Device for separating and concentrating microfluidic particles

1. A flow unit for microfluidic particle separation and concentration, the unit comprising:

a first member and a second member wherein each of the members is in the form of a wedge, each of said wedges comprising

a first corner which flares outwardly to define a turn segment;

a second corner at which point the wedge is more narrow than at the first corner; and

a flat edge acting as a diffuser segment;

wherein the first and second members are arranged such that a channel is formed;

wherein the channel is laid out such that each of the members' second corners define a nozzle segment having an opening through which fluid and microfluidic particles enter the flow unit, and

such that downstream of the nozzle segment the channel defines a narrowing portion at which the distance between the first and second members narrows from the opening to increase momentum of the fluid through the nozzle segment;

wherein the edge which defines the diffuser segment of the second member extends past the corner which defines the turn segment of the first member along an axis defined by the flow through the channel; and

wherein the turn segment defined by the first corner of the first member changes the flow direction of the fluid consistent with the first member causing a separation based on the relative size of particles contained within the fluid.

2. The unit of claim 1 further comprising a flow dividing segment through which fluid flow is divided into at least two flow sides, one side of which the flow dividing segment carries relatively smaller particle size and particle density than the particles that flow through the other side.

3. The flow unit of claim 1 wherein the turn segment is a U shaped turn.

4. The unit of claim 1 wherein the first and second members are identical members.

5. The unit of claim 1 wherein the momentum and flow direction of the fluid through the flow unit is modeled as follows:

ρ

P

⁢

V

P

⁢

ⅆ

U

⇀

P

ⅆ

t

=

C

D

⁢

ρ

L

⁡

(

U

⇀

L

-

U

⇀

P

)

⁢



U

⇀

L

-

U

⇀

P



⁢

A

P

2

+

ρ

P

⁢

V

P

⁢

G

⇀

+

S

.

wherein ρ p , V p , and U p are the density, volume, and velocity of the particle, respectively, wherein C D is the drag coefficient of particle, wherein ρ L and U L are the density and velocity of surrounding liquid, wherein A p is the particle projected area, wherein a spherical particle, V p , is πd P 3 /6 and A P is πd P 2 /4, wherein d P is the particle diameter, and wherein G is the vector describing the acceleration of a particle due to a gravitational field and S is additional source term.

6. The unit of claim 5 wherein the fluid may be evaluated in incompressible flow as follows:

C

D

=

24

Re

for

Re

<

1

C

D

=

24

Re

⁢

(

1

+

0.15

⁢

⁢

Re

0.687

)

for

1

<

Re

<

10

3

C

D

=

0.44

for

Re

>

10

3

wherein C D is a function of Reynolds number Re and wherein Re equals ρ L |U L −U P |d p /μ.

7. A flow unit for microfluidic particle separation and concentration, the unit comprising:

a plurality of flow units for microfluidic particle separation and concentration, each unit comprising:

a first member and a second member wherein each of the members is in the form of a wedge, each of said wedges comprising

a first corner which flares outwardly to define a turn segment;

a second corner at which point the wedge is more narrow than at the first corner; and

a flat edge acting as a diffuser segment;

wherein the first and second members are arranged such that a channel is formed;

wherein the channel is laid out such that each of the members' second corners define a nozzle segment having an opening through which fluid and microfluidic particles enter the flow unit, and

such that downstream of the nozzle segment the channel defines a narrowing portion at which the distance between the first and second members narrows from the opening to increase momentum of the fluid through the nozzle segment;

wherein the edge which defines the diffuser segment of the second member extends past the corner which defines the turn segment of the first member along an axis defined by the flow through the channel; and

wherein the turn segment defined by the first corner of the first member changes the flow direction of the fluid consistent with the first member causing a separation based on the relative size of particles contained within the fluid,

the flow units being disposed in an array and arranged in a cascading fashion.

8. The device of claim 7 further comprising a flow dividing segment defined by staggering each flow unit with offset.

9. The device of claim 8 wherein the flow dividing segment receives fluid flow that is divided into at least two flow sides, one side of which the flow dividing segment carries relatively smaller particle size and particle density than the particles that flow through the other side.

10. The device of claim 7 wherein the turn segment is a U-shaped turn.

11. The device of claim 7 wherein the first and second members are identical members.

12. The device of claim 7 wherein the momentum and flow direction of the fluid through the flow unit is modeled as follows:

ρ

P

⁢

V

P

⁢

ⅆ

U

⇀

P

ⅆ

t

=

C

D

⁢

ρ

L

⁡

(

U

⇀

L

-

U

⇀

P

)

⁢



U

⇀

L

-

U

⇀

P



⁢

A

P

2

+

ρ

P

⁢

V

P

⁢

G

⇀

+

S

.

wherein ρ p , V p , and U p are the density, volume, and velocity of the particle, respectively, wherein C D is the drag coefficient of particle, wherein ρ L and U L are the density and velocity of surrounding liquid, wherein A p is the particle projected area, wherein a spherical particle, V p , is πd P 3 /6 and A P is πd P 2 /4, wherein d P is the particle diameter, and wherein G is the vector describing the acceleration of a particle due to a gravitational field and S is additional source term.

13. The device of claim 5 wherein the fluid may be evaluated in incompressible flow as follows:

C

D

=

24

Re

for

Re

<

1

C

D

=

24

Re

⁢

(

1

+

0.15

⁢

⁢

Re

0.687

)

for

1

<

Re

<

10

3

C

D

=

0.44

for

Re

>

10

3

wherein C D is a function of Reynolds number Re and wherein Re equals ρ L |U L −U P |d p /μ.