High-speed micro-particle manipulation in a microfluidic chip by directional femtosecond laser impulse

[Display omitted] •A femtosecond laser was focused into a microfluidic chip and applied to particle manipulation.•Intensity and directionality of the impulse were optimized by a pocket structure fabricated in the channel of the chip.•The femtosecond laser-induced impulse realized on-chip particle manipulation within 10 μs. We report a high-speed manipulation method to control flow direction of micro-particles in microfluidic chip activated by a femtosecond (fs) laser impulse. When the femtosecond laser pulse is focused in the channel, a micro-explosion is induced and generates an impulsive force at the laser focal point. In this method, the impulsive force initiated inside a micro-structure in the channel is applied to manipulate micro-particles flowing in the channel. Specifically, a directional force loading to the particle is realized by an additive pocket structure fabricated in the channel. When the laser is focused at the entrance of the pocket fabricated perpendicular to the channel, we could enhance directionality and intensity of the impulsive force and realize an effective particle manipulation compared with the chip without assistance of the pocket structure. The enhancement was apparently observed in a longer and wider pocket, especially whose entrance width is narrower than the pocket end width. The manipulation process occurs in less than 10 micro-seconds which is a potential high-speed manipulation method for single micro-particles.