Microfluidic chip and device for preparing thermally induced rapid-setting microcapsules

Abstract

The present invention provides a microfluidic chip and device for preparing thermally induced rapid-setting microcapsules. The microfluidic chip includes a droplet generator, a flow resistor, a heating plate, and a heat sink. The droplet generator is provided with an external phase fluid inlet channel, an internal phase fluid inlet channel, and a driving fluid inlet channel for respectively introducing an external phase fluid, an internal phase fluid inlet channel, and a driving fluid inlet channel. Microcapsule droplets are generated in the microfluidic channels. The external phase fluid is a thermotropic polymer, and the driving fluid is a surfactant. The flow resistor is connected to the droplet generator. The heating plate is arranged outside the droplet generator, and the heat sink is arranged outside the flow resistor to cool the microcapsule droplets passing therethrough so as to semi-solidify. Alternatively, the heat sink is arranged outside the droplet generator, and the heating plate is arranged outside the flow resistor to heat the microcapsule droplets passing therethrough so as to semi-solidify. The microfluidic chip can improve the stability of microcapsule droplets, and the microfluidic device prepared in this way can be mass-produced.

Description

Technical Field

[0001] The invention relates to the technical field of microcapsule preparation and building materials, and in particular to a microfluidic chip and a device for preparing thermally induced rapid-setting microcapsules. Background Art

[0002] Microcapsule granulation methods can be categorized into three types based on their principles. Physical methods include spray drying, spray congealing, and air suspension; physicochemical methods include aqueous phase separation, oil phase separation, extrusion, and core-capsule exchange; and chemical methods include interfacial polymerization, in situ polymerization, molecular encapsulation, and radiation encapsulation. Currently, with the exception of spray drying, which is relatively mature and can meet the needs of industrial production, the other methods fall short in terms of efficiency, mechanization, and automation. However, the spray drying method, which uses spray drying equipment, suffers from low encapsulation efficiency, the core material may adhere to the surface of the microcapsule particles, affecting product quality. Furthermore, the equipment is large, expensive, and energy-intensive.

[0003] Microfluidic chip technology is a technology that manipulates fluids at the micron scale. The main feature of this technology is the ability to perform operations such as sample preparation, reaction, and separation in an extremely small space, thereby miniaturizing traditional laboratory functions. Microfluidic chips are usually made of materials such as glass wafers, silicon wafers, or plastics. Tiny flow channels are made on the substrate using micro-electromechanical processing technology (such as photolithography, etching, laser, injection molding, etc.). In a microfluidic chip, fluid flows through a network of tiny channels. The size and shape of these channels can affect the movement behavior of the fluid, such as speed and flow state. Microfluidic chips use methods such as micromechanical pumps, electrohydraulic pumps, and electroosmosis to drive fluid flow, form microchannels, and perform a series of predetermined reactions on the chip.

[0004] The device, made based on microfluidic technology, is small in size and can be used to splice chips to achieve large-scale mass production. The resulting microcapsules have a high production rate, a high coverage rate, and uniform and controllable particles.

[0005] Microfluidic chips in microfluidic devices can be broadly divided into four categories based on the shape of the microchannels they contain: T-shaped microchannels, stepped microchannels, and fluid-focusing microchannels. The droplet formation process in microchannels of various shapes is generally the same, resulting from the interaction between two fluids: the dispersed phase and the continuous phase. In a T-shaped microchannel, the dispersed phase enters the continuous phase and is dispersed into droplets under the shear force of the continuous phase. In a stepped microchannel, the dispersed phase is squeezed into the channel and expands into round droplets at the steps due to surface tension. In a fluid-focusing microchannel, the dispersed phase and the continuous phase mix at the small holes, resulting in an unstable interface at the small holes. The dispersed phase is then dispersed into droplets under the action of interfacial tension. However, during the preparation process, microcapsules still face stability issues. Summary of the Invention

[0006] To solve the problems existing in the background technology, the present invention provides a microfluidic chip and device for preparing thermally induced rapid-setting microcapsules, which can quickly prepare thermally induced rapid-setting microcapsules in large quantities and ensure the stability of the microcapsules.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] In the first aspect, the present invention provides a microfluidic chip for preparing thermally induced rapid-setting microcapsules, comprising a droplet generator, a flow resistor, a heating plate and a heat sink; a microfluidic channel is provided in the droplet generator, the microfluidic channel comprising a fluid focusing microchannel and a driving fluid inlet channel, the fluid focusing channel comprising an external phase fluid inlet channel, an internal phase fluid inlet channel and a mixing channel formed by the intersection of the two, the driving fluid inlet channel is connected to the mixing channel, the external phase fluid, the internal phase fluid and the driving fluid are respectively pumped into the microfluidic channel through the external phase fluid inlet channel, the internal phase fluid inlet channel and the driving fluid inlet channel, and microcapsule droplets are generated in the microfluidic channel, the external phase fluid is a thermotropic polymer or a thermotropic polymer dissolved in a low A low-boiling-point solution of a thermotropic polymer formed by a boiling-point solvent, the driving fluid is a surfactant; the flow resistor is connected to the droplet generator, and is provided with an inlet and an outlet for the inflow and discharge of microcapsule droplets, respectively, and the inlet is connected to the outlet of the microfluidic channel; when the external phase fluid is a thermotropic polymer, the heating plate is arranged outside the droplet generator to heat it so that the external phase fluid remains in a liquid state, and the heat sink is arranged outside the flow resistor to cool it so that the microcapsule droplets flowing therethrough are semi-solidified; when the external phase fluid is a low-boiling-point solution of a thermotropic polymer, the heat sink is arranged outside the droplet generator to cool it, and the heating plate is arranged outside the flow resistor to heat it so that the microcapsule droplets flowing therethrough are semi-solidified.

[0009] Common thermotropic polymers include low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA, which have varying molecular weights.

[0010] The low boiling point solvent is one or more of dichloromethane, acetone, and methyl formate.

[0011] When the molecular weight of the thermotropic polymer is lower than its critical molecular weight, the thermotropic polymer can be directly used as the external phase fluid. Under the heating effect of the heating plate, the thermotropic polymer as the microcapsule wall material remains in a fluid state. The external phase fluid and the internal phase fluid as the core material are dispersed into microcapsule droplets in the microfluidic channel and enter the flow resistor. Under the action of the heat sink, the temperature is reduced and the microcapsule droplets semi-solidify. On the one hand, the driving fluid can improve the stability of the microcapsule droplets, so that they maintain a complete and regular shell-core structure. On the other hand, it can drive the microcapsule droplets to flow throughout the microfluidic channel and the flow resistor, so that the semi-solidified microcapsule droplets are discharged from the microfluidic chip for collection.

[0012] When the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, its fluidity in the fluid state is poor. At this time, the thermotropic polymer is dissolved in a low-boiling point solvent to obtain a low-boiling point solution of the thermotropic polymer as the external phase fluid. Under the action of the heat sink, the low-boiling point solution of the thermotropic polymer remains in a fluid state. The external phase fluid and the internal phase fluid as the core material are dispersed into microcapsule droplets in the microfluidic channel and enter the flow resistor. Under the action of the heating plate, the temperature rises. At this time, the temperature in the flow resistor is lower than the melting point of the thermotropic polymer and higher than the boiling point of the low-boiling point solvent. The low-boiling point solvent evaporates, and the thermotropic polymer semi-solidifies to form semi-solidified microcapsule droplets.

[0013] According to the above solution, the microfluidic chip further comprises a gasket, which is arranged between the heating plate and the heat sink. The gasket is made of a poor heat conductor and acts as a transition temperature between the heating plate and the heat sink.

[0014] In the second aspect, the present invention provides a microfluidic device for preparing thermally induced rapid-setting microcapsules, comprising a substrate, a plurality of the above-mentioned microfluidic chips, a first multi-channel peristaltic pump, a second multi-channel peristaltic pump, a third multi-channel peristaltic pump and a shaker; a plurality of the microfluidic chips are arrayed on the substrate; the first multi-channel peristaltic pump is connected to the external phase fluid inlet channels of the plurality of the microfluidic chips for pumping in the external phase fluid, the second multi-channel peristaltic pump is connected to the internal phase fluid inlet channels of the plurality of the microfluidic chips for pumping in the internal phase fluid, and the third multi-channel peristaltic pump is connected to the driving fluid inlet of the plurality of the microfluidic chips for pumping in the driving fluid; the shaker is arranged under the substrate.

[0015] According to the above solution, electromagnetic induction heating powder is provided on the shaking table.

[0016] The microfluidic device has multiple microfluidic chips, which can achieve large-scale mass production. The production efficiency of microcapsules is high. To prepare 1 kilogram of microcapsules per hour, 5,000 to 8,000 microfluidic chips are required.

[0017] According to the above scheme, multiple microfluidic chips are modularly arranged to form a modular chip group. The modular arrangement of the microfluidic chips makes the device scalable and facilitates the replacement and maintenance of the chips.

[0018] In a third aspect, the present invention provides a method for preparing thermally induced rapid-setting microcapsules based on electromagnetic induction heating, which is prepared using the above-mentioned microfluidic device, comprising the following steps:

[0019] S1. Turn on the microfluidic device, set the temperatures of the heater and heat sink, start the third multichannel peristaltic pump to pump the driving fluid until the driving fluid fills the flow resistor, then adjust the second multichannel peristaltic pump to pump the inner phase fluid, and adjust the first multichannel peristaltic pump to pump the outer phase fluid. After stable microcapsule droplets are formed, collect the sample;

[0020] S2. Place electromagnetic induction heating powder on a shaker, wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

[0021] According to the above scheme, when the external phase fluid is a thermotropic polymer, the set temperature of the heating plate is higher than the melting point of the external phase fluid, and the set temperature of the heat sink is lower than the melting point of the thermotropic polymer; when the external phase fluid is a low-boiling point solution of the thermotropic polymer, the temperature of the heat sink is lower than the boiling point of the low-boiling point solvent, and the set temperature of the heating plate is lower than the melting point of the thermotropic polymer and higher than the boiling point of the low-boiling point solvent.

[0022] In a fourth aspect, the present invention provides a method for preparing base activator microcapsules based on electromagnetic induction heating, which is prepared using the above-mentioned microfluidic device and comprises the following steps:

[0023] S1. Turn on the microfluidic device, set the temperatures of the heater and heat sink, start the third multi-channel peristaltic pump to pump the driving fluid until the driving fluid fills the flow resistor, then adjust the second multi-channel peristaltic pump to pump the inner phase fluid, and adjust the first multi-channel peristaltic pump to pump the outer phase fluid. After stable microcapsule droplets are formed, collect the sample. The inner phase fluid is an alkaline activator, and the outer phase fluid is a low-boiling-point polymer mixed solution of a thermotropic polymer or a low-melting-point polymer.

[0024] S2. Place electromagnetic induction heating powder on a shaker, wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

[0025] According to the above scheme, the internal phase fluid is one or more of anhydrous sodium silicate, liquid water glass solution, and sodium hydroxide solution; the driving fluid is one or more of VA aqueous solution, ABILEM90 (cetyl polyethylene glycol / polypropylene glycol-10 / 1 dimethylsiloxane), glycerol monooleate, Tween-80, and Span-80 (sorbitan monooleate); and the electromagnetic induction heating powder is one or more of graphite, nano-iron oxide, and magnetic powder.

[0026] According to the above scheme, if the molecular weight of the thermotropic polymer is lower than its own critical molecular weight, the thermotropic polymer is directly used as the external phase fluid. If the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, the thermotropic polymer low-boiling point solution formed by dissolving the thermotropic polymer in a low-boiling point solvent is used as the external phase fluid.

[0027] According to the above scheme, the thermotropic polymer is one or more of low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA;

[0028] The low boiling point solvent is one or more of dichloromethane, acetone, and methyl formate.

[0029] The beneficial effects of the present invention are as follows: electromagnetic heating powder is coated on the outside of semi-solid microcapsule droplets. After the microcapsule wall material is solidified and formed, the electromagnetic heating powder is attached to the outer wall of the microcapsule wall material. When the microcapsules are added to the alkali-activated gelling material, the electromagnetic heating powder heats up under the action of electromagnetic induction, and the wall material melts at high temperature, releasing the alkali activator in the core material, promoting hydration and thus achieving self-repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of a microfluidic chip for preparing thermally induced rapid-setting microcapsules according to Example 1 of the present invention;

[0031] Figure 2 Schematic diagram of the structure of a microfluidic chip for preparing thermally induced rapid-setting microcapsules according to Example 2 of the present invention;

[0032] Figure 3 Schematic diagram of the structure of the microfluidic channel of the microfluidic chip used for preparing the thermally induced rapid-setting microcapsules in Examples 1 and 2 of the present invention;

[0033] Figure 4 Schematic diagram of the structure of the microfluidic device for preparing thermally induced rapid-setting microcapsules of the present invention;

[0034] Figure 5 This is a schematic diagram of the self-healing of alkali-activated gel materials using alkali-activated microcapsules prepared in the present invention.

[0035] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0036] 1. Microfluidic chip, 11. Droplet generator, 12. Flow resistor, 13. Heating plate, 14. Gasket, 15. Heat sink, 21. First multi-channel peristaltic pump, 22. Third multi-channel peristaltic pump, 23. Second multi-channel peristaltic pump, 31. External phase fluid, 32. Driving fluid, 33. Internal phase fluid, 4. Shaking table. DETAILED DESCRIPTION

[0037] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0038] Example 1

[0039] like Figure 1 and 3 As shown, this embodiment provides a microfluidic chip for preparing thermally induced rapid-setting microcapsules, comprising a droplet generator 11, a flow resistor 12, a heating plate 13, and a heat sink 15; the droplet generator 11 is provided with a microfluidic channel, the microfluidic channel comprising a fluid focusing microchannel and a driving fluid inlet channel, the fluid focusing channel comprising an external phase fluid inlet channel, an internal phase fluid inlet channel, and a mixing channel formed by the intersection of the two, the driving fluid inlet channel being connected to the mixing channel, the external phase fluid 31, the internal phase fluid 33, and the driving fluid 32 being pumped into the microfluidic channel through the external phase fluid inlet channel, the internal phase fluid inlet channel, and the driving fluid inlet channel, respectively, and generating microcapsule droplets in the microfluidic channel, the external phase fluid 31 being a thermotropic polymer, and the driving fluid 32 being a surfactant; the flow resistor 12 is connected to the droplet generator 11, and is provided with an inlet and an outlet for the inflow and discharge of microcapsule droplets, respectively, and its inlet is connected to the outlet of the microfluidic channel;

[0040] The heating plate 13 is arranged outside the droplet generator 11 to heat it so that the external phase fluid 31 remains in liquid state, and the heat sink 15 is arranged outside the flow resistor 12 to cool it so that the microcapsule droplets flowing therethrough are semi-solidified.

[0041] The microfluidic chip 1 can be used for preparing thermally induced rapid-setting microcapsules.

[0042] Common thermotropic polymers include low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA, which have varying molecular weights.

[0043] When the molecular weight of the thermotropic polymer is lower than its critical molecular weight, the thermotropic polymer can be directly used as the external phase fluid. Under the heating effect of the heating plate 13, the thermotropic polymer as the microcapsule wall material remains in a fluid state. The external phase fluid 31 and the internal phase fluid 33 as the core material are dispersed into microcapsule droplets in the microfluidic channel and enter the flow resistor 12. Under the action of the heat sink 15, the temperature is reduced and the microcapsule droplets semi-solidify. The driving fluid 32 can improve the stability of the microcapsule droplets, so that they maintain a complete and regular shell-core structure, and can drive the microcapsule droplets to flow throughout the microfluidic channel and the flow resistor 12, so that the semi-solidified microcapsule droplets are discharged from the chip for collection.

[0044] The heating plate can adopt existing heating methods, such as interlayer heating.

[0045] Preferably, a gasket 14 is provided between the heating plate 13 and the heat sink 15 . The gasket 14 is made of a poor heat conductor and serves as a temperature transition between the heating plate 13 and the heat sink 15 .

[0046] Example 2

[0047] like Figure 2 and 3 As shown, this embodiment provides a microfluidic chip for preparing thermotropic quick-setting microcapsules. The difference from Example 1 is that the external phase fluid 31 is a thermotropic polymer low-boiling point solution formed by dissolving a thermotropic polymer in a low-boiling point solvent, the heat sink 15 is arranged outside the droplet generator 11 to cool it, and the heating plate 13 is arranged outside the flow resistor 12 to heat it so that the microcapsule droplets flowing therethrough are semi-solidified. The other structures are the same as those in the embodiment.

[0048] The low boiling point solvent is one or more of dichloromethane, acetone and methyl formate.

[0049] Common thermotropic polymers include low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA, which have varying molecular weights.

[0050] When the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, its fluidity in the fluid state is poor. At this time, the thermotropic polymer is dissolved in a low-boiling point solvent to obtain a low-boiling point solution of the thermotropic polymer as the external phase fluid. Under the action of the heat sink 15, the low-boiling point solution of the thermotropic polymer maintains a fluid state. The external phase fluid 31 and the internal phase fluid 33 as the core material are dispersed into microcapsule droplets in the microfluidic channel and enter the flow resistor 12. Under the action of the heating plate 13, the temperature rises. At this time, the temperature in the flow resistor 12 is lower than the melting point of the thermotropic polymer and higher than the boiling point of the low-boiling point solvent. The low-boiling point solvent evaporates, and the thermotropic polymer semi-solidifies to form semi-solidified microcapsule droplets.

[0051] Example 3

[0052] like Figure 4 As shown, this embodiment provides a microfluidic device for preparing thermally induced rapid-setting microcapsules, comprising a substrate, a plurality of microfluidic chips 1 of embodiment 1 or embodiment 2, a first multi-channel peristaltic pump 21, a second multi-channel peristaltic pump 23, a third multi-channel peristaltic pump 22 and a shaker 4; the plurality of microfluidic chips 1 are arrayed on the substrate; the first multi-channel peristaltic pump 21 is connected to the external phase fluid inlet channels of the plurality of microfluidic chips 1 for pumping in the external phase fluid 31, the second multi-channel peristaltic pump 23 is connected to the internal phase fluid inlet channels of the plurality of microfluidic chips 1 for pumping in the internal phase fluid 33, and the third multi-channel peristaltic pump 22 is connected to the driving fluid inlet of the plurality of microfluidic chips 1 for pumping in the driving fluid 32; the shaker 4 is arranged below the substrate, and is used to collect the semi-solidified microcapsules flowing out of the outlet of the flow resistor 12.

[0053] The microfluidic device has multiple microfluidic chips, which can achieve large-scale mass production. The production efficiency of microcapsules is high. To prepare 1 kilogram of microcapsules per hour, 5,000 to 8,000 microfluidic chips are required.

[0054] Preferably, multiple microfluidic chips 1 are modularly arranged to form a modular chip group.

[0055] The modular configuration of the microfluidic chip 1 makes the device scalable and facilitates chip replacement and maintenance.

[0056] Preferably, the shaking table 4 is provided with electromagnetic induction heating powder.

[0057] The semi-solidified microcapsule droplets formed are collected at the outlet of the flow resistor 12, placed on the shaking table 4, wrapped with electromagnetic induction powder, and solidified microcapsules are collected.

[0058] Example 4

[0059] This embodiment provides a method for preparing thermally induced rapid-setting microcapsules based on electromagnetic induction heating, which is prepared using the above-mentioned microfluidic device and includes the following steps:

[0060] S1. Turn on the microfluidic device, set the temperatures of the heater 13 and the heat sink 15, start the third multi-channel peristaltic pump 22 to pump the driving fluid 32 until the driving fluid 32 fills the flow resistor 12, then adjust the second multi-channel peristaltic pump 23 to pump the inner phase fluid 33, and adjust the first multi-channel peristaltic pump 21 to pump the outer phase fluid 31. After stable microcapsule droplets are formed, collect the sample;

[0061] S2. Place electromagnetic induction heating powder on the shaker 4, wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

[0062] When the external phase fluid 31 is a thermotropic polymer, the set temperature of the heating plate 13 is higher than the melting point of the external phase fluid, and the set temperature of the heat sink 15 is lower than the melting point of the thermotropic polymer. When the external phase fluid 31 is a low-boiling point solution of the thermotropic polymer, the temperature of the heat sink 15 is lower than the boiling point of the low-boiling point solvent, and the set temperature of the heating plate 13 is lower than the melting point of the thermotropic polymer and higher than the boiling point of the low-boiling point solvent.

[0063] Optionally, the flow rate of the first multi-channel peristaltic pump 21 is 0.1-10 ml / min, the flow rate of the second multi-channel peristaltic pump 23 is 0.1-10 ml / min, and the flow rate of the third multi-channel peristaltic pump 22 is 50-80 ml / min.

[0064] Preferably, the particle size distribution of the prepared microcapsules is between 40 and 120 microns.

[0065] Electromagnetic heating powder is coated around the semi-solid microcapsule droplets. Once the microcapsule wall material solidifies, the powder adheres to the outer surface of the microcapsule wall material. When the microcapsules are in use, electromagnetic heating powder heats up under the action of electromagnetic waves, causing the wall material to melt at high temperatures, releasing the core material.

[0066] The above-mentioned method for preparing thermally induced rapid-setting microcapsules based on electromagnetic induction heating can be used to prepare any thermally induced rapid-setting microcapsules.

[0067] Example 5

[0068] Alkali-activated concrete refers to concrete prepared with materials containing volcanic ash activity or potential hydraulic properties as cementitious materials under the stimulation of alkaline substances. Its raw materials are fly ash, slag, kaolin, etc. The preparation process has low energy consumption, low carbon emissions and has properties similar to cement. It is a new type of green and environmentally friendly material and is considered to be an ideal substitute for Portland cement. However, alkali-activated concrete coagulates and hardens quickly. Part of the alkali activator is dissolved and released in the cementitious material slurry through coating and other treatments, and continuously participates in the hydration reaction process, thereby achieving self-repair. The microfluidic device of the present invention can be used to prepare alkali activator microcapsules. The specific preparation method comprises the following steps:

[0069] S1. Turn on the microfluidic device, set the temperatures of the heater 13 and the heat sink 15, start the third multichannel peristaltic pump 22 to pump the driving fluid 32 until the driving fluid 32 fills the flow resistor 12, then adjust the second multichannel peristaltic pump 23 to pump the inner phase fluid 33, and adjust the first multichannel peristaltic pump 21 to pump the outer phase fluid 31. After stable microcapsule droplets are formed, collect the sample. The inner phase fluid 33 is an alkaline activator, and the outer phase fluid 31 is a thermotropic polymer.

[0070] S2. Place electromagnetic induction heating powder on the shaker 4, wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

[0071] The alkaline activator of the internal phase fluid is one or more of anhydrous sodium silicate, liquid water glass solution, and sodium hydroxide solution.

[0072] Optionally, the driving fluid is one or more of VA aqueous solution, ABILEM90 (cetyl polyethylene glycol / polypropylene glycol-10 / 1 dimethylsiloxane), glycerol monooleate, Tween-80, and Span80 (sorbitan monooleate).

[0073] Optionally, the electromagnetic induction heating powder is one or more of graphite, nano-iron oxide, and magnetic powder.

[0074] If the molecular weight of the thermotropic polymer is lower than its own critical molecular weight, the thermotropic polymer is directly used as the external phase fluid. If the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, a low-boiling-point solution of the thermotropic polymer formed by dissolving the thermotropic polymer in a low-boiling-point solvent is used as the external phase fluid.

[0075] Optionally, the thermotropic polymer is one or more of low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA, and the low-boiling point solvent is one or more of dichloromethane, acetone, and methyl formate.

[0076] like Figure 5 As shown, electromagnetic heating powder is coated around semi-solid microcapsule droplets. After the microcapsule wall material solidifies and forms, the powder adheres to the outer wall of the resulting microcapsule wall material. During use, the microcapsules are added to an alkali-activated gelling material. Under electromagnetic induction, the electromagnetic heating powder heats up, causing the wall material to melt at high temperatures, releasing the alkali activator in the core material and promoting hydration, thereby achieving self-healing.

[0077] The following is a specific application example of preparing thermally induced rapid-setting microcapsules using a microfluidic device for preparing thermally induced rapid-setting microcapsules.

[0078] Application Example 1

[0079] This application example uses a microfluidic device fabricated using the microfluidic chip described in Example 1 to prepare microcapsules. The flow channel of microfluidic chip 1 has a width of 0.5 mm and a depth of 0.1 mm. The external phase fluid 31 is tetraethyl orthosilicate, the internal phase fluid 33 is water, and the driving fluid 32 is Span80. Water-in-oil microspheres are prepared. The flow rate of the first multichannel peristaltic pump 21 is controlled at 1.2 ml / min, the flow rate of the third multichannel peristaltic pump 22 is controlled at 10 ml / min, and the flow rate of the second multichannel peristaltic pump 23 is controlled at 0.6 ml / min. The resulting sample microcapsules have a particle size of 250-400 μm.

[0080] Application Example 2

[0081] Similar to Application Example 1, the microfluidic chip's flow channel width was 0.1 mm and its depth was 0.02 mm. The external phase fluid 31 was a 1.5% gelatin-gum arabic solution with sodium dodecyl sulfate (SDS) as a surfactant. The internal phase fluid 33 was a tetrachloroethylene (C₂Cl₄) solution. The flow rate of the first multichannel peristaltic pump 21 was controlled at 1.2 ml / min, the flow rate of the third multichannel peristaltic pump 22 was controlled at 10 ml / min, and the flow rate of the second multichannel peristaltic pump 23 was controlled at 0.6 ml / min. The resulting capsules had a particle size of 40-50 μm.

[0082] Application Example 3:

[0083] This application example uses the microfluidic device fabricated using the microfluidic chip described in Example 2 to prepare microcapsules. The microfluidic channel width and depth of the microfluidic chip are 0.5 mm and 0.1 mm. The external phase fluid 31 is a solution of polycaprolactone (PLC) (molecular weight 80,000) dissolved in dichloromethane (CH2Cl2), with acetylene glycol as a surfactant. The internal phase fluid 33 is anhydrous sodium silicate. The flow rate of the first multichannel peristaltic pump 21 is controlled at 1.5 ml / min, the flow rate of the third multichannel peristaltic pump 22 is controlled at 15 ml / min, and the flow rate of the second multichannel peristaltic pump 23 is controlled at 0.9 ml / min. The temperature in the flow resistor increases, and the CH2Cl2 evaporates. The resulting capsules have a particle size of 200-375 μm.

[0084] Application Example 4

[0085] This application example prepared alkaline activator microcapsules, similar to those in Example 1. The microfluidic chip channel width was 0.1 mm and the depth was 0.02 mm. The external phase fluid 31 consisted of hydrophobically treated polyethylene glycol, with Span 80 as the surfactant. The internal phase fluid 33 consisted of anhydrous sodium silicate. The flow rate of the first multichannel peristaltic pump 21 was controlled at 1.2 ml / min, the flow rate of the third multichannel peristaltic pump 22 was controlled at 10 ml / min, and the flow rate of the second multichannel peristaltic pump 23 was controlled at 0.6 ml / min. The resulting capsules had a particle size of 37-48 μm.

[0086] Application Example 5

[0087] This application example provides an alkali activator microcapsule based on electromagnetic induction heating. Alkali-activated cementitious materials are green, low-carbon, and environmentally friendly, and will cause the alkali-activated cementitious materials to hydrate rapidly. Consistent with the microfluidic chip of Application Example 3, this application example prepared an alkali activator microcapsule, the external phase fluid 31 is low-temperature wax, a 10% SDS alcohol solution is used as a surfactant, and the internal phase fluid 33 is an alkali activator. When the concrete cracks, electromagnetic induction heating is used to melt the paraffin wax on the surface, allowing the alkali activator to take effect and promote further hydration, thereby achieving self-repair of the concrete. Calculated by mass fraction, the components are 42% limestone powder, 58% slag, and 8% alkali activator. The initial setting time is shortened by 74.5% and the final setting time is shortened by 79.7%.

[0088] Application Example 6

[0089] Alkali activator microcapsules were prepared using the same method as in Application Example 5. When concrete cracks, electromagnetic induction heating melts the paraffin on the surface, allowing the alkali activator to take effect and promote further hydration, thereby achieving self-repair of the concrete. The composition, calculated by mass, is 44% limestone powder, 56% slag, and 12% alkali activator. Initial setting time is shortened by 86.3% and final setting time by 84.8%.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microfluidic chip for preparing thermally induced rapid-setting microcapsules, characterized in that: It includes a droplet generator (11), a flow resistor (12), a heating plate (13) and a heat sink (15); The droplet generator (11) is provided with a microfluidic channel, the microfluidic channel includes a fluid focusing microchannel and a driving fluid inlet channel, the fluid focusing channel includes an external phase fluid inlet channel, an internal phase fluid inlet channel and a mixing channel formed by the intersection of the two, the driving fluid inlet channel is connected to the mixing channel, the external phase fluid (31), the internal phase fluid (33) and the driving fluid (32) are pumped into the microfluidic channel through the external phase fluid inlet channel, the internal phase fluid inlet channel and the driving fluid inlet channel respectively, and are discharged into the microfluidic channel. Microcapsule droplets are generated in the channel, the external phase fluid (31) is a thermotropic polymer or a thermotropic polymer low-boiling point solution formed by dissolving the thermotropic polymer in a low-boiling point solvent, the driving fluid (32) is a surfactant, if the molecular weight of the thermotropic polymer is lower than its own critical molecular weight, the thermotropic polymer is directly used as the external phase fluid (31), if the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, the thermotropic polymer low-boiling point solution formed by dissolving the thermotropic polymer in a low-boiling point solvent is used as the external phase fluid (31); The flow resistor (12) is connected to the droplet generator (11), and is provided with an inlet and an outlet for the inflow and discharge of microcapsule droplets, respectively, and the inlet is connected to the outlet of the microfluidic channel; When the external phase fluid (31) is a thermotropic polymer, the heating plate (13) is arranged outside the droplet generator (11) to heat it so that the external phase fluid (31) remains in a liquid state, and the heat sink (15) is arranged outside the flow resistor (12) to cool it so that the microcapsule droplets flowing therethrough are semi-solidified; when the external phase fluid (31) is a low-boiling-point solution of a thermotropic polymer, the heat sink (15) is arranged outside the droplet generator (11) to cool it, and the heating plate (13) is arranged outside the flow resistor (12) to heat it so that the microcapsule droplets flowing therethrough are semi-solidified.

2. The microfluidic chip for preparing thermally induced rapid-setting microcapsules according to claim 1, characterized in that: It also includes a gasket (14), which is arranged between the heating plate (13) and the heat sink (15).

3. A microfluidic device for preparing thermally induced rapid-setting microcapsules, characterized in that: It comprises a substrate, a plurality of microfluidic chips (1) as claimed in claim 1, a first multi-channel peristaltic pump (21), a second multi-channel peristaltic pump (23), a third multi-channel peristaltic pump (22) and a shaking table (4); A plurality of microfluidic chips (1) are arrayed on the substrate; The first multi-channel peristaltic pump (21) is connected to the external phase fluid inlet channels of the plurality of microfluidic chips (1) for pumping in the external phase fluid (31), the second multi-channel peristaltic pump (23) is connected to the internal phase fluid inlet channels of the plurality of microfluidic chips (1) for pumping in the internal phase fluid (33), and the third multi-channel peristaltic pump (22) is connected to the driving fluid inlets of the plurality of microfluidic chips (1) for pumping in the driving fluid (32); The shaking table (4) is arranged below the base.

4. The microfluidic device for preparing thermally induced rapid-setting microcapsules according to claim 3, characterized in that: The shaking table (4) is provided with electromagnetic induction heating powder.

5. A method for preparing thermally induced rapid-setting microcapsules based on electromagnetic induction heating, characterized in that: The preparation method of the microfluidic device according to claim 3 or 4 comprises the following steps: S1. Turn on the microfluidic device, set the temperature of the heating plate (13) and the heat sink (15), turn on the third multi-channel peristaltic pump (22) to pump the driving fluid (32) so that the driving fluid (32) fills the flow resistor (12), then adjust the second multi-channel peristaltic pump (23) to pump the inner phase fluid (33), adjust the first multi-channel peristaltic pump (21) to pump the outer phase fluid (31), and collect the sample after stable microcapsule droplets are formed; S2. Place electromagnetic induction heating powder on the shaking table (4), wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

6. The method for preparing thermally induced rapid-setting microcapsules based on electromagnetic induction heating according to claim 5, characterized in that: When the external phase fluid (31) is a thermotropic polymer, the set temperature of the heating plate (13) is higher than the melting point of the external phase fluid (31); When the external phase fluid (31) is a low-boiling-point solution of a thermotropic polymer, the set temperature of the heating plate (13) is lower than the melting point of the thermotropic polymer and higher than the boiling point of the low-boiling-point solvent.

7. A method for preparing alkali activator microcapsules based on electromagnetic induction heating, characterized in that: The preparation method of the microfluidic device according to claim 3 or 4 comprises the following steps: S1. Turn on the microfluidic device, set the temperature of the heating plate (13) and the heat sink (15), turn on the third multi-channel peristaltic pump (22) to pump the driving fluid (32) so that the driving fluid (32) fills the flow resistor (12), then adjust the second multi-channel peristaltic pump (23) to pump the inner phase fluid (33), adjust the first multi-channel peristaltic pump (21) to pump the outer phase fluid (31), and collect the sample after stable microcapsule droplets are formed, wherein the inner phase fluid (33) is an alkaline activator, and the outer phase fluid (31) is a low-boiling point solution of a thermotropic polymer or a low-melting-point polymer; S2. Place electromagnetic induction heating powder on the shaking table (4), wrap the collected semi-solid microcapsule droplets with the electromagnetic induction heating powder, and then collect the sample.

8. The method for preparing alkali activator microcapsules based on electromagnetic induction heating according to claim 6, characterized in that: The internal phase fluid (33) is one or more of anhydrous sodium silicate, liquid water glass solution, and sodium hydroxide solution; The driving fluid (32) is one or more of VA aqueous solution, ABILEM90, glycerol monooleate, Tween-80, and Span-80; The electromagnetic induction heating powder is one or more of graphite, nano iron oxide, and magnetic powder.

9. The method for preparing alkali activator microcapsules based on electromagnetic induction heating according to claim 7, characterized in that: If the molecular weight of the thermotropic polymer is lower than its own critical molecular weight, the thermotropic polymer is directly used as the external phase fluid (31). If the molecular weight of the thermotropic polymer is higher than its own critical molecular weight, a low-boiling-point solution of the thermotropic polymer formed by dissolving the thermotropic polymer in a low-boiling-point solvent is used as the external phase fluid (31).

10. The method for preparing alkali activator microcapsules based on electromagnetic induction heating according to claim 9, characterized in that: The thermotropic polymer is one or more of low-temperature wax, gelatin, PEG, PEG-PPG copolymer, polycaprolactone, PVA, PA-6, PLA, and EVA; The low boiling point solvent is one or more of dichloromethane, acetone, and methyl formate.

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