CN113049454A - Method for measuring and calculating dynamic interfacial tension of multi-phase emulsion in micro-channel - Google Patents
Method for measuring and calculating dynamic interfacial tension of multi-phase emulsion in micro-channel Download PDFInfo
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Abstract
The invention provides a method for measuring and calculating dynamic interfacial tension of multiphase emulsion in a microchannel, which combines the structural change rule under the adsorption balance of a surfactant and the dynamic adsorption effect of the surfactant and provides a method for deducing the instantaneous dynamic interfacial tension according to the change of the instantaneous emulsion structure. In order to measure the dynamic interfacial tension value caused by the dynamic adsorption effect of the surfactant, the emulsion structure is taken as a research object, and the dynamic interfacial tension of the multiphase emulsion in the microchannel is obtained by comparing an emulsion simulation image with a high-speed camera micrograph and an emulsion experiment image obtained by a scanning electron microscope.
Description
Technical Field
The invention belongs to the technical field of measurement of dynamic interfacial tension of multiphase emulsion, and particularly relates to a method for measuring and calculating the dynamic interfacial tension of the multiphase emulsion in a microchannel, which starts from the structure of the multiphase emulsion and reversely deduces the dynamic interfacial tension by taking an experimental photo obtained by simulating the structure and scanning electron microscope image nuclear high-speed photomicrography.
Background
A multiphase emulsion is a suspension of droplets, surrounded by one or more microdroplets, in a continuous phase. Because the multiphase emulsion can simultaneously contain various active substances and diversified structures thereof, the multiphase emulsion also has a great number of applications in the aspects of controllable release of substances, substance separation, controlled and slow release of foods, cosmetics and medicines, increased biocompatibility and the like: patent CN111763292A discloses a snowman-shaped Janus particle and a preparation method thereof, and the obtained product has high strength and toughness and good oil resistance and chemical resistance. Patent CN110639444A discloses a method for preparing aromatic vegetable oil microcapsules based on a microfluidic technology, which can realize burst release through pH response and has important significance for efficient packaging, controllable structure and controllable release of aromatic vegetable oil microcapsule products.
The preparation method of the multiphase emulsion comprises a two-step emulsion emulsification method and a membrane emulsification method, but the two methods still have the defects of wider distribution particle size, poor controllability and more complex preparation process. The micro-fluidic technology has the advantages of good monodispersity, high controllability, simple operation and the like, and makes up for the defects of the traditional method, so the micro-fluidic technology becomes an important method for preparing the multi-phase emulsion.
In the process of preparing the emulsion by microfluidics, a surfactant is usually added to reduce the interfacial tension so that the emulsion can be stably prepared, but the addition of the surfactant brings a dynamic adsorption effect. The dynamic adsorption effect means that in the process of generating and flowing the emulsion, new interfaces are generated continuously, and the surfactant can be enriched to the new interfaces, so that the interfacial tension in the process is not a fixed value but a dynamic value which changes continuously. The speed of the adsorption process mainly depends on the nature, concentration, diffusion coefficient, micelle dissociation kinetics and the like of the surfactant.
In the current stage of research on dynamic interfacial tension, researchers utilize a glass capillary to research the dynamic interfacial tension in a liquid drop generation process, and the main methods comprise a liquid drop volume method, a maximum bubble pressure method and a liquid drop growing method, but the liquid drop generation time of the methods is long, the diameter of a capillary pipe opening is large, and the methods are not suitable for being used in a micro-channel. In recent years, there have been many researchers studying dynamic adsorption processes in microchannels, Wang et al, by measuring the dispersion size of droplets [ Wang K, Lu Y C, Xu J H, et a1.langmuir, 2009, 25 (4): 2153-. Research indicates that in the micro-dispersion process, the generation time of droplets is in millisecond order, the dynamic effect of the surfactant is researched through the dispersion size of the droplets only under the condition that the surfactant exists at a high concentration, the surfactant is not sensitive to trace concentration change, meanwhile, the change of the droplet size only occurs in the droplet formation process, the size is not changed in the flowing process after the droplets are formed, but the interfacial tension of the emulsion still dynamically changes, and meanwhile, the size measurement method cannot measure the structural change of the multiphase emulsion, so that a new means for determining the dynamic interfacial tension in the flowing process of the multiphase emulsion needs to be developed.
Structural change is an important characteristic of multiphase emulsion, and a plurality of researchers research and control the structure of the emulsion, and Zarza and the like skillfully realize structural control of double emulsion by utilizing the difference of the tension reducing effects of two surfactants on different interfaces and regulating the concentrations of the two surfactants [ ZarL D, Sresht V, Sletten E M, et a1.Nature, 2015, 518 (7540): 520-524]. Friberg et al used a geometric analysis method to predict the Janus morphology, yielding a relationship between contact angle, interfacial tension and flux ratio of three phases based on geometry [ Hasinovic H, S E Friberg, I Kovach, et a1.jdisper Sci Technol, 2013.34 (12): 1683-1689]. However, in the existing research, the research on the structure of the multiphase emulsion mainly focuses on the adsorption equilibrium of the surfactant, and the dynamic adsorption process of the surfactant in the generation process of the multiphase emulsion is rarely researched.
Disclosure of Invention
Considering that the multi-phase emulsion is often used in the aspects of biological medicine, daily skin care, preparation of new materials and the like due to the structural characteristics of the multi-phase emulsion. The addition of surfactants in the preparation of multiphase emulsions by microfluidics brings about a dynamic adsorption effect. The existing research on dynamic adsorption only focuses on the formation stage of the two-phase emulsion in view of the limitation of the method, and the research on the multi-phase emulsion and the change of the emulsion in the channel flowing process cannot be researched. The invention provides a novel method for estimating the dynamic interfacial tension of an emulsion according to the structural change of a multiphase emulsion, which has universality in the process of forming the multi-emulsion in a micro-channel by any three-phase immiscible liquid.
Aiming at the problems in the prior art, the invention aims to provide a method for measuring and calculating the dynamic interfacial tension of a multiphase emulsion in a microchannel, which combines the structure change rule under the adsorption balance of a surfactant and the dynamic adsorption effect of the surfactant and provides a method for deriving the instantaneous dynamic interfacial tension according to the change of the instantaneous emulsion structure. In order to measure a dynamic interfacial tension value caused by a dynamic adsorption effect of a surfactant, an emulsion structure is taken as a research object, and the dynamic interfacial tension of a multiphase emulsion in a microchannel is obtained by comparing an emulsion simulation image obtained by MATLAB with an emulsion experimental image obtained by a high-speed image-taking micrograph and a scanning electron microscope.
The invention specifically adopts the following technical scheme:
a method for measuring and calculating the dynamic interfacial tension of a multi-phase emulsion in a micro-channel is characterized by comprising the following steps: and comparing the emulsion simulation image with the high-speed shooting micrograph and the emulsion experiment image obtained by a scanning electron microscope to obtain the dynamic interfacial tension of the multiphase emulsion in the microchannel.
Preferably, the method comprises the following steps:
step S1: three immiscible liquids are selected as follows: the composite material comprises an internal phase, an intermediate phase and an external phase, wherein the internal phase and the intermediate phase are dispersed phases, and the external phase is a continuous phase; preparing continuous phases containing different surfactant concentrations, and respectively measuring the equilibrium interfacial tension between every two phases of the three-phase emulsion;
step S2: according to the interfacial tension, calculating the spreading coefficient S between the solution of the surfactant with different concentrations and the other two phases when the solution is a continuous phasei(ii) a Judging the configuration of the emulsion to determine the type and concentration of the adopted surfactant;
step S3: respectively introducing the three liquids into a micro-channel, shearing a dispersed phase into emulsion by a continuous phase in the channel in the fluid flowing process, and adding a surfactant into the continuous phase to stably prepare a three-phase emulsion;
step S4: shooting a dynamic picture of the structural change of the three-phase emulsion in the microchannel by adopting high-speed microscopic shooting, enabling a dispersed phase of the emulsion to be self-polymerized by irradiating the flowing process of the emulsion with ultraviolet light to obtain an instantaneous structure, and shooting a scanning electron microscope;
step S5: according to the analysis of the geometric structure, making simulation images of different three-phase emulsion structures;
step S6: and comparing the simulated image with the experimental values shot by a scanning electron microscope picture and a high-speed microscopic camera by using a trial and error method, and determining the dynamic interfacial tension corresponding to the three-phase emulsion structure.
Preferably, the method further comprises the step S7: and analyzing a plurality of dynamic pictures of the three-phase emulsion in the flow process of the micro-channel to obtain the dynamic interfacial tension of the emulsion along with the change of time.
Preferably, the micro-channel comprises a tertiary channel with the relative deviation of the coaxiality not more than 5%, and the diameter of a capillary tube opening of the channel is 50-1000 mu m.
Preferably, in step S3, a three-phase emulsion is obtained by smoothly pushing three immiscible liquids into a channel using a syringe pump, wherein the inner phase is pushed into a first-stage channel, the intermediate phase is pushed into a second-stage channel, and the outer phase is pushed into a third-stage channel.
Preferably, the equilibrium interfacial tension in step S1 is obtained by one of the measurement of the pendant drop method, the loop method, the capillary rise method, and the maximum bubble method.
Preferably, in step S2, the spreading factor relationship of the three immiscible liquids is required to satisfy the requirement of being able to form a core-shell type, namely: si＞0、Sj＜0、Sk< 0, towards the Janus type, i.e.: si＜0、Sj＜0、Sk< 0, requirements for a converted emulsion.
Preferably, in step S2, whether the selected emulsion system meets the requirement is judged according to the relation of spreading coefficients, if not, the type and concentration of the surfactant are changed until the requirement is met: the kind and concentration of the surfactant are regulated to ensure that the given three immiscible liquids meet the conditions; the measuring formula of the spreading coefficient is as follows: si＝γjk-(γij+γik) Wherein γ isjk、γij、γikThe interfacial tension of a three-phase emulsion system between two phases is shown, i, j and k respectively represent an internal phase, an intermediate phase and an external phase in the three-phase emulsion; calculating the spreading coefficient of each phase according to a formula by interfacial tension to obtain Si、Sj、SkWhen S isi＞0、Sj＜0、SkWhen less than 0, the emulsion structure is core-shell type, when S isi＜0、Sj＜0、SkBelow 0, the emulsion is Janus type. The scheme is suitable for any three-phase system, and the emulsion can be judged to be turned from a core-shell type to a Janus type after the spreading coefficient is calculated only when different surfactant solutions are used as external phases.
Preferably, the inner phase employs polyesters TPGDA, ETPTA,One of PEGDA, so as to carry out ultraviolet curing, and facilitate the subsequent experimental characterization; the surfactant is: one of SDS (sodium dodecyl sulfate), glyceride, span80 (sorbitan oleate), TX-100 (octylphenyl polyoxyethylene ether), Tween20, Tween40, CTAB (dodecyl trimethyl ammonium bromide), Capstone FS-30 and Dow Corning 749; the surfactant concentration is 1X 10-7mol·L-1To 1 mol. L-1(ii) a The continuous phase can adopt water or oil.
Preferably, in step S4, a high-speed photographic micrograph is taken of the emulsion from generation to dropping to each stage where the structural change of the emulsion is complete; curing the emulsion by using ultraviolet light, taking out the emulsion from the tail end of the channel after curing to obtain the emulsion, and shooting an SEM image of the cured emulsion; the formation of the emulsion was recorded by high speed microscopy and the time of emulsion flow and structural change was recorded by software associated with the high speed microscopy.
In step S5, the relationship between the geometry and the three-phase contact angle, the interfacial tension and the flow ratio is obtained by geometric analysis of the emulsion structure, and an MATLAB simulation image is calculated by using a MATLAB program. The analysis of the emulsion geometry and interfacial tension is given by the following equation:
α+β+δ＝180°
μ-η-β＝0
η-ε-δ＝0
r1sinμ＝r2sinη＝r3sinε
where α, β, δ are the contact angles of the three phases, μ, η, ε are angles in the geometric figure, not specifically defined, γWDenotes the interfacial tension, gamma, of the intermediate phase in the dispersed phase and the continuous phaseEDenotes the interfacial tension, gamma, of the internal phase in the dispersed phase with the continuous phaseEWDenotes the interfacial tension, r, between two separate phases1The radius of the circle, r, corresponding to the inner phase portion (smaller circle) in the geometric analysis of FIG. 1 is shown2The radius r of the circle corresponding to the mesophase portion (larger circle) in the geometric analysis of FIG. 1 is shown3Denotes the radius of the circle corresponding to the interface of the internal phase and the intermediate phase when forming the Janus configuration, Q1Represents the internal phase flow rate (in. mu.L/min), Q, in the dispersed phase2The flow rate of the intermediate phase in the dispersed phase (unit. mu.L/min) is shown, and q represents the flow rate ratio of the two dispersed phases, and the geometric analysis is shown in the attached figure 1 of the specification.
In step S6, the suitability of the MATLAB simulation image to the scanning electron microscope picture and the high-speed photomicrograph of the emulsion is determined according to the picture taken by the scanning electron microscope, the MATLAB simulation picture and the high-speed photomicrograph, and the interfacial tension of the emulsion is obtained in a trial and error manner. And (3) snapshotting different configurations of the emulsion at the moment of changing at a high speed, and comparing MATLAB simulation to obtain the dynamic interfacial tension of the multi-phase emulsion at each moment.
Compared with the prior art, the invention and the preferred scheme thereof have the following advantages:
1. the existing method for measuring the dynamic interfacial tension of the emulsion in the microchannel mainly predicts according to the size, the generation frequency and the like of liquid drops, firstly, the characteristics of the size and the like of the liquid drops are not intuitive, and some measurement methods are required to be assisted;
2. the existing measuring method for the dynamic interfacial tension of the emulsion is mainly concentrated on the two-phase emulsion, and is rarely proposed for the three-phase emulsion, so that the method can well predict the interfacial tension of more complicated three-phase emulsion between two and two, and is a breakthrough in the existing research;
3. for the existing research, the method mainly aims at the generation process of two-phase emulsion droplets, and the method selected by the research cannot be applied to the measurement of the dynamic interfacial tension in low concentration, or a multi-phase emulsion system, or the flow process of the emulsion droplets. The method can realize the generation of the multi-phase emulsion under high concentration and low concentration and the measurement of the dynamic interfacial tension of the emulsion in the flowing process, thereby researching the dynamic adsorption effect of the surfactant in the whole channel process, and being a breakthrough compared with the previous research on the dynamic adsorption of the surfactant.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is a schematic diagram of the geometric analysis of the emulsion structure according to the embodiment of the present invention;
FIG. 2 is a schematic diagram of a microchannel structure according to an embodiment of the present invention;
FIG. 3 is a schematic diagram showing a high speed photomicrograph of a multiphase emulsion flow process in comparison to an SEM image of the emulsion after solidification in accordance with an embodiment of the present invention;
FIG. 4 is a schematic diagram showing a comparison of an emulsion high speed photomicrograph with an MATLAB simulation in accordance with an embodiment of the present invention;
FIG. 5 is a graphical representation of dynamic interfacial tension measurements according to an embodiment of the present invention.
Detailed Description
In order to make the features and advantages of this patent more comprehensible, 4 embodiments accompanied with figures are described in detail below:
example 1
(1) A microchannel with an internal phase channel orifice diameter of 50 μm, an intermediate phase orifice diameter of 200 μm and an external phase orifice diameter of 750 μm was prepared, and the channel schematic diagram is shown in FIG. 2.
(2) Selecting an aqueous solution of SDS with an internal phase of ETPTA, an intermediate phase of dimethicone and an external phase of 0.0347mol/L, wherein the internal phase and the intermediate phase are dispersed phases, stably pushing the dispersed phases into a microchannel by using a syringe pump, the internal phase is introduced into a first stage of a channel, the intermediate phase is introduced into a second stage of the channel, a continuous phase is introduced into a third stage, and capillaries from left to right of the channel are respectively a first-stage channel, a second-stage channel and a third-stage channel, and the schematic diagram is shown in figure 2. Adjusting the flow rate to 5-50 mu L/min of the internal phase, 10-100 mu L/min of the intermediate phase and 100-1000 mu L/min of the external phase, and stably preparing the emulsion.
(3) SDS concentration of 6.935X 10 was measured-7～6.935×10-1The interfacial tension value of the mol/L aqueous solution and the dimethyl silicone oil, ETPTA and the dimethyl silicone oil.
(4) The spreading factor of each phase was calculated according to the spreading factor calculation formula, as shown in Table 1, at a low concentration of 6.935X 10-7At mol/L, the spreading factor is Si＝28.56、Sj＝-42.68、Sk-47.91, corresponding to Si＞0、Sj＜0、SkLess than 0, the emulsion belongs to a core-shell structure, and the spreading coefficient of the emulsion is S at a high concentration of 0.0347mol/Li＝-0.02、Sj＝-14.1、Sk-11.74, corresponding to Si＜0、Sj＜0、Sk< 0, at which the emulsion is in the Janus configuration, the structure of the emulsion in the present system will vary with increasing concentration of surfactant.
TABLE 1 calculated values of spreading factor and determination of emulsion structure
(5) High-speed photographic micrographs of the emulsion from generation to dripping to each stage of complete structural change of the emulsion were taken. And (3) solidifying the emulsion by using ultraviolet light, taking out the solidified emulsion from the tail end of the channel, and shooting an SEM image of the solidified emulsion, wherein a picture of the structural change of the emulsion in the liquid drop flowing process and an SEM picture are shown in figure 3.
(6) Simulating an MATLAB image according to the static interfacial tension value, and when the emulsion is changed from the core-shell type to the Janus type at each moment, considering that the Janus structure in each moment under the unstable state has a corresponding Janus structure in the equilibrium state corresponding to the Janus structure, so that each Janus structure under the unstable state has a corresponding interfacial tension relationship, and the interfacial tension does not reach the equilibrium interfacial tension when the emulsion and an SDS solution reach the surfactant adsorption equilibrium state in an experiment, so that by means of the MATLAB program simulation, writing an MATLAB program according to a geometric structure diagram in a figure I, deducing the interfacial tension value of the critical point of the structural change according to the spreading coefficient relationship through the static interfacial tension value measured in the step (4), inputting the interfacial tension after the critical value in the MATLAB program, combining the image simulated by the MATLAB with a shot emulsion high-speed photographic picture, as shown in figure 4, comparing similar emulsion configurations, combining SEM images, and determining the dynamic interfacial tension value at the moment of each emulsion structure change by back-stepping in a trial-error manner to obtain a result, wherein the result is shown in FIG. 5. The MATLAB program code is shown below.
MATLAB program
clear；
clc；
format long
digits(8)
0＝[11.27，5.76，7.06]；％[Interfacial tension
between：ETPTA/Paraffin，W/Paraffin，ETPTA/W]
q＝0.3；％[volume rati5o of water to ETPTA]
a＝acos(0.5*(0(1)^2+0(3)^2-0(2)^2)/(0(1)*0(3)))；
b＝acos(0.5*(0(1)^2+O(2)^2-o(3)^2)/(O(1)*0(2)))；
c＝acos(0.5*(0(2)^2+O(3)^2-O(1)^2)/(O(3)*O(2)))；
J1＝a*180/3.14；
J2＝b*180/3.14；
J3＝c*180/3.14；
x0＝[2，1.5，pi/4，pi/4，pi/4]；％Initial Value
opt＝optimset(’MaxFunEvals’，10000，’MaxIter’，10000)；
[x1，fvl，efl，out1]＝fsolve(@exam314，x0，opt，q，c，b)；
if ef1＝＝1
h＝sin(x1(3)-x1(4))/sin(x1(3))；
[X，Y，Z]＝sphere(30)；
X1＝X；
Y1＝Y；
Z1＝Z；
h0＝cos(x1(4))；
surf(X1，Y1，Z1，’facealpha’，1，’linestyle’，’-’)；
hold on
X2＝x1(1)*X；
Y2＝x1(1)*Y；
Z2＝x1(1)*Z+h；
surf(X2，Y2，Z2，’facealpha’，1，’linestyle’，’-’)；
hold off
h1＝sin(x1(4)-x1(5))/sin(x1(5))；axis equal，axis off
view(20，10)
q
angle＝[J1 J2 J3]％[The angle results of，and，] ’＝180 R＝[x1(1)
1x1(2)]
h＝[h 0-h1]
w＝abs(cos(acos((1+(-h1)^2-(x1(2))^2)/(2*abs(-h1)))))
colormap([00.70；100])
caxis([w-5w+5])
else
x0＝[1，1.5，pi/4，pi/4，-pi/4]；
[x2，fv2，ef2，out2]＝fsolve(@Janus，x0，opt，q，c，b)；
h＝sin(x2(3)-x2(4))/sin(x2(3))；
[X，Y，Z]＝sphere(30)；
X1＝X；
Y1＝Y；
Z1＝Z；
h0＝cos(x2(4))；
surf(X1，Y1，Z1，’facealpha’，1，’linestyle’，’-’)；
hold on
X2＝x2(1)*X；
Y2＝x2(1)*Y；Z2＝x2(1)*Z+h；
surf(X2，Y2，Z2，’facealpha’，1，’linestyle’，’-’)
h1＝sin(x2(4)-x2(5))/sin(x2(5))；
hold off
axis equal，axis off
view(20，10)
q
angle＝[J1 J2 J3]
R＝[x2(1)1x2(2)]
h＝[h 0-h1]
w＝abs(cos(acos((1+(-h1)^2-(x2(2))^2)/(2*abs(-h1)))))
colormap([100；00.70])
caxis([w-5w+5])
end
Specifically, the description of the present embodiment refers to FIG. 2, which is an assembly of channels, from left to right, comprising first, second and third stage channels, wherein the first stage channels have capillary openings of about 50-100 μm diameter, into which one of the dispersed phases, which we generally refer to as the internal phase, passes. The capillary orifice of the second stage channel has a diameter of about 150 to 350 μm and is filled with another dispersed phase, commonly called an intermediate phase, and a continuous phase from the square tube between the second stage channel and the third stage channel.
Table 1 shows the spreading factor calculated from the interfacial tension of the emulsion when solutions of different surfactant concentrations were used as the continuous phase. Whether the selected system is usable or not can be judged according to the spreading coefficient, and the method is an index of whether the method is usable or not.
FIG. 3 is a high-speed photomicrograph of structural changes during the flow of the multi-phase emulsion in the microchannel and a scanning electron microscope image of the photocurable portion in the emulsion dispersed phase after self-curing in the presence of ultraviolet light, which can correspond to the high-speed photomicrograph.
Fig. 4 is a comparison of the MATLAB simulated image with the high speed photomicrograph, with the lighter colored portion representing the internal phase in the dispersed phase and the darker colored portion representing the intermediate phase in the dispersed phase, and the MATLAB simulated image can be in one-to-one correspondence with the high speed photomicrograph.
a) Middle comparison to obtain gammaAC＝13.25mN/m，γBC＝6.21mN/m，γAB＝7.06mN/m
b) Middle comparison to obtain gammaAC＝11.27mN/m，γBC＝5.76mN/m，γAB＝7.06mN/m
c) Middle comparison to obtain gammaAC＝10.56mN/m，γBC＝5.4mN/m，γAB＝7.06mN/m
Wherein A represents intermediate phase dimethyl silicone oil in a dispersed phase, B represents inner phase ETPTA in the dispersed phase, and C represents continuous phase SDS aqueous solution gamma to represent the interfacial tension relationship between two phases.
FIG. 5 is a value of the dynamic interfacial tension in example 1 with time according to the method of the present invention.
By adopting the scheme, the change value of interfacial tension between every two phases of ETPTA/dimethicone/0.0347 mol/L SDS aqueous solution in the micro-channel with the specification along with time can be obtained.
Example 2
(1) A microchannel with an internal phase channel orifice diameter of 50 μm, an intermediate phase orifice diameter of 200 μm and an external phase orifice diameter of 750 μm was fabricated.
(2) Selecting an SDS aqueous solution with an internal phase of TPGDA, an intermediate phase of dimethicone and an external phase of 0.06935mol/L, wherein the internal phase and the intermediate phase are dispersed phases, stably pushing the dispersed phases into a microchannel by using a syringe pump, the internal phase is introduced into a first stage of a channel, the intermediate phase is introduced into a second stage of the channel, a continuous phase is introduced into a third stage, and capillaries from left to right of the channel are respectively a first stage channel, a second stage channel and a third stage channel, and the schematic diagram is shown in figure 2. Adjusting the flow rate to 5-50 mu L/min of the internal phase, 10-100 mu L/min of the intermediate phase and 100-1000 mu L/min of the external phase, and stably preparing the emulsion.
(3) SDS concentration of 6.935X 10 was measured-7～6.935×10-1The interfacial tension values of the mol/L aqueous solution, the dimethyl silicone oil, the TPGDA and the dimethyl silicone oil.
(4) The spreading factor of each phase was calculated according to the spreading factor calculation formula, and as shown in Table 1, the spreading factor of each phase was calculatedIs at low concentration of 6.935 × 10-7At mol/L, the spreading factor is Si＝28.56、Sj＝-42.68、Sk-47.91, corresponding to Si＞0、Sj＜0、SkLess than 0, the emulsion belongs to a core-shell structure, and the spreading coefficient of the emulsion is S at high concentration of 0.06935mol/Li＝-0.67、Sj＝-13.45、SkIs-10.71, corresponds to Si＜0、Sj＜0、Sk< 0, at which the emulsion is in the Janus configuration, the structure of the emulsion in the present system will vary with increasing concentration of surfactant.
(5) High-speed photographic micrographs of the emulsion from generation to dripping to each stage of complete structural change of the emulsion were taken. And (3) curing the emulsion by using ultraviolet light, taking out the cured emulsion from the tail end of the channel, and shooting an SEM image of the cured emulsion.
(6) Simulating an MATLAB image according to the static interfacial tension value, and when the emulsion is changed from the core-shell type to the Janus type at each moment, considering that the Janus structure in each moment under the unstable state has a corresponding Janus structure in the equilibrium state corresponding to the Janus structure, so that each Janus structure under the unstable state has a corresponding interfacial tension relationship, the interfacial tension does not reach the equilibrium interfacial tension when the emulsion and an SDS solution reach the surfactant adsorption equilibrium state in an experiment, therefore, simulating by means of an MATLAB program, compiling an MATLAB program according to a geometric structure diagram in a figure I, deducing the interfacial tension value of a critical point of the structural change according to the spreading coefficient relationship through the static interfacial tension value measured in the step (3), inputting the interfacial tension after the critical value in the MATLAB program, and combining the image simulated by the MATLAB with a shot high-speed photographic image and an SEM image of the emulsion, and comparing the similar emulsion configurations, and reversely calculating and judging the dynamic interfacial tension value of each emulsion at the moment of structural change in a trial and error manner.
By adopting the scheme, the change value of interfacial tension of every two interphase TPGDA/dimethicone/0.06935 mol/L SDS aqueous solution in the micro-channel with the specification along with time can be obtained.
Example 3
(1) A microchannel with an internal phase channel orifice diameter of 50 μm, an intermediate phase orifice diameter of 200 μm and an external phase orifice diameter of 750 μm was fabricated.
(2) Selecting an internal phase as ETPTA, an intermediate phase as deionized water, an external phase as liquid paraffin containing 0.01mol/L Span, wherein the internal phase and the intermediate phase are dispersed phases, stably pushing the dispersed phases into a microchannel by using a syringe pump, leading the internal phase into a first stage of a channel, leading the intermediate phase into a second stage of the channel, leading a continuous phase into a third stage, and leading capillaries from left to right of the channel to be a first-stage channel, a second-stage channel and a third-stage channel respectively, wherein the schematic diagram is shown in figure 2. Adjusting the flow rate to 5-50 mu L/min of the internal phase, 10-100 mu L/min of the intermediate phase and 100-1000 mu L/min of the external phase, and stably preparing the emulsion.
(3) The concentration of Span80 was measured to be 1X 10-80.1mol/L of liquid paraffin, deionized water, ETPTA and the interfacial tension value of ETPTA and deionized water.
(4) The spreading factor of each phase was calculated from the spreading factor calculation formula, and it was considered that the concentration was 1X 10 at a low concentration-8At mol/L, the spreading factor is Si＝30.2、Sj＝-37.54、Sk-35.78, corresponding to Si＞0、Sj＜0、SkLess than 0, the emulsion belongs to a core-shell structure, and the spreading coefficient of the emulsion is S at high concentration of 0.1mol/Li＝-2.15、Sj＝-9.81、SkIs-0.61, corresponds to Si＜0、Sj＜0、Sk< 0, at which the emulsion is in the Janus configuration, the structure of the emulsion in the present system will vary with increasing concentration of surfactant.
(5) High-speed photographic micrographs of the emulsion from generation to dripping to each stage of complete structural change of the emulsion were taken. And (3) curing the emulsion by using ultraviolet light, taking out the cured emulsion from the tail end of the channel, and shooting an SEM image of the cured emulsion.
(6) Simulating an MATLAB image according to the static interfacial tension value, and when the emulsion is changed from the core-shell type to the Janus type at each moment, considering that the Janus structure in each moment under the unstable state has a corresponding Janus structure in the equilibrium state corresponding to the Janus structure, so that each Janus structure under the unstable state has a corresponding interfacial tension relationship, the interfacial tension does not reach the equilibrium interfacial tension when the emulsion and an SDS solution reach the surfactant adsorption equilibrium state in an experiment, therefore, simulating by means of an MATLAB program, compiling an MATLAB program according to a geometric structure diagram in a figure I, deducing the interfacial tension value of a critical point of the structural change according to the spreading coefficient relationship through the static interfacial tension value measured in the step (3), inputting the interfacial tension after the critical value in the MATLAB program, and combining the image simulated by the MATLAB with a shot high-speed photographic image and an SEM image of the emulsion, and comparing the similar emulsion configurations, and reversely calculating and judging the dynamic interfacial tension value of each emulsion at the moment of structural change in a trial and error manner.
By adopting the scheme, the change value of the interfacial tension of every two phases of ETPTA/deionized water/0.06935 mol/L liquid paraffin containing Span80 along with time in the micro-channel with the specification can be obtained.
Example 4
(1) A microchannel with an internal phase channel orifice diameter of 50 μm, an intermediate phase orifice diameter of 200 μm and an external phase orifice diameter of 750 μm was fabricated.
(2) Selecting a TX-100 aqueous solution with an internal phase of ETPTA, an intermediate phase of dimethicone and an external phase of 0.1mol/L, wherein the internal phase and the intermediate phase are dispersed phases, stably pushing the dispersed phases into a microchannel by using a syringe pump, the internal phase is introduced into a first stage of a channel, the intermediate phase is introduced into a second stage of the channel, a continuous phase is introduced into a third stage, and capillaries from left to right of the channel are respectively a first stage channel, a second stage channel and a third stage channel, and the schematic diagram is shown in figure 2. Adjusting the flow rate to 5-50 mu L/min of the internal phase, 10-100 mu L/min of the intermediate phase and 100-1000 mu L/min of the external phase, and stably preparing the emulsion.
(3) Measuring the concentration of TX-100 at 1X 10-70.1mol/L of aqueous solution and dimethyl silicone oil, ETPTA, and the interfacial tension value of ETPTA and dimethyl silicone oil.
(4) The spreading factor of each phase was calculated from the spreading factor calculation formula, and it was considered that the concentration was 1X 10 at a low concentration-8At mol/L, the spreading factor is Si＝25.32、Sj＝-37.27、Sk-43.50, corresponding to Si＞0、Sj＜0、SkLess than 0, the emulsion belongs to a core-shell structure and has a high concentration of 0.1mAt ol/L, the spreading factor is Si＝-6.547、Sj＝-5.407、Sk-5.029, corresponding to Si＜0、Sj＜0、Sk< 0, at which the emulsion is in the Janus configuration, the structure of the emulsion in the present system will vary with increasing concentration of surfactant.
(5) High-speed photographic micrographs of the emulsion from generation to dripping to each stage of complete structural change of the emulsion were taken. And (3) curing the emulsion by using ultraviolet light, taking out the cured emulsion from the tail end of the channel, and shooting an SEM image of the cured emulsion.
(5) Simulating an MATLAB image according to the static interfacial tension value, and when the emulsion is changed from the core-shell type to the Janus type at each moment, considering that the Janus structure in each moment under the unstable state has a corresponding Janus structure in the equilibrium state corresponding to the Janus structure, so that each Janus structure under the unstable state has a corresponding interfacial tension relationship, the interfacial tension does not reach the equilibrium interfacial tension when the emulsion and an SDS solution reach the surfactant adsorption equilibrium state in an experiment, therefore, simulating by means of an MATLAB program, compiling an MATLAB program according to a geometric structure diagram in a figure I, deducing the interfacial tension value of a critical point of the structural change according to the spreading coefficient relationship through the static interfacial tension value measured in the step (3), inputting the interfacial tension after the critical value in the MATLAB program, and combining the image simulated by the MATLAB with a shot high-speed photographic image and an SEM image of the emulsion, and comparing the similar emulsion configurations, and reversely calculating and judging the dynamic interfacial tension value of each emulsion at the moment of structural change in a trial and error manner.
By adopting the scheme, the change value of interfacial tension of two-to-two interphase dimethylsilicone/ETPTA/0.1 mol/LTX-100 aqueous solution in the micro-channel with the specification along with time can be obtained.
The present invention is not limited to the above-mentioned preferred embodiments, and all other methods for measuring and calculating the dynamic interfacial tension of a multi-phase emulsion in a microchannel can be obtained from the teaching of the present invention.
Claims (10)
1. A method for measuring and calculating the dynamic interfacial tension of a multi-phase emulsion in a micro-channel is characterized by comprising the following steps: and comparing the emulsion simulation image with the high-speed shooting micrograph and the emulsion experiment image obtained by a scanning electron microscope to obtain the dynamic interfacial tension of the multiphase emulsion in the microchannel.
2. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 1, wherein: the method comprises the following steps:
step S1: three immiscible liquids are selected as follows: the composite material comprises an internal phase, an intermediate phase and an external phase, wherein the internal phase and the intermediate phase are dispersed phases, and the external phase is a continuous phase; preparing continuous phases containing different surfactant concentrations, and respectively measuring the equilibrium interfacial tension between every two phases of the three-phase emulsion;
step S2: according to the interfacial tension, calculating the spreading coefficient S between the solution of the surfactant with different concentrations and the other two phases when the solution is a continuous phasei(ii) a Judging the configuration of the emulsion to determine the type and concentration of the adopted surfactant;
step S3: respectively introducing the three liquids into a micro-channel, shearing a dispersed phase into emulsion by a continuous phase in the channel in the fluid flowing process, and adding a surfactant into the continuous phase to stably prepare a three-phase emulsion;
step S4: shooting a dynamic picture of the structural change of the three-phase emulsion in the microchannel by adopting high-speed microscopic shooting, enabling a dispersed phase of the emulsion to be self-polymerized by irradiating the flowing process of the emulsion with ultraviolet light to obtain an instantaneous structure, and shooting a scanning electron microscope;
step S5: according to the analysis of the geometric structure, making simulation images of different three-phase emulsion structures;
step S6: and comparing the simulated image with the experimental values shot by a scanning electron microscope picture and a high-speed microscopic camera by using a trial and error method, and determining the dynamic interfacial tension corresponding to the three-phase emulsion structure.
3. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: further comprising, step S7: and analyzing a plurality of dynamic pictures of the three-phase emulsion in the flow process of the micro-channel to obtain the dynamic interfacial tension of the emulsion along with the change of time.
4. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: the micro-channel comprises a three-stage channel with the relative deviation of the coaxiality not exceeding 5%, and the diameter of a capillary tube opening of the channel is 50-1000 mu m.
5. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: in step S3, a three-phase emulsion is obtained by smoothly pushing three immiscible liquids into a channel using a syringe pump, wherein the internal phase is pushed into a first-stage channel, the intermediate phase is pushed into a second-stage channel, and the external phase is pushed into a third-stage channel.
6. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: the equilibrium interfacial tension in step S1 is obtained by one of the measurement of the pendant drop method, the pendant ring method, the capillary rise method, and the maximum bubble method.
7. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: in step S2, the spreading coefficients of the three immiscible liquids are required to satisfy the relationship of core-shell type, that is: si＞0、Sj＜0、Sk< 0, towards the Janus type, i.e.: si＜0、Sj＜0、Sk< 0, requirements for a converted emulsion.
8. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 7, wherein: in step S2, whether the selected emulsion system meets the requirements is judged according to the relation of spreading coefficients, if not, the type and concentration of the surfactant are changed until the requirements are met: by regulating the type and concentration of the surfactantThe three immiscible liquids meet the conditions; the measuring formula of the spreading coefficient is as follows: si＝γjk-(γij+γik) Wherein γ isjk、γij、γikThe interfacial tension of a three-phase emulsion system between two phases is shown, i, j and k respectively represent an internal phase, an intermediate phase and an external phase in the three-phase emulsion; calculating the spreading coefficient of each phase according to a formula by interfacial tension to obtain Si、Sj、SkWhen S isi＞0、Sj＜0、SkWhen less than 0, the emulsion structure is core-shell type, when S isi＜0、Sj＜0、SkBelow 0, the emulsion is Janus type.
9. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: the inner phase adopts one of TPGDA, ETPTA and PEGDA; the surfactant is: one of sodium dodecyl sulfate, glyceride, sorbitan oleate, octyl phenyl polyoxyethylene ether, Tween20, Tween40, dodecyl trimethyl ammonium bromide, Capstone FS-30 and Dow Corning 749; the surfactant concentration is 1X 10-7mol·L-1To 1 mol. L-1。
10. The method for measuring and calculating the dynamic interfacial tension of the multi-phase emulsion in the micro-channel according to claim 2, wherein: in step S4, a high-speed image micrograph of the emulsion from generation to dropping to each stage when the structural change of the emulsion is complete is taken; curing the emulsion by using ultraviolet light, taking out the emulsion from the tail end of the channel after curing to obtain the emulsion, and shooting an SEM image of the cured emulsion; in step S5, the relationship between the geometry and the three-phase contact angle, the interfacial tension and the flow ratio is obtained by geometric analysis of the emulsion structure, and an MATLAB simulation image is calculated by using a MATLAB program.
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