Multi-dimensional double spiral device and methods of use thereof

A method of separating sperm cells from a sample fluid comprising a mixture of particles, wherein the sample fluid is a semen sample and the mixture of particles comprises the sperm cells and other particles, the method comprising the steps of:

• a. introducing the sample fluid into the inlet of the first spiral microchannel of a microfluidic device comprising a multidimensional double spiral (MDDS), wherein the MDDS comprises:
• i. a first spiral microchannel comprising a first inlet;
• ii. a second spiral microchannel in fluid communication with the first spiral microchannel and comprising an inner wall outlet and an outer wall outlet, wherein the inner wall outlet is located on the inner wall side of the microchannel and the outer wall outlet is located on the outer wall side of the microchannel;
• and
• iii. a transition region, wherein the transition region is a microchannel that connects the first and second spiral microchannels, wherein the output from the first spiral microchannel is directed into the second spiral microchannel in the transition region;
• wherein the first spiral microchannel has a smaller cross-sectional area than the second spiral microchannel;
• wherein the cross-sectional area of the first spiral microchannel remains constant along its length and wherein the cross-sectional area of the second spiral microchannel remain constant along its length;
• and
• wherein the MDDS is configured to separate particles from a sample fluid comprising a mixture of particles;
• b. directing the sample fluid through the first spiral microchannel to the transition region of the device and into the second spiral microchannel, and
• c. directing a first particle stream to the inner wall outlet and directing a second particle stream to the outer wall outlet, and optionally wherein the first particle stream comprises particles having a larger average diameter than that of the particles in the second particle stream.