrophobic agent, and after drying, hydrophobic areas are formed. The second modified paper substrate is first soaked to form an overall hydrophobic paper substrate, and then a hydrophilic additive is printed on the patterned areas to make the patterned areas hydrophilic. Thus, this invention obtains a modified paper substrate with a hydrophilic array pattern through a one-step or two-step method. Then, a series of sensitive indicator inks are coated on the patterned areas of the first or second modified paper substrate. The hydrophobic boundary avoids the free diffusion of the hydrophilic indicator, ensuring clear patterns. Furthermore, the addition of hydroxyethyl cellulose as a binder to the sensitive indicator ink can effectively enhance the bonding force between the indicator ink and the modified paper substrate. The paper-based microfluidic chip obtained by this invention has good consistency, high reliability, and is flexible and foldable. It can obtain clear patterns on the paper substrate surface, thereby playing a better role in gas cross-response and specific substance detection in solutions.

[0016] Preferably, in step S1, the hydrophobic agent includes an alkyl ketene dimer.

[0017] In a further preferred embodiment, during the preparation of the first modified paper base, the alkyl ketene dimer is melted and then printed.

[0018] More preferably, the hydrophobic agent solution is a solution of alkyl ketene dimer n-hexane with a volume fraction of 0.3-0.5%.

[0019] In this invention, paper-based materials such as filter paper are fully immersed in a hexane solution of AKD. Under normal temperature conditions, the lactone ring in the AKD structure will open and undergo an esterification reaction with the hydroxyl groups in cellulose, thereby fixing it on the fiber surface. The two hydrocarbon chains then impart hydrophobicity to the fiber surface.

[0020] Preferably, in step S1, the paper base includes filter paper.

[0021] Preferably, in step S1, the soaking time is 10 to 30 minutes.

[0022] Preferably, in step S1, the hydrophilic auxiliary includes triethanolamine.

[0023] Triethanolamine itself has a high viscosity, and the present invention uses screen printing technology, which has the advantages of strong compatibility and wide applicability. Therefore, the present invention directly uses analytical grade (AR) triethanolamine without dilution, and the process is simple.

[0024] Preferably, in step S2, the mass fraction of hydroxyethyl cellulose in the sensitive indicator ink is 1 to 2.5%.

[0025] In this invention, the printing effect is controlled by adjusting the concentration of hydroxyethyl cellulose. If the concentration is too high, it will easily clog the screen, and if the concentration is too low, printing cannot be achieved by screen printing.

[0026] Preferably, in step S2, the series of sensitive indicator inks includes sensitive indicator inks of different concentrations and / or different types.

[0027] Preferably, in step S2, the mass fraction of the sensitive indicator in the sensitive indicator ink is 0.4–11 mg / mL. It should be noted that the mass fraction of the sensitive indicator here refers to the concentration of a single type, not the total concentration, and the concentration of each sensitive indicator exists independently; that is, the concentrations of different sensitive indicators can be the same or different.

[0028] Preferably, in step S2, the sensitive indicator in the sensitive indicator ink is a pH indicator. Specifically, synthetic or natural pigments that are sensitive to pH changes can be used as acid-base (pH) indicators.

[0029] Further preferably, the pH indicator includes one or more of the following: bromophenol blue, bromocresol purple, methyl red, cresol red, curcumin, thymol blue, bromothymol blue, phenolphthalein, black carotene, purple sweet potato pigment, curcumin, purple cabbage pigment, radish red pigment, and black rice pigment.

[0030] Preferably, in step S2, the drying temperature is less than 40 °C.

[0031] Secondly, the present invention provides a paper-based microfluidic chip prepared by the above-described preparation method.

[0032] Thirdly, the present invention provides an application of the above-mentioned paper-based microfluidic chip in the preparation of paper-based colorimetric sensor array tags.

[0033] Fourthly, the present invention provides an application of the above-mentioned paper-based microfluidic chip in gas cross-response or solution detection, including one or more of acid and alkaline gases, acid and alkaline solutions, and protein solutions; specifically, for example, ammonia, acetic acid, serum protein, or hydrochloric acid.

[0034] Preferably, the application of the paper-based microfluidic chip provided by the present invention includes the following steps: 1) The paper-based microfluidic chip is photographed or scanned by an image acquisition device to obtain a digital image of the sensor array, and the color information data (Lab value) of each sensor unit in the initial stage is automatically identified and extracted by a color recognition device; 2) The microfluidic paper-based chip is placed in a certain gas atmosphere of the object to be detected. The color of each sensor unit of the sensor array label will change over time. The digital image of the sensor array is acquired in real time from the outside of the food packaging by an image acquisition device, and the color information data (Lab value) of each sensor unit in the storage stage is automatically extracted by a color recognition device; 3) The color information data of each sensor unit in the storage stage is subtracted from the color information data in the initial stage by a processing terminal, and a new difference data is output. The array unit diagram is plotted in the drawing software based on the generated difference data to obtain the "fingerprint spectrum" of the object to be detected.

[0035] The main mechanism of action and advantages of this invention are as follows: 1. The paper-based microfluidic chip of the present invention has good biocompatibility of paper substrate, can be naturally degraded, has no pollution after post-processing, and has a good environmental effect.

[0036] 2. The paper-based microfluidic chip of the present invention obtains a hydrophobic paper substrate with a hydrophilic array pattern on the surface of filter paper through modification. The hydrophobic boundary avoids the free diffusion of hydrophilic indicators, resulting in good consistency of the sensing units and high reliability of the prepared labels, which are also flexible and foldable.

[0037] 3. The paper-based microfluidic chip of the present invention can scan the paper chip (which can reflect the freshness of food in real time) placed inside the product packaging in real time through monitoring and photography or handheld scanning terminal. It realizes the cross-response of the substrate through multimodal color changes. Moreover, the color scanning of the paper chip is carried out on the outside of the transparent packaging, so the real-time freshness information of the food can be obtained without damaging the packaging, which is simple and efficient.

[0038] The present invention will be further described in detail below through specific embodiments.

[0039] Example 1 This embodiment provides a one-step method for preparing a modified paper base, and then coating the modified paper base with a series of pH-sensitive indicator inks to obtain a paper-based microfluidic chip capable of detecting ammonia. Since ammonia causes an increase in pH within the packaging, pH-sensitive acid-base indicators are selected for ammonia concentration detection. In this embodiment, 2% hydroxyethyl cellulose (HEC) is used as the binder, and bromocresol purple (1 mg / mL), methyl red (1 mg / mL), cresol red (0.4 mg / mL), curcumin (1 mg / mL), thymol blue (1 mg / mL), bromothymol blue (1 mg / mL), phenolphthalein (1 mg / mL), black carotene (1 mg / mL), purple sweet potato pigment (3 mg / mL), purple cabbage pigment (3 mg / mL), radish red pigment (3 mg / mL), and black rice pigment (1 mg / mL) are added to the binder to prepare a series of pH-sensitive indicator inks.

[0040] This embodiment describes a method for fabricating a cross-responsive screen-printed paper-based microfluidic chip, which specifically includes the following steps: S1. Place an appropriate amount of AKD in a beaker and heat it to melt it. Use screen printing to print the molten AKD onto the surface of filter paper and dry it with a hair dryer to obtain modified filter paper. Take it out and put it in a sealed bag for storage at low temperature for later use.

[0041] S2, the prepared series of pH-sensitive indicator inks are transferred in 0.5 mL onto the corresponding pattern array area of ​​the modified filter paper using a microsampler. After drying the solvent at 40 °C, a sensing unit is formed, thus obtaining an array-type paper-based microfluidic chip, which is stored in the dark for later use.

[0042] A schematic diagram of the one-step method for preparing modified paper base according to the present invention is shown below. Figure 1 As shown in the figure, the dot array area is the hydrophilic region, and the gray area is the hydrophobic region formed by AKD. This method uses AKD to print the area on the paper chip surface excluding the circular holes, thus forming the hydrophobic region. Since the paper fibers themselves are hydrophilic, the circular array does not require further hydrophilic treatment; the indicator can be applied directly. Therefore, the one-step preparation method is relatively simple and saves materials and time. A physical image of the resulting modified paper base is shown below. Figure 2 As shown, the pattern is uniform and the edges are clear; the actual image of the array-type paper-based microfluidic chip coated with pH-sensitive indicator ink on the modified paper substrate is shown below. Figure 3 As shown in (a), the color is also uniform and clear.

[0043] The paper-based microfluidic chip obtained in Example 1 was used as a colorimetric sensor array tag for ammonia detection. The ammonia sensing effect was as follows: Figure 3 As shown, Figure 3(b) is a physical image showing the color change after being placed in an ammonia atmosphere. The color change from (a) to (b) shows that different indicators in the sensor array produce different color-changing reactions to ammonia. The fingerprint spectrum (c) of the color-changing reaction is obtained by processing the image (b) with the instrument, thereby realizing the cross-response of ammonia concentration. The ammonia concentration can be obtained through the color data in the image (c). This shows that the paper-based microfluidic chip obtained by the present invention has a responsive effect to volatile alkaline gases.

[0044] Example 2 This embodiment describes a method for fabricating a cross-responsive screen-printed paper-based microfluidic chip, which specifically includes the following steps: S1 is the same as step S1 in Example 1.

[0045] S2, using 2% hydroxyethyl cellulose (HEC) as a binder and bromophenol blue, which is sensitive to protein concentration, as an indicator, a series of protein-sensitive indicator inks with different concentrations were prepared at concentrations of 1 mg / ml, 3 mg / ml, 5 mg / ml, 7 mg / ml, 9 mg / ml, and 11 mg / ml. The prepared protein-sensitive indicator inks of different concentrations were transferred in 0.5 mL onto the corresponding pattern array area of ​​the modified filter paper using a microsampler. After drying the solvent at 40 °C, a sensing unit was formed, thus obtaining a flower-shaped microfluidic paper-based chip, which was stored in the dark for later use.

[0046] Example 2 shows the sensing effect on protein freshness as follows: Figure 4 As shown, different concentrations of indicators in the flower-shaped sensor array produced different color-changing reactions to bovine serum albumin. The instrument obtained the Lab value of the color-changing reaction and plotted a standard linear curve to realize the linear correlation between the Lab value and the protein concentration, thereby enabling the detection of proteins of unknown concentration.

[0047] Example 3 This embodiment describes a method for fabricating a cross-responsive screen-printed paper-based microfluidic chip, which specifically includes the following steps: S1. The filter paper was immersed in a hexane solution containing 0.3% AKD for 20 min and dried to obtain a hydrophobic filter paper with overall hydrophobic modification. Triethanolamine was printed on the hydrophobic filter paper using a pre-designed screen printing plate and dried at 40 °C to obtain a modified filter paper with hydrophilic areas and hydrophobic periphery. S2, using 2% hydroxyethyl cellulose (HEC) as a binder, selected pH-responsive indicators sensitive to volatile acidic gases in food: bromocresol purple (1 mg / mL), methyl red (1 mg / mL), cresol red (0.4 mg / mL), curcumin (1 mg / mL), thymol blue (1 mg / mL), bromothymol blue (1 mg / mL), phenolphthalein (1 mg / mL), black carotene (1 mg / mL), purple sweet potato pigment (3 mg / mL), purple cabbage pigment (3 mg / mL), radish red pigment (3 mg / mL), black rice pigment (1 mg / mL), etc., to prepare a series of pH-sensitive indicator inks; The prepared series of pH-sensitive indicator inks were transferred in 0.5 mL onto the corresponding array area of ​​the modified filter paper using a microsampler. After drying the solvent at 40 °C, an array-type paper-based microfluidic chip was obtained and stored in the dark for later use.

[0048] See Figure 5 and Figure 6 In this invention, a two-step method for preparing modified filter paper involves immersing the filter paper and other paper-based materials in a hexane solution of AKD. At room temperature, the lactone ring in the AKD structure opens and undergoes esterification with the hydroxyl groups in cellulose, thus fixing it to the fiber surface. The two hydrocarbon chains impart hydrophobicity to the fiber surface. Triethanolamine is then screen-printed onto the overall hydrophobically modified filter paper to form an array of patterned areas, resulting in a modified filter paper with hydrophilic patterned areas and hydrophobic non-patterned areas. In the diagram, the dark gray dot array area represents the hydrophilic area, and the lighter gray area represents the hydrophobic area. Hydroxyethyl cellulose (HEC) aqueous solution is then used as a binder, and various pH indicators are selected to prepare pH-sensitive indicator inks. These pH-sensitive indicator inks are transferred to the corresponding patterned areas of the modified filter paper, and after drying the solvent, a sensing unit is formed, resulting in a paper-based microfluidic chip prepared using the two-step method, with clearly defined patterned areas.

[0049] Test Example 3: Sensing effect on acetic acid. The paper chip was placed in a 98% acetic acid atmosphere and sealed for 10 minutes. The paper chip was then removed and a color test was performed. The results are as follows: Figure 7 As shown, the color changes before and after detection from (a) to (b), indicating that different indicators in the sensor array produce different color-changing reactions to the volatile acidic gas - acetic acid gas. The fingerprint spectrum of the color-changing reaction (c) is obtained by the instrument, thereby realizing the cross-response of acetic acid concentration.

[0050] Example 4 This embodiment describes a method for fabricating a cross-responsive screen-printed paper-based microfluidic chip, which specifically includes the following steps: S1, the preparation of the modified filter paper is the same as step S1 in Example 3; S2, using 2% hydroxyethyl cellulose (HEC) as a binder, and selecting bromothymol blue, a chemically responsive indicator sensitive to the pH of the solution, a series of sensitive indicator inks were prepared at concentrations of 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, and 4 mg / mL. The prepared series of pH-sensitive indicator inks were transferred in 0.5 mL onto the corresponding array area of ​​the modified filter paper using a microsampler. After drying the solvent at 40 °C, the flower-shaped paper-based microfluidic chip was obtained and stored in the dark for later use.

[0051] Example 4 shows the sensing effect on 5% hydrochloric acid solution as follows: Figure 8 As shown, hydrochloric acid is added to the sample area. Different concentrations of indicators in the flower-shaped sensor array produce different color-changing reactions to the hydrochloric acid. The instrument obtains the Lab value of the color-changing reaction and plots a standard linear curve to realize the linear correlation between the Lab value and the hydrochloric acid concentration. The instrument obtains the Lab value of the color-changing reaction, thereby realizing the detection of the hydrochloric acid concentration in the solution.

[0052] Comparative Example 1 Compared with Example 1, the only difference is that hydroxyethyl cellulose is replaced with carboxymethyl cellulose (CMC), while the other steps and conditions are the same as in Example 1.

[0053] The results showed that the indicator using CMC as a binder did not respond as clearly to color as hydroxyethyl cellulose. This was mainly because the CMC solution itself was alkaline, which affected the pH accuracy of the analyte.

[0054] Comparative Example 2 Compared with Example 3, the only difference is that the concentration of the AKD solution used to soak the paper base is 0.1%, while the other steps and conditions are the same as in Example 3.

[0055] The results showed that when the AKD solution concentration was 0.1%, the contact angle of the formed hydrophobic portion with pure water was only 83.8°, which was insufficient to meet the application requirements. However, the 0.3% AKD solution used in Example 3 achieved a contact angle of 113.3° with pure water, demonstrating a better hydrophobic effect.

[0056] Comparative Example 3 Compared with Example 3, the only difference is that the concentration of the AKD solution used to soak the paper base is 0.5%, while the other steps and conditions are the same as in Example 3.

[0057] The results showed that when the AKD solution concentration was 0.5%, the contact angle of the formed hydrophobic portion with pure water was 118.6°, indicating a good hydrophobic effect. However, the 0.3% AKD solution used in Example 3 resulted in a contact angle of 113.3° with pure water. These results indicate that further increasing the ADK solution concentration beyond 0.3% did not significantly improve the hydrophobic effect.

[0058] Comparative Example 4 Compared with Example 3, the only difference is that the paper base is soaked in AKD solution for 1 minute, while the other steps and conditions are the same as in Example 3.

[0059] The results showed that when the soaking time was 1 min, the contact angle of the formed hydrophobic part with pure water was 92.4°, and its hydrophobic effect was not ideal.

[0060] Comparative Example 5 Compared with Example 3, the only difference is that the paper base is soaked in AKD solution for 30 min, while the other steps and conditions are the same as in Example 3.

[0061] The results showed that when the soaking time was 30 min, the contact angle of the formed hydrophobic portion with pure water was 104°. In contrast, the hydrophobic portion formed in Example 3 achieved a contact angle of 113.3° with pure water, demonstrating a significant hydrophobic effect. The results indicate that further increasing the soaking time does not improve the hydrophobic effect of the paper base.

[0062] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for fabricating a cross-responsive screen-printed paper-based microfluidic chip, characterized in that, Includes the following steps: S1, using screen printing technology, a hydrophobic agent is printed on the non-patterned area of ​​the paper base surface, and then cooled to obtain the first modified paper base; Alternatively, the paper base is soaked in a hydrophobic agent solution to obtain a hydrophobic paper base, and then a hydrophilic additive is printed on the patterned area on the surface of the hydrophobic paper base using screen printing technology to obtain a second modified paper base; S2, a series of sensitive indicator inks are coated on the patterned areas of the first modified paper base or the second modified paper base respectively. The sensitive indicator inks contain hydroxyethyl cellulose. After drying, a paper-based microfluidic chip is obtained.

2. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S1, the hydrophobic agent includes an alkyl ketene dimer; In the preparation process of the first modified paper base, the alkyl ketene dimer is melted and then printed; The hydrophobic agent solution is a solution of alkyl ketene dimer n-hexane with a volume fraction of 0.3-0.5%.

3. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S1, the paper base includes filter paper; the soaking time is 10 to 30 minutes.

4. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S1, the hydrophilic auxiliary agent includes triethanolamine.

5. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S2, the mass fraction of hydroxyethyl cellulose in the sensitive indicator ink is 1-2.5%.

6. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S2, the series of sensitive indicator inks includes sensitive indicator inks of different concentrations and / or different types.

7. The method for fabricating a cross-responsive screen-printed paper-based microfluidic chip according to claim 1, characterized in that, In step S2, the mass fraction of the sensitive indicator in the sensitive indicator ink is 0.4–11 mg / mL; the sensitive indicator in the sensitive indicator ink is a pH indicator.

8. A paper-based microfluidic chip prepared by the preparation method according to any one of claims 1-7.

9. The application of the paper-based microfluidic chip as described in claim 8 in the preparation of paper-based colorimetric sensor array tags.

10. The application of the paper-based microfluidic chip as described in claim 8 in the cross-response of gases or the detection of solutions.

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