Pulsed Laser Activated Cell Sorting with Three Dimensional Sheathless Inertial Focusing

We present a Pulsed Laser Activated Cell Sorter (PLACS) integrated with 3D sheathless inertial focusing that is capable to sort at 10,000 particles sec-1 with >90% sort purity and 6,000 cells sec-1 with >80% sort purity. It is realized by exciting laser induced cavitation bubbles in a single layer PDMS microfluidic channel to create high speed liquid jets to deflect detected fluorescent samples. Fluid inertia and secondary flows induced by stepped microchannels are used to focus samples in 3 dimensions. After focusing, samples go through an expansion chamber whose function is to enlarge the separation distance between two closely positioned particles by particle-particle interaction in inertial flows and reduce the coincident events within the switching window (16 μsec in time or 32 μm in distance). This sorter uses 10 times lower initial concentration cell samples than that in sheath-based PLACS in order to avoid severe dilution effects from high volume sheath flows at the same throughput.