Classifying – separating – and assorting solids – Electrostatic – Attracting and repelling
Reexamination Certificate
2001-12-06
2004-11-23
Wang, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Electrostatic
Attracting and repelling
C209S214000, C209S223100, C209S232000, C209S906000, C436S052000, C436S063000, C422S081000
Reexamination Certificate
active
06822180
ABSTRACT:
RELATED APPLICATIONS
This application is based on Japanese Patent Application Nos. 2000-374852 and 2001-305231 filed in Japan on Dec. 8, 2000 and Oct. 1, 2001, respectively, the entire contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a particle separation mechanism. In one embodiment, the present invention relates to a particle separation mechanism which can be used to separate particles contained in a solution.
BACKGROUND OF THE INVENTION
Recent attention has focused on &mgr;-TAS (micro total analysis system) for miniaturizing devices for use in various processes of chemical analysis and synthesis and the like, and for applications to micromachine art.
For example, there is a concept of a separation system using &mgr;-TAS for separating particles contained in a solution. A microstructure is formed in a flow pass by micro processing art, and loaded in a polymer gel to form a filter for separating particles by size.
In this case, the filter is formed from the bottom surface to the top surface of a flow pass, over the entire cross section of the flow pass. For this reason, when particles are separated by the filter, and a pump is used to provide the propulsion force for the solution containing the particles, the size of the holes of the filter generally used for separation (which can range from sub micron level to approximately 30 &mgr;m) are too small and increase the flow pass resistance, such that it is difficult for the solution to pass through the filter.
Furthermore, when a solution passes through a filter having relatively large holes, the solution being propelled via a pump which generates an extremely strong pressure, although particle separation is initially possible, eventually the separated particles block the holes of the filter, thereby greatly increasing the flow pass resistance such that the solution cannot be transported.
SUMMARY OF THE INVENTION
Accordingly, a problem of the art to be resolved by the present invention is to provide a particle separation mechanism capable of efficient and continuous particle separation.
To resolve the previously mentioned problems of the art, one embodiment of the present invention provides a microchip having a particle separation mechanism with the structure described below.
The microchip comprises a flow pass in which a solution containing particles can flow, and a particle separation mechanism. The particle separation mechanism comprises a deflection mechanism, which generates an electric field or magnetic field in a transverse direction of the flow pass. The field is generated in a deflection region of the flow pass so as to alter a direction of flow of the particles. The particle separation mechanism further comprises a particle capture unit disposed on a side of the flow pass to which the particles are directed by the deflecting mechanism so as to capture the particles.
In this structure, as the particles in the solution flowing through the flow pass approach the deflection region, the particles are directed to one side of the flow pass. The direction of flow of the particles is deflected in the direction of an electric field or a magnetic field (or in a direction opposite the electric field or the magnetic field) by the deflection mechanism. The particles can thus be captured by the particle capture unit disposed at this location. In this way, the desired particles can be separated from a solution containing the particles.
According to this structure, an electric field or magnetic field is generated in a direction transverse to the flow pass to separate the particles. Since a direction transverse to the flow pass (e.g., the width direction or the height direction of the flow pass) has an extremely small dimension when compared to the length direction of the flow pass, only a small voltage or magnetic force is required to generate a desired electric field or magnetic field.
Accordingly, a structure generating a relatively low electric field or magnetic field may be used as the deflection mechanism, such that the particle separation mechanism can be made compact and inexpensive.
Specifically, the particle capture unit may be structured in various embodiments as described below.
In a first embodiment, it is desirable that the particle capture unit include a projection. The projection has a radix end on a surface on the deflection side of a surface forming the flow pass. The projection partially extends into the flow pass and thus occupies only a part of the cross section of the flow pass.
In this structure, the projection of the particle capture unit is disposed on one side of the flow pass (the deflection side) in a direction traverse to a direction of flow of the flow pass. The particles in the solution are attracted by the electric field or the magnetic field, and are captured on the projection. The particles accumulated on the particle capture unit are released from the particle capture unit by, for example, the deflection mechanism generating an electric field or a magnetic field in the opposite direction, and are collected when they flow downstream.
According to this structure, since the particle capture unit does not have exclusive possession of the entire outflow cross section of the flow pass, and is only disposed in a portion of the deflection side of the flow pass, the captured particles do not block the entire cross section of the flow pass, and do not hinder the flow of the solution. Accordingly, continuous, efficient particle separation occurs.
The projection may have an optional form. For example, the projection may be a plate extending in a direction transverse to a direction of flow of the flow pass. Alternatively, an indentation may be formed by circumscription by the projection, such that this indentation opens to the center of the flow pass. In order to efficiently capture particles, it is desirable that a plurality of columnar projections are provided, such that a solution flows among the columns.
It is desirable that the particle capture unit includes a plurality of columnar projections. In one embodiment, the space between adjacent projections is 0.1 &mgr;m or more, but less than 50 &mgr;m.
This structure is suitable for extracting blood plasma components by attracting erythrocytes, leukocytes, and thrombocytes to the projections for removal from whole blood.
In a second embodiment, the flow pass includes a single main flow pass on the upstream side (in the direction of flow), and includes two or more branch flow passes branching from the main flow pass in the downstream direction (in the direction of flow). In this case, the deflection region is near the junction (branch point) of the main flow pass and the branch flow passes, and a deflection mechanism is provided with electrodes (or other types of field generators) in or near each branch flow pass and proximate the junction (branch point). In a more specific embodiment, the branch flow passes are arranged so as to be between the electrodes.
In this embodiment, in one branch flow pass, voltages of different electrical potentials are applied to the electrodes, which are arranged on bilateral sides of the branch flow pass, with the branch flow pass therebetween. The electrodes generate an electric field in a transverse direction to the branch flow pass. In the other branch flow pass, however, voltages of identical electric potential are applied to the electrodes, which are arranged on bilateral sides of the branch flow pass, with the branch flow pass therebetween. In this way, particles in the solution are attracted to the branch flow pass in which an electric field is generated in the transverse direction of the branch flow pass, so as to flow into this branch flow pass.
In this structure, voltages of different electric potential are applied to electrodes disposed bilaterally on the branch flow passes, such that the branch flow pass in which the electric field is generated in a transverse direction of the branch flow pass can selectively become the particle capture unit.
According to this
Fujii Yasuhisa
Sando Yusuhiro
Minolta Co. , Ltd.
Rodriguez Joseph
Sidley Austin Brown & Wood LLP
Wang Donald P.
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