Keywords:femtosecond laser, microfluidics, focusing
Control over the positions of particles into a focused stream serves as a prerequisite step for the downstream processing, such as detection, imaging and separation in microfluidics . In this study, we demonstrate the focusing of polystyrene (PS) particles in a microfluidic channel with a glass surficial pattern achieved by femtosecond pulse (fs) laser micromachining (Fig. 1). The fs laser micromachining shows advantages over other methods such as wet etching and deep reactive ion etching (DRIE) for small area direct writing in glasses. Results showed 10-µm PS particles with flow velocity ranging from 600 to 1000 µm/s are able to be driven close to channel center by the pattern induced hydrodynamic forces. Our results hold potential in the development of innovative microfluidic devices requiring the low-speed particle alignment, e.g. contact imaging and fluorescence lifetime-resolved imaging, for wider applications in biology and biomedicine.