阅读说明：本技术 一种密封式微流控乳化芯片及其制作工艺和使用方法 (Sealed micro-fluidic emulsification chip and manufacturing process and using method thereof ) 是由 周洪波 夏智敏 李志远 余志彬 于 2019-11-18 设计创作，主要内容包括：本发明涉及一种密封式微流控乳化芯片,包括基底和固定于该基底上的物理结构,该物理结构对应所制造的芯片的微流沟道和液滴收集池,包括与进样口相连通的微流沟道,具有引流作用的微流沟道、用于液滴乳化产生的微流沟道以及呈圆饼状的微流沟道,微流沟道与其上的水珠状固化后的预聚体构成液滴收集池。本发明利用可固化的预聚体,在表面张力作用下,自发形成液滴收集池结构,简化制造工艺,将原本需要多次刻蚀工艺降低成本。同时,基于此工艺制造的模具,开发了一种无排气孔微流体乳化器芯片的使用方法,简化进样方式,有效避免反应体系与大气接触而引起的交叉污染,同时避免连续相在反应过程中释放其溶解的空气,保证反应环境的稳定。(The invention relates to a sealed micro-fluidic emulsification chip, which comprises a substrate and a physical structure fixed on the substrate, wherein the physical structure corresponds to a micro-flow channel and a liquid drop collecting pool of the manufactured chip, the sealed micro-fluidic emulsification chip comprises the micro-flow channel communicated with a sample inlet, the micro-flow channel with a drainage function, the micro-flow channel used for liquid drop emulsification generation and the micro-flow channel in a round cake shape, and the micro-flow channel and a prepolymer on the micro-flow channel after water bead-shaped solidification form the liquid drop collecting pool. The invention utilizes the solidifiable prepolymer to spontaneously form a liquid drop collecting pool structure under the action of surface tension, simplifies the manufacturing process and reduces the cost of the originally needed multiple etching process. Meanwhile, based on the die manufactured by the process, a using method of the micro-fluid emulsifier chip without the vent hole is developed, the sample introduction mode is simplified, the cross contamination caused by the contact of a reaction system and the atmosphere is effectively avoided, meanwhile, the release of dissolved air of a continuous phase in the reaction process is avoided, and the stability of the reaction environment is ensured.)

1. A sealed micro-fluidic emulsification chip comprises a micro-flow channel communicated with a sample inlet, a micro-flow channel with a drainage function, a micro-flow channel used for generating droplet emulsification and a micro-flow channel in a round cake shape, wherein the micro-flow channel and prepolymer on the micro-flow channel after water bead-shaped solidification form a droplet collection pool.

2. The encapsulated microfluidic emulsification chip of claim 1 wherein the microfluidic channel is configured to generate droplets upon emulsification of the droplets, and the microfluidic channel has a spatial gradient such that the aqueous phase is released at a nozzle of the microfluidic channel under pressure to spontaneously generate droplets.

3. The encapsulated microfluidic emulsification chip of claim 1 wherein the droplet collection chamber is circular, rectangular, and most preferably circular.

4. A manufacturing process method of a sealed microfluidic emulsification chip is characterized by comprising the following steps: s1, manufacturing a micro-fluidic chip die; s2, filling the prepolymer to form a liquid drop collecting tank mold; s3, pouring a cover plate material on the die, heating and curing, stripping the cover plate material, wherein the cover plate material is provided with a microflow channel and a liquid drop collecting pool, and holes are sequentially punched along the longitudinal central axis of the cover plate material to form a cover plate structure with an oil phase sampling hole; and S4, placing the cover plate and the substrate into a plasma cleaning machine for cleaning and modification, taking out the cover plate and the substrate, and bonding the cover plate and the substrate together to obtain the chip.

5. The manufacturing method of the sealed microfluidic emulsification chip of claim 4 wherein the chip mold is a layer of structures with the same height manufactured by the conventional microfluidic device manufacturing process, and comprises a microfluidic channel and a quasi-droplet collection pool.

6. The manufacturing method of the sealed microfluidic emulsion chip according to claim 4, wherein the drop collecting tank mold is formed by dropping a certain volume of prepolymer under the action of surface tension.

7. The manufacturing method of the sealed microfluidic emulsion chip according to claim 6, wherein the prepolymer is a curable liquid material such as epoxy resin and photoresist.

8. The manufacturing method of the sealed microfluidic emulsion chip according to claim 6, wherein the volume V of the added prepolymer is estimated according to the following formula

9. The use method of the sealed microfluidic emulsification chip is characterized by comprising the following steps of:

s1, the hollow fitting 7 is reversely buckled on the chip as shown in figure 4;

s2, the sample inlet 51 is connected with a conduit (10 muL of disperse phase and the rest is continuous phase) filled with continuous phase (fluorinated oil) in the conduit, the negative pressure conduit 71 is connected with a vacuum pump;

s3, adjusting the air pressure of a vacuum pump to-0.55 to-0.60 psi (the vacuum degree is higher than-0.55 psi, the vacuum pump starts working until 0.60psi), starting sample injection, and after the disperse phase sample injection is finished, adjusting the air pressure of the vacuum pump to the maximum to quickly fill the continuous phase in the device;

s4, after the device is filled, sealing the injection port 51 (filling the prepared PDMS prepolymer), and moving to a reaction instrument for reaction.

Technical Field

The invention relates to the field of microfluidic devices, in particular to a sealed microfluidic emulsification chip and a manufacturing process and a using method thereof.

Background

The Droplet Spontaneous Generation structure (DSG) is a structure that spontaneously generates droplets by using the interfacial tension of two-phase fluid independently of the shear force of fluid (e.g., a tap for dripping water). In the fabrication of such structures, it is common to fabricate multi-layered microstructures, creating spatial gradients for driving droplet generation, with the size of the droplets produced being dependent primarily on the geometry. Compared with other structures, the structure is more suitable for realizing the large-scale parallel generation of the liquid drops through the large-scale parallel integration of the structure, so that the liquid drop generation flux is promoted in a number-step mode, and the industrialization is facilitated. At present, the existing liquid drop spontaneous generation structures are an open structure, a double-step structure, a slope step structure, an edge structure and a focusing-single-layer step structure. To ensure the consistency of parallel spatially graded structures, these structures typically require multiple high precision manufacturing tools (e.g., deep reactive ion etching) to process the mold, as well as alignment processes, thereby increasing manufacturing costs and limiting the application of such structures. This patent provides a new technology of manufacturing space gradient, only needs to make one deck microstructure, utilizes surface tension self-align to form space gradient, has both guaranteed the structure uniformity, reduces the technology degree of difficulty and cost again, simultaneously, can combine with 3D printing technique, reduces the whole manufacturing cost of device.

Principle of spontaneous generation of droplets: in the droplet spontaneous generation device, rectangular channels (such as the microfluidic channel 4 in fig. 2) which are communicated with the droplet collection pool and have the same size are droplet generation units, also called nozzles, and are generally integrated in parallel along the edge of the droplet collection pool; from the droplet generation unit to the droplet collection tank, the channel size becomes larger suddenly in the horizontal direction and the vertical direction, i.e. the spatial gradient; when the dispersed phase enters the droplet collection pool from the nozzle, the dispersed phase spreads at the edge of the droplet collection pool (as shown in fig. 3a), as the dispersed phase continuously enters the droplet collection pool, due to the existence of the spatial gradient, a pressure difference exists between the inside of the dispersed phase in the droplet collection pool and the inside of the dispersed phase at the nozzle, and the pressure difference increases as the amount of the dispersed phase entering the droplet collection pool increases, and meanwhile, the balance of the interface of the dispersed phase and the continuous phase at the junction of the nozzle and the droplet collection pool is destroyed, and the phenomenon of dispersed phase shrinkage occurs (as shown in fig. 3 b); eventually, the dispersed phase breaks down to produce droplets, as shown in fig. 3 c.

In droplet spontaneous generation devices, fluorinated oils (FC40, HFE7500, etc.) with viscosities close to water are commonly used as the continuous phase for droplet generation, with the droplets completely immersed in the continuous phase. However, the fluorinated oil has strong volatility and can dissolve air, and in the heating reaction process, gas is often released, bubbles are formed in a liquid drop collecting tank, the stability of liquid drops is damaged, the liquid drops are mutually fused, and even demulsification is an important factor for limiting the application of the devices. The invention provides a sample injection strategy, which is characterized in that a negative pressure area in a certain range is constructed above a chip liquid drop collecting pool area without manufacturing an exhaust port, and air in a chip is gradually exhausted by utilizing the air permeability of a chip material to realize sample injection. After the sample injection is finished, the sample injection port is sealed, a reaction instrument is placed for reaction, and no bubble is generated when the sample is heated for more than 1 hour at 63 ℃.

Disclosure of Invention

The invention aims to provide a manufacturing process of a micro-fluid emulsifier and a chip using strategy. The process simplifies the original processing process on the basis of keeping the original precision, and reduces the economic cost and the time cost; the strategy simplifies a sample introduction mode, avoids a vent hole structure commonly used by the prior microfluidic chip, effectively avoids cross contamination caused by contact of a reaction system and the atmosphere, simultaneously avoids the release of dissolved air of a continuous phase in the reaction process, and ensures the stability of a reaction environment.

According to the sealed microfluidic emulsifying chip, the chip comprises a microfluidic channel communicated with a sample inlet, a microfluidic channel with a drainage function, a microfluidic channel for droplet emulsification and a disc-shaped microfluidic channel, wherein the microfluidic channel and a prepolymer which is solidified in a water bead shape on the microfluidic channel form a droplet collecting pool.

In some embodiments, the microfluidic channel has a spatial gradient such that the aqueous phase can be pressure released at the microfluidic channel nozzle to spontaneously generate droplets.

In some embodiments, the droplet collection tank may be circular, rectangular, etc., wherein a circular shape is optimal.

A manufacturing process of a sealed microfluidic emulsification chip is characterized by comprising the following steps: s1, manufacturing a micro-fluidic chip die; s2, filling the prepolymer to form a liquid drop collecting tank mold; s3, pouring a cover plate material on the die, heating and curing, stripping the cover plate material, wherein the cover plate material is provided with a microflow channel and a liquid drop collecting pool, and holes are sequentially punched along the longitudinal central axis of the cover plate material to form a cover plate structure with an oil phase sampling hole; and S4, placing the cover plate and the substrate into a plasma cleaning machine for cleaning and modification, taking out the cover plate and the substrate, and bonding the cover plate and the substrate together to obtain the chip.

In some embodiments, the chip mold is a layer of structure with the same height, which is manufactured by using a common microfluidic device processing technology, and comprises a microfluidic channel and a quasi-droplet collecting pool;

in some embodiments, the drip collection tank mold is formed by dropping a certain volume of prepolymer, and molding the prepolymer under the action of surface tension.

In some embodiments, the prepolymer is a curable liquid material such as an epoxy resin or a photoresist.

The volume V of the added prepolymer can be estimated according to the following formula

The radius α is the contact angle of the prepolymer on the mould, the volume can be excessive 5% -10%, and the test is needed in specific situations.

The use strategy of the sealed microfluidic emulsification chip is characterized in that the chip is used by the following steps:

s1, the hollow fitting 7 is reversely buckled on the chip as shown in figure 4;

s2, the sample inlet 51 is connected with a conduit (10 muL of disperse phase and the rest is continuous phase) filled with continuous phase (fluorinated oil) in the conduit, the negative pressure conduit 71 is connected with a vacuum pump;

s3, adjusting the air pressure of a vacuum pump to-0.55 to-0.60 psi (the vacuum degree is higher than-0.55 psi, the vacuum pump starts working until 0.60psi), starting sample injection, and after the disperse phase sample injection is finished, adjusting the air pressure of the vacuum pump to the maximum to quickly fill the continuous phase in the device;

s4, after the device is filled, sealing the injection port 51 (filling the prepared PDMS prepolymer), and moving to a reaction instrument for reaction.

Drawings

FIG. 1 is a schematic view of a mold having a layer of microstructures fabricated using a common fabrication process for microfluidic devices;

FIG. 2 is a schematic view of a mold for dropping a prepolymer to form a liquid drop collecting tank;

FIG. 3 is a micrograph of an emulsifier droplet produced according to the process of this patent;

FIG. 4 is a schematic of a device employing a non-vent use strategy;

FIG. 5 is a front and cross-sectional view of the device of FIG. 4;

FIG. 6 is a micrograph of the liquid drop storage condition of the chip which is injected by the strategy after being heated at 63 ℃ for 1 h.

Detailed Description

The technical solution of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments of the present invention, but the following embodiments are only for understanding the present invention and do not limit the present invention, the embodiments and features of the embodiments of the present invention may be combined with each other, and the present invention may be implemented in various different ways as defined and covered by the claims.

The mold manufactured by the manufacturing process of the microfluidic emulsifier mold according to a preferred embodiment of the invention comprises a substrate and a physical structure fixed on the substrate, wherein the physical structure corresponds to a microfluidic channel and a droplet collection tank of a manufactured chip, and comprises a microfluidic channel 21 communicated with a sample inlet, a microfluidic channel 2 with a drainage function, a microfluidic channel 4 for droplet generation and a disc-shaped microfluidic channel 31, as shown in fig. 1, the microfluidic channel 31 and a prepolymer solidified in a water bead shape on the microfluidic channel form a droplet collection tank 3, as shown in fig. 2. Droplets are generated at the intersection of the microfluidic channel 4 and the droplet collection reservoir 3.

The mold material and the prepolymer material are both flame-retardant epoxy insulation pouring sealant (Hangzhou Wuhui adhesive limited), the width of a microfluidic channel 21 is 1000 μm, the width of a microfluidic channel 2 is 2000 μm, the width of a microfluidic channel 4 is 50 μm, the microfluidic channel 31 is a circular area (or other shapes, but the circular situation has the maximum parallel integration efficiency) with the diameter of 5000 μm, and the heights of all the microfluidic channels are 30 μm.

Wherein, the main process flow comprises the following steps:

s1, preparing a mold with a microstructure:

drawing a required graph according to the structure of the microfluidic chip, and preparing a film mask; in the embodiment, a silicon wafer is taken as a substrate, and a micro-flow channel and a quasi-droplet collecting pool are etched through photoetching or deep reactive ion etching; obtaining a mould with a corresponding structure; according to the weight ratio of 10: 1, respectively weighing PDMS prepolymer and curing agent, then mixing and uniformly stirring, placing in a vacuum drying oven for vacuumizing, and standing for about 30 min; pouring PDMS on a silicon wafer mould after the PDMS is basically free of bubbles, standing for about 30min, and then putting the PDMS into an oven to be heated for 1-3 hours, preferably 2 hours; the oven temperature is set between 55 ℃ and 90 ℃, preferably 65 ℃; finally, stripping the cured PDMS layer from the silicon wafer mold; with the PDMS layer according to the dicing, place in clean plastic culture dish bottom, the structure faces upwards, according to weight ratio 4: 1, respectively weighing the flame-retardant epoxy insulating pouring sealant (A) and the flame-retardant epoxy insulating pouring sealant (B), then mixing and uniformly stirring, pouring into a culture dish, taking out after curing, and removing a PDMS layer to obtain a mold 1, as shown in figure 1.

S2, manufacturing a liquid drop collecting pool:

placing the die 1 on a horizontal plane, and mixing the materials in a weight ratio of 4: 1, respectively weighing the flame-retardant epoxy insulating pouring sealant (A) and the flame-retardant epoxy insulating pouring sealant (B), then mixing and uniformly stirring, quantitatively pouring the mixture in a quasi-droplet collecting pool area by using a liquid transfer gun, after the prepolymer is paved in the quasi-droplet collecting area, standing for solidification, and obtaining a mold 2, as shown in fig. 2.

A non-venting vent use strategy according to a preferred embodiment of the present invention involves the inclusion of a chip, associated fittings, and a vacuum pump, as shown in fig. 4.

The preparation method of the chip comprises the following steps:

s1, casting PDMS on the mold, heating to cure, peeling off the PDMS and punching to form a cover sheet:

according to the weight ratio of 10: 1, respectively weighing PDMS prepolymer and curing agent, then mixing and uniformly stirring, placing in a vacuum drying oven for vacuumizing, and standing for about 30 min; after the PDMS is basically free of bubbles, the PDMS is poured on a mould 2 and stands for about 30min, and then the PDMS is placed in an oven to be heated for 1-3 hours, preferably 2 hours; the oven temperature is set between 55 ℃ and 90 ℃, preferably 65 ℃; finally, stripping the cured PDMS layer from the silicon wafer mold; a punch is used to punch holes at the microfluidic channels 21 to form the cover plate 5 with the microfluidic channels 21, 2, 31, 4 and the droplet collection and collection well 3.

S4: the cover sheet 5 and the base sheet 6 are attached:

and (3) putting the cover plate 5 and the base plate 6 into a plasma cleaning machine for cleaning for about 50-80S, preferably 70S, taking out, then adhering the cover plate 5 and the base plate 6 together, and placing the chip into an oven at 105 ℃ for baking for more than 8 hours at constant temperature to complete the preparation of the chip.

The accessory is a hollow object block, the material can be non-air-permeable materials such as PMMA, PC, glass and the like, the size of the middle cavity is slightly larger than that of the quasi-droplet collecting region, and the middle cavity is connected with a guide pipe which is connected with a vacuum pump. The vacuum pump is a purchased vacuum pump with adjustable vacuum degree.

In the use strategy without the vent hole, the sample injection process comprises the following steps:

s1, the accessory 7 is buckled on the chip in an inverted mode as shown in the figure 4;

s2, the sample inlet 51 is connected with a conduit (10 muL of disperse phase and the rest is continuous phase) filled with continuous phase (fluorinated oil) in the conduit, the negative pressure conduit 71 is connected with a vacuum pump;

s3, adjusting the air pressure of a vacuum pump to-0.55 to-0.60 psi (the vacuum degree is higher than-0.55 psi, the vacuum pump starts working until 0.60psi), starting sample injection, and after the disperse phase sample injection is finished, adjusting the air pressure of the vacuum pump to the maximum to quickly fill the continuous phase in the device;

s4, after the device is filled, sealing the injection port 51 (filling the prepared PDMS prepolymer), and moving to a reaction instrument for reaction.

According to the manufacturing process of the microfluid emulsifier mould, provided by the invention, the curable prepolymer is utilized to spontaneously form a liquid drop collecting tank structure under the action of surface tension, the manufacturing process is simplified, the process which needs multiple times of etching originally is simplified into a single time, meanwhile, the structural precision is ensured, and the cost is reduced. Meanwhile, based on the mold manufactured by the process, a use strategy of the micro-fluid emulsifier chip without the vent hole is developed, a sample introduction mode is simplified, cross contamination caused by contact of a reaction system and the atmosphere is effectively avoided, meanwhile, dissolved air of a continuous phase is prevented from being released in the reaction process, the stability of a reaction environment is ensured, no air is released when heating is carried out at 63 ℃, and no air bubbles are generated continuously for one hour.

The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present invention fall within the scope of the claims of the present invention. The invention has not been described in detail in order to avoid obscuring the invention.