High-profile-quality microchannels fabricated by UV picosecond laser for microfluidic mixing

Abstract

Ultrafast laser direct writing technology has been widely investigated in the fabrication of glass-based microfluidic devices. However, in the machining of microchannels, the importance of cross-sectional profile quality is overlooked. Therefore, we have investigated the influence of scanning strategies and process parameters on the cross-sectional profile characteristics of microchannels. A picosecond laser with a pulse duration of 10 ps and a wavelength of 355 nm was employed to engrave microchannels. To achieve symmetrical cross-sectional profiles and smooth channel bottoms, a combined strategy of the offset method combined with the double bidirectional method (OM + DBM) has been proposed. Compared to the traditional sequential method (SM) and the improved bidirectional method (BM) strategy, the new strategy eliminates the protrusions at the starting edge and in the middle of the channel bottom. The new strategy also demonstrates quality optimization of the microchannel edges. A microfluidic mixing channel with a width of 400 µm and a depth of 240 µm has been successfully manufactured without defects. A split and recombine structure, known for its high mixing efficiency, has been utilized to conduct microfluidic mixing experiments. The mixing results of liquid–liquid and liquid–gas demonstrate that microfluidic channels with high-quality profiles exhibit high efficiency and stability of flow. The input flux of the mixing liquids reached 20 mL/min.