The present application claims priority of Chinese application No. 201711416785.0, filed on Dec. 25, 2017. The disclosed content of the Chinese application is hereby entirely incorporated into the present disclosure.

FIELD OF THE DISCLOSURE

The disclosure relates to the technical field of microsphere preparation, in particular to a microfluidic chip and a control method thereof, a droplet generation device and a microsphere preparation device.

BACKGROUND OF THE DISCLOSURE

Microspheres have shown advantages in many applications, including building blocks for complex tissue simulation, co-culture systems for developing three-dimensional organ models, and tissue regeneration. The cell-loaded microgel is dropletized to form the microspheres, and then the microspheres are applied to 3D bioprinter to prepare tissues or three-dimensional organs after solidification culture, so the microspheres are important raw materials of the 3D bioprinter.

During the preparation of the microspheres, separate droplets need to be formed at first, there are many kinds of droplet preparation technologies, such as emulsification, mixing, embedding, extraction, microreaction, and the like. However, since the method of preparing the droplets by macroscopic techniques tends to be more intense and generates large damage to cells, it is not suitable for 3D biological printing, therefore the droplets in required sizes are generally prepared by using the microfluidic technology.

At present, cell-loaded microgel droplets are typically synthesized using the microfluidic technology. The microfluidic technology as a common method in liquid or gas control, is a technology for precise operation, processing and controlling of fluid or samples at several nanometer scales, and is generally for operating and controlling the sample fluids in microchannels with a range of 100 μm. The microfluidic technology is used for separating cell fluid on the basis of the flow channel of 100 μm and is applied to bioanalysis without restrictions or requirements on cell activity.

Microfluidic chip micro-droplet generation structures include active and passive types, wherein the active type uses the external force such as an electric field force, thermal energy and the like to generate an energy gradient locally to control the micro-droplets, mainly including electrowetting, dielectrophoresis, pneumatic method and thermal capillary method or the like, and the methods can be used for operating and controlling a single microdroplet. However, the active electrical, magnetic, acoustic, optical, thermal and the like generates adverse effects on the cells inevitably. Therefore, in order to improve the activity of the cells, the passive method is preferred in practical applications, that is, a microfluidic structure is designed to locally generate a velocity gradient to operate and control the micro-droplets, and the adverse effects generated by the electrical, magnetic, acoustic, optical, thermal and the like in the active microfluidic technology to the cells can be avoided.

The research on microfluidic chips in the prior art is generally directed to chips with flow channel sizes within 100 μm, such as 20 μm, 40 μm, 60 μm, 80 μm, but there is no specific research on how to ensure the activity of the solution mixture containing cells, how to improve the yield or the shearing method of high-viscosity raw materials and the like.

One bottleneck of 3D biological printing is that the production efficiency of the raw materials (such as the droplets formed by cell-loaded microgels) is low, and the work of one 3D bioprinter can be met only by multiple biological raw material preparation instruments, therefore it is necessary to improve the yield of the raw materials urgently. As the bioprinting raw materials can be applied to the 3D biological printing to generate micro-tissues, even construct three-dimensional organs, however, an important premise is that the cell activity in the biological raw materials needs to be maintained to be higher than 60%, if the activity is too low, the printed tissues or the three-dimensional organs cannot survive. The higher the cell activity in the biological raw materials, the higher the survival rate of the organs printed by the 3D biological printing. Therefore, it is a problem to be solvent urgently at present that the preparation yield of the biological raw materials is improved while ensuring the cell activity.

SUMMARY OF THE DISCLOSURE

Embodiments of the present disclosure provide a microfluidic chip and a control method thereof, a droplet generation device and a microsphere preparation device, which can improve the efficiency of forming droplets on the basis of ensuring the desired activity of cells in the sheared phase fluid.

In order to achieve the above object, a first aspect of the embodiments of the present disclosure provides a microfluidic chip, including a matrix, a first flow channel and a second flow channel provided in the matrix, the first flow channel and the second flow channel intersect to form an intersection area, sheared phase fluid can flow in from the first flow channel, shearing phase fluid can flow in from the second flow channel so as to separate the sheared phase fluid into discrete droplets in the intersection area, and the cross-sectional areas of the first flow channel and the second flow channel range from 0.1 mm2to 1 mm2.

Further, the cross-section of a portion of the first flow channel located upstream of the intersection area is constant, or gradually increases along the flow direction of the sheared phase fluid.

Further, two second flow channels are respectively provided on two sides of the first flow channel to form a flow sandwiching focusing flow channel in the intersection area.

Further, the first flow channel and the two second flow channels form a cross structure in the intersection area.

Further, each of the second flow channels is of an L-shaped structure in the intersection area, the lateral portion of the L-shaped structure is communicated with a first flow channel and is vertical to the first flow channel, and a vertical portion of the L-shaped structure is parallel to the first flow channel.

Further, the distance between the vertical portion of the L-shaped structure and the first flow channel ranges from 0.1 mm to 20 mm.

Further, the two second flow channels are provided at an angle to the first flow channel, and an included angle between the second flow channels and the first flow channel is less than 90°.

Further, the two second flow channels are symmetrically provided with respect to the first flow channel.

Further, the cross sections of the first flow channel and the second flow channel are rectangular, circular or trapezoidal.

Further, the cross sections of the first flow channel and the second flow channel are rectangular, and the rectangular cross section has a length ranging from 0.7 mm to 2 mm, and/or a width ranging from 0.2 mm to 0.6 mm.

Further, the viscosity ratio of the sheared phase fluid to the shearing phase fluid ranges from 10:1 to 30:1.

Further, the viscosity of the sheared phase fluid is less than 3000 cp.

Further, the flow rate ratio of the sheared phase fluid to shearing phase fluid in each of the second flow channels in the intersection area ranges from 1:10 to 1:20.

Further, the flow rate of the shearing phase fluid in each of the second flow channels in the intersection area ranges from 100 μL/min to 400 μL/min, and the flow rate of the sheared phase fluid in the intersection area ranges from 10 μL/min to 40 μL/min.

Further, the droplet has a diameter ranging from 200 μm to 400 μm.

Further, the shearing phase fluid is injected into both ends of the two second flow channels through a common fluid inlet, or the shearing phase fluid is respectively injected into the both ends of the two second flow channels through independent fluid inlets.

Further, a plurality of microfluidic units are provided in the matrix, each microfluidic unit is provided with the flow sandwiching focusing flow channel, and the microfluidic units can work simultaneously or alternately.

Further, the sheared phase fluid includes core liquid, coating liquid or a curing agent, and the microfluidic chip is used for forming core liquid droplets, coating liquid droplets or curing agent droplets.

Further, the core liquid is a collagen solution containing cells, and the shearing phase fluid is an oily solvent.

In order to achieve the above object, a second aspect of the embodiments of the present disclosure provides a droplet generation device, including the microfluidic device in the above embodiments.

Further, the droplet generation device further includes a pumping device communicated with the first flow channel and the second flow channel, for controlling the flow rate of the sheared phase fluid entering the first flow channel, and controlling the flow rate of the shearing phase fluid entering the second flow channel.

Further, the droplet generation device further includes an input component communicated with the inlets of the first flow channel and the second flow channel for conveying the fluid for forming droplets to the first flow channel and the second flow channel; or

the droplet generation device further includes an output component communicated with the outlets of the first flow channel and the second flow channel for outputting the formed droplets.

In order to achieve the above object, a third aspect of the embodiments of the present disclosure provides a microsphere preparation device, including the droplet generation device in the above embodiments.

In order to achieve the above object, a fourth aspect of the embodiments of the present disclosure provides a control method of the above microfluidic chip, wherein the flow rate ratio of the sheared phase fluid to shearing phase fluid in each of the second flow channels in the intersection area ranges from 1:10 to 1:20.

Further, the flow rate of the shearing phase fluid in each of the second flow channels in the intersection area ranges from 100 μL/min to 400 μL/min, and the flow rate of the sheared phase fluid in the intersection area ranges from 10 μL/min to 40 μL/min.

Based on the above technical solutions, according to the microfluidic chip in one embodiment of the present disclosure, by increasing the cross-sectional areas range of the first flow channel and the second flow channel to 0.1 mm2˜1 mm2, the pass rate of the fluid can be increased, thereby the flow rate is increased, and then the efficiency of forming the droplets can be improved; moreover, the flow velocity of the fluid can also be reduced by increasing the sizes of the flow channels, so that the shear force caused by the friction between the cells flowing in the flow channels and the flow channel walls is reduced, thereby reducing the damage to the cells and ensuring the activity of the cells, and the sheared phase fluid is separated into discrete droplets by a sufficient shear force generated by adjusting the flow rate in the control process. Therefore, the microfluidic chip of the embodiments of the present disclosure can improve the efficiency of generating the droplets on the basis of ensuring the cell activity to meet the requirements of 3D biological printing.

