A three-dimensional micro-mixer based on DNA double helix structure

Abstract

This invention discloses a three-dimensional micromixer based on the DNA double helix structure, belonging to the field of microfluidics technology. The micromixer has two spatial helical channels with a π-phase difference, periodically coupled through staggered, "base pair"-like connecting channels. The centrifugal force generated by the three-dimensional helical microchannels induces Dean's vortexes, producing a "rotation-revolution" composite effect during fluid flow. Furthermore, the mass transfer between the two channels is enhanced through the splitting-recombination effect of the "base pair" connecting channels. Compared with existing technologies, this invention has the following advantages: 1. It induces complex three-dimensional flow through the three-dimensional DNA double helix structure, realizing continuous renewal and stretching of the fluid interface; 2. It utilizes the curvature and torsion of the three-dimensional helical structure to generate a "revolution" enhanced mixing effect under the superposition effect of rotation and deflection, forming a "rotation-revolution composite flow" similar to planetary motion, overcoming the mixing difficulties caused by low diffusion efficiency and difficulty in forming chaotic convection in high-viscosity oil phase systems; 3. Under the same mixing efficiency, the pressure drop of this device is much smaller than that of traditional two-dimensional planar serpentine and split-and-merge micromixers, enabling rapid and uniform mixing of high-viscosity fluids with low energy consumption, and is particularly suitable for mixing and mass transfer enhancement of high-viscosity oil phase systems in fine chemical processes.

Description

Technical Field

[0001] This invention relates to the field of microfluidic systems and microchemical process enhancement technology, specifically to a high-viscosity fluid micromixer based on the DNA double helix structure and its applications. Background Technology

[0002] Micromixers are crucial components in microfluidic systems for achieving rapid and uniform mixing of liquids, and they are widely used in biomedical detection, drug synthesis, and chemical reaction enhancement. Based on their driving method, micromixers are classified into active and passive types. Passive micromixers have attracted considerable attention due to their lack of external energy input and simple structure. Common structures include two-dimensional serpentine channels and staggered groove structures, primarily enhancing mixing through induced Dean vortices or chaotic convection.

[0003] However, existing technologies face significant challenges when handling high-viscosity fluids such as oil-oil or oil-water systems. This is because oil-phase liquids generally exhibit high viscosity and low diffusion coefficients (typically above 10). -12 Passive micromixers, operating on the order of m² / s, exhibit extremely slow mixing rates in laminar flows at low Reynolds numbers. Traditional two-dimensional serpentine micromixers struggle to generate effective Dean's vortices in high-viscosity systems, or require extremely high flow velocities to achieve effective mixing, resulting in excessively high system pressure drops and hindering integrated application. Furthermore, while active mixers offer higher efficiency, their complex system architecture and cumbersome operation make them challenging. Therefore, designing a passive micromixer that achieves efficient mixing of high-viscosity fluids with low energy consumption is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a three-dimensional micromixer based on the DNA double helix structure and its application, which can significantly improve the mixing efficiency of high-viscosity oil phase fluids while maintaining a low pressure drop.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a three-dimensional micromixer based on the DNA double helix structure, comprising two spatial helical channels with a phase difference of π, which are coupled to each other through periodically connected "base pair" type connection channels to form a continuous three-dimensional network structure.

[0006] The working principle of this invention is as follows: Utilizing the curvature κ and torsion τ of the helical channel, the fluid, during its flow, not only experiences radial centrifugal force to generate Dean vortices (i.e., "rotation"), but also generates an additional tangential velocity component due to the three-dimensional torsional effect, causing the vortex core to migrate spatially along the overall direction of the channel (i.e., "revolution"). This "rotation-revolution" composite flow greatly increases the stretching, folding, and overturning of the fluid interface. Simultaneously, the connecting channel acts as a splitting and reorganizing mechanism, further enhancing chaotic convection.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] 1. Enhanced mixing through three-dimensional spatial structure: Compared with the traditional two-dimensional serpentine structure, the DNA double helix structure of this invention can induce more complex "rotation-revolution" composite motion, and can effectively generate interface renewal even under high viscosity conditions, thus significantly improving mixing efficiency.

[0009] 2. Low energy consumption and high efficiency: When achieving the same mixing index (e.g., 95%-99%), the voltage drop of the device of this invention (8.6 × 10⁻⁶) is significantly lower. 4 The Pa is much lower than that of a two-dimensional serpentine micromixer (approximately 2.2 × 10⁻⁶ Pa). 5 The Pa) and split-type micro-mixer significantly reduce operating energy consumption.

[0010] 3. Optimized operating range: This invention defines the optimal operating Reynolds number range (Re = 40-60). Within this range, strong chaotic convection can be generated while avoiding the "vortex trapped liquid" phenomenon at high Reynolds numbers. Chaotic convection and pressure drop are in optimal balance, ensuring the uniformity of mixing. Attached Figure Description

[0011] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0012] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0013] Figure 2 The present invention relates to the mixing index of the device when mixing silicone oils of different viscosities at different Reynolds numbers;

[0014] Figure 3 The present invention relates to the streamline distribution and Dean vortex morphology of the cross section when the device is applied to the mixing of 10 cst viscosity silicone oil at different Reynolds numbers.

[0015] Figure 4 The streamline distribution of the device of the present invention at different Reynolds numbers when applied to silicone oils of different viscosities;

[0016] Figure 5 This refers to the eddy current trapping phenomenon that occurs in the device of the present invention at high Reynolds numbers;

[0017] Figure 6 This invention compares the device of the present invention with the Q extreme value distribution calculated based on the Q criterion in a planar serpentine microchannel (demonstrating the rotation-revolution effect).

[0018] Figure 7 This refers to the pressure drop of the device of the present invention under silicone oil systems of different viscosities;

[0019] Figure 8This is a comparison of the mixing index and pressure drop between the device of the present invention and a traditional two-dimensional planar micro-mixer; Detailed Implementation

[0020] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0021] Example 1

[0022] like Figure 1 As shown, this embodiment constructs a micromixer based on the DNA double helix structure. The device consists of two wound polytetrafluoroethylene (PTFE) tubes, connected by a tee and short pipe fittings to form a "base pair" structure. The microchannel has a circular cross-section with a diameter d = 0.8 mm, an inlet length L0 = 10 mm, a straight segment length L1 = 8 mm, and an outlet length L2 = 8 mm. The entire helical segment corresponds to three complete rotations.

[0023] Example 2

[0024] Two types of 10 cSt silicone oil, one red and one blue, were selected as high-viscosity oil phase fluids and injected into a micromixer using a precision injection pump. Experimental results (e.g.) Figure 2 , Figure 3 When the Reynolds number (Re) increases to 10, the streamlines begin to bend, and the initial form of a Dean vortex appears, with the mixing index reaching over 75%. When Re reaches 30-50, a distinct double-core Dean vortex structure forms within the cross-section, and the vortexes stabilize, with the mixing index rapidly rising to 97%-99%, achieving complete and thorough mixing. As the Reynolds number continues to rise to 80-120, due to the dominance of inertial forces, a vortex-trapped fluid effect forms in the central region of the Dean vortex, and the mixing index decreases slightly. Figure 5 As shown, the mixing index M decreases by about 2-3 percentage points, revealing that at high Reynolds numbers, the excessive stability of the Dean vortex is actually detrimental to fluid mixing. In summary, as... Figure 2 As shown, the three-dimensional DNA double helix micromixer can achieve the best mixing effect in the medium Reynolds number range (Re=40-60), which can generate effective chaotic convection and avoid the occurrence of vortex trapping phenomenon. At this time, the pressure drop of the micromixer is maintained within a reasonable range, balancing mixing efficiency and energy consumption.

[0025] Example 3

[0026] For silicone oil with a viscosity of 10 cSt, obvious vortex disturbances can be observed at a Reynolds number of 10. As the Reynolds number continues to increase to 50, a clearly shaped symmetrical double-core Dean vortex structure is formed in the cross-section of the spiral microchannel, with a mixing index of up to 99%. In the test of silicone oil with a viscosity of 50 cSt, the mixing process slows down significantly. When the Reynolds number is less than 30, due to the stronger kinematic viscosity of the high-viscosity fluid and the greater viscous drag, the inertial force is difficult to excite effective radial disturbances, and the critical Reynolds number required for vortex generation increases significantly, with a mixing index of only 57%. When the Reynolds number reaches 40-50, the secondary flow gradually develops into a double-vortex structure of Dean vortices, and the mixing process is dominated by chaotic convection, with a mixing index of about 90%. Within this range, the disturbance in the fluid mainstream gradually extends to the boundary layer region, the interface is constantly renewed, and the mixing effect is significantly improved, but the energy consumption increases accordingly. When the Reynolds number continues to increase to 80, a clear Dean vortex structure is formed in the microchannel, and the chaotic convection is further enhanced, with a mixing index of over 95%. In tests with high-viscosity silicone oil (100 cSt), the critical Reynolds number for chaotic convection increased further. Due to the strong damping effect caused by the high-viscosity fluid, the radial velocity component near the microchannel wall was significantly weakened, leading to the lateral circulation of the fluid being compressed to the central region of the cross-section, while the peripheral fluid maintained almost stable axial motion, thus shrinking the effective mixing area. Even at a Reynolds number of 100, the mixing index was only 90%, and the pressure drop increased to 1.7 × 10⁻⁶. 6 Pa, the pressure drop is extremely large, and the system energy consumption increases significantly.

[0027] Example 4

[0028] To reveal the fundamental reason for the efficient mixing achieved by the three-dimensional DNA double-helix micromixer, a quantitative analysis of the flow field vortex structure was conducted. The Q-criterion was used to identify the vortex region, which is defined as follows:

[0029]

[0030]

[0031]

[0032] Where Ω is the antisymmetric part of the velocity gradient tensor (curl tensor), and S is the symmetric part (strain rate tensor). When Q>0, the local rotation rate is greater than the strain rate, and this region is considered the vortex-dominant region. The extreme region of Q can be regarded as the rotation center.

[0033] Flow field analysis using Q-criterion (e.g.) Figure 6Under the condition of Reynolds number R=50, the extreme point of the vortex (Q maximum) within the cross-section of the device of the present invention rotates and migrates clockwise along the length of the channel, proving the existence of the "revolution" effect. This unique flow field characteristic causes the fluid trajectory to change continuously, avoiding the mixing dead zone caused by the fixed position of the vortex in the traditional two-dimensional curved channel. Therefore, the Q extreme value is always located at the two rotation centers of the Dean vortex, and the Dean vortex is always symmetrically distributed vertically. The fluid rotates around the fixed vortex center, and the vortex position remains stable along the length of the channel, thus significantly superior to the traditional serpentine channel.

[0034] Example 5

[0035] The voltage drop of the device of the present invention is compared with that of traditional two-dimensional snake-shaped micromixers and split-and-combine (SAR) micromixers (e.g.) Figure 8 At the efficient mixing point (Re = 50) where the mixing index reaches 99%, the pressure drop of the device of this invention is only 8.6 × 10⁻⁶. 4 Pa. In contrast, a serpentine micromixer requires Re = 120 to achieve a mixing index of 96%, at which point the pressure drop is as high as 2.2 × 10⁻⁶ Pa. 5 Pa. The results show that the present invention significantly reduces energy consumption while achieving the same or higher mixing effect.

[0036] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A three-dimensional micromixer based on the DNA double helix structure, characterized in that, It includes an inlet segment, an outlet segment, a confluence segment, and a mixing segment; the mixing segment consists of two spatial helical channels with a phase difference of π between them, and the two spatial helical channels are periodically connected by several connecting channels to form a three-dimensional structure similar to a DNA double helix.

2. The three-dimensional micromixer for high-viscosity fluids based on a DNA double helix structure as described in claim 1, characterized in that, The geometric trajectories of the two spatial spiral channels satisfy the parameterization process: ； ； Where r is the helix radius and t is a parameter variable.

3. The three-dimensional micromixer based on the DNA double helix structure as described in claim 1, characterized in that, The "base pair" connecting channels are distributed perpendicular to the helical axis, playing a role similar to the splitting and recombination of a splitting and recombination (SAR) structure. This forces the fluid to be redistributed when passing through the connecting channels, causing the fluid in the two helical channels to be periodically dispersed and recombine.

4. The three-dimensional micromixer based on the DNA double helix structure as described in claim 1, characterized in that, The micro-mixer is made of polytetrafluoroethylene (PTFE) flexible tubing, and a spiral path is constructed through tees, elbows, and short pipe fittings.

5. The three-dimensional micromixer based on the DNA double helix structure as described in claim 1, characterized in that, By utilizing the curvature κ and torsion τ geometric properties of the three-dimensional spiral microchannel, a combined effect of rotation and deflection is generated on the fluid. Based on the Q-criterion, the Q extremum in the microchannel is calculated to rotate periodically along the channel direction, thereby enhancing chaotic convection.

6. A method of applying the micromixer as described in any one of claims 1-5, characterized in that, It is mainly used for mixing and mass transfer enhancement of high viscosity oil phase fluids or oil-water two-phase systems.

7. The application method as described in claim 5, characterized in that, By controlling the inlet fluid velocity, the Reynolds number (Re) in the microchannel is kept within the range of 40-60. The inertial force generated by the three-dimensional spiral structure forms a Dean vortex, and the vortex core migrates spatially along the overall direction of the channel, generating a "rotation-revolution" composite flow, thereby achieving the best mixing effect and avoiding the phenomenon of vortex trapping.

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