RAPID SPERM SEPARATION BASED ON SPERM MORPHOLOGY AND MOTILITY

1 . A method of isolating sperm of a fluid sample, comprising:

separating, in an initial separation operation, the fluid sample via a microfluidic separating system into a first debris fluid volume and a first sperm fluid volume;

reflowing the first sperm fluid volume and a dilution fluid through the microfluidic separating system to reprocess the first sperm fluid volume; and

separating, in a subsequent separation operation, the first sperm fluid volume into a second debris fluid volume and a second sperm fluid volume via the microfluidic separating system.

2 . The method of claim 1 , further comprising repeating the reflowing operation and the subsequent separation operation to produce consecutive sperm fluid volumes and corresponding debris fluid volumes separated by the microfluidic separating system, such that a dilution fluid is combined with each consecutive sperm fluid volume flowed through the microfluidic separating system.

3 . The method of claim 2 , wherein repeating the reflowing operation and subsequent separation operation produces a final fluid sample, the final fluid sample comprising at least 65 percent of the sperm cells that were contained in the fluid sample prior to the initial separation operation.

4 . The method of claim 3 , wherein the final fluid sample comprises at least 80 percent of the sperm cells that were contained in the fluid sample prior to the initial separation operation.

5 . The method of claim 3 , wherein the final fluid sample is produced in less than 20 minutes from the initial separation operation.

6 . The method of claim 3 , wherein the final fluid sample is 2.5 mL or less.

7 . The method of claim 3 , wherein the final fluid sample comprises 3 percent or less of white blood cells that were contained in the fluid sample prior to the initial separation operation.

8 . The method of claim 2 , wherein the final fluid sample comprises a Newtonian fluid.

9 . The method of claim 2 , wherein repeating the reflowing operation and the subsequent separation operation is performed at least four times.

10 . The method of claim 2 , further comprising transitioning the fluid sample from a viscoelastic or non-Newtonian fluid to a Newtonian fluid as a result of repeating the flowing operation and subsequent separation operation.

11 . The method of claim 10 , wherein transitioning the fluid sample to a Newtonian fluid is achieved within 5 percent of linear dependency of viscosity as a function of shear rate.

12 . The method of claim 2 , wherein at least one of the consecutive sperm fluid volumes from repeating the reflowing operations exhibits a bimodal distribution due to morphological differences between sperm and other cells in the microfluidic separating system.

13 . The method of claim 2 , wherein at least one of the consecutive sperm fluid volumes includes sperm distinctly separated from other non-sperm particles of similar size in the corresponding debris fluid volume, at least partially due to shape differences driving separation of similarly sized particles.

14 . The method of claim 1 , wherein the first sperm fluid volume has a viscosity greater than a viscosity of the second sperm fluid volume.

15 . The method of claim 1 , wherein the microfluidic separating system comprises a spiral microchannel structure, and wherein the reflowing operation and subsequent separation operation occurs via the spiral microchannel structure.

16 . The method of claim 15 , wherein the microfluidic separating system comprises a complementary spiral microchannel structure, and wherein the reflowing operation and subsequent separation operation occurs via the spiral microchannel structure and the complementary spiral microchannel structure.

17 . The method of claim 15 , wherein the spiral microchannel structure includes an inlet and an outlet, wherein the outlet includes a branched flow splitter having a sperm fluid outlet oriented to receive the first sperm fluid volume and a debris outlet oriented to receive the first debris fluid volume, and wherein the inlet includes a sperm fluid inlet to receive the first sperm fluid volume and a dilution fluid inlet to receive the dilution fluid.

18 . The method of claim 1 , wherein the microfluidic separating system comprises a separation instrument comprising a controller, pumps, and a spiral microchannel structure, the controller configured to control the pumps for flowing the fluid sample through the spiral microchannel structure.

19 . The method of claim 18 , further comprising automatically repeating the reflowing operation and the subsequent separation operation, via the controller, to produce consecutive sperm fluid volumes separated by the spiral microchannel structure.

20 . The method of claim 18 , wherein the controller is configured to control valves and further comprising an incubator which heats at least portions of the sperm fluid volume.

21 . The method of claim 1 , further washing cells from seminal plasma using a tangential filtration unit so as to reduce a total volume.