Patent Application
20080115849
1. Field of the Invention
The present invention relates to a micro-fluidic oscillator and, more particularly, to a micro-fluidic oscillator having a sudden-expansion micro nozzle to conquer fluid viscous force due to increase of instability of fluid so as to generate a self oscillation phenomenon at slow flow.
2. Description of Related Art
A fluidic oscillator makes use of instability of the fluid itself to generate oscillation. Because of restrictions of physical parameters, general fluidic oscillators can only generate oscillation under some flow speeds. If the flow speed is too low, the fluidic oscillators cannot successfully generate oscillation. This will result in much limit in applications, especially in the applications of micro fluidic.
As shown in FIG. 1, U.S. Pat. No. 3,902,367 discloses a fluidic oscillator 2, which comprises an oscillation chamber 4 with attachment walls 61 and 62 at two sides thereof, a fluid inlet 8, a fluid outlet 10, two feedback channels 12 and 14, and a flow splitter 16. As shown in FIG. 2, U.S. Pat. No. 4,610,162 discloses a fluidic oscillator 18, which comprises an oscillation chamber 20 with attachment walls 221 and 222 at two sides thereof, a fluid inlet 24, a fluid outlet 26, two feedback channels 28 and 30, and a fluid splitter 32. As shown in FIG. 3, U.S. Pat. No. 6,860,157 discloses a fluidic oscillator 34, which comprises an oscillation chamber 36 with attachment walls 381 and 382 at two sides thereof, a fluid inlet 40, a fluid outlet 42, two feedback channels 44 and 46, and two fluid splitters 48.
The above prior art fluidic oscillators 2, 18 and 34 can still successfully operate under ordinary millimeter or micrometer scales to generate oscillation. However, it is found that fluid will move in a mode of stable laminar flow in the micrometer-scaled micro channels of the miniaturized fluidic oscillators 2, 18 and 34 once the fluidic oscillators 2, 18 and 34 are miniaturized with the same ratio. That is, the viscous force of fluid in the micrometer-scaled micro channels will increase substantially so that the micro fluidic will be very stable and can hardly generate oscillation. Therefore, the fluidic oscillators cannot function normally. Although active micro elements can be integrated in the micro channels to perturb the micro fluidic in advance, the fabrication process of the active elements is cumbersome and they are subject to damage.
Accordingly, the present invention aims to propose a more perfect micro-fluidic oscillator to solve the above problems in the prior art.
An object of the present invention is to provide a micro fluidic oscillator, which has a sudden-expansion micro nozzle and a special design of feedback channels to solve the problem of increased viscous force of fluid in the micro channels in the prior art. Therefore, fluid can still generate oscillation under very slow flow speeds.
To achieve the above object, the present invention provides a micro fluidic oscillator, which comprises a main body and a cover body for covering the main body. The main body comprises an oscillation chamber with two sides composed of two attachment walls, a sudden-expansion micro nozzle, an outlet passage, and two flow splitters. The oscillation chamber is used to provide an oscillation space for a fluid. The sudden-expansion micro-nozzle has a jet stream passage and a sudden-expansion region. One end of the sudden-expansion region is connected with the jet stream passage, and the other end of the sudden-expansion region is connected with one end of the oscillation chamber. The outlet passage is connected with the other end of the oscillation chamber. The two flow splitters are located at connection positions of the outlet passage and the oscillation chamber. The two feedback channels are located at outer sides of the two attachment walls and extended from the two flow splitters to the sudden-expansion region, respectively. The two feedback channels have different lengths or inside diameters, or the outlet positions of the two feedback channels are not completely opposite to each other, or the angle between the two feedback channels and the sudden-expansion region are different.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:
As shown in
Moreover, the cover body 54 has an inlet hole 78 corresponding to the inlet passage 62. An inlet duct 80 is inserted into the inlet hole 78 so that the fluid can flow from the inlet duct 80 into the inlet passage 62. The cover body 54 also has an outlet hole 82 corresponding to the outlet passage 68. An outlet duct 84 is inserted into the outlet hole 82 so that the fluid can flow out from the outlet duct 84.
The operation of the micro fluidic oscillation 50 of the present invention is illustrated below. Fluid flows from the inlet duct 80 into the inlet passage 62 the jet stream passage 64, the sudden-expansion region 66 and the oscillation chamber 56, and then hits the flow splitters 70 and 72 so that part of the fluid flows into the outlet passage 68, and part of the fluid flows into the two feedback channel inlets 741 and 761 and then the two feedback channels 74 and 76, and then flows from out the two feedback channel outlets 742 and 762 and finally into the oscillation chamber 56. The above process is repeated to cause instability of the fluid so as to generate oscillation.
The lengths or inside diameters of the two feedback channels 74 and 76 can be different. The positions of the feedback channel outlets 742 and 762 can further be staggered and are not totally opposite to each other. The angles θ1 and θ2 between the sudden-expansion region 66 and the two feedback channels 74 and 76 can be different. The range of the angles θ1 and θ2 are between 30° and 120°. The above design manner can enhance the oscillation driving force and increase the instability of the fluidic oscillation. Even under very low fluid speeds, the fluid can still generate oscillation. The fluid flow rate of the present invention is between 10 micro-liter/min and 100 micro-liter/min.
The material of the main body 52 and the cover body 54 can be selected among silicon, glass, polymer and electroform metal. The main body 52 and the cover body 54 can be joined together by means of glue adhesion or direct application of pressure. If the main body 52 and the cover body 54 are joined together by means of glue adhesion, the joint place of the main body 52 and the cover body 54 should be kept smooth. Or the surfaces of the main body 52 and the cover body 54 to be joined together are processed to produce molecule bonding between them without the need of applying glue or applying pressure to the joint place.
To sum up, the micro fluidic oscillator of the present invention makes use of a sudden-expansion micro nozzle to break the viscous shear stress between fluid and walls so as to generate unstable flow and thus oscillation. Collocated with a special design of two feedback channels, wherein the lengths and inside diameters of the two feedback channels are different, or the outlet positions of the two feedback channels are staggered and are not totally opposite to each other, or the angles between the two feedback channels and the sudden-expansion region are different, the oscillation driving force can be enhanced and the instability of the fluidic oscillation can be increased to keep a self oscillation of the fluid.
Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
