JP-2022526064-A5 -

Dates

Publication Date

20230517

Application Date

20190503

Description

Patent Document 1 discloses a method and apparatus for separating particles according to their size. For this purpose, obstacles that provide an asymmetric flow are used. It is disclosed that the obstacle array is aligned within a microfluidic channel and that the obstacle array is positioned asymmetrically with respect to the direction of the applied flow. However, the obstacles are not in the form of hydrofoils, and the obstacle array is essential for separation. [Description of the components and parts of the present invention] The components shown in the diagram, prepared to better illustrate the microfluidic particle separation and enhancement, are numbered separately, and the explanation for each number is as follows: (1) Hydrofoil (le) leading edge (te) trailing edge (2) chord line (3) Main axis (4) Streamlines coinciding with the main axis (5) Larger particles (6) Smaller particles (7) Diversion point (8) Vortex region (9) Streamlines above the main axis of the hydrofoil (10) Streamlines below the main axis of the hydrofoil (11) 14 μm diameter particles (12) 10 μm diameter particles (13) Separation wall (T) Separation wall tip (14) Distribution of larger particles (15) Distribution of smaller particles (16) Upstream channel (17) a, b Downstream channel (18) a, b Particles of different sizes (19) a, b Distribution of particles of different sizes (20) Inlet (21) Helical channel (22) a, b Outlet (23) Streamline carrying 20 μm diameter fluorescent particles (24) Streamline carrying 10 μm diameter fluorescent particles (α) Angle of attack (a) Distance between streamlines upstream of the hydrofoil (h) Projection height of the hydrofoil (d) Distance between very close streamlines downstream of the vortex region The present invention utilizes a hydrofoil to enable and enhance the separation of particles of different sizes having the same density. As shown in Figure 1, an asymmetrical, arched hydrofoil (1) located in the stream at a non-zero angle of attack (α), which is the angle between the chord line and the main axis (3) measured from the main axis such that the angle of attack (α) is positive , generates a pressure gradient along the blade with a velocity gradient, in accordance with the conservation of momentum. Thus, the average velocity on one side of the blade is higher than the average velocity on the opposite side. In this case, when the streamline (4) coincides with the main axis and the supported particles of two different sizes meet at the leading edge of the blade, the larger particles (5) in the stream tend to flow along one side of the blade at a slower average velocity due to their relatively higher inertia. Meanwhile, the smaller particles (6) flow along the faster stream, as they can be accelerated more easily due to their lower inertia. Therefore, the hydrofoil can be used to separate particles in a stream based on their size. Another embodiment of utilizing hydrofoils with a non-zero angle of attack is flow separation and downstream vortices, as shown in Figure 2. When the flow velocity is sufficiently high, the viscous effect becomes less effective, and the fluid's inertia prevails. Consequently, the flow cannot follow the hydrofoil surface and separates. The point at which this occurs is called the flow separation point (7). Downstream of the flow separation point, a vortex forms to satisfy the conservation of the fluid's angular momentum. When a particle-carrying flow separates from the hydrofoil surface, the particles in the stream tend not to drift toward the vortex region (8). Therefore, particles separated at the leading edge of the hydrofoil according to their size do not rejoin downstream of the hydrofoil within the vortex region. As a result, when two parallel streamlines carrying particles meet the hydrofoil, one streamline (9) is above the main axis (3) of the hydrofoil and the other streamline (10) is below the main axis (3) of the hydrofoil, and there is a distance (a) between the upstream streamlines of the hydrofoil that is shorter than the projected height (h) of the hydrofoil. Since particles that have passed through the hydrofoil cannot drift into the vortex region (8), the distance (d) between the very close streamlines downstream of the vortex region is greater than (a), as shown in Figure 2, thus enhancing particle separation. Since the streamlines cannot intersect the main axis (3) passing through the leading edge of the hydrofoil upstream, this result is independent of whether streamline (9) or streamline (10) carries larger or smaller particles. Figure 3 shows the results of a simulation showing the trajectories of 14 μm diameter particles (11) and 10 μm diameter particles (12) carried by streamlines below and above the main axis, respectively. Figure 4 shows the case where 14 μm diameter particles (11) and 10 μm diameter particles (12) are supported by streamlines above and below the main axis, respectively. One embodiment of the present invention discloses a m