阅读说明：本技术 基于单孔光纤的光热微流混合器 (Photo-thermal micro-flow mixer based on single-hole optical fiber ) 是由 苑婷婷 张晓彤 苑立波 于 2020-04-10 设计创作，主要内容包括：本发明提供了一种基于单孔光纤的光热微流混合器。其特征是,该光热微流混合器由一段经微加工处理过的单孔光纤和光源组成。在空气孔外侧制备多个微孔,当不同种液体通过微孔进入到空气孔内后,由于光纤芯与空气孔位置相切,通入光能后对微流液体产生热能辐射,使得液体分子加速运动从而达到混合的目的。这种能用于微流控芯片的单孔光纤光热微流混合器制备简单,一致性好,便于配合微流控芯片使用,与光源连接方便快捷,适合规模化大批量生产。(The invention provides a photo-thermal micro-flow mixer based on a single-hole optical fiber. The photo-thermal micro-flow mixer is characterized by comprising a section of micro-processed single-hole optical fiber and a light source. The micro-holes are formed in the outer sides of the air holes, and after different liquids enter the air holes through the micro-holes, the optical fiber cores are tangent to the air holes, so that heat energy radiation is generated on the micro-flow liquid after optical energy is introduced, and liquid molecules move in an accelerated manner, and the purpose of mixing is achieved. The single-hole optical fiber photo-thermal micro-flow mixer for the micro-fluidic chip is simple to prepare, good in consistency, convenient to use in cooperation with the micro-fluidic chip, convenient and fast to connect with a light source, and suitable for large-scale mass production.)

1. The utility model provides a light and heat miniflow blender based on haplopore optic fibre which characterized by: the micro-flow mixer is formed by processing a single-hole single-core optical fiber, wherein a middle fiber core of the single-hole optical fiber is used as an optical interface which is mutually connected with an external light source, a single-hole optical fiber air hole can be used as a micro-flow channel of liquid, one end of the optical fiber is fused and contracted through heating until the air hole is collapsed and sealed, a micro hole is prepared outside the air hole through a femtosecond punching processing technology and is used as a liquid inlet, and an unprocessed open end at the other end of the single-hole optical fiber is used as a liquid outlet.

2. A photothermal microfluidic mixer based on a single-hole optical fiber as claimed in claim 1, wherein the single-hole optical fiber used in the microfluidic mixer is characterized in that: the optical fiber has a middle fiber core as an optical channel, and an air hole which is circumscribed with the geometric position of the fiber core is arranged beside the fiber core.

3. The photothermal microfluidic mixer based on a single-hole optical fiber as claimed in claim 1, wherein: the photothermal microfluidic mixer may have a structure of m micro wells, each of which may serve as an inlet for one liquid, i.e., m micro wells may simultaneously mix m liquids (m >1, m being an integer).

4. A photothermal microfluidic mixer based on a single-hole optical fiber as claimed in claim 1 and claim 3, wherein: the required sizes and shapes of micropores, such as round micropores, square micropores, oval micropores, rectangular micropores and the like, can be prepared by a femtosecond punching technology according to the length of the photothermal microfluidic mixer and the sampling requirement.

5. The photothermal microfluidic mixer based on a single-hole optical fiber as claimed in claim 1, wherein: the photo-thermal micro-fluidic mixer can adjust the mixing degree of various liquids in the air hole by changing the energy of injected light.

6. The photothermal and microfluidic mixer based on single-hole optical fiber as claimed in claim 1, wherein the microfluidic mixing device is further combined with a conventional microfluidic chip, and the liquid outlet of the mixer can be connected with the microfluidic chip to mix the liquid that has not entered the chip.

(I) technical field

The invention relates to a photothermal microfluidic mixer based on a single-hole optical fiber, which is convenient to be used by matching with a microfluidic chip, can replace a microfluidic channel structure unit with an in-chip mixing function in micro-scale operation micro-liquid, and belongs to the technical field of optical flow control.

(II) background of the invention

Microfluidic technology (Microfluidics or Lab-on-a-chip) refers to systems that process or manipulate tiny fluids using microchannels of tens or hundreds of microns. Microfluidic technology has developed over decades and has become an emerging interdiscipline of chemistry, fluid physics, optics, microelectronics, new materials, biology, and biomedical engineering. Because the sample in the micro-fluidic chip is small in volume, the detection optical path is short, the sensitivity is high, the response time is fast, the power consumption is low, the optical detector and the novel detection method are very important for the practical development of the micro-fluidic technology, and no matter biological detection, drug testing, chemical analysis and environmental monitoring are carried out, more and more systems needing micro-upgrading of liquid are needed.

The micro-fluidic system generally comprises various functional units such as a micro-channel, a micro-fluidic mixer, a micro-valve, a micro-reactor, a micro-sensor, a micro-detector and the like, and is integrated on a micro chip, and the micro-analysis system can complete the functions of sample preparation, mixing, reaction, separation, detection, biochemical analysis and the like in the biological and chemical fields by controlling the flow of micro liquid in the micro-fluidic system. The microfluidic system has the unique properties of extremely high analysis speed, extremely low reagent consumption, volume integration, function integration, simplicity in operation, low price and the like.

The application of the micro-flow control system in the fields of chemistry and biology and the like is mainly based on the mixing reaction of different micro-liquid substances, so that mixing and stirring are one of important links of the micro-flow control system. The purpose of mixing and stirring is to realize uniform distribution of different substances participating in the reaction chamber. In general, the mixing of solutes in a solution is based on two principles: convective mixing and diffusive mixing. Under the action of convection, solute groups can be divided into fine fragments, so that the contact area between solutions is increased, the diffusion distance is reduced, and the mixing efficiency between microflows is increased. The diffusion coefficient of the solute in the solution is temperature dependent, so the temperature also affects the mixing and stirring efficiency of the micro-flow.

Depending on the mixing method, the micro-stirrer can be divided into active mixing and passive mixing. Active mixing means that mixing of a solution is achieved through input of external energy, and for example, pressure, magnetic force, electric force, acoustic force, thermal force and the like can be used as an energy source for active mixing; passive mixing relies primarily on channel geometry, and mixing is achieved by diffusion. More uniform and rapid mixing can often be achieved by designing the structure of the microfluidic channel, for example, Brody et al first propose a cross-shaped microfluidic channel, in which a narrow band is formed by squeezing the medium solution by the side solution, which is mixed with the medium solution by diffusion [ Brody, James P., et al. "Biotechnology at low Reynolds numbers." Biophysic journal,1996:71(6), 3430-. Still others have adopted the method of adding modifiers in the channel to increase the mixing efficiency, for example, Strook et al in 2002 first proposed a structure with "man" in the microfluidic channel arranged in a staggered manner, which effectively improves the mixing effect [ Stroock, A.D., et al, "channel mixer for microchannels." Science,2002:295(5555), 647-. Patent CN106582903 proposes a microfluidic chip of photothermal waveguide, which is immersed in the bottom of a rectangular parallelepiped microfluidic chamber and requires that the length, width and height of the microfluidic chamber and the volume of injected liquid are constant, and the surface of the optical waveguide is coated with a heat-conducting nano material, and the liquid near the waveguide is in a vortex shape and then mixed.

The microfluidic mixer is based on active or passive or photothermal effect, complex technology and size requirements are mostly needed, the preparation method is complex, and the cost is high. Based on the photo-thermal micro-flow mixer, the photo-thermal micro-flow mixer based on the holey optical fiber and with a simple structure is provided. From the manufacturing material and cost, the optical fiber has an air hole in the structure, the size of the air hole is matched with the microliter scale of the microfluidic chip, the optical fiber has a relatively large production capacity, and the micro-processing technology used in the preparation process of the micro-mixer is simple and easy to realize. The micro mixer prepared in the way has low average manufacturing cost, is suitable for batch production, and is also beneficial to optimizing the integration level and miniaturization of a micro-flow system. In terms of mixing effect, the invention adopts the photo-thermal effect to form a temperature gradient, and after the liquid absorbs the light energy, the diffusion speed of molecules in the solution can be increased.

In order to further improve the integration level and miniaturization of the microfluidic chip and overcome the defects and shortcomings in the advanced technology, the invention provides the optothermal microfluidic mixer based on the single-hole optical fiber.

Disclosure of the invention

The invention aims to provide a mixer for operating micro-liquid at a micron scale, which can replace an integrated unit for mixing micro-liquid in a micro-fluidic chip through the geometrical shape of a micro-fluidic channel, and further improve the integration level and miniaturization of the micro-fluidic chip.

The purpose of the invention is realized as follows:

a photo-thermal micro-flow mixer based on a single-hole optical fiber is composed of a section of micro-processed single-hole optical fiber and a light source. A plurality of micropores are prepared on the outer side of the air hole of the single-hole optical fiber shown in the figure 1, when different liquids enter the air hole through the micropores, as the optical fiber core is tangent to the air hole, the micro-flow liquid generates heat energy radiation after light energy is introduced, so that liquid molecules move at an accelerated speed, and the aim of mixing is fulfilled. The single-hole optical fiber photo-thermal micro-flow mixer for the micro-fluidic chip is simple to prepare, good in consistency, convenient to use in cooperation with the micro-fluidic chip, convenient and fast to connect with a light source, and suitable for large-scale mass production.

Further, the photo-thermal micro-fluidic mixer can adjust the mixing degree of various liquids in the air hole by changing the energy of the injected light.

Furthermore, the microfluidic mixer uses a single-hole optical fiber, which has a middle fiber core as an optical channel and an air hole beside the fiber core and only circumscribed with the geometric position of the fiber core.

Further, the liquid inlet of the photothermal mixer can be further expanded to have a structure of m micropores, each of which can serve as an inlet for one liquid, i.e., m micropores can simultaneously mix m liquids (m >1, m is an integer).

Furthermore, the required size and shape of the micropores, such as round micropores, square micropores, oval micropores, rectangular micropores and the like, can be prepared by the femtosecond punching technology according to the length of the photothermal microfluidic mixer and the sampling requirement.

In order to realize the function of the micro-flow mixer in the micro-fluidic chip, the middle fiber core is connected with an external light source, when the single-hole optical fiber is injected with light energy, the light is transmitted along the fiber core, when the air hole in the optical fiber is filled with liquid, the heat of the fiber core can be quickly transmitted to the liquid in the air hole due to the tangency of the fiber core and the air hole, and the light energy is converted into the heat energy absorbed by the liquid and then converted into molecular kinetic energy. The heated liquid is diffused and accelerated, thereby achieving the effect of fully mixing various liquids.

The specific principle is as follows:

as is known, light is one kind of electromagnetic wave, light energy provided by a light source connected with the photothermal microfluidic mixer is the electromagnetic wave, and is emitted out through the surface of a fiber core, and as the fiber core is adjacent to the microfluidic liquid, the electromagnetic wave is transmitted in the fiber core and reaches the microfluidic liquid again to be converted into internal energy, and when the energy of the light source is stronger, the temperature of the fiber core is higher, and the radioactive energy is larger. The microfluidic mixer transfers heat from a high temperature object (fiber core) to a low temperature object (microfluidic liquid) in the form of electromagnetic waves.

How are different microfluidic liquids mixed uniformly? The two convection heat transfer phenomena can be simply understood to occur in the microfluidic mixer at the same time, so that the molecular internal energy in the microfluidic liquid is increased, the movement is accelerated, and the diffusion phenomenon of various liquids in the air holes is accelerated. The first cause of liquid mixing is: the heat transfer mode of the fluid heated on the surface of the high-temperature object (near the fiber core) moving to the surface of the low-temperature object (far the fiber core) is convection heat transfer. The second cause of liquid mixing is: the heat transfer mode between the heated liquid in the air hole of the single-hole optical fiber photothermal and microfluidic mixer and the slightly lower temperature liquid just entering the air hole belongs to convection heat transfer, and the liquid density is changed after the temperature of the liquid is raised, so that convection is generated.

Considering that the photothermal microfluidic mixer provided by the invention is mainly applied to the field of microfluidic chips, and the microfluidic mixer structure and the chip microfluidic channel are both micron-sized, so that the Reynolds number is lower, the liquid flow is laminar flow, and the temperature difference between the optical fiber core and the fluid is smaller. Accordingly, the physical property values such as the viscosity, the thermal conductivity and the specific heat of the fluid are fixed values, and the influence of the internal heat generation and the buoyancy of the fluid caused by viscous friction is also negligible. In this case we briefly analysed the principle within the air-hole of the photo-thermal microfluidic mixer.

If the light intensity injected by the single-hole fiber is constant and the energy is stable, the fiber core temperature of the fiber is assumed to be T₁Surface area A, ambient temperature T₂Because there is a temperature difference between the fluid at the near-beam core and the fluid at the far-beam core, convective heat transfer occurs. The fluid on the surface of the air hole of the near-light fiber core is adjacent to the optical fiber core, and has the same temperature as the surface of the optical fiber core, and the temperature of the fluid far enough away from the optical fiber core is T₂A boundary layer in which temperature and flow velocity change exists near the optical fiber core. Assuming an area of dA (m)²) The heat transfer amount isThen local heat flux densityThe relationship with temperature difference can be expressed by newton's law of cooling,

q＝h(T₁-T₂) (1)

wherein h (W/(m)²gK)) is a heat transfer coefficient, which is different from a thermal conductivity, which is an inherent physical property of a substance, and which changes with the flow state of a fluid.

In addition, when the micro-flow liquid contacts the fiber core, a thin layer of hot fluid with the temperature changing from the temperature of the fiber core to the liquid temperature is formed on the surface of the air hole near the fiber core, which is called a temperature boundary layer, and similarly, when the liquid flows, the fluid is attached to the air hole near the fiber core, and a thin layer of flowing with the temperature changing from zero speed to the liquid temperature is formed on the surface of the air hole, which is called a speed boundary layer (as shown in fig. 2). And the faster the fluid flow near the core, the thicker the boundary layer thickness.

It is known that the thermal conductivity equation can be derived from fourier law and energy conservation equation, and that the following thermal equilibrium exists during the Δ t(s) time interval:

(amount of change in thermodynamic energy) ([ (amount of heat introduced into the micelle) - (amount of heat derived from the micelle) ] + (amount of heat generated in the micelle) × Δ t(s) (2)

In the environment of the microfluidic liquid in the air hole, the case where the fluid is surrounded by a solid wall surface is a classical flow in the tube.

The thermal conductance equation of the cylindrical coordinate system is:

wherein the thermal conductivity k is constant, r is the radius of the cylinder, ρ (kg/m)³) C (J/(kg. K)) is specific heat, and further,

is the calorific value per unit time and unit volume in the infinitesimal body.

The optical fiber micro-flow mixer can be further combined with a traditional micro-flow control chip, and a body outlet of the mixer can be connected with the used micro-flow control chip, so that the liquid which does not enter the chip is mixed.

In practical applications, the microfluidic mixer is selected according to specific system requirements. Microfluidic mixers are widely used in microsensors, microbiology, chemical analysis, and in a variety of applications involving microfluidic transport. At present, the mixer has been greatly developed, the structural form and the principle are rich and various, and the stability is also greatly improved. In order to further improve the integration level and miniaturization of the microfluidic chip and overcome the defects and shortcomings in the advanced technology, the invention provides the optothermal microfluidic mixer based on the single-hole optical fiber. The micro-flow channel structure unit with the mixing function in the chip can be replaced in micro-scale operation micro-liquid, an excellent research and application platform is provided for high-throughput chemical, biological and medical analysis and detection, and a variety of choices are provided for the mixing function unit in the micro-flow control chip.

(IV) description of the drawings

FIG. 1(a) is a schematic cross-sectional structure of a single-hole optical fiber; (b) the optical fiber is a real figure of a section of a single-hole optical fiber, and comprises air holes 1-1, a fiber core 1-2 and a cladding 1-3.

FIG. 2 is a schematic representation of the boundary layer in the case of convective heat transfer.

FIG. 3 is a schematic view of a single-hole fiber optic photothermal microfluidic mixer, including an inlet port 3-1, a light source 3-2, and an outlet port 3-3.

FIG. 4 is a schematic view of a single-well fiber optic photothermal microfluidic mixer with multiple microporous liquid entry ports.

(V) detailed description of the preferred embodiments

The invention is further illustrated with reference to the following figures and specific examples.

FIG. 1 shows the cross-sectional structure of a single-hole fiber consisting of a core 1-2 and cladding 1-3 structure with air holes 1-1 for micro-fluid to enter, and a refractive index slightly higher than that of the cladding material.

Fig. 3 shows a structure of a photo-thermal micro-flow mixer prepared by processing a single-hole optical fiber, wherein a plurality of micropores are prepared outside an air hole, and when various liquids enter the air hole through the micropores, as the optical fiber core is tangent to the air hole, heat energy radiation is generated on the micro-flow liquid after light energy is introduced, so that liquid molecules move at an accelerated speed, and the purpose of mixing is achieved.

Without loss of generality, the specific implementation steps and implementation method of the invention are described in detail by using the specific embodiment of the single-hole optical fiber photothermal microfluidic mixer shown in fig. 3.

(1) Firstly, taking a section of single-hole optical fiber shown in figure 1(B), removing a coating layer for standby application, taking micropores on the surface of an air hole of the optical fiber as liquid inlet ports which respectively correspond to the positions of injection ports 4-1 of liquid to be detected outside a chip, injecting the liquid to be detected into the air hole of a photothermal micro-flow mixer through an injection pump 4-2, simultaneously introducing different liquids A and B, and welding a middle fiber core serving as a light wave channel with the single-hole optical fiber 4-3 to be connected with a light source 4-4.

(3) Then, 2 round micropores are etched on the outer surface of the air hole by adopting a femtosecond laser etching technology and are used as an inlet of liquid.

(6) And finally, embedding the mixer into a chip 4-5, wherein a liquid outlet is correspondingly connected with a micro-channel in the micro-fluidic chip, the liquid AB absorbs heat energy radiated by the middle fiber core after entering the air hole, and generates a violent diffusion phenomenon, and finally the liquid AB is discharged from the open air hole on the end surface of the optical fiber, and mixed liquid K of 2 different liquids is discharged into the micro-fluidic channel in the chip and then enters other functional units 4-6 in the chip.

Because different liquids have different absorptions to different wavelength light sources, the light source wavelength and the liquid absorptance to be measured that combine to be connected can adjust the mixed degree of miniflow liquid according to the functional needs of chip.

In this embodiment, the single-hole optical fiber used in the photothermal microfluidic mixer has 2 entry ports of micro-holes, 2 injection liquid types, and a circular micro-hole shape. Similarly, the number of the micropores of the single-hole optical fiber can be expanded to other numbers, and the shape can also be expanded to be square, oval, rectangle and the like. These changes in number, shape, and size all affect the testing criteria of the microfluidic mixer, which requires specific design parameters according to the functional requirements of the chip in specific practical applications.