Obstacle Trenches for Enhanced Microplastic Trapping in 3D-Printed Microfluidics

The particle trapping efficiency of a microwell primarily depends on the flow's velocity and particle size. If the flow velocity is too fast, the trapping efficiency decreases. Therefore, decelerating local flow velocity just before reaching the microwell is important for enhancing trapping efficiency. Similarly, particle size also influences trapping efficiency due to the effects of gravitational force. This research employed obstacle trenches to reduce the local velocity of microplastic particles to enhance trapping efficiency. Additionally, the effects of using resin-based 3D printing to fabricate the microfluidic system on trapping efficiency are examined. The experiments compared two models: one with obstacle trenches placed in front of the microwells and one without using $30 \mu \mathrm{m}$ polystyrene beads as representative microplastics. The results demonstrated that the presence of obstacle trenches increases the trapping of microplastics by about 2 times. This indicated that triangular obstacle trenches effectively reduce local fluid velocity and improve trapping efficiency. Moreover, flow disturbances caused by raised rims creeping from 3D printing process were observed behind both obstacle trenches and microwells, which potentially influence local flow behavior and reduce the overall trapping efficiency.