Method and device for preparing lubricating oil microspheres based on microfluidic technology and application

Abstract

The invention discloses a method for preparing lubricating oil microspheres based on a microfluidic technology. The method comprises the following steps: preparing an external phase solution, an intermediate phase solution, an internal phase solution and a collection solution; firstly, the internal phase solution is introduced into the micro-fluidic chip, and after the flow of the internal phase solution is stable, the intermediate phase solution is introduced into the micro-fluidic chip to be sheared with the internal phase solution to form nuclear layer liquid drops. After the core layer liquid drops are generated stably, the external phase solution is introduced into the micro-fluidic chip to be sheared with the core layer liquid drops, so that the external phase solution wraps the outer layer of the core layer to form a shell layer with a core-shell structure, and then the double liquid drops are dropped into a collecting solution containing glutaraldehyde to be crosslinked and cured to form the chitosan lubricating oil microspheres. The chitosan lubricating oil microsphere has the following beneficial effects that the lubricating oil is wrapped in the microsphere through a microfluidic technology, so that the chitosan lubricating oil microsphere is of a core-shell structure, and when the lubricating oil is needed, the lubricating oil in the microsphere is released to improve the friction performance of parts.

Description

Technical Field

[0001] The present invention belongs to the field of material technology preparation and sustained release, and specifically relates to a method, device and application of preparing lubricating oil microspheres based on microfluidic technology. Background Art

[0002] In some fields that have particularly high requirements for lubricants, such as food and pharmaceuticals, microsphere-encapsulated lubricants can be used to ensure the hygienic performance of equipment and prevent lubricants from contaminating products. In the aerospace field, microsphere-encapsulated lubricants can release lubricants when a certain temperature is reached when there is a lack of lubricants in spacecraft parts to improve the lubrication effect of spacecraft parts. Microsphere-encapsulated lubricant technology may play a role in various application scenarios that require efficient, long-lasting, low-friction lubrication. The advantage of this technology is that it provides a longer-lasting lubrication effect, reduces the need for frequent maintenance, and is expected to improve the overall performance of mechanical systems.

[0003] In the process of making microspheres, it is necessary to consider the size and particle size distribution of the microspheres, the loading amount and release performance of the microspheres, and the stability and storage conditions of the microspheres. Among them, the size and particle size distribution have the greatest impact on the controlled release microspheres. The droplet microfluidic technology is relatively simple to operate. The prepared microspheres are uniform in size, the system is closed, and the monodispersity is good. The particle size deviation can be stably controlled below 5%. Therefore, using microfluidic chips to make microspheres is a good choice. At present, the microfluidic chips for preparing double droplets mainly include PDMS microfluidic chips and capillary microfluidic chips. When preparing core-shell microspheres based on microfluidic chips, it is necessary to use microfluidic chips to prepare O / W / O or W / O / W type double droplets. Therefore, for the preparation of the above two types of double droplets, the inside of the microfluidic chip needs to be modified. Since the channel of the PDMS microfluidic chip is etched inside the substrate by photolithography and other technologies, it is difficult to modify the inside of the chip. The glass capillary microfluidic chip forms a channel by assembling capillaries, and the modification of the inside of the channel only needs to be processed before assembly. After the solution is passed into the microfluidic chip, the inside of its channel will be corroded by the solution, thus affecting the experimental results. Therefore, the microfluidic chip is a consumable material and needs to be replaced for a long time. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages according to the present invention, a method for preparing lubricating oil microspheres based on microfluidic technology is provided, comprising:

[0006] S1, preparing an external phase solution, an intermediate phase solution, an internal phase solution and a collection solution, wherein the external phase solution is a high-viscosity mineral oil solution, the intermediate phase solution is a chitosan solution, and the internal phase solution is a low-viscosity mineral oil solution;

[0007] S2, firstly pass the inner phase solution into the inner phase glass capillary, and after it fills the inner phase glass capillary, inject the middle phase solution from the middle phase glass capillary, and adjust the flow rate of the middle phase solution so that it shears with the inner phase solution to form a single emulsion droplet with stable flow; then inject the outer phase solution from the outer phase glass capillary, and adjust the flow rate of the outer phase solution so that the outer phase solution and the middle phase solution form a shear to wrap the single emulsion droplet to form a double droplet;

[0008] S3. Then, the double liquid droplets are added to the collected liquid to obtain microspheres after a cross-linking and curing reaction occurs. The mineral oil remaining on the surface of the microspheres is washed with isopropanol, and the microspheres are then washed with deionized water. The microspheres are then placed in a vacuum drying oven for drying to obtain lubricating oil microspheres.

[0009] Preferably, in S1, the external phase solution is prepared by mixing mineral oil with a viscosity of 35 and surfactant Span 80 in a volume ratio of 98-99:1-2, and then filtering the mineral oil solution through a 0.45 μm syringe filter membrane to obtain a high-viscosity mineral oil solution with added surfactant for standby use.

[0010] Preferably, in S1, the preparation method of the intermediate phase solution is: dissolving chitosan powder with a deacetylation degree greater than 90% in deionized water, adding glacial acetic acid for dissolution, stirring and reacting in a heated stirrer for 2 hours, adding 1-3g of polyvinyl alcohol, continuing to heat and stir at 90°C for 1 hour, and then filtering the chitosan solution through a 0.45μm syringe filter membrane for standby use, wherein the mass volume ratio of chitosan, deionized water, and glacial acetic acid is 0.5-1.5g:97-99mL:1-3mL.

[0011] Preferably, in S1, the preparation method of the inner phase solution is: mixing mineral oil with a viscosity of 25 and surfactant Span 80 in a volume ratio of 98-99:1-2, and then filtering the mineral oil solution through a 0.45 μm syringe filter membrane to obtain a low-viscosity mineral oil solution with added surfactant for standby use.

[0012] Preferably, in S1, the collecting solution is prepared by taking another external phase solution, dropping 1% of a 50% glutaraldehyde solution therein, and centrifuging the mixed solution in a centrifuge for 10 minutes to obtain a coagulation bath of the two, which is the collecting solution.

[0013] Preferably, in S2, the flow rate of the inner phase solution is controlled at 0-5 ml / h, the flow rate of the intermediate phase solution is controlled at 0-5 ml / h, and the flow rate of the outer phase solution is controlled at 1-5 ml / min. In S3, the ratio of the outer diameter to the inner diameter of the shell is 2, the outer diameter is 600-1200 μm, and the inner diameter is 300-600 μm.

[0014] An application of lubricating oil microspheres prepared by a method for preparing lubricating oil microspheres based on microfluidic technology, wherein the prepared lubricating oil microspheres are used in bearings and gear systems of spacecraft.

[0015] A device for preparing lubricating oil microspheres based on microfluidic technology, comprising:

[0016] Fluid injection unit;

[0017] A microfluidic chip, comprising a cover glass, a dispensing needle a is arranged on one side of the cover glass, the dispensing needle a is connected to an inner phase glass capillary, the inner phase glass capillary is partially nested in an intermediate phase glass capillary, the intermediate phase glass capillary is partially nested in an outer phase glass capillary, a dispensing needle b is vertically arranged above one end of the intermediate phase glass capillary overlapping with the inner phase glass capillary, and the dispensing needle b is communicated with the intermediate phase glass capillary, a dispensing needle c is vertically arranged above one end of the outer phase glass capillary overlapping with the intermediate phase glass capillary, and the dispensing needle c is communicated with the outer phase glass capillary; the inner phase glass capillary, the intermediate phase glass capillary, and the outer phase glass capillary are coaxially arranged;

[0018] a micro-droplet collecting unit, which is located below the outer phase glass capillary;

[0019] The fluid injection unit comprises a microprocessor controller, a sealed liquid inlet bottle and a pressure pump, wherein the microprocessor controller is electrically connected to the pressure pump, the sealed liquid inlet bottle is connected to the pressure pump, and the pressure pump is connected to the microfluidic chip.

[0020] Preferably, the overlapping portion of the inner phase glass capillary and the middle phase glass capillary forms a shear zone a, and the overlapping portion of the middle phase glass capillary and the outer phase glass capillary forms a shear zone b.

[0021] Preferably, the dispensing needle a includes a needle portion a and a bottom portion a, the dispensing needle b includes a needle portion b and a bottom portion b, the dispensing needle c includes a needle portion c and a bottom portion c, the bottom portion b is provided with a groove I, the bottom portion c is provided with a groove II, the intermediate phase glass capillary is inserted into the groove I, the outer phase glass capillary is inserted into the groove II, the bottom portion b is bonded to one end of the intermediate phase glass capillary overlapping with the inner phase glass capillary, and the bottom portion c is bonded to one end of the outer phase glass capillary overlapping with the intermediate phase glass capillary.

[0022] Preferably, the inner diameter of the dispensing needle a is consistent with the outer diameter of the inner phase glass capillary, the inner diameter of the inner phase glass capillary is 0.2 mm, and the outer diameter is 0.34 mm; the inner diameter of the intermediate phase glass capillary is 0.5 mm, and the outer diameter is 0.76 mm; the inner diameter of the outer phase glass capillary is 0.9 mm, and the outer diameter is 1.2 mm.

[0023] The present invention has at least the following beneficial effects:

[0024] (1) The chitosan lubricant microspheres prepared by the present invention have uniform particle size distribution and high loading capacity; and the lubricant is wrapped inside the microspheres by microfluidic technology, so that the chitosan lubricant microspheres have a core-shell structure, and when the lubricant is needed, the lubricant inside the microspheres is released to improve the friction performance of parts;

[0025] (2) The present invention uses chitosan material as the shell layer of the lubricating oil microspheres, and further cross-links and solidifies with glutaraldehyde to wrap the lubricating oil inside. The chitosan microspheres have good biocompatibility and biodegradability, which means that they can be naturally decomposed in the body or the environment, and will not cause long-term environmental pollution or have a negative impact on human health;

[0026] (3) The present invention does not require expensive experimental equipment, has high precision, is simple to operate, and can be flexibly adjusted by experimenters according to actual requirements; it has extremely high practical value;

[0027] (4) The lubricating oil microspheres prepared by the present invention have a core-shell structure, in which the core layer is lubricating oil and the shell layer is made of chitosan material. The core-shell microspheres can release lubricating oil in a specific environment to improve the friction environment;

[0028] (5) The experimental process can be carried out at room temperature and pressure, without the need for a special experimental environment such as a dust-free, constant temperature environment; at the same time, a large number of microspheres can be prepared in a relatively short period of time.

[0029] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is an overall schematic diagram of the present invention;

[0031] Figure 2 Schematic diagram of the structure of the microfluidic chip in the present invention;

[0032] Figure 3 is a cross-sectional view of the microfluidic chip of the present invention;

[0033] Figure 4 For the present invention Figure 2 Enlarged view of point A in the middle;

[0034] Figure 5 For the present invention Figure 2 Enlarged view of point B in the middle;

[0035] Figure 6 This is a structural diagram of the dispensing needle b of the present invention;

[0036] Figure 7 This is a structural diagram of the dispensing needle c of the present invention;

[0037] Figure 8 This is a light microscope image of a double droplet prepared in Example 1 of the present invention;

[0038] Fig. 9 This is a light microscopic image of the lubricating oil microspheres prepared in Example 1 of the present invention;

[0039] Fig.10 This is a picture of the lubricating oil microspheres prepared in Example 1 of the present invention taken under an optical camera. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0041] Example 1

[0042] like Figures 1 to 7 As shown, a device for preparing chitosan lubricating oil microspheres comprises:

[0043] Fluid injection unit 1;

[0044] A microfluidic chip 2, comprising a cover glass 21, a dispensing needle a22 is arranged on one side of the cover glass 21, the dispensing needle a22 is connected to an inner phase glass capillary 25, the inner phase glass capillary 25 is partially nested in an intermediate phase glass capillary 26, the intermediate phase glass capillary 26 is partially nested in an outer phase glass capillary 27, a dispensing needle b23 is vertically arranged above one end of the intermediate phase glass capillary 26 overlapping with the inner phase glass capillary 25, and a dispensing needle c24 is vertically arranged above one end of the outer phase glass capillary 27 overlapping with the intermediate phase glass capillary 26;

[0045] The micro-droplet collecting unit 3 is located below the external phase glass capillary 27 .

[0046] Working principle:

[0047] The inner phase solution, the middle phase solution, and the outer phase solution in the fluid injection unit 1 are sequentially introduced into the microfluidic chip 2. The cover glass 21 is used to carry the entire microfluidic chip 2. The specific process is as follows:

[0048] The inner phase solution is injected into the inner phase glass capillary 25 with an inner diameter of 0.2 mm and an outer diameter of 0.35 mm at a flow rate of 2 ml / h by using the dispensing needle a 22. After the inner phase glass capillary 25 is fully filled, the dispensing needle b 23 is connected with the intermediate phase glass capillary 26, and the intermediate phase solution is injected into the intermediate phase glass capillary 26 with an inner diameter of 0.5 μm and an outer diameter of 0.8 mm by using the dispensing needle b 23, and the flow rate of the intermediate phase solution is adjusted to 3.5 ml / h; the intermediate phase solution enters the intermediate phase glass capillary 26, and the inner phase solution and the intermediate phase solution are sheared at the end of the inner phase glass capillary 25 to form a single emulsion drop after stable flow, and the dispensing needle c 24 is connected with the outer phase glass capillary 27, and the dispensing needle c 24 is used to inject the intermediate phase solution into the intermediate phase glass capillary 26. 24. Inject the external phase solution into the external phase glass capillary 27 with an inner diameter of 1 mm and an outer diameter of 1.3 mm. The external phase solution enters the intermediate phase glass capillary 27. The intermediate phase solution and the external phase solution shear at the end of the intermediate phase glass capillary to wrap the single emulsion droplets to form double droplets. The double droplets are then dropped into the collecting liquid of the micro-droplet collecting unit 3, where they solidify to form chitosan lubricating oil microspheres. The mineral oil remaining on the surface of the microspheres is then cleaned with isopropanol. The microspheres are then cleaned with deionized water and placed in a vacuum drying oven for drying.

[0049] In the above technical solution, the inner phase glass capillary 25, the middle phase glass capillary 26, and the outer phase glass capillary 27 are coaxially arranged. The coaxial arrangement of the inner phase glass capillary 25, the middle phase glass capillary 26, and the outer phase glass capillary 27 is conducive to manually building the microfluidic chip 2.

[0050] In the above technical solution, the overlapping portion of the inner phase glass capillary 25 and the middle phase glass capillary 26 forms a shear zone a 261, and the overlapping portion of the middle phase glass capillary 26 and the outer phase glass capillary 27 forms a shear zone b 271. The inner phase solution and the middle phase solution form single emulsion droplets in the shear zone a 261, and the single emulsion droplets and the outer phase solution form double droplets in the shear zone b 271.

[0051] In the above technical solution, the dispensing needle a 22 includes a needle part a 221 and a bottom part a 222, the dispensing needle b 23 includes a needle part b 231 and a bottom part b 232, and the dispensing needle c 24 includes a needle part c 241 and a bottom part c 242. The needle parts of all dispensing needles are used to inject solutions, and the bottom parts are used to fix the components.

[0052] In the above technical solution, a groove I 41 is formed on the bottom b 232 , a groove II 42 is formed on the bottom c 242 , the intermediate phase glass capillary 26 is passed through the groove I 41 , and the outer phase glass capillary 27 is passed through the groove II 42 .

[0053] In the above technical solution, the bottom b 232 is bonded to the end of the middle phase glass capillary 26 overlapping with the inner phase glass capillary 25, and the dot bottom c 242 is bonded to the end of the outer phase glass capillary 27 overlapping with the middle phase glass capillary 26. The groove I 41 and the groove II 42 are used to clamp and fix the middle phase glass capillary 26 and the outer phase glass capillary 27, respectively. At the same time, epoxy resin glue is also required to fix each dispensing needle and each glass capillary, and the gap is sealed.

[0054] In the above technical solution, the inner diameter of the inner phase glass capillary 25 is 0.2 mm and the outer diameter is 0.34 mm; the inner diameter of the middle phase glass capillary 26 is 0.5 mm and the outer diameter is 0.76 mm; the inner diameter of the outer phase glass capillary 27 is 0.9 mm and the outer diameter is 1.2 mm. Setting the inner and outer diameters of each glass capillary in this way allows the middle phase solution and the outer phase solution to flow smoothly into the middle phase glass capillary 26 and the outer phase glass capillary 27, which is conducive to the formation of double droplets.

[0055] In the above technical solution, the inner diameter of the dispensing needle a 22 is consistent with the outer diameter of the inner phase glass capillary 25. The inner diameter of the dispensing needle a 22 is consistent with the outer diameter of the inner phase glass capillary 25 to prevent leakage of the inner phase solution.

[0056] In the above technical solution, the fluid injection unit 1 includes a microprocessor controller 11, a sealed liquid inlet bottle 13 and a pressure pump 12, wherein the microprocessor controller 11 is electrically connected to the pressure pump 12, the sealed liquid inlet bottle 13 is connected to the pressure pump 12, and the pressure pump 12 is connected to the microfluidic chip. The microprocessor controller 11 is used to control the pressure pump 12 to further control the injection and flow rate of the fluid, and the sealed liquid inlet bottle 13 is used to store the fluid.

[0057] A method for preparing lubricating oil microspheres based on microfluidic technology, comprising:

[0058] S1. Prepare the external phase solution, the intermediate phase solution, the internal phase solution and the collection solution. The specific steps are as follows:

[0059] S11. Prepare the external phase solution: select 98 ml of mineral oil with a viscosity of 35, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with 2 wt% of surfactant added, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0060] S12, preparing the intermediate phase solution: dissolving 0.5 g of chitosan powder with a deacetylation degree greater than 90% in 99 ml of deionized water, adding 1 ml of glacial acetic acid for dissolution, stirring the reaction in a magnetic heating stirrer for 2 h to allow the chitosan powder to be fully dissolved in the deionized water to obtain a 0.5% chitosan solution, adding 2 g of polyvinyl alcohol, continuing to heat and stir at 90° C. for 1 h, filtering the chitosan solution through a 0.45 μm syringe filter membrane, and storing for later use.

[0061] S13. Prepare the internal phase solution: select 98 ml of mineral oil with a viscosity of 25, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with a surfactant added at a volume fraction of 2%, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0062] S14. Prepare the collecting solution: take another 5 mL of the external phase solution, drop 0.05 mL of 50% glutaraldehyde into it, and centrifuge the mixed solution in a centrifuge for 10 minutes to obtain a coagulation bath of the two, which is the collecting solution.

[0063] S2, the inner phase solution, the middle phase solution, and the outer phase solution are sequentially introduced into the microfluidic chip 2, wherein: the dispensing needle a 22 injects the inner phase solution from the inner phase glass capillary 25 with an inner diameter of 0.2 mm and an outer diameter of 0.34 mm at a flow rate of 2 ml / h, and after the inner phase glass capillary 25 is fully filled, the dispensing needle b 23 is used to inject the middle phase solution from the middle phase glass capillary 26 with an inner diameter of 0.5 mm and an outer diameter of 0.76 mm; the flow rate of the middle phase solution is adjusted to 3.5 ml / h, and after the middle phase solution can shear with the inner phase solution to form a single emulsion droplet after stable flow, the dispensing needle c 24 is used to inject the outer phase solution from the outer phase glass capillary 27 with an inner diameter of 0.9 mm and an outer diameter of 1.2 mm; the flow rate of the outer phase solution is adjusted to 2 ml / min, so that the outer phase solution and the middle phase solution form a shear to wrap the single emulsion droplet to form a double droplet;

[0064] S3, then dripping the double droplets into the collection liquid of the micro-droplet collection unit 3, so that chitosan and glutaraldehyde undergo cross-linking and curing reaction to obtain microspheres, washing the mineral oil remaining on the surface of the microspheres with isopropanol, then washing the microspheres with deionized water, and then placing them in a vacuum drying oven for drying to obtain lubricating oil microspheres.

[0065] Figure 8 The double droplets obtained from S2 show that the double droplets form a core-shell structure, and the chitosan completely encapsulates the lubricating oil. The outer diameter is about 980 μm before solidification.

[0066] Fig. 9 This is the optical microscope image of the final lubricating oil microspheres. It can be seen that the slightly yellowish outer part is chitosan, and the inner shadow part is the encapsulated lubricating oil. In addition, chitosan lubricating oil microspheres encapsulating one or two lubricating oils can be prepared. The outer diameter of the microspheres after curing becomes about 760μm, and the shrinkage rate is about 23%;

[0067] Fig.10 This is a picture of the final lubricating oil microspheres under an optical camera. It can be seen that the outer shell is slightly yellowish chitosan, and the inner layer is the encapsulated lubricating oil.

[0068] Example 2

[0069] A method for preparing lubricating oil microspheres based on microfluidic technology, comprising:

[0070] S1. Prepare the external phase solution, the intermediate phase solution, the internal phase solution and the collection solution. The specific steps are as follows:

[0071] S11. Prepare the external phase solution: select 98 ml of mineral oil with a viscosity of 35, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with 2 wt% of surfactant added, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0072] S12, preparing the intermediate phase solution: dissolving 1 g of chitosan powder with a deacetylation degree greater than 90% in 99 ml of deionized water, adding 1 ml of glacial acetic acid for dissolution, stirring the reaction in a magnetic heating stirrer for 2 h to allow the chitosan powder to be fully dissolved in the deionized water to obtain a 1% chitosan solution, adding 2 g of polyvinyl alcohol, continuing to heat and stir at 90° C. for 1 h, filtering the chitosan solution through a 0.45 μm syringe filter membrane, and storing for later use.

[0073] S13. Prepare the internal phase solution: select 98 ml of mineral oil with a viscosity of 25, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with a surfactant added at a volume fraction of 2%, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0074] S14. Prepare the collecting solution: take another 5 mL of the external phase solution, drop 0.05 mL of 50% glutaraldehyde into it, and centrifuge the mixed solution in a centrifuge for 10 minutes to obtain a coagulation bath of the two, which is the collecting solution.

[0075] S2, the inner phase solution, the middle phase solution, and the outer phase solution are sequentially introduced into the microfluidic chip 2, wherein: the dispensing needle a 22 injects the inner phase solution from the inner phase glass capillary 25 with an inner diameter of 0.2 mm and an outer diameter of 0.34 mm at a flow rate of 2 ml / h, and after the inner phase glass capillary 25 is fully filled, the dispensing needle b 23 is used to inject the middle phase solution from the middle phase glass capillary 26 with an inner diameter of 0.5 mm and an outer diameter of 0.76 mm; the flow rate of the middle phase solution is adjusted to 3.5 ml / h, and after the middle phase solution can shear with the inner phase solution to form a single emulsion droplet after stable flow, the dispensing needle c 24 is used to inject the outer phase solution from the outer phase glass capillary 27 with an inner diameter of 0.9 mm and an outer diameter of 1.2 mm; the flow rate of the outer phase solution is adjusted to 2 ml / min, so that the outer phase solution and the middle phase solution form a shear to wrap the single emulsion droplet to form a double droplet;

[0076] S3, then dripping the double droplets into the collection liquid of the micro-droplet collection unit 3, so that chitosan and glutaraldehyde undergo cross-linking and curing reaction to obtain microspheres, washing the mineral oil remaining on the surface of the microspheres with isopropanol, then washing the microspheres with deionized water, and then placing them in a vacuum drying oven for drying to obtain lubricating oil microspheres.

[0077] Example 3

[0078] A method for preparing lubricating oil microspheres based on microfluidic technology, comprising:

[0079] S1. Prepare the external phase solution, the intermediate phase solution, the internal phase solution and the collection solution. The specific steps are as follows:

[0080] S11. Prepare the external phase solution: select 98 ml of mineral oil with a viscosity of 35, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with 2 wt% of surfactant added, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0081] S12, preparing the intermediate phase solution: dissolving 1.5 g of chitosan powder with a deacetylation degree greater than 90% in 99 ml of deionized water, adding 1 ml of glacial acetic acid for dissolution, stirring the reaction in a magnetic heating stirrer for 2 h to allow the chitosan powder to be fully dissolved in the deionized water to obtain a 1.5% chitosan solution, adding 2 g of polyvinyl alcohol, continuing to heat and stir at 90° C. for 1 h, filtering the chitosan solution through a 0.45 μm syringe filter membrane, and storing for later use.

[0082] S13. Prepare the internal phase solution: select 98 ml of mineral oil with a viscosity of 25, add 2 ml of Span 80, put it into a magnetic heating stirrer and stir it at room temperature to obtain a mineral oil solution with a surfactant added at a volume fraction of 2%, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane and store it for later use.

[0083] S14. Prepare the collecting solution: take another 5 mL of the external phase solution, drop 0.05 mL of 50% glutaraldehyde into it, and centrifuge the mixed solution in a centrifuge for 10 minutes to obtain a coagulation bath of the two, which is the collecting solution.

[0084] S2, the inner phase solution, the middle phase solution, and the outer phase solution are sequentially introduced into the microfluidic chip 2, wherein: the dispensing needle a 22 injects the inner phase solution from the inner phase glass capillary 25 with an inner diameter of 0.2 mm and an outer diameter of 0.34 mm at a flow rate of 2 ml / h, and after the inner phase glass capillary 25 is fully filled, the dispensing needle b 23 is used to inject the middle phase solution from the middle phase glass capillary 26 with an inner diameter of 0.5 mm and an outer diameter of 0.76 mm; the flow rate of the middle phase solution is adjusted to 3.5 ml / h, and after the middle phase solution can shear with the inner phase solution to form a single emulsion droplet after stable flow, the dispensing needle c 24 is used to inject the outer phase solution from the outer phase glass capillary 27 with an inner diameter of 0.9 mm and an outer diameter of 1.2 mm; the flow rate of the outer phase solution is adjusted to 2 ml / min, so that the outer phase solution and the middle phase solution form a shear to wrap the single emulsion droplet to form a double droplet;

[0085] S3, then dripping the double droplets into the collection liquid of the micro-droplet collection unit 3, so that chitosan and glutaraldehyde undergo cross-linking and curing reaction to obtain microspheres, washing the mineral oil remaining on the surface of the microspheres with isopropanol, then washing the microspheres with deionized water, and then placing them in a vacuum drying oven for drying to obtain lubricating oil microspheres.

[0086] Application Examples

[0087] The lubricating oil microspheres prepared in Example 1 are added to the lubricating oil and used in the bearing and gear system of the spacecraft to conduct a space simulation experiment. Since the bearing and gear system of the spacecraft need to work in a low temperature or vacuum environment, they are sealed during use. When the internal lubricating oil is consumed and cannot be replenished in time in a low temperature and vacuum environment, the friction heat of the bearing and gear system causes the temperature to reach 60-80°C, and the chitosan outside the lubricating oil microspheres begins to soften the molecular chain, which may cause the rupture or leakage of the microsphere shell under continuous high temperature, and the microspheres can release the lubricating oil. The microspheres slowly release the lubricating oil, which can ensure that the surface of the mechanical parts maintains a low friction coefficient, and the slowly released lubricating oil can increase the life of the bearing from 1000 hours to more than 4000 hours. If the lubricating oil microspheres are not used, the life of the gear system will be shortened by 60-80%, and it will fail quickly even when running under light load conditions. In addition, the chitosan shell can also be chemically modified to decompose when exposed to certain environmental stimuli (such as acidification of the friction surface). Polyethylene glycol or graphene can be added to the chitosan solution at a later stage to improve the overall flexibility and strength of the microspheres.

[0088] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing lubricating oil microspheres based on microfluidic technology, characterized in that: include: S1, preparing an external phase solution, an intermediate phase solution, an internal phase solution and a collection solution, wherein the external phase solution is a high-viscosity mineral oil solution, the intermediate phase solution is a chitosan solution, and the internal phase solution is a low-viscosity mineral oil solution; S2, firstly pass the inner phase solution into the inner phase glass capillary, and after it fills the inner phase glass capillary, inject the middle phase solution from the middle phase glass capillary, and adjust the flow rate of the middle phase solution so that it shears with the inner phase solution to form a stable flowing single emulsion droplet; Then, the external phase solution is injected from the external phase glass capillary, and the flow rate of the external phase solution is adjusted so that the external phase solution and the intermediate phase solution form a shearing effect to wrap the single emulsion droplet to form a double droplet; S3. Add the double liquid droplets into the collection liquid to obtain microspheres, wash the microspheres, and dry them to obtain lubricating oil microspheres whose core layer is lubricating oil and whose shell layer is chitosan.

2. The method for preparing lubricating oil microspheres based on microfluidic technology according to claim 1, characterized in that: In the S1, the external phase solution is prepared by mixing mineral oil with a viscosity of 35 and surfactant Span 80 at a volume ratio of 98-99:1-2, and then filtering the mineral oil solution through a 0.45 μm syringe filter membrane to obtain a high-viscosity mineral oil solution with added surfactant for standby use.

3. The method for preparing lubricating oil microspheres based on microfluidic technology according to claim 1, characterized in that: In the S1, the preparation method of the intermediate phase solution is: dissolving chitosan powder with a deacetylation degree greater than 90% in deionized water, adding glacial acetic acid for dissolution, stirring and reacting in a heated stirrer for 2 hours, adding 1-3g of polyvinyl alcohol, continuing to heat and stir at 90°C for 1 hour, and then filtering the chitosan solution through a 0.45μm syringe filter membrane for standby use; wherein the mass volume ratio of chitosan, deionized water, and glacial acetic acid is 0.5-1.5g:97-99mL:1-3mL.

4. The method for preparing lubricating oil microspheres based on microfluidic technology according to claim 1, characterized in that: In S1, the preparation method of the inner phase solution is: mix mineral oil with a viscosity of 25 and surfactant Span 80 at a volume ratio of 98-99:1-2, and then filter the mineral oil solution through a 0.45 μm syringe filter membrane to obtain a low-viscosity mineral oil solution with added surfactant for standby use.

5. The method for preparing lubricating oil microspheres based on microfluidic technology according to claim 1, characterized in that: In S1, the preparation method of the collecting solution is: separately take the external phase solution, drop 1% of a 50% glutaraldehyde solution therein, put the mixed solution into a centrifuge and centrifuge for 10 minutes to obtain a coagulation bath of the two, which is the collecting solution.

6. The method for preparing lubricating oil microspheres based on microfluidic technology according to claim 1, characterized in that: In the S2, the flow rate of the inner phase solution is controlled at 0-5 ml / h, the flow rate of the intermediate phase solution is controlled at 0-5 ml / h, and the flow rate of the outer phase solution is controlled at 1-5 ml / min. In the S3, the ratio of the outer diameter to the inner diameter of the shell is 2, the outer diameter size is 600-1200 μm, and the inner diameter size is 300-600 μm.

7. An application of lubricating oil microspheres prepared by the method for preparing lubricating oil microspheres according to any one of claims 1 to 6, characterized in that: The prepared lubricating oil microspheres are used in the bearing and gear systems of spacecraft.

8. A device for preparing lubricating oil microspheres based on microfluidic technology, characterized in that: include: Fluid injection unit; A microfluidic chip, comprising a cover glass, a dispensing needle a is arranged on one side of the cover glass, the dispensing needle a is connected to an inner phase glass capillary, the inner phase glass capillary is partially nested in an intermediate phase glass capillary, the intermediate phase glass capillary is partially nested in an outer phase glass capillary, a dispensing needle b is vertically arranged above one end of the intermediate phase glass capillary overlapping with the inner phase glass capillary, and the dispensing needle b is communicated with the intermediate phase glass capillary, a dispensing needle c is vertically arranged above one end of the outer phase glass capillary overlapping with the intermediate phase glass capillary, and the dispensing needle c is communicated with the outer phase glass capillary; the inner phase glass capillary, the intermediate phase glass capillary, and the outer phase glass capillary are coaxially arranged; a micro-droplet collecting unit, which is located below the outer phase glass capillary; The fluid injection unit comprises a microprocessor controller, a sealed liquid inlet bottle and a pressure pump, wherein the microprocessor controller is electrically connected to the pressure pump, the sealed liquid inlet bottle is connected to the pressure pump, and the pressure pump is connected to the microfluidic chip; The overlapping portion of the inner phase glass capillary and the middle phase glass capillary forms a shear zone a, and the overlapping portion of the middle phase glass capillary and the outer phase glass capillary forms a shear zone b.

9. The device for preparing lubricating oil microspheres based on microfluidic technology according to claim 8, characterized in that: The dispensing needle a includes a needle part a and a bottom part a, the dispensing needle b includes a needle part b and a bottom part b, the dispensing needle c includes a needle part c and a bottom part c, the bottom part b is provided with a groove I, the bottom part c is provided with a groove II, the intermediate phase glass capillary is passed through the groove I, the outer phase glass capillary is passed through the groove II, the bottom part b is bonded to one end of the intermediate phase glass capillary overlapping with the inner phase glass capillary, and the bottom part c is bonded to one end of the outer phase glass capillary overlapping with the intermediate phase glass capillary.

10. The device for preparing lubricating oil microspheres based on microfluidic technology according to claim 8, characterized in that: The inner diameter of the dispensing needle a is consistent with the outer diameter of the inner phase glass capillary, the inner diameter of the inner phase glass capillary is 0.2mm, and the outer diameter is 0.34mm; the inner diameter of the intermediate phase glass capillary is 0.5mm, and the outer diameter is 0.76mm; the inner diameter of the outer phase glass capillary is 0.9mm, and the outer diameter is 1.2mm.

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