Scanning opposed migration aerosol classifier

1. An opposed migration classifier comprising:

(a) a classification channel through which passes a sample comprising one or more particles suspended within a sample fluid, the classification channel comprising a first wall and a second wall that are both permeable to a flow of fluid;

(b) a sample flow distribution input channel and sample flow distribution output channel that are located asymmetrically with respect to a center of the classification channel wherein a voltage applied to a channel wall varies during a transit of the one or more particles in the sample fluid such that trajectories of the one or more particles deviate from constant voltage operation trajectories;

(c) a cross-flow fluid that enters the classification channel through one of the permeable walls, wherein the cross-flow fluid flows at a first velocity and exits in a first direction through the other permeable wall;

(d) an imposed field that is applied causes one or more particles to migrate in a direction opposite to that of the cross-flow fluid, at a second velocity that at times during the scan is not equal to the first velocity of the cross-flow fluid, such that the one or more particles are carried along the classification channel between the permeable walls, wherein:

(i) the particles in the sample are classified in the classification channel based on their mobility;

(ii) the mobility comprises a migration velocity per unit of applied force;

(iii) the imposed field is created by a time varying field imposed in a second direction normal to the permeable walls; and

(iv) the sample fluid enters through or within a first threshold distance of one of the permeable walls, travels through the classification channel, and the classified particles exit through or within a second threshold distance of the same permeable wall.

2. The opposed migration classifier of claim 1 , wherein the cross-flow fluid rate is uniform.

3. The opposed migration classifier of claim 1 , wherein the time varying field is an electric field created by a scanning voltage on one of the permeable walls.

4. The opposed migration classifier of claim 1 , wherein a shape of the opposed migration classifier is radial.

5. The opposed migration classifier of claim 1 , wherein a shape of the opposed migration classifier is defined using parallel plates.

6. The opposed migration classifier of claim 1 , wherein a shape of the opposed migration classifier is defined by a coaxial cylinder.

7. An opposed migration classifier comprising:

(a) a classification channel through which passes a sample comprising one or more particles suspended within a sample fluid, the classification channel comprising a first wall and a second wall that are both permeable to a flow of fluid;

(b) a sample flow distribution input channel and sample flow distribution output channel that are located asymmetrically with respect to a center of the classification channel wherein a voltage applied to a channel wall varies during a transit of the one or more particles in the sample fluid such that trajectories of the one or more particles deviate from constant voltage operation trajectories;

(c) a cross-flow fluid that enters the classification channel through one of the permeable walls, wherein the cross-flow fluid flows at a first velocity and exits in a first direction through the other permeable wall, wherein the first velocity varies with time;

(d) an imposed field that is applied causes one or more particles to migrate in a direction opposite to that of the cross-flow fluid, at a second velocity that at times during the scan is not equal to the first velocity of the cross-flow fluid, such that the one or more particles are carried along the classification channel between the permeable walls, wherein:

(i) the particles in the sample are classified in the classification channel based on their mobility;

(ii) the mobility comprises a migration velocity per unit of applied force; and

(iii) the sample fluid enters through or within a threshold distance of one of the permeable walls, travels through the classification channel, and the classified particles exit through or within the threshold distance of the same permeable wall.

8. The opposed migration classifier of claim 7 , wherein the imposed field is gravity.

9. The opposed migration classifier of claim 7 , wherein a shape of the opposed migration classifier is radial.

10. The opposed migration classifier of claim 7 , wherein a shape of the opposed migration classifier is defined using parallel plates.

11. The opposed migration classifier of claim 7 , wherein a shape of the opposed migration classifier is defined by a coaxial cylinder.

12. A method for separating particles comprising:

(a) introducing a sample, comprising one or more particles suspended within a sample fluid, from a sample flow distribution input channel into a classification channel, wherein the sample flows through the classification channel and exits via the sample flow distribution output channel, and wherein the sample flow distribution input channel and sample flow distribution output channel are located asymmetrically with respect to a center of the classification channel wherein a voltage applied to a channel wall varies during a transit of the one or more particles in the sample fluid such that trajectories of the one or more particles deviate from constant voltage operation trajectories;

(b) passing the sample through the classification channel, wherein the classification channel comprises a first wall and a second wall that are both permeable to a flow of fluid;

(c) introducing a cross-flow fluid to the classification channel through one of the permeable walls, wherein the cross-flow fluid flows at a first velocity and exits in a first direction through the other permeable wall;

(d) applying an imposed field on the one or more particles, wherein the imposed field causes the one or more particles to migrate in a direction opposite to that of the cross-flow fluid, at a second velocity that at times during a scan is not equal to the first velocity of the cross-flow fluid, such that the one or more particles are carried along the classification channel between the permeable walls, wherein:

(i) the particles in the sample are classified in the classification channel based on their mobility;

(ii) the mobility comprises a migration velocity per unit of applied force;

(iii) the imposed field is created by a time varying field imposed in a second direction normal to the permeable walls; and

(iv) the sample fluid enters through or within a first threshold distance of one of the permeable walls, travels through the classification channel, and the classified particles exit through or within a second threshold distance of the same permeable wall; and

(e) discharging the particles that travel through the classification channel.

13. The method of claim 12 , wherein the cross-flow fluid rate is uniform.

14. The method of claim 12 , wherein the time varying field is an electric field created by a scanning voltage on one of the permeable walls.

15. The method of claim 12 , wherein a shape of a system performing the method is radial.

16. The method of claim 12 , wherein a shape of a system performing the method is defined using parallel plates.

17. The method of claim 12 , wherein a shape of a system performing the method is defined by a coaxial cylinder.