Preparation method of monodisperse structural color double emulsion

Abstract

The present application relates to a kind of monodisperse structural color double emulsion preparation method, it is a kind of preparation and color change control method of large batch monodisperse structural color double emulsion.By the different dispersed phase and continuous phase fluid of preparation, using microfluidic device, the flow of dispersed phase fluid, continuous phase fluid is adjusted, and large batch monodisperse structural color double emulsion is formed.The method described in the present application is simple to operate, easy to adjust, can be mass-produced, can accurately control the structural color of double emulsion, and the structural color microemulsion prepared has good monodispersity;The structural color microdroplet phenomenon prepared by the method described in the present application is obvious, and the system has good biocompatibility, and can be used for precise and complex biological active substance detection system.

Description

Technical Field

[0001] This invention belongs to the field of structural color preparation methods, and relates to a method for preparing monodisperse structural color dual emulsions. Specifically, it relates to a method for preparing and controlling the color change of structural colors in large quantities based on water-in-oil-in-water monodisperse dual emulsion droplets using droplet microfluidics. Background Technology

[0002] Structural color, also known as physical color, is a variety of colors produced by phenomena such as reflection, refraction, interference, and diffraction of light, based on microscopic physical structures. Common chemical colors rely on the absorption and reflection of specific wavelengths of light by fixed molecular structures. Once the molecular structure changes, such as during redox reactions, its optical properties are greatly affected, resulting in "fading." Compared to chemical colors, structural colors have advantages such as resistance to fading, environmental friendliness, and iridescent effects, making them promising for applications in display, anti-counterfeiting, and information encryption.

[0003] The following are some of the reported methods for preparing structured color microdroplets: (1) Thin film interference method, such as using mechanical stirring to randomly obtain a double emulsion with a thickness of submicron level. Since the thickness of the intermediate phase is close to the wavelength of light, thin film interference is generated to produce structured color. This method is simple to operate and the phenomenon is obvious, but it is difficult to produce structured color microdroplets with high monodispersity and has a large degree of randomness. Moreover, due to the limitation of thin film thickness, the operating window is narrow. (2) Micro-concave interface total internal reflection interference method, such as using the microscale concave interface of the two oil phases in a water-in-oil-in-oil double emulsion with an asymmetric Janus structure as a total internal reflection surface. Visible light undergoes total internal reflection and interference through this interface to produce structured color. This method can accurately control the generated structured color by controlling the structure of the double emulsion, but since it is an interface composed of two oil phases, its applicable range is limited. (3) Photonic crystal embedding method, such as using an external hyperpermeable environment to shrink the water-in-oil-in-water emulsion droplets, thereby causing the polystyrene nanoparticles encapsulated in the inner phase to form a long-range or short-range ordered structure, thereby producing structured color. This method can form iridescent or non-iridescent structural colors by controlling the permeation gradient, but the internal phase environment filled with colloidal nanoparticles requires a stable solid structure to maintain, and it is difficult to restore the original state after environmental disturbance, which poses a significant obstacle to its application. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing monodisperse structurally colored dual emulsions, specifically a method for preparing and controlling the color change of large-scale monodisperse dual emulsions with iridescent structural colors. This method is simple to operate, easy to control, and can precisely control the generation of different structural colors from a large number of microdroplets.

[0005] The objective of this invention can be achieved through the following methods:

[0006] This invention provides a method for preparing a monodisperse structural color dual emulsion, the steps of which are as follows:

[0007] (1) Preparation of dispersed phase and continuous phase fluid

[0008] Preparation of the first dispersed phase fluid: Add water-soluble emulsifier to deionized water and stir evenly to form the first dispersed phase fluid;

[0009] Preparation of the second dispersed phase fluid: Add oil-soluble surfactant to the oil phase and stir evenly to form the second dispersed phase fluid;

[0010] Preparation of the third dispersed phase fluid: Add water-soluble emulsifier and high osmotic pressure solution to deionized water and stir evenly to form the third dispersed phase fluid;

[0011] Preparation of the fourth dispersed phase fluid: Benzyl benzoate and soybean oil are mixed evenly to obtain a mixture, and then an oil-soluble surfactant is added to the mixture and stirred evenly to form the fourth dispersed phase fluid;

[0012] Preparation of the first continuous phase fluid: Water-soluble emulsifier and water-soluble surfactant are added to deionized water and stirred evenly to form the first continuous phase fluid;

[0013] Preparation of the second continuous phase fluid: Add water-soluble surfactant to deionized water and stir evenly to form the second continuous phase fluid;

[0014] (2) Preparation of structural color dual emulsion droplets

[0015] The structural color dual emulsion droplets include one of the following: ultrathin-walled structural color water-in-oil-in-water (W / O / W) emulsion droplets, monodisperse eccentric thin-walled structural color water-in-oil-in-water (W / O / W) emulsion droplets, and monodisperse eccentric thick-walled structural color water-in-oil-in-water (W / O / W) emulsion droplets; wherein,

[0016] The preparation steps of the ultrathin-walled structured water-in-oil-in-water (W / O / W) emulsion droplets are as follows:

[0017] The first dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid prepared in step (1) are injected into different inlets of the microfluidic device, so that the first dispersed phase fluid first enters the second dispersed phase fluid to form water-in-oil emulsion droplets, and then enters the first continuous phase fluid (the first dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid respectively form the inner phase, intermediate phase, and outer phase of the emulsion droplets); the flow rates of the three fluids are adjusted so that the water-in-oil emulsion droplets fully expand at the conical inlet and are sheared by the first continuous phase fluid into ultra-thin-walled water-in-oil emulsion droplets, which enter the collection tube for further collection and observation;

[0018] The preparation steps for the monodisperse eccentric thin-walled structured water-in-oil-in-water (W / O / W) emulsion droplets are as follows:

[0019] The third dispersed phase fluid, the second dispersed phase fluid, the first continuous phase fluid, and the second continuous phase fluid prepared in step (1) are injected into the microfluidic device. The third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid converge at the conical opening of the device and shear to form monodisperse water-in-oil-in-water emulsion droplets. The second dispersed phase encapsulates the third dispersed phase and is distributed in the first continuous phase (the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid respectively form the inner phase, intermediate phase, and outer phase of the emulsion droplets). The flow rates of the three fluids are adjusted to stabilize the three-phase interface at the conical opening, and a large number of monodisperse thick-walled water-in-oil-in-water emulsion droplets are sheared to form. Then, they meet with the second continuous phase fluid and are fully mixed and homogeneous, and enter the collection tube for further collection and observation.

[0020] The preparation steps for the monodisperse eccentric thick-walled structured water-in-oil-in-water (W / O / W) emulsion droplets are as follows:

[0021] The first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid prepared in step (1) are injected into the microfluidic device. The three fluids converge at the conical opening of the device and shear to form monodisperse water-in-oil-in-water emulsion droplets. The fourth dispersed phase encapsulates the first dispersed phase and is distributed in the first continuous phase (the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid respectively form the inner phase, intermediate phase, and outer phase of the emulsion droplets). The flow rates of the three fluids are adjusted to stabilize the three-phase interface at the conical opening. A large number of monodisperse thick-walled water-in-oil-in-water emulsion droplets are sheared and enter the collection tube for further collection and observation.

[0022] (3) Collect monodisperse structural color water-in-oil-in-water double emulsions

[0023] The monodisperse water-in-oil-in-water dual emulsion droplets formed in step (2), together with the continuous phase, are introduced into a separate collection container through a polytetrafluoroethylene output tube connected to the receiving tube of the microfluidic device for incubation, thus obtaining the corresponding type of monodisperse structural color dual emulsion.

[0024] In one embodiment of the present invention, in step (1) of preparing the first dispersed phase fluid, the water-soluble emulsifier is one of polyvinyl alcohol, polyethylene glycol, and hydroxyethyl cellulose; the mass ratio of the water-soluble emulsifier to deionized water is 0.05 to 0.1:1. The water-soluble emulsifier used should be able to stabilize the interface, have a suitable refractive index, and be clear and transparent.

[0025] As one embodiment of the present invention, in the preparation of the second dispersed phase fluid in step (1), the oil-soluble surfactant is one of sorbitol fatty acid ester (Span 80), polyglycerol ricinoleate (PGPR), and polysorbate 80 (Tween 80), and the oil phase includes one of ethoxylated trimethylolpropane triacrylate (ETPTA), soybean oil, and n-octanol; the amount of oil-soluble surfactant is 0.005-0.02g per 1ml of oil phase. The oil-soluble surfactant and the oil phase should have a stable interface, a suitable refractive index, be clear and transparent, and have good light transmittance. However, the oil should have good light transmittance, the oil-soluble surfactant should be able to stabilize the interface, and the oil phase should be clear and transparent with a refractive index greater than that of water.

[0026] In one embodiment of the present invention, in step (1) of preparing the third dispersed phase fluid, the high osmotic pressure solution is a sodium chloride solution, and the water-soluble emulsifier is polyvinyl alcohol; the mass ratio of the water-soluble emulsifier, sodium chloride, and deionized water is 0.005–0.05:0.02–0.1:1. The high osmotic pressure solution needs to have a higher osmotic pressure than the outermost phase fluid, but it cannot be too high. Too high a pressure will lead to excessive expansion and droplet bursting; too low a pressure will lead to insufficient expansion, insufficient oil film, and lack of structural color.

[0027] In one embodiment of the present invention, in step (1) of preparing the fourth dispersed phase fluid, benzyl benzoate and soybean oil are in a volume ratio of 0.5 to 1:1; the amount of the oil-soluble surfactant is 0.005 to 0.02 g per 1 ml of the mixture. The system of benzyl benzoate and soybean oil can stabilize the interface, and the interfacial energy between it and the other two phases is suitable, allowing it to spontaneously form a suitable structure through interfacial tension. If the system ratio changes, the interfacial energy may change, preventing the formation of a suitable structure and thus resulting in a lack of structural color.

[0028] In one embodiment of the present invention, in step (1) of preparing the first continuous phase fluid, the water-soluble emulsifier is polyvinyl alcohol, and the mass ratio of the water-soluble emulsifier, water-soluble surfactant, and deionized water is 0.05-0.1:0.005-0.02:1. The emulsifier and surfactant need to be able to stabilize the emulsion and have suitable viscosity.

[0029] As one embodiment of the present invention, in step (1) the preparation of the second continuous phase fluid, the water-soluble surfactant is... F-68; the mass ratio of water-soluble surfactant to deionized water is 0.005 to 0.02:1. This continuous phase fluid is used only for diluting the first continuous phase fluid.

[0030] As one embodiment of the present invention, the preparation of the dispersed phase fluid and the continuous phase fluid in step (1) are carried out at normal pressure and room temperature.

[0031] As one embodiment of the present invention, in step (2) the preparation of ultrathin-walled structured water-in-oil-in-water (W / O / W) emulsion droplets, the flow rate Q of the first dispersed phase fluid is... A =200~300L / h, the flow rate Q of the second dispersed phase fluid B =50~150L / h, the flow rate Q of the first continuous phase fluid F =4000~8000L / h.

[0032] As one embodiment of the present invention, in step (2) of preparing monodisperse eccentric thin-walled structure water-in-oil-in-water (W / O / W) emulsion droplets, the flow rate Q of the third dispersed phase fluid is... C =200~300L / h, the flow rate Q of the second dispersed phase fluid D =150~250L / h, the flow rate Q of the first continuous phase fluid F =2000~4000L / h, the flow rate Q of the second continuous phase fluid F =8000~16000L / h. Adjusting the flow rate of the second dispersed phase fluid changes the osmotic pressure of the external phase aqueous solution, affecting the osmotic pressure difference between the internal and external phases of the double emulsion, further adjusting the thickness of the intermediate oil film in the thin-walled double emulsion, thereby changing the structural color of the droplets.

[0033] As one embodiment of the present invention, in step (2) of preparing monodisperse eccentric thick-walled structure water-in-oil-in-water (W / O / W) emulsion droplets, the flow rate Q of the first dispersed phase fluid is... A =200~400L / h, the flow rate Q of the fourth dispersed phase fluid E =300~400L / h, the flow rate Q of the first continuous phase fluid F =2000~4000L / h.

[0034] As one embodiment of the present invention, in step (2) preparation of monodisperse eccentric thick-walled structure water-in-oil-in-water (W / O / W) emulsion droplets, the microfluidic device (third microfluidic device) includes a square tube, an injection tube and a receiving tube respectively nested inside the inlet and outlet ends of the square tube; both the injection tube and the receiving tube have a pointed end and a flat end, the pointed end is inside the square tube and is coaxial with each other, used for shearing the emulsion, the flat end is used for solution entry and exit, and the flat end is located outside the square tube; the flat end of the injection tube is the first inlet (inner phase solution inlet), the gap between it and the inlet end of the square tube is the second inlet (intermediate phase solution inlet), and the gap between the flat end of the receiving tube and the outlet end of the square tube is the third inlet (outer phase solution inlet).

[0035] As one embodiment of the present invention, in step (2) the preparation of ultrathin-walled water-in-oil-in-water (W / O / W) emulsion droplets, the microfluidic device (first microfluidic device) is a thin round tube inserted into the flat end of the injection tube of the above-mentioned microfluidic device (third microfluidic device); the thin round tube is the fourth liquid inlet, and the gap between it and the flat end of the injection tube is the first liquid inlet (intermediate phase solution inlet), and the second liquid inlet is the outer phase solution inlet. In the present invention, after the second dispersed phase fluid shears the first dispersed phase fluid into droplets, the first dispersed phase droplets themselves have a large volume, while the space at the tip of the injection tube is narrow. Therefore, the first dispersed phase droplets occupy a large space at the tip, and only a thin layer of the second dispersed phase adheres tightly to the inner wall of the glass tube. Therefore, when it is sheared by the first continuous phase fluid at the tip, it is itself an ultrathin-walled structure. The water-in-oil emulsion droplets should expand sufficiently in the injection tube (conical opening) to form a thin film of oil phase adhering to the inner wall, and remain stable and not break when the water-in-oil emulsion droplets are sheared into ultra-thin-walled water-in-oil emulsion droplets by the first continuous phase fluid.

[0036] As one embodiment of the present invention, in step (2) preparation of monodisperse eccentric thin-walled structure water-in-oil-in-water (W / O / W) emulsion droplets, the microfluidic device (second microfluidic device) is a thick square tube sleeved on the outside of the flat end of the receiving tube of the above-mentioned microfluidic device (third microfluidic device), and the gap between them is the fifth liquid inlet (external phase solution inlet).

[0037] As one embodiment of the present invention, the outer diameter of the monodisperse structural color dual emulsion is 60-200 μm.

[0038] As one embodiment of the present invention, the monodisperse structural color dual emulsion is an ultrathin-walled structural color dual emulsion, based on the principle of thin-film interference; the monodisperse structural color dual emulsion is an eccentric thin-walled structural color dual emulsion, based on the principle of total internal reflection and interference; the monodisperse structural color dual emulsion is an eccentric thick-walled structural color dual emulsion, based on the principle of total internal reflection and interference.

[0039] This invention also provides an application of the monodisperse structural color dual emulsion in information encryption. A brightly colored droplet reflection halo can only be observed from a specific observation angle when light meeting the incident angle requirements illuminates the structural color droplet, thus enabling its use in fields such as information encryption. The structural color microdroplet phenomenon obtained by this method is obvious, and the system exhibits good biocompatibility, making it suitable for sophisticated and complex bioactive substance detection systems.

[0040] The method for preparing ultrathin-walled structurally colored water-in-oil-in-water emulsion droplets described in this invention is based on the mechanism of thin-film interference. The principle is as follows: the oil phase layer in the water-in-oil-in-water double emulsion has a thickness at the sub-micron level, close to the visible light wavelength range. When visible light irradiates the double emulsion, part of the incident light is reflected at the interface between the oil phase and the outer phase, and part of the incident light is refracted at the interface between the oil phase and the outer phase, entering the oil phase layer, reflected at the interface between the oil phase and the inner phase, and then refracted again at the interface between the oil phase and the outer phase before exiting the oil phase layer. At this time, the two beams of light interfere constructively or destructively, resulting in increased intensity of visible light in some wavelength ranges and decreased intensity in others, ultimately causing the water-in-oil-in-water double emulsion to exhibit a specific color. By adjusting the flow rate of the first continuous phase solution, the size of the ultrathin-walled water-in-oil-in-water emulsion droplets can be controlled, thereby affecting the thickness of the intermediate oil phase and thus influencing the different structural colors of the ultrathin-walled water-in-oil-in-water emulsion droplets. A schematic diagram of thin-film interference occurring in ultrathin-walled water-in-oil-in-water emulsion droplets in this invention is shown below. Figure 1 As shown, the inner phase is the first dispersed phase 1, the intermediate phase is the second dispersed phase 2, and the outer phase is the first continuous phase 5.

[0041] The method for preparing monodisperse eccentric thin-walled water-in-oil-in-water emulsion droplets described in this invention is based on the mechanism of total internal reflection and interference. The principle is as follows: the osmotic pressure of the inner aqueous phase in the prepared monodisperse thick-walled water-in-oil-in-water emulsion is greater than that of the outer aqueous phase. Therefore, the aqueous phase inside the double emulsion droplet absorbs water and expands, while the thickness of the intermediate oil phase continuously decreases. The osmotic pressure gradient between the inner and outer phases continuously decreases until the osmotic pressures of the inner and outer phases reach equilibrium, forming a thin-walled water-in-oil-in-water emulsion droplet. Since the density of the inner aqueous phase is greater than that of the outer aqueous phase, which is greater than that of the intermediate oil phase, the water-in-oil-in-water double emulsion has an eccentric core-shell structure, with the inner aqueous phase core shifting downwards. The lower oil film of the water-in-oil-in-water double emulsion droplet is thinner than the upper oil film. The refractive index of the intermediate oil phase is greater than that of both the inner and outer aqueous phases, satisfying the condition for total internal reflection. When visible light shines on the double emulsion from below, a portion of the incident light enters from the lower oil film on one side of the double emulsion droplet. Because the oil phase has the highest refractive index, the light undergoes continuous total internal reflection within the oil film and is transmitted out through the lower oil film of the other double emulsion droplet, where it is received by the detector below. Due to the total internal reflection, the light intensity in the middle oil phase of the double emulsion droplet is significantly higher than the ambient light intensity. Simultaneously, during the total internal reflection, both constructive and destructive interference occur, resulting in a structural color circular halo appearing on the double emulsion droplet. By adjusting the osmotic pressure of the inner phase solution, the internal and external osmotic pressure gradients can be controlled, thereby affecting the thickness of the middle oil phase when the final osmotic pressure stabilizes, and consequently influencing the structural color of the eccentric thin-walled water-in-oil-in-water emulsion droplet. A schematic diagram of total internal reflection and interference occurring in the eccentric thin-walled structural color water-in-oil-in-water emulsion droplet in this invention is shown below. Figure 2 As shown, the inner phase is the third dispersed phase 3, the intermediate phase is the second dispersed phase 2, and the outer phase is the first continuous phase 5 and the second continuous phase 6.

[0042] The preparation mechanism of the monodisperse eccentric thick-walled structural color water-in-oil-in-water emulsion droplets described in this invention is similar to that of the monodisperse eccentric thin-walled structural color water-in-oil-in-water emulsion droplets mentioned above. The principle is as follows: the prepared monodisperse thick-walled water-in-oil-in-water emulsion droplets undergo a spontaneous dehumidification process driven by the interfacial tension of the three phases. The inner aqueous phase core deviates from the center and comes into contact with the outer aqueous phase, separated by a double layer of surfactant, forming an eccentric core-shell structure in the double emulsion droplets. Because the density of the inner aqueous phase is greater than that of the outer aqueous phase, which is greater than that of the intermediate oil phase, the inner aqueous phase core shifts downwards. Since the intermediate oil phase has the highest refractive index, light rays emitted from below enter the oil film and undergo total internal reflection and interference, ultimately resulting in a structural color circular halo appearing in the double emulsion droplets. By adjusting the concentration of surfactant in the continuous phase solution, the interfacial tension of the three-phase solution can be controlled, thereby affecting the thickness of the intermediate oil phase when the final interfacial tension is stable, and consequently influencing the different structural colors of the eccentric thick-walled water-in-oil-in-water emulsion droplets. A schematic diagram of total internal reflection and interference occurring in droplets of an eccentrically thick-walled water-in-oil-in-water emulsion in this invention is shown below. Figure 3 As shown, the inner phase is the first dispersed phase 1, the intermediate phase is the fourth dispersed phase 4, and the outer phase is the first continuous phase 5.

[0043] The present invention allows the use of various types of coaxial capillary glass tube microfluidic devices, with a preferred microfluidic device having the following structure: the microfluidic device is constructed from a glass slide, a circular capillary glass tube, a rectangular glass square tube, and an injection needle (construction method see N.-N. Deng, M. Yelesswarapu and W. Huck. Monodisperse uni-and multicompartment liposomes. J. Am. Chem. Soc. 2016, 138, 24, 7584-7591). The process of generating a dual emulsion within the first microfluidic device with a two-stage coaxial capillary glass tube used in the production of ultrathin-walled structural color dual emulsions according to the present invention is as follows: Figure 4 As shown, high-speed camera images are as follows Figure 5 As shown, a rectangular capillary glass tube and a circular capillary glass tube constitute the first-stage droplet generator. The first dispersed phase fluid and the second dispersed phase fluid shear to form an oil-in-water emulsion. Two circular capillary glass tubes constitute the second-stage droplet generator. The oil-in-water emulsion and the first continuous phase fluid shear to form an ultrathin-walled water-in-oil-in-water dual emulsion. The process of generating the dual emulsion in the second microfluidic device with a single-stage coaxial capillary glass tube used in this invention to produce the thin-walled eccentrically structured color dual emulsion is as follows: Figure 6 As shown, high-speed camera images are as follows Figure 7 As shown, the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are sheared to form a water-in-oil-in-water emulsion, which is subsequently mixed with the second continuous phase fluid. The process of generating the dual emulsion in the third microfluidic device with a single-stage coaxial capillary glass tube used in the production of the thick-walled eccentric structured color dual emulsion of this invention is as follows: Figure 8 As shown, high-speed camera images are as follows Figure 9 As shown, the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid are sheared to form a water-in-oil-in-water emulsion; the microfluidic channels of the above three microfluidic devices have four, four, and three inlets, respectively, and the collection tube has an enlarged chamber to avoid collision and contact of emulsion droplets. The microfluidic channel has one outlet; the number of injection needles is the same as the number of microfluidic channel inlets, and they are fixed at the inlets of the microfluidic channels. A polytetrafluoroethylene output tube is fixed at the outlet of the receiving tube of the microfluidic device.

[0044] In this application, the first type of ultrathin-walled droplet is directly formed into the desired structure after being collected, without the need for incubation. The latter two types are not the desired specific structures and require an incubation period. By utilizing the coordination of the osmotic gradient (second type) or interfacial tension (third type) and gravity, they can be transformed into specific structures with structural colors.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The method described in this invention is simple to operate, easy to adjust, and can be mass-produced. It can accurately control the structural color of the dual emulsion, and the structural color microemulsion prepared has good monodispersity.

[0047] (2) The structured color microdroplets prepared by the method of the present invention exhibit obvious phenomena and the system has good biocompatibility, and can be used in precise and complex bioactive substance detection systems. Attached Figure Description

[0048] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0049] Figure 1 This is a schematic diagram of the monodisperse colored ultrathin-walled water-in-oil emulsion structure described in this invention;

[0050] Figure 2 This is a schematic diagram of the monodisperse thin-walled eccentric structure color water-in-oil-in-water emulsion described in this invention;

[0051] Figure 3 This is a schematic diagram of the monodisperse thick-walled eccentric structure color water-in-oil-in-water emulsion described in this invention;

[0052] Figure 4 This is a schematic diagram of the first microfluidic device using a coaxial capillary glass tube for preparing ultrathin-walled structural color emulsions as described in this invention.

[0053] Figure 5 This is a high-speed camera photograph of the first dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid of the present invention being sheared at the conical opening of the first microfluidic device to form a water-in-oil-in-water emulsion.

[0054] Figure 6 This is a schematic diagram of the coaxial capillary glass tube second microfluidic device used in the preparation of thin-walled eccentric structured color emulsions according to the present invention;

[0055] Figure 7 This is a high-speed camera photograph of a water-in-oil-in-water emulsion formed by shearing the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid at the conical opening of the second microfluidic device, as described in this invention.

[0056] Figure 8 This is a schematic diagram of the coaxial capillary glass tube third microfluidic device used in the preparation of thick-walled eccentric structured color emulsions according to the present invention;

[0057] Figure 9 This is a high-speed camera photograph of the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid of the present invention being sheared at the conical opening of the third microfluidic device to form a water-in-oil-in-water emulsion.

[0058] Figure 10 These are microscope images of large-sized colored ultrathin-walled water-in-oil-in-water droplets prepared in Experiment 1 of Example 1;

[0059] Figure 11 These are microscope images of medium-sized colored ultrathin-walled water-in-oil-in-water droplets prepared in Experiment 2 of Example 1;

[0060] Figure 12 These are microscope images of small-sized colored ultrathin-walled water-in-oil-in-water droplets prepared in Experiment 3 of Example 1;

[0061] Figure 13 These are microscope images of the green monodisperse eccentric thin-walled water-in-oil-in-water droplets prepared in Experiment 1 of Example 2;

[0062] Figure 14 These are microscope images of pink monodisperse eccentric thin-walled water-in-oil-in-water droplets prepared in Experiment 2 of Example 2;

[0063] Figure 15 These are microscope images of purple monodisperse eccentric thin-walled water-in-oil-in-water droplets prepared in Experiment 3 of Example 2;

[0064] Figure 16 These are microscope images of the cyan monodisperse eccentric thick-walled water-in-oil-in-water droplets prepared in Experiment 1 of Example 3;

[0065] Figure 17 These are microscope images of green monodisperse eccentric thick-walled water-in-oil-in-water droplets prepared in Experiment 2 of Example 3;

[0066] Figure 18 These are microscope images of pink monodisperse eccentric thick-walled water-in-oil-in-water droplets prepared in Experiment 3 of Example 3;

[0067] Figure 19 These are microscope images of the emulsion droplets prepared in Comparative Example 1.

[0068] Figure 20 These are microscope images of the emulsion droplets prepared in Comparative Example 2.

[0069] Figure 21 These are microscope images of the emulsion droplets prepared in Comparative Example 3.

[0070] Figure 22 These are microscope images of the emulsion droplets prepared in Comparative Example 4.

[0071] Figure 23 These are microscope images of the emulsion droplets prepared in Comparative Example 5.

[0072] In the figure, 1-first dispersed phase, 2-second dispersed phase, 3-third dispersed phase, 4-fourth dispersed phase, 5-first continuous phase, 6-second continuous phase, 7-first inlet, 8-second inlet, 9-third inlet, 10-fourth inlet, 11-fifth inlet, 12-injection tube, 13-receiving tube, 14-square tube, 15-thin round tube, 16-coarse square tube. Detailed Implementation

[0073] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0074] The preparation method of the mass production of monodisperse structural color dual emulsions of the present invention will be further described below with reference to the accompanying drawings and examples. In the following examples, F-68 is a type of poloxamer, traded as Pluronic, which is a block copolymer of polyoxyethylene polyoxypropylene ether and was purchased from Sigma-Aldrich (Shanghai Trading Co., Ltd.); the polyvinyl alcohol (PVA, Mw 13-23k), sorbitan fatty acid ester (Span 80), sodium chloride, benzyl benzoate, mineral oil, n-octanol, and ethoxylated trimethylolpropane triacrylate (ETPTA) were all purchased from Sigma-Aldrich (Shanghai Trading Co., Ltd.); the medical soybean oil is of injection grade and was purchased from Tieling Beiya Pharmaceutical Oil Co., Ltd.

[0075] Example 1

[0076] This embodiment uses the method described in this invention to prepare large quantities of ultrathin-walled structured color water-in-oil-in-water (W / O / W) emulsions. The process steps are as follows:

[0077] (1) Preparation of dispersed phase and continuous phase fluid

[0078] Preparation of the first dispersed phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) was added to deionized water and stirred evenly at normal pressure and room temperature to form the first dispersed phase fluid. The mass ratio of PVA to deionized water in the first dispersed phase fluid was 1:9.

[0079] Preparation of the second dispersed phase fluid: Span 80 (dehydrated sorbitol fatty acid ester) was added to ethoxylated trimethylolpropane triacrylate (ETPTA) / soybean oil / n-octanol at ambient pressure and room temperature, and stirred until homogeneous to form the second dispersed phase fluid. The amount of Span 80 was 0.02 g per 1 ml of oil phase; (the three oils were used in experiments 1, 2, and 3, respectively).

[0080] Preparation of the first continuous phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) and F-68 are added to deionized water at normal pressure and room temperature and stirred evenly to form a continuous phase fluid. The mass ratio of PVA, F-68 and deionized water in the continuous phase fluid is 10:1:89.

[0081] (2) Preparation of ultrathin-walled structural color W / O / W emulsion droplets

[0082] Figure 4 This is a schematic diagram of the structure of the first microfluidic device used in this embodiment, and a high-speed camera image of the water-in-oil-in-water emulsion droplets generated in its microfluidic channels is shown below. Figure 5As shown. The first microfluidic device is a coaxial capillary glass tube device. The injection tube 12, receiving tube 13, square tube 14, thin round tube 15, and four needles are assembled on a clean and flat glass plate. The injection tube 12 and receiving tube 13 are nested inside the inlet and outlet ends of the square tube 14. The thin round tube 15 is inserted into the flat end of the injection tube 12. The thin round tube 15 is a hollow square tube with an outer diameter of 350 μm (the inlet end (outer side) of the thin round tube 15 is also a flat surface, and the other end is a tapered tip. The outer diameter of the thin round tube 15 is 330 μm, the inner diameter is 200 μm, and the inner diameter of the tapered tip is 50 μm. It is also hydrophobic). The injection tube 12 and receiving tube 13 are both hollow round tubes with an inner diameter of 400 μm and an outer diameter of 960 μm, with a flat surface at one end and a tapered tip at the other end. The first-stage conical square tube has an inner diameter of 50 μm at its tip, and the injection tube 12 has an inner diameter of 100 μm at its conical tip. Its surface is treated with a mixed solution of hexane and trimethylchlorosilane to make it hydrophobic. The receiving tube 13 has an inner diameter of 150 μm at its conical tip and is treated with a 10% aqueous solution of 2-[methoxy(polyoxyethylene)propyl]trimethoxysilane to make its surface hydrophilic. The rectangular square tube 14 is a hollow square tube with an inner diameter of 1 mm. The thin round tube 15 is nested inside the injection tube 12, with its conical tip 600 μm away from the conical tip of the injection tube 12. The tips of the injection tube 12 and the receiving tube 13 are inserted into the rectangular square tube 14, coaxially aligned, and 150 μm apart, and are fixed to the glass slide surface using epoxy resin adhesive. Three needles serve as liquid injection channels, respectively fixed to the fourth inlet 10 of the flat section of the thin round tube 15, the first inlet 7 of the flat end of the injection tube 12, and the second inlet 8 between the flat end of the injection tube 12 and the end of the rectangular square tube 14 near the injection tube. One needle serves as a spare injection channel. The inlet 9 can be used to remove air bubbles or dirt from the device and can be plugged when in use.

[0083] The first dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid prepared in step (1) are injected into the microfluidic device via syringes connected to the injection pump. The injection is injected into needles 1 (the fourth inlet 10 of the first single-stage droplet generator of the first microfluidic device), 2 (the first inlet 7 of the first single-stage droplet generator of the first microfluidic device), and 3 (the second inlet 8 of the second single-stage droplet generator of the first microfluidic device). The first dispersed phase fluid enters through the thin round tube 15, the second dispersed phase fluid enters through the injection tube 12, and the first continuous phase fluid enters through the gap inlet of the rectangular tube 14 near the end of the injection tube 12. The first dispersed phase fluid and the second dispersed phase fluid converge and shear at the tip of the thin round tube 15 inside the injection tube 12 to form an oil-in-water emulsion. The emulsion droplets meet the first continuous phase fluid at the tip of the injection tube 12 and shear to form a water-in-oil-in-water emulsion droplet. The flow rates of the first dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are adjusted to allow the first-stage oil-in-water emulsion droplets to fully expand. The second dispersed phase fluid forms a stable ultra-thin oil film. The oil-in-water emulsion droplets are sheared at the tip of the injection tube to form an ultra-thin-walled structural color water-in-oil-in-water emulsion droplet and enter the receiving tube 13 at the tip of the receiving tube 13, and are finally received by the flat end of the receiving tube 13.

[0084] Experiment 1: When the flow rate Q of the first dispersed phase fluid A =200 L / h, the flow rate Q of the second dispersed phase fluid (ETPTA) B =100L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 8000 L / h, the water-in-oil emulsion droplets expand fully in the chamber of the injection tube, with only a thin oil film separating them from the inner wall of the injection tube. The water-in-oil emulsion droplets expand fully at the tip of the injection tube and are sheared by the first continuous phase fluid to form colored ultrathin wall structured W / O / W emulsion droplets.

[0085] Experiment 2: When the flow rate Q of the first dispersed phase fluid A =200L / h, the flow rate Q of the second dispersed phase fluid (soybean oil) B =100L / h, the flow rate Q of the first continuous phase fluid F = 5000L / h, the water-in-oil emulsion droplets fully expand in the chamber of the injection tube, with only a thin oil film separating them from the inner wall of the injection tube. The water-in-oil emulsion droplets fully expand at the tip of the injection tube and are sheared by the first continuous phase fluid to form colored ultrathin wall structured W / O / W emulsion droplets.

[0086] Experiment 3: When the flow rate Q of the first dispersed phase fluid A =200 L / h, the flow rate Q of the second dispersed phase fluid (n-octanol) B =100L / h, the flow rate Q of the first continuous phase fluid F= 4000L / h, the water-in-oil emulsion droplets fully expand in the chamber of the injection tube, with only a thin oil film separating them from the inner wall of the injection tube. The water-in-oil emulsion droplets fully expand at the tip of the injection tube and are sheared by the first continuous phase fluid to form colored ultrathin wall structured W / O / W emulsion droplets.

[0087] (3) Collect droplets of ultrathin-walled structural color W / O / W emulsion.

[0088] The ultrathin-walled structural color W / O / W emulsion droplets in the receiving tube formed in step (2), together with the first continuous phase fluid, are introduced into a separate collection container through a polytetrafluoroethylene output tube connected to the receiving tube of the microfluidic device, thus obtaining the corresponding ultrathin-walled structural color W / O / W emulsion droplets.

[0089] Optical microscope images of monodisperse colored ultrathin-walled structural color W / O / W emulsion droplets prepared according to the conditions in Experiment 1 are shown below. Figure 10 , 11 As shown in Figure 12, the emulsion droplets are uniform in size and colorful. Under a bright-field transmitted light microscope, the edges of individual ultrathin-walled emulsion droplets exhibit a bright monochromatic halo.

[0090] The monodisperse colored ultrathin-walled structural color W / O / W emulsion droplets prepared in this embodiment exhibit high biocompatibility and can encapsulate biological reaction systems within the inner phase solution. As the reaction proceeds, the physicochemical properties of the inner phase solution, such as osmotic pressure, change, affecting the thickness of the intermediate oil phase, ultimately resulting in a color change in the ultrathin-walled structural color W / O / W emulsion droplets.

[0091] Example 2

[0092] This embodiment uses the method described in this invention to prepare large quantities of monodisperse eccentric thin-walled color water-in-oil-in-water (W / O / W) emulsions. The process steps are as follows:

[0093] (1) Preparation of dispersed phase and continuous phase fluid

[0094] Preparation of the third dispersed phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) and sodium chloride are added to deionized water under normal pressure and room temperature and stirred evenly to form the third dispersed phase fluid. The mass ratio of PVA, sodium chloride and deionized water in the third dispersed phase fluid is 1:0.12:10.

[0095] Preparation of the second dispersed phase fluid: Span 80 (dehydrated sorbitol fatty acid ester) was added to ethoxylated trimethylolpropane triacrylate (ETPTA) / soybean oil / n-octanol at ambient pressure and room temperature, and stirred until homogeneous to form the second dispersed phase fluid. The amount of Span 80 was 0.02 g per 1 ml of oil phase; (the three oils were used in experiments 1, 2, and 3, respectively).

[0096] Preparation of the first continuous phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) and F-68 are added to deionized water and stirred evenly at normal pressure and room temperature to form a continuous phase fluid. The mass ratio of PVA, F-68 and deionized water in the continuous phase fluid is 10:1:89.

[0097] Preparation of the second continuous phase fluid: F-68 is added to deionized water and stirred evenly at normal pressure and room temperature to form the second continuous phase fluid. The mass ratio of F-68 to deionized water in the second continuous phase fluid is 1:99.

[0098] (2) Preparation of eccentric thin-walled structural color W / O / W emulsion droplets

[0099] Figure 6 This is a schematic diagram of the structure of the second microfluidic device used in this embodiment, and a high-speed camera image of the water-in-oil-in-water emulsion droplets generated within its microfluidic channels is shown below. Figure 7 As shown. The second microfluidic device is a coaxial capillary glass tube device, consisting of an injection tube 12, a receiving tube 13, a square tube 14, and a thick square tube 16, assembled with four needles on a clean, flat glass plate. The injection tube 12 and the receiving tube 13 are nested inside the inlet and outlet ends of the square tube 14. A thick square tube 16 is fitted over the flat end of the receiving tube 13, with the gap between them forming the fifth inlet 11. Both the injection tube 12 and the receiving tube 13 are hollow cylindrical tubes with an inner diameter of 400 μm and an outer diameter of 960 μm, with one end having a flat cut and the other end having a tapered tip. The tapered tip of the injection tube 12 has an inner diameter of 100 μm and is treated with a mixed solution of hexane and trimethylchlorosilane to make its surface hydrophobic. The tapered tip of the receiving tube 13 has an inner diameter of 150 μm and is treated with a 10% aqueous solution of 2-[methoxy(polyoxyethylene)propyl]trimethoxysilane to make its surface hydrophilic. The rectangular square tube 14 is a hollow square tube with an inner diameter of 1 mm. The tips of the injection tube 12 and the receiving tube 13 are inserted into the rectangular square tube 14, coaxially aligned with each other, and 150 μm apart, and fixed to the surface of the glass slide using epoxy resin adhesive. The tail of the receiving tube 13 is inserted into the thick square tube 16 for mixing with the second dispersed phase fluid. Four needles serve as liquid injection channels, respectively fixed to the first inlet 7 at the flat end of the injection tube, the second inlet 8 and the third inlet 9 at both ends of the rectangular square tube, and the fifth inlet 11 at the connection between the receiving tube and the receiving square tube.

[0100] The third dispersed phase fluid, the second dispersed phase fluid, the first continuous phase fluid, and the second continuous phase fluid prepared in step (1) are injected into the microfluidic device through syringes connected to the injection pump. The injection is carried out through needles 5 (first inlet 7 of the second microfluidic device), 6 (second inlet 8 of the second microfluidic device), 7 (third inlet 9 of the second microfluidic device), and 8 (fifth inlet 11 of the second microfluidic device). The third dispersed phase fluid enters through the injection tube, while the second dispersed phase fluid and the first continuous phase fluid enter through both ends of the rectangular tube 14. The second dispersed phase fluid enters through the connection between the receiving tube 13 and the coarse square tube 16. The three fluids converge and shear at the tips of the injection tube 12 and the receiving tube 13. The flow rates of the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are adjusted to stabilize the interface, forming monodisperse W / O / W emulsion droplets that enter the receiving tube 13 at the tip of the receiving tube. These droplets mix with the second dispersed phase fluid in the receiving square tube and are finally received by the coarse square tube 16.

[0101] Experiment 1: When the flow rate Q of the third dispersed phase fluid A =250 L / h, the flow rate Q of the second dispersed phase fluid (ETPTA) B =100L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 8000 L / h, the flow rate Q of the second continuous phase fluid is... G At a flow rate of 8000 L / h, the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are sheared at the conical opening of the injection tube to form a thick-walled water-in-oil-in-water double emulsion.

[0102] Experiment 2: When the flow rate Q of the third dispersed phase fluid A =250L / h, the flow rate Q of the second dispersed phase fluid (soybean oil) B =200L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 2000 L / h, the flow rate Q of the second continuous phase fluid is... G When the flow rate is 12000 L / h, the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are sheared at the conical opening of the injection tube to form a thick-walled water-in-oil-in-water double emulsion.

[0103] Experiment 3: When the flow rate Q of the third dispersed phase fluid A =250 L / h, the flow rate Q of the second dispersed phase fluid (n-octanol) B =200L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 2000 L / h, the flow rate Q of the second continuous phase fluid is... G When the flow rate is 12000 L / h, the third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid are sheared at the conical opening of the injection tube to form a thick-walled water-in-oil-in-water double emulsion.

[0104] (3) Collect and incubate eccentric thin-walled structural color W / O / W emulsion droplets

[0105] The monodisperse W / O / W emulsion droplets formed in step (2), together with the first continuous phase fluid and the second continuous phase fluid, are introduced into a separate collection container through a polytetrafluoroethylene output tube connected to the microfluidic device receiving tube. They are incubated until the internal and external phase osmotic pressures are balanced to obtain the corresponding monodisperse eccentric thin-walled structural color W / O / W emulsion droplets.

[0106] Optical microscope images of monodisperse eccentric thin-walled structured color W / O / W emulsion droplets prepared according to the conditions in Experiment 1 are shown below. Figure 13 , 14 As shown in Figure 15. Experiment 1 yielded green monodisperse eccentric thin-walled emulsion droplets ( Figure 13 Experiment 2 yielded pink monodisperse eccentric thin-walled emulsion droplets. Figure 14 Experiment 3 yielded purple monodisperse eccentric thin-walled emulsion droplets. Figure 15 In Experiment 1, the droplet structural color requires light to be shone directly above the sample, and the reflected light must be observed from directly above to capture the structural color halo. In Experiments 2 and 3, the droplet structural color requires light to be shone directly below the sample, and the reflected light must be observed from directly below to capture the structural color halo. Therefore, it can be used in fields such as information encryption.

[0107] Example 3

[0108] This embodiment uses the method described in this invention to prepare large quantities of monodisperse eccentric thick-walled color water-in-oil-in-water (W / O / W) emulsions. The process steps are as follows:

[0109] (1) Preparation of dispersed phase and continuous phase fluid

[0110] Preparation of the first dispersed phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) was added to deionized water and stirred evenly at normal pressure and room temperature to form the first dispersed phase fluid. The mass ratio of PVA to deionized water in the first dispersed phase fluid was 1:9.

[0111] Preparation of the fourth dispersed phase fluid: Benzyl benzoate and soybean oil are mixed evenly at a volume ratio of 0.5 to 1:1 under normal pressure and room temperature to obtain a mixed solution. Then, sorbitol fatty acid ester (Span 80) is added to the mixed solution and stirred evenly to form the third dispersed phase fluid. The amount of Span 80 is 0.04g per 1ml of the mixed solution.

[0112] Preparation of the first continuous phase fluid: Polyvinyl alcohol (PVA, Mw 13-23k) and F-68 are added to deionized water and stirred evenly at normal pressure and room temperature to form a continuous phase fluid. The mass ratio of PVA, F-68 and deionized water in the continuous phase fluid is 10:0.2 to 1:89.

[0113] (2) Preparation of eccentric thick-walled structural color W / O / W emulsion droplets

[0114] Figure 8 This is a schematic diagram of the third microfluidic device used in this embodiment, and a high-speed camera image of the water-in-oil-in-water emulsion droplets generated within its microfluidic channels is shown below. Figure 9 As shown. The third microfluidic device is a coaxial capillary glass tube assembly, consisting of an injection tube 12, a receiving tube 13, a square tube 14, and three needles, assembled on a clean, flat glass plate. The injection tube 12 and receiving tube 13 are nested inside the inlet and outlet ends of the square tube 14. Both the injection tube 12 and the receiving tube 13 are hollow cylindrical tubes with an inner diameter of 400 μm and an outer diameter of 960 μm, with one end having a flat cut and the other end having a tapered tip. The tapered tip of the injection tube 12 has an inner diameter of 100 μm and is treated with a mixed solution of n-hexane and trimethylchlorosilane to make its surface hydrophobic. The tapered tip of the receiving tube 13 has an inner diameter of 150 μm and is treated with a 10% aqueous solution of 2-[methoxy(polyoxyethylene)propyl]trimethoxysilane to make its surface hydrophilic. The rectangular square tube 14 is a hollow square tube with an inner diameter of 1 mm. The tips of the injection tube 12 and the receiving tube 13 are inserted into the rectangular square tube, coaxially aligned with each other and 150 μm apart, and fixed to the surface of the glass slide using epoxy resin adhesive. Three needles serve as liquid injection channels, respectively fixed to the first inlet 7 at the flat end of the injection tube and the second and third inlets 8 and 9 at both ends of the rectangular square tube.

[0115] The first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid prepared in step (1) are injected into the microfluidic device via syringes connected to the injection pump, using needles 9 (first inlet 7 of the third microfluidic device), 10 (second inlet 8 of the third microfluidic device), and 11 (third inlet 9 of the third microfluidic device), respectively. The first dispersed phase fluid enters through injection tube 12, while the fourth dispersed phase fluid and the first continuous phase fluid enter through both ends of rectangular tube 14. The three-phase fluids converge and shear at the tips of injection tube 12 and receiving tube 13. The flow rates of the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid are adjusted to stabilize the interface, forming monodisperse W / O / W emulsion droplets that enter the receiving tube at the tip and are finally received by the flat end of receiving tube 13.

[0116] Experiment 1: When the flow rate Q of the first dispersed phase fluid A =300L / h, the flow rate Q of the fourth dispersed phase fluid B =300L / h, the flow rate Q of the first continuous phase fluidF When the flow rate is 3000 L / h, and the concentration of benzyl benzoate in the fourth dispersed phase is adjusted to 40%, the first dispersed phase, the fourth dispersed phase, and the first continuous phase form a thick-walled water-in-oil-in-water double emulsion at the conical inlet of the injection tube. Figure 19 As shown.

[0117] Experiment 2: When the flow rate Q of the first dispersed phase fluid A =300L / h, the flow rate Q of the fourth dispersed phase fluid B =300L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 3000 L / h, and the concentration of benzyl benzoate in the fourth dispersed phase fluid is adjusted to 45%, the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid are sheared at the conical opening of the injection tube to form a thick-walled water-in-oil-in-water double emulsion.

[0118] Experiment 3: When the flow rate Q of the first dispersed phase fluid A =300L / h, the flow rate Q of the fourth dispersed phase fluid B =300L / h, the flow rate Q of the first continuous phase fluid F When the flow rate is 3000 L / h, and the concentration of benzyl benzoate in the fourth dispersed phase fluid is adjusted to 50%, the first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid are sheared at the conical opening of the injection tube to form a thick-walled water-in-oil-in-water double emulsion.

[0119] (3) Collect and incubate eccentric thick-walled structural color W / O / W emulsion droplets

[0120] The monodisperse W / O / W emulsion droplets formed in step (2) are introduced together with the first continuous phase fluid into a separate collection container through a polytetrafluoroethylene output tube connected to the microfluidic device receiving tube. The droplets are incubated until the three-phase interfacial tension is balanced to obtain the corresponding monodisperse eccentric thick-walled structural color W / O / W emulsion droplets.

[0121] Optical microscope images of monodisperse eccentric thick-walled structural color W / O / W emulsion droplets prepared according to the conditions in Experiment 1 are shown below. Figure 16 , 17 As shown in Figure 18, with the continuous increase of the concentration of benzyl benzoate in the fourth dispersed phase fluid, the monodisperse eccentric thick-walled structural color W / O / W emulsion droplets exhibit cyan, pink, and green colors, respectively, which can be used in fields such as information encryption.

[0122] Comparative Example 1

[0123] The eccentric thick-walled water-in-oil-in-water (W / O / W) emulsion prepared in this comparative example follows essentially the same process as in Example 3, except that the fourth dispersed phase fluid mixture is replaced with benzyl benzoate. The resulting water-in-oil-in-water (W / O / W) emulsion is as follows: Figure 19 As shown, since the system does not meet the three-phase interfacial tension requirements, it does not meet the structural requirements for generating eccentric thick-walled structural color, and therefore no structural color is generated.

[0124] Comparative Example 2

[0125] The eccentric thick-walled water-in-oil-in-water (W / O / W) emulsion prepared in this comparative example follows essentially the same process as in Example 3, except that the fourth dispersed phase fluid mixture is replaced with a volume ratio of benzyl benzoate and soybean oil of 3:7. The resulting water-in-oil-in-water (W / O / W) emulsion is as follows: Figure 20 As shown, since the system does not meet the three-phase interfacial tension requirements, it does not meet the structural requirements for generating eccentric thick-walled structural color, and therefore no structural color is generated.

[0126] Comparative Example 3

[0127] The eccentric thick-walled water-in-oil-in-water (W / O / W) emulsion prepared in this comparative example follows essentially the same process as in Example 3, except that the surfactant in the first continuous phase fluid is replaced with F-127. The resulting water-in-oil-in-water (W / O / W) emulsion is as follows: Figure 21 As shown, since the system does not meet the three-phase interfacial tension requirements, it does not meet the structural requirements for generating eccentric thick-walled structural color, and therefore no structural color is generated.

[0128] Comparative Example 4

[0129] The ultrathin-walled water-in-oil-in-water (W / O / W) emulsion prepared in this comparative example follows essentially the same process as in Example 1, except that the second dispersed phase fluid mixture is replaced with cinnamon oil. The resulting water-in-oil-in-water (W / O / W) emulsion is as follows: Figure 22 As shown, due to the difficulty in stabilizing the water-oil two-phase interface in this system, ultrathin-walled water-in-oil-in-water (W / O / W) emulsions cannot exist stably and all break into oil droplets, thus no structural color is generated.

[0130] Comparative Example 5

[0131] The eccentric thin-walled water-in-oil-in-water (W / O / W) emulsion prepared in this comparative example follows essentially the same process as in Example 2, except that sodium chloride is removed from the third dispersed phase fluid mixture. The resulting water-in-oil-in-water (W / O / W) emulsion is as follows: Figure 23 As shown, since the system does not meet the internal and external osmotic pressure requirements, the thickness of the intermediate oil layer does not meet the structural requirements for generating eccentric thin-walled structural color, therefore no structural color is generated.

[0132] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a monodisperse structural color dual emulsion, characterized in that, The preparation method comprises the following steps: (1) Preparation of dispersed phase and continuous phase fluid Preparation of the first dispersed phase fluid: Add water-soluble emulsifier to deionized water and stir evenly to form the first dispersed phase fluid; Preparation of the second dispersed phase fluid: Add oil-soluble surfactant to the oil phase and stir evenly to form the second dispersed phase fluid; Preparation of the third dispersed phase fluid: Add water-soluble emulsifier and high osmotic pressure solution to deionized water and stir evenly to form the third dispersed phase fluid; Preparation of the fourth dispersed phase fluid: Benzyl benzoate and soybean oil are mixed evenly to obtain a mixture, and then an oil-soluble surfactant is added to the mixture and stirred evenly to form the fourth dispersed phase fluid; Preparation of the first continuous phase fluid: Water-soluble emulsifier and water-soluble surfactant are added to deionized water and stirred evenly to form the first continuous phase fluid; Preparation of the second continuous phase fluid: Add water-soluble surfactant to deionized water and stir evenly to form the second continuous phase fluid; (2) Preparation of structural color dual emulsion droplets The structural color dual emulsion droplets include one of monodisperse eccentric thin-walled structural color water-in-oil-in-water emulsion droplets and monodisperse eccentric thick-walled structural color water-in-oil-in-water emulsion droplets; wherein... The preparation steps of the monodisperse eccentric thin-walled structured water-in-oil-in-water emulsion droplets are as follows: The third dispersed phase fluid, the second dispersed phase fluid, the first continuous phase fluid, and the second continuous phase fluid prepared in step (1) are injected into the microfluidic device. The third dispersed phase fluid, the second dispersed phase fluid, and the first continuous phase fluid converge at the conical opening of the device and shear to form monodisperse water-in-oil-in-water emulsion droplets. The second dispersed phase encapsulates the third dispersed phase and is distributed in the first continuous phase. The flow rates of the three fluids are adjusted to stabilize the three-phase interface at the conical opening, and a large number of monodisperse eccentric thin-walled structured water-in-oil-in-water emulsion droplets are sheared to form. Then, they meet with the second continuous phase fluid and are fully mixed and homogeneous. The droplets are collected. The preparation steps of the monodisperse eccentric thick-walled structured water-in-oil-in-water emulsion droplets are as follows: The first dispersed phase fluid, the fourth dispersed phase fluid, and the first continuous phase fluid prepared in step (1) are injected into the microfluidic device. The three fluids converge at the conical opening of the device and shear to form monodisperse water-in-oil-in-water emulsion droplets. The fourth dispersed phase encapsulates the first dispersed phase and is distributed in the first continuous phase. The flow rates of the three fluids are adjusted to stabilize the three-phase interface at the conical opening, and a large number of monodisperse thick-walled water-in-oil-in-water emulsion droplets are sheared and formed. The droplets are collected. (3) Collect monodisperse water-in-oil-in-water double emulsions. The monodisperse water-in-oil-in-water dual emulsion droplets formed in step (2) are introduced together with the continuous phase into a separate collection container through a polytetrafluoroethylene output tube connected to the receiving tube of the microfluidic device for incubation, thus obtaining the corresponding type of monodisperse structural color dual emulsion. In step (1), the water-soluble emulsifier is one of polyvinyl alcohol, polyethylene glycol, and hydroxyethyl cellulose; the mass ratio of the water-soluble emulsifier to deionized water is 0.05~0.1:

1. In step (1), the preparation of the second dispersed phase fluid, the oil-soluble surfactant is one of sorbitol fatty acid ester, polyglycerol ricinoleate, and polysorbate 80, and the oil phase includes one of ethoxylated trimethylolpropane triacrylate, soybean oil, and n-octanol; the amount of oil-soluble surfactant is 0.005 ~ 0.02 g per 1 ml of oil phase; In step (1) of preparing the third dispersed phase fluid, the high osmotic pressure solution is a sodium chloride solution, and the water-soluble emulsifier is polyvinyl alcohol; the mass ratio of water-soluble emulsifier, sodium chloride and deionized water is 0.005~0.05:0.02~0.1:1, respectively. In step (1), the fourth dispersed phase fluid is prepared by benzyl benzoate and soybean oil in a volume ratio of 0.5 to 1:1; the amount of the oil-soluble surfactant is 0.005 to 0.02 g per 1 ml of the mixture. In step (1), the water-soluble emulsifier is polyvinyl alcohol, the water-soluble surfactant is Pluronic® F-68, and the mass ratio of water-soluble emulsifier, water-soluble surfactant and deionized water is 0.05~0.1:0.005~0.02:1; in the preparation of the second continuous phase fluid, the water-soluble surfactant is Pluronic® F-68, and the mass ratio of water-soluble surfactant and deionized water is 0.005~0.02:

1.

2. The method for preparing a monodisperse structural color dual emulsion according to claim 1, characterized in that, In step (2) of preparing monodisperse eccentric thin-walled colored water-in-oil-in-water emulsion droplets, the flow rate of the third dispersed phase fluid is 200~300 L / h, the flow rate of the second dispersed phase fluid is 150~250 L / h, the flow rate of the first continuous phase fluid is 2000~4000 L / h, and the flow rate of the second continuous phase fluid is 8000~16000 L / h.

3. The method for preparing a monodisperse structural color dual emulsion according to claim 1, characterized in that, In step (2) of preparing monodisperse eccentric thick-walled structured water-in-oil-in-water emulsion droplets, the flow rate of the first dispersed phase fluid is 200~400 L / h, the flow rate of the fourth dispersed phase fluid is 300~400 L / h, and the flow rate of the first continuous phase fluid is 2000~4000 L / h.

4. The application of a monodisperse structural color dual emulsion obtained by the preparation method as described in claim 1 in information encryption or bioactive substance detection systems.

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