In-situ measurement method, device and system for charge density at the interface of immiscible liquids

Abstract

A method, device, and system for in-situ measurement of charge density at an immiscible liquid interface. The method comprises: acquiring multiple sets of data for parallel flow channels in a microfluidic chip, including a first liquid pressure drop and a first liquid potential drop at both ends of the parallel flow channels, wherein a first liquid and a second immiscible liquid flow side by side in the parallel flow channels; performing curve fitting with the first liquid pressure drop as the abscissa and the first liquid potential drop as the ordinate to obtain a slope α; and obtaining the charge density of the liquid-liquid interface according to the formula #imgabs0#, where the liquid-liquid interface is the interface between the first liquid and the second liquid; Q s‑l,eff The method represents the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel. The first liquid potential drop is obtained by in-situ measurement of the first liquid by electrodes located in the parallel flow channel, which simplifies the requirements for the measuring device and improves the accuracy of the immiscible liquid interface charge density measurement. It is suitable for charge density measurement in various numerical ranges and is easy to promote and apply.

Description

Technical Field

[0001] This article relates to the field of fluid interface measurement, especially to an in-situ measurement method, device and system for the charge density of an immiscible liquid interface. Background Art

[0002] The charge density at the liquid-liquid interface is generally proportional to the interfacial zeta potential and is a key parameter for measuring the stability of colloidal dispersions. It is widely used in industrial and research fields such as geology, petroleum, and chemical engineering. In particular, in unconventional oil and gas production, ion flooding is a method of increasing reservoir recovery using a displacement fluid containing chemical ions. The electrostatic interaction between the displacement fluid and the oil droplets and the double electric layer of the rock has a significant impact on the displacement process. In non-contact geological exploration, the flow potential method based on interfacial charge is an important method for obtaining the distribution of groundwater and mineral resources. In food, pharmaceutical, and chemical production, the charge density at the liquid-liquid interface is crucial for controlling the stability of emulsions and suspensions. Therefore, a clear understanding of the charge density at the liquid-liquid interface is crucial for promoting petroleum exploration and development, geological exploration, and chemical production.

[0003] Currently, there are methods for measuring the charge density at the liquid-liquid interface of immiscible liquids, but they have certain limitations. First, they are based on flow channels with polymer coatings on the inner wall surface to prevent the solid-liquid interface between the inner wall material and the liquid from interfering with the liquid-liquid interface within the flow channel. This requires the flow channel to be polymer-coated, making the measurement method cumbersome and complex. Second, in existing measurement methods, the streaming potential is measured by electrodes located in the liquid storage container, which does not represent the actual streaming potential of the liquid in the flow channel, resulting in low accuracy of the obtained charge density. In addition, there are strict requirements on the size of the pipeline connecting the flow channel and the liquid storage tank, which increases the measurement difficulty. Third, existing measurement methods are based on the principle of surface conductivity and are suitable for measuring large charge densities and narrow flow channel sizes. The restrictions on the measurement device are relatively strict, making it difficult to promote and apply. Summary of the Invention

[0004] The present application provides a method, device and system for in-situ measurement of charge density at the interface of immiscible liquids, which simplifies the requirements for the measurement device, improves the accuracy of the measurement of charge density at the interface of immiscible liquids, has a wide range of applications, and is easy to promote and apply.

[0005] In one aspect, an embodiment of the present application provides an in-situ measurement method for charge density at an immiscible liquid interface, comprising:

[0006] Acquiring multiple sets of data for parallel flow channels in a microfluidic chip, wherein each set of data includes a first liquid pressure drop and a first liquid potential drop across two ends of the parallel flow channel, wherein a first liquid and a second liquid immiscible in each other flow side by side in the parallel flow channel;

[0007] Based on the multiple sets of data, curve fitting is performed with the first liquid pressure drop as the abscissa and the first liquid potential drop as the ordinate to obtain a slope α of the fitted curve;

[0008] According to the formula Obtain the charge density at the liquid-liquid interface;

[0009] Wherein, the liquid-liquid interface is the interface between the first liquid and the second liquid in the parallel flow channel; Q l-l represents the charge density, μ represents the dynamic viscosity of the first liquid, σ0 represents the bulk conductivity of the first liquid, H represents the total height of the parallel flow channel, β represents the geometric parameters of the parallel flow channel, β = 6W / H 2 , W represents the total width of the parallel flow channels, H< <W;Q s-l,eff represents the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel; the first liquid potential drop is obtained by in-situ measurement of the first liquid by a microelectrode located in the parallel flow channel, γ represents the percentage of the pre-obtained first liquid pressure drop to the pressure drop of the microfluidic chip, and the length of the parallel flow channel is less than a preset length threshold.

[0010] On the other hand, an embodiment of the present application further provides an in-situ measurement device for charge density at an immiscible liquid interface, comprising a processor and a memory:

[0011] The memory is used to store an in-situ measurement program of the charge density at the interface of an immiscible liquid;

[0012] The processor is used to read the immiscible liquid interface charge density in-situ measurement program and perform the immiscible liquid interface charge density in-situ measurement method as described in the above embodiment.

[0013] On the other hand, an embodiment of the present application further provides an in-situ measurement system for charge density at an immiscible liquid interface, comprising: a microfluidic chip, the in-situ measurement device for charge density at an immiscible liquid interface as described in the above embodiment, and a first liquid and a second liquid that are immiscible with each other;

[0014] The microfluidic chip includes parallel flow channels and microelectrodes located in the parallel flow channels, wherein the length of the parallel flow channels is less than a preset length threshold;

[0015] The parallel flow channel is used for the parallel flow of the first liquid and the second liquid. The total height of the parallel flow channel is H, the total width of the parallel flow channel is W, and the geometric parameter of the parallel flow channel is β=6W / H 2 , H《W;

[0016] The microelectrode is used to perform in-situ measurement of the first liquid in the parallel flow channel to obtain the first liquid potential drop and send it to the immiscible liquid interface charge density in-situ measurement device, wherein the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel is Q s-l,eff ;

[0017] The in-situ measurement device for the charge density at the interface of the immiscible liquid is used to obtain multiple sets of data of the parallel flow channels, each set of data including the first liquid pressure drop and the first liquid potential drop at both ends of the parallel flow channels; and based on the multiple sets of data, a curve fitting is performed with the first liquid pressure drop as the horizontal coordinate and the first liquid potential drop as the vertical coordinate to obtain the slope α of the fitted curve; and according to the formula Obtaining the charge density of the liquid-liquid interface; wherein the liquid-liquid interface is the interface between the first liquid and the second liquid; Q l-l represents the charge density, μ represents the dynamic viscosity of the first liquid, σ0 represents the bulk conductivity of the first liquid, and γ represents the percentage of the pre-obtained pressure drop of the first liquid to the pressure drop of the microfluidic chip.

[0018] Compared with related technologies, the in-situ measurement method, device and system of the charge density at the interface of immiscible liquids in the embodiments of the present application use microelectrodes located in the parallel flow channels of the microfluidic chip to measure the electric potential, which can represent the actual first liquid potential drop, improve the accuracy of the measurement of the charge density at the interface of immiscible liquids, and are suitable for the measurement of the charge density at the interface of immiscible liquids in various numerical ranges. There are no restrictions on the inner wall material and the width of the flow channel, and the restrictions on the inner wall material of the parallel flow channel, the width of the parallel flow channel and the length of the fluid pipeline outside the microfluidic chip are removed, which simplifies the requirements for the measurement device and is easy to promote and apply.

[0019] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. Other advantages of the present application can be realized and obtained by the solutions described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0021] Figure 1 This is a flow chart of the in-situ measurement method of the charge density at the interface of immiscible liquids according to an embodiment of the present application;

[0022] Figure 2 This is an enlarged top view of the microfluidic chip according to an embodiment of the present application;

[0023] Figure 3 Schematic diagram of an in-situ measurement device for charge density at an immiscible liquid interface according to an embodiment of the present application;

[0024] Figure 4 Schematic diagram of an in-situ measurement system for charge density at an immiscible liquid interface according to an embodiment of the present application;

[0025] Figure 5 Schematic diagram of an in-situ measurement system for charge density at an immiscible liquid interface according to a specific example of the present application;

[0026] Figure 6 This is an enlarged top view of the parallel flow channels of a specific example of this application. DETAILED DESCRIPTION

[0027] This application describes multiple embodiments, but this description is exemplary rather than restrictive, and it will be apparent to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described herein. Although many possible feature combinations are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0028] This application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features, and elements disclosed in this application may also be combined with any conventional features or elements to form a unique inventive solution defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other inventive solutions to form another unique inventive solution defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the appended claims and their equivalents, the embodiments are not subject to other limitations. In addition, various modifications and changes may be made within the scope of protection of the appended claims.

[0029] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps in the specific order described. As will be understood by those skilled in the art, other orders of steps are also possible. Therefore, the specific order of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to performing their steps in the order written, and those skilled in the art can readily understand that these orders can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0030] The present invention provides an in-situ measurement method for the charge density at the interface of an immiscible liquid, including steps S1000-S3000. Figure 1 As shown,

[0031] S1000: Acquire multiple sets of data for parallel flow channels in a microfluidic chip, wherein each set of data includes a first liquid pressure drop and a first liquid potential drop at both ends of the parallel flow channel, wherein a first liquid and a second liquid that are immiscible with each other flow side by side in the parallel flow channel;

[0032] S2000: Based on the multiple sets of data, curve fitting is performed with the first liquid pressure drop as the abscissa and the first liquid potential drop as the ordinate to obtain a slope α of the fitted curve;

[0033] S3000: According to the formula Obtain the charge density at the liquid-liquid interface.

[0034] In this embodiment, the liquid-liquid interface is the interface between the first liquid and the second liquid in the parallel flow channel; Q l-l Represents the charge density in C·m -2 ; μ represents the dynamic viscosity of the first liquid, in Pa·s; σ0 represents the bulk conductivity of the first liquid, in S·m -1 ; H represents the total height of the parallel flow channel, in meters; β represents the geometric parameters of the parallel flow channel, β = 6W / H 2 , W represents the total width of the parallel flow channel, the unit is m, H<<W; Q s-l,eff represents the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel, in C·m -2 ; The first liquid potential drop is obtained by in-situ measurement of the first liquid by a microelectrode located in the parallel flow channel, γ represents the percentage of the pre-obtained first liquid pressure drop to the pressure drop of the microfluidic chip, and the length of the parallel flow channel is less than a preset length threshold.

[0035] In this embodiment, the first liquid and the second liquid are immiscible with each other, which means that under the experimental temperature T, the solubility between the two liquids is less than 0.01g / 100g. In the parallel flow channel, the first liquid and the second liquid flow side by side, and the contact interface between the two liquids is the liquid-liquid interface.

[0036] In this embodiment, there is no limitation on the inner wall material of the parallel flow channel. s-l,eff It is the solid-liquid interface property determined by the first liquid and the inner wall material.

[0037] In this embodiment, the first liquid and the second liquid can be sodium chloride aqueous solution and n-decane, potassium chloride aqueous solution and n-decane, sodium chloride aqueous solution and hexane, sodium chloride aqueous solution and chloroform, potassium chloride aqueous solution and diesel, respectively. The above examples are illustrative descriptions and are not intended to limit the present application, and will not be described in detail herein.

[0038] In this embodiment, the total height H of the parallel flow channels is much smaller than the total width W of the parallel flow channels, that is, the parallel flow channels are flat, and the total height H of the parallel flow channels is much smaller than the inner diameter D of the fluid pipeline outside the microfluidic chip, so that the actual pressure generated by the pressure generating device is the same as the pressure drop applied by the pressure generating device to the two ends of the microfluidic chip. γ represents the percentage of the parallel flow channels in the pressure drop at both ends of the microfluidic chip. γ can be calculated using a numerical simulation method before performing in situ measurement of the charge density at the interface of immiscible liquids.

[0039] In this embodiment, the microfluidic chip includes an upstream separation channel, the parallel channel and the downstream separation channel connected in sequence; wherein, the upstream separation channel includes an upstream first channel, a first separation layer and an upstream second channel, and the first separation layer is used to separate the upstream first channel and the upstream second channel; the downstream separation channel includes a downstream first channel, a second separation layer and a downstream second channel, and the second separation layer is used to separate the downstream first channel and the downstream second channel; the parallel channel includes a first parallel channel and a second parallel channel, and there is no separation layer between the first parallel channel and the second parallel channel, and the microelectrode is located in the first parallel channel; the upstream first channel, the first parallel channel, the first parallel channel The flow channel and the downstream flow channel are connected in sequence, and are used for the first liquid to flow from the upstream flow channel inlet H1 to the downstream flow channel outlet H2; the upstream two flow channels, the second parallel flow channels and the downstream two flow channels are connected in sequence, and are used for the second liquid to flow from the upstream two flow channel inlet H3 to the downstream two flow channel outlet H4; the first separation layer has a pointed shape at one end facing the parallel flow channel, and the second separation layer has a convex surface structure at one end facing the parallel flow channel; a microelectrode is included upstream and downstream of the first parallel flow channel respectively, one end of the microelectrode is located in the first parallel flow channel, and the other end of the microelectrode is located outside the parallel flow channel, and the length of the parallel flow channel is less than a preset length threshold, such as Figure 2 An enlarged top view of the microfluidic chip is shown.

[0040] In this embodiment, the use of a microfluidic chip can ensure a sufficiently large liquid-liquid interfacial tension, ensuring that the first liquid and the second liquid maintain a stable liquid-liquid interface shape during the flow process, and the length of the parallel flow channel is less than the preset length threshold to further ensure the stability of the liquid-liquid interface shape; the first separation layer has a pointed shape at one end facing the parallel flow channel to ensure that the first liquid and the second liquid stably converge in the parallel flow channel at the leading edge of the liquid-liquid interface, and the second separation layer has a convex surface structure at one end facing the parallel flow channel to ensure that the liquid-liquid interface is stably pinned at the trailing edge.

[0041] The in-situ measurement method of the charge density at the interface of immiscible liquids of this embodiment uses microelectrodes located in the parallel flow channels of the microfluidic chip to measure the potential, which can represent the actual first liquid potential drop, improves the accuracy of the measurement of the charge density at the interface of immiscible liquids, and is applicable to the measurement of the charge density at the interface of immiscible liquids in various numerical ranges. There are no restrictions on the inner wall material and flow channel width of the flow channel, and the restrictions on the inner wall material of the parallel flow channel, the parallel flow channel width, and the length of the fluid pipeline outside the microfluidic chip are removed. This simplifies the requirements for the measurement device and facilitates popularization and application.

[0042] In an exemplary embodiment, step S1000 may include steps S1100-S1200:

[0043] S1100: At time t, the first predetermined time interval T1 is divided J times j Obtain the pressure difference P applied by the pressure generating device to the microfluidic chip j , γP j As the first liquid pressure drop, wherein the pressure difference P obtained each time j Different, j = 1, 2, ..., J;

[0044] S1200: At time t j +T2, obtain the first liquid potential drop at both ends of the parallel flow channel, wherein T2 is the second predetermined time interval, T2 <T1。

[0045] In this embodiment, the pressure generating device can be a pressure pump to achieve gas pressure modulation. The modulated pressure generated by the pressure generating device is the pressure difference P applied to both ends of the microfluidic chip. j , thereby realizing pressure driving for the first liquid and the second liquid. During the measurement process, it is necessary to avoid gas dissolving into the first liquid and the second liquid, and to avoid negative impact of dissolved gas in the first liquid and the second liquid on the measurement results. Therefore, the first liquid and the second liquid should be selected according to their properties. For example, when the first liquid and the second liquid can be sodium chloride aqueous solution and n-decane respectively, nitrogen that is insoluble in sodium chloride aqueous solution and n-decane can be selected as the pressure driving gas.

[0046] In this embodiment, the first predetermined time interval T1 and the second predetermined time interval T2 can be reasonably set as long as the two sets of data obtained twice adjacently do not affect each other, thereby ensuring the accuracy of the entire measurement process and further ensuring the accuracy of the measurement results, that is, the charge density of the liquid-liquid interface.

[0047] In an exemplary embodiment, step S1200 may include step S1210:

[0048] S1210: Obtain the potential difference of the first liquid at both ends of the parallel flow channel as the first liquid potential drop, wherein the potential upstream of the parallel flow channel is measured by an upstream microelectrode located in the first liquid, and the potential downstream of the parallel flow channel is measured by a downstream microelectrode located in the first liquid.

[0049] In an exemplary embodiment, the upstream microelectrode and the downstream microelectrode may both be connected to an ammeter, and the first liquid potential drop may be obtained by combining the current measured by the ammeter with the bulk conductivity σ0 of the first liquid.

[0050] In another exemplary embodiment, a potentiometer or the like may be selected and connected to the upstream electrode and the downstream electrode to achieve measurement of the potential drop of the first liquid.

[0051] In an exemplary embodiment, step S3000 may include steps S3100-S3200:

[0052] S3100: According to the formula Calculate the Debye length λ, where λ is the approximate thickness of the double layer at the liquid-liquid interface, ε represents the absolute dielectric constant of the first liquid, and k B represents the Boltzmann constant, T represents the experimental temperature, e represents the elementary charge, represents the molar concentration of the i-th electrolyte ion in the first liquid, z i represents the charge number of the i-th electrolyte ion in the first liquid;

[0053] S3200: Calculate Q based on λ s-l,eff , where Q s-l,eff The calculation formula is Q s-l representing the charge density of the solid-liquid interface between the first liquid and the inner wall material, determined by the type of the first liquid and the type of the inner wall material; is the charged reduced geometric parameter of the solid-liquid interface, which is a dimensionless constant and is calculated as follows:

[0054] In an exemplary embodiment, the liquid-liquid interface is flat, and the interface floating amount of the liquid-liquid interface is less than or equal to 0.1W.

[0055] The present application also provides an in-situ measurement device for the charge density at the interface of an immiscible liquid. Figure 3 As shown, including a processor and a memory,

[0056] The memory is used to store an in-situ measurement program of the charge density at the interface of an immiscible liquid;

[0057] The processor is used to read the immiscible liquid interface charge density in-situ measurement program and perform the immiscible liquid interface charge density in-situ measurement method as described in the above embodiment.

[0058] The present application also provides an in-situ measurement system for the charge density at the interface of an immiscible liquid. Figure 4 As shown, it includes a microfluidic chip, an in-situ measurement device for charge density at an immiscible liquid interface as described in the above embodiment, and a first liquid and a second liquid that are immiscible with each other;

[0059] The microfluidic chip includes parallel flow channels and microelectrodes located in the parallel flow channels, wherein the length of the parallel flow channels is less than a preset length threshold;

[0060] The parallel flow channel is used for the parallel flow of the first liquid and the second liquid. The total height of the parallel flow channel is H, the total width of the parallel flow channel is W, and the geometric parameter of the parallel flow channel is β=6W / H 2 , H<<W;

[0061] The microelectrode is used to perform in-situ measurement of the first liquid in the parallel flow channel to obtain the first liquid potential drop and send it to the immiscible liquid interface charge density in-situ measurement device, wherein the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel is Q s-l,eff ;

[0062] The in-situ measurement device for the charge density at the interface of the immiscible liquid is used to obtain multiple sets of data of the parallel flow channels, each set of data including the first liquid pressure drop and the first liquid potential drop at both ends of the parallel flow channels; and based on the multiple sets of data, a curve fitting is performed with the first liquid pressure drop as the horizontal coordinate and the first liquid potential drop as the vertical coordinate to obtain the slope α of the fitted curve; and according to the formula Obtaining the charge density of the liquid-liquid interface; wherein the liquid-liquid interface is the interface between the first liquid and the second liquid; Q l-l represents the charge density, μ represents the dynamic viscosity of the first liquid, σ0 represents the bulk conductivity of the first liquid, and γ represents the percentage of the pre-obtained pressure drop of the first liquid to the pressure drop of the microfluidic chip.

[0063] In this embodiment, the microelectrode includes an upstream microelectrode and a downstream microelectrode, the upstream microelectrode is located at the upstream end of the parallel flow channel, and the downstream microelectrode is located at the downstream end of the parallel flow channel. One end of the upstream microelectrode and the downstream microelectrode is located in the parallel flow channel, and the other end of the upstream microelectrode and the downstream microelectrode is connected to the in-situ measurement device for the charge density at the interface of the immiscible liquid.

[0064] In an exemplary embodiment, the in-situ measurement system for charge density at the interface of immiscible liquids may further include a pressure generating device and an ammeter;

[0065] The pressure generating device is used to generate a pressure at a first predetermined time interval T1 J times at time t j Apply a pressure difference P to the microfluidic chip j , wherein the pressure difference P obtained each time j Different, j=1,2,……,J, and γP j sending the first liquid pressure drop to the immiscible liquid interface charge density in-situ measurement device;

[0066] The ammeter is used to j+T2 acquiring the potential difference at both ends of the parallel flow channel measured by the microelectrode as the first liquid potential drop, and sending it to the immiscible liquid interface charge density in-situ measurement device;

[0067] Wherein, T2 is the second predetermined time interval, T2 <T1。

[0068] In this embodiment, the ammeter may be connected to the electrodes, and the ammeter and the electrodes may together constitute a potential measurement system in the in-situ measurement system for charge density at the interface of an immiscible liquid.

[0069] In an exemplary embodiment, the microfluidic chip further comprises an upstream separation flow channel and a downstream separation flow channel;

[0070] The upstream separation channel comprises an upstream first channel, a first separation layer and an upstream second channel, wherein the first separation layer is used to separate the upstream first channel from the upstream second channel;

[0071] The downstream separation channel comprises a first downstream channel, a second separation layer and a second downstream channel, wherein the second separation layer is used to separate the first downstream channel from the second downstream channel;

[0072] The parallel flow channel includes a first parallel flow channel and a second parallel flow channel, and the microelectrode is located in the first parallel flow channel;

[0073] The upstream flow channel, the first parallel flow channel and the downstream flow channel are connected in sequence, so that the first liquid flows from the inlet of the upstream flow channel to the outlet of the downstream flow channel;

[0074] The upstream second flow channel, the second parallel flow channel and the downstream second flow channel are connected in sequence, so that the second liquid flows from the inlet of the upstream second flow channel to the outlet of the downstream second flow channel;

[0075] One end of the first separation layer facing the parallel flow channel is in a pointed shape, and one end of the second separation layer facing the parallel flow channel is in a convex curved surface structure.

[0076] In order to illustrate the in-situ measurement system of the charge density at the interface of an immiscible liquid according to an embodiment of the present application, a specific example is used below to describe in detail:

[0077] This specific example uses a microfluidic chip, the first liquid is a potassium chloride aqueous solution, the second liquid is n-decane, and the first, second, third, and fourth liquid storage containers are connected to ports H1, H2, H3, and H4 of the microfluidic chip, respectively. The first and second liquid storage containers are filled with potassium chloride aqueous solution, and the third and fourth liquid storage containers are filled with n-decane. The output port of the pressure pump is connected to the first and third liquid storage containers, and the input port of the pressure pump is connected to a nitrogen cylinder. The pressure pump can modulate the gas pressure of the nitrogen cylinder to generate a modulated pressure P j , modulation pressure P j The pressure difference is applied to both ends of the microfluidic chip; the microelectrode of the microfluidic chip is connected to the ammeter, which is connected to the in-situ measurement device of the charge density at the interface of the immiscible liquid; the in-situ measurement device of the charge density at the interface of the immiscible liquid is used to receive the modulated pressure P j , and calculate the first liquid pressure drop γP j , is also used to receive the current measured by the ammeter and combine the current with the bulk conductivity σ0 of the first liquid to obtain the first liquid potential drop. Figure 5 As shown, the dotted box is a top view of the microfluidic chip and microelectrode, and the black rectangle represents the microelectrode; the enlarged top view of the parallel flow channel of this specific example is shown in FIG. Figure 6 As shown, potassium chloride aqueous solution and n-decane flow in the parallel flow channel, and there are upstream microelectrodes and downstream microelectrodes in the parallel flow channel for measuring the first liquid potential drop of the potassium chloride aqueous solution at both ends of the parallel flow channel.

[0078] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As is well known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable, and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those skilled in the art that communication media generally embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for in-situ measurement of charge density at an immiscible liquid interface, characterized in that: include: Acquiring multiple sets of data for parallel flow channels in a microfluidic chip, wherein each set of data includes a first liquid pressure drop and a first liquid potential drop across two ends of the parallel flow channel, wherein a first liquid and a second liquid immiscible in each other flow side by side in the parallel flow channel; Based on the multiple sets of data, curve fitting is performed with the first liquid pressure drop as the abscissa and the first liquid potential drop as the ordinate to obtain a slope α of the fitted curve; According to the formula Obtain the charge density at the liquid-liquid interface; Wherein, the liquid-liquid interface is the interface between the first liquid and the second liquid in the parallel flow channel; Q l-l represents the charge density, μ represents the dynamic viscosity of the first liquid, σ0 represents the bulk conductivity of the first liquid, H represents the total height of the parallel flow channel, β represents the geometric parameters of the parallel flow channel, β = 6W / H 2 , W represents the total width of the parallel flow channel, H<<W; Q s-l,eff represents the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel; the first liquid potential drop is obtained by in-situ measurement of the first liquid by a microelectrode located in the parallel flow channel, γ represents the percentage of the pre-obtained first liquid pressure drop to the pressure drop of the microfluidic chip, and the length of the parallel flow channel is less than a preset length threshold.

2. The in-situ measurement method for charge density at the interface of immiscible liquids according to claim 1, wherein: The step of obtaining multiple sets of data of parallel flow channels in the microfluidic chip includes: At the first predetermined time interval T1, J times at time t j Obtain the pressure difference P applied by the pressure generating device to the microfluidic chip j , γP j As the first liquid pressure drop, wherein the pressure difference P obtained each time j Different, j = 1, 2, ..., J; At time t j +T2, obtain the first liquid potential drop at both ends of the parallel flow channel, wherein T2 is the second predetermined time interval, T2 <T1。 3. The in-situ measurement method of charge density at the interface of immiscible liquids according to claim 2, characterized in that: The obtaining of the first liquid potential drop at both ends of the parallel flow channel comprises: The potential difference of the first liquid at both ends of the parallel flow channel is obtained as the first liquid potential drop, wherein the potential upstream of the parallel flow channel is measured by an upstream microelectrode located in the first liquid, and the potential downstream of the parallel flow channel is measured by a downstream microelectrode located in the first liquid.

4. The in-situ measurement method of charge density at an immiscible liquid interface according to claim 3, wherein: The upstream microelectrode and the downstream microelectrode are both connected to an ammeter.

5. The in-situ measurement method of charge density at the interface of immiscible liquids according to claim 1, wherein: According to the formula Obtain the charge density at the liquid-liquid interface, including: According to the formula Calculate the Debye length λ, where λ is the approximate thickness of the double layer at the liquid-liquid interface, ε represents the absolute dielectric constant of the first liquid, and k B represents the Boltzmann constant, T represents the experimental temperature, e represents the elementary charge, represents the molar concentration of the i-th electrolyte ion in the first liquid, z i represents the charge number of the i-th electrolyte ion in the first liquid; Calculate Q based on λ s-l,eff , where Q s-l,eff The calculation formula is Q s-l representing the charge density of the solid-liquid interface between the first liquid and the inner wall material, determined by the type of the first liquid and the type of the inner wall material; is the charged reduced geometric parameter of the solid-liquid interface, which is a dimensionless constant and is calculated as follows:

6. The in-situ measurement method of charge density at an immiscible liquid interface according to claim 1, wherein: The liquid-liquid interface is flat, and the interface floating amount of the liquid-liquid interface is less than or equal to 0.1W.

7. An in-situ measurement device for charge density at an immiscible liquid interface, comprising a processor and a memory, characterized in that: The memory is used to store an in-situ measurement program of the charge density at the interface of an immiscible liquid; The processor is used to read the immiscible liquid interface charge density in-situ measurement program and perform the immiscible liquid interface charge density in-situ measurement method according to any one of claims 1 to 6.

8. An in-situ measurement system for charge density at an immiscible liquid interface, characterized in that: include: A microfluidic chip, the device for in-situ measurement of charge density at an immiscible liquid interface according to claim 7, and a first liquid and a second liquid that are immiscible with each other; The microfluidic chip includes parallel flow channels and microelectrodes located in the parallel flow channels, wherein the length of the parallel flow channels is less than a preset length threshold; The parallel flow channel is used for the parallel flow of the first liquid and the second liquid. The total height of the parallel flow channel is H, the total width of the parallel flow channel is W, and the geometric parameter of the parallel flow channel is β=6W / H 2 , H< <W; The microelectrode is used to perform in-situ measurement of the first liquid in the parallel flow channel to obtain the first liquid potential drop and send it to the immiscible liquid interface charge density in-situ measurement device, wherein the equivalent solid-liquid interface charge density between the first liquid and the inner wall material of the parallel flow channel is Q s-l,eff ; The in-situ measurement device for the charge density at the interface of the immiscible liquid is used to obtain multiple sets of data of the parallel flow channels, each set of data including the first liquid pressure drop and the first liquid potential drop at both ends of the parallel flow channels; and based on the multiple sets of data, a curve fitting is performed with the first liquid pressure drop as the horizontal coordinate and the first liquid potential drop as the vertical coordinate to obtain the slope α of the fitted curve; and according to the formula Obtaining the charge density of the liquid-liquid interface; wherein the liquid-liquid interface is the interface between the first liquid and the second liquid; Q l-l represents the charge density, μ represents the dynamic viscosity of the first liquid, σ0 represents the bulk conductivity of the first liquid, and γ represents the percentage of the pre-obtained pressure drop of the first liquid to the pressure drop of the microfluidic chip.

9. The in-situ measurement system for charge density at an immiscible liquid interface according to claim 8, wherein: Also included is a pressure generating device and an ampere meter; The pressure generating device is used to generate a pressure at a first predetermined time interval T1 J times at time t j Apply a pressure difference P to the microfluidic chip j , wherein the pressure difference P obtained each time j Different, j=1,2,……,J, and γP j sending the first liquid pressure drop to the immiscible liquid interface charge density in-situ measurement device; The ammeter is used to j +T2 acquiring the potential difference between the two ends of the parallel flow channel measured by the microelectrode as the first liquid potential drop, and sending it to the immiscible liquid interface charge density in-situ measurement device; Wherein, T2 is the second predetermined time interval, T2 <T1。 10. The in-situ measurement system for charge density at an immiscible liquid interface according to claim 8, wherein: The microfluidic chip further includes an upstream separation flow channel and a downstream separation flow channel; The upstream separation channel comprises an upstream first channel, a first separation layer and an upstream second channel, wherein the first separation layer is used to separate the upstream first channel from the upstream second channel; The downstream separation channel comprises a first downstream channel, a second separation layer and a second downstream channel, wherein the second separation layer is used to separate the first downstream channel from the second downstream channel; The parallel flow channel includes a first parallel flow channel and a second parallel flow channel, and the microelectrode is located in the first parallel flow channel; The upstream flow channel, the first parallel flow channel and the downstream flow channel are connected in sequence, so that the first liquid flows from the inlet of the upstream flow channel to the outlet of the downstream flow channel; The upstream second flow channel, the second parallel flow channel and the downstream second flow channel are connected in sequence, so that the second liquid flows from the inlet of the upstream second flow channel to the outlet of the downstream second flow channel; One end of the first separation layer facing the parallel flow channel is in a pointed shape, and one end of the second separation layer facing the parallel flow channel is in a convex curved surface structure.

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