All Issues
CFD based investigation of Microfluidic thermophoresis
Author : Niraj Kumara, Kartik Chandra Ghantab and Abhiram Hens*b
DOWNLOAD PDF
ABSTRACT
Microfluidics is an emerging area of research where fluid flow through microchannel is studied and it has wide range of applications in the areas of microscale reactor technologies, process intensification, lab-on-chip devices etc. Particularly, in biomedical and biochemical applications of lab-on-chip devices, such microscale transport phenomena offers a number of advantages related to heat and mass transfer, controlled mixing etc. In the present study, particle laden flow inside such a microchannel was considered along with a thermal gradient and the whole phenomenon was investigated though the route of computational fluid dynamics (CFD). Main objective of the study was to understand the phenomenon of ‘thermophoresis’ inside such a microchannel. Thermophoresis is basically the motion of the particles under the influence of a temperature gradient. Thermophoresis inside a microchannel has lot of application in biomedical and other sectors. Although, a number of earlier works reported different aspects of thermophoresis at macroscale, its application in microfluidic system was not explored in detail. In the present work, microfluidic thermophoresis was simulated on a COMSOL based CFD platform where a three dimensional microchannel was constructed and a fluid flow inside this channel was simulated considering a low flow rate. For determining the velocity field, incompressible flow Navier-Stokes equation was solved along with the continuity equation. No slip boundary condition was adopted at the channel wall. After evaluating the velocity field, the same system was again simulated with a temperature gradient along the perpendicular direction to the flow. Next, particle tracing module was imposed on this system to study the particle dynamics inside such a channel. The particle trajectories clearly reveal the thermophoresis process inside the microchannel and it was found that particles motion is significantly influenced by the presence of thermal field. Effect of the temperature difference, particle concentration, flow rates on the particle motion was thoroughly investigated and presented in details. Fig. 1 shows the schematic diagram of the thermophoresis process inside a microchannel to briefly depict the system of investigation.
KEYWORD
Thermophoresis, temperature gradient, movement of microparticle, microchannel, CFD