Pulsed laser triggered high speed fluorescence activated microfluidic switch

We report a high speed fluorescence activated microfluidic switch capable of achieving a switching time of 50 μsec with a detection efficiency of 86.6% and a switching efficiency of 86.5% at a particle flow speed of ~0.7 m/s. The switching mechanism is realized by exciting dynamic vapor bubbles with focused laser pulses in a microfluidic PDMS channel. The explosive bubble expansion generates fast fluid flows which are directed into a neighboring particle channel to switch the particle flow. Fluorescence activated switching of 10 micron polystyrene microspheres in a Y channel has been demonstrated. This ultrafast laser triggered switching mechanism has the potential to advance the sorting speed of the state-of-the-art microscale fluorescent activated cell sorting devices.