Inertial focusing and extraction of microparticles using a microchannel with rectangular notches

Abstract

In this work we propose a novel microfluidic device comprising of three stages with sudden contraction- expansion regions for single stream focusing and extraction of different size particles at the outlet of microchannel The single stream focusing at the outlet has a variety of applications in flow cytometry biomedicine filtration purification and other industrial applications The non-fluorescent particles with diameters 1 μm 6 μm and 12 μm were utilized to study the focusing mechanism and fluorescent particles with diameters 1 μm (red) 5 μm (green) and 10 μm (green) to analyze the extraction process The microchannel was fabricated using the lithography process an inverted optical microscope equipped with high-speed camera used to observe the motion of different size non- fluorescent particles and fluorescence camera captures the motion of fluorescent particles The randomly distributed particles first align to two-equilibrium position in a first stage of the microchannel and with the introduction of notches in the second stage a secondary flow arises which modifies the two streams of particles to a single stream at the outlet of the channel Another horizontal vortex arises in horizontal plane which acts as an imaginary wall and forces the large size particles to get away from the wall The 6 μm and 12 μm diameter particle shows a maximum focusing efficiency of 94% and 99% respectively with a length ratio (ratio of length of expansion region to the length of contraction region) of 10 and changes abruptly as the length ratio changes from 10 to 5 As the length ratio decreases the particles do not get enough distance after secondary flow decay in the expansion region to maintain themselves to an equilibrium position with the aid of shear gradient and wall induced forces in the expansion region of the microchannel With the decrease in the concentration of the 6 μm particles the focusing efficiency increases up to 5% Minimum number of 30 notches are required to focus all the particles to a single focusing stream This microchannel has the ability to focus and extract the specific size of particles from the mixture with high efficiency which has many applications in the field of flow cytometry and other biomedical applications

Date of Award	2021
Original language	English
Supervisor	Szu-I Yeh (Supervisor)