Mechanism of Reducing Local Flow Velocity Using Obstacle Trenches in Microfluidics

Abstract

Trapping efficiency in microwell technique is influenced by both microwell geometry and flow velocity. At higher flow velocity, microplastics tend to flow over microwells resulting in reduced trapping efficiency. Therefore, decreasing flow velocity to enhance trapping efficiency is important. This research introduces triangular obstacle trenches in front of the microwells to reduce local flow velocity leading to the improvement of trapping efficiency. The simulation results show that two mechanisms must occur concurrently to effectively reduce local flow velocity. They are the spreading of streamlines from the apex to the back of triangular trench, and the suitable recirculation inside the trench. In this study, the obstacle trench has dimensions of 600 µm on each side with a depth of 300 µm while the square microwell measured 1,000 µm on each side with a depth of 600 µm. The flow rate was at 0.3 ml/min. Experiments confirmed that the use of triangular obstacle trenches significantly enhanced trapping efficiency by 30 times compared to the case without trenches.