Daewkon Jin1,Jumin Kim1
Ajou University1
Microfluidics-based technologies have been extensively used to count and sort particles, as well as synthesize functional micro- and nanoparticles. Until now, the dynamics of microparticles or the synthesis process in the microchannel have been observed with conventional optical microscopes equipped with a vertically aligned objective lens. Therefore, there are limitations to the observation of particle dynamics or polymer photopolymerization, which requires direct observation in both the depth and width directions of the microchannel simultaneously. However, existing methods employing holography or micromirrors have the disadvantage of requiring costly optical setups or complicated channel fabrication techniques.<br/>In this work, we demonstrate that it is possible to build up a system capable of simultaneously capturing images in the width and depth directions of a poly(dimethyl siloxane) (PDMS)-based microchannel by installing two objective lenses in the vertical and horizontal directions together with two cameras that are controlled with a trigger. We also showed that by coating the channel side-wall with PDMS and stacking it with a glass slide, the scattered reflection of light caused by the roughness of the channel side-wall as a result of the inevitable channel cutting procedure can be minimized. Using this method, we demonstrated that our system can be used to investigate the three-dimensional distribution of particles in non-Newtonian viscoelastic fluids with shear-thinning viscosities. We expect that our method will be widely used to understand the particle dynamics in numerous solution-based processes employing viscoelastic fluids where the particle distribution is strongly affected by medium viscoelasticity. In addition, we anticipate that this system will contribute to the understanding of the particle synthesis procedures of stop-flow lithography which has been widely used to fabricate non-spherical particles in microchannels.