University of Oxford

    Physical and Theoretical Chemistry Laboratory - Colloid Group 

    Scientific visitor (2012)

    Supervisors: PhD Dirk Aarts  /  PhD Roel Dullens

 

 

Title of the work developed: "Hydrodynamics of planar extensional two-phase flow cross-slot microchannel"

On the pursue of the "Development and optimization of Extensional-Rheometer-on-a-Chip (ExRheCs)", which is the the main topic of my present research activities, during this short visit I have been exploring the possibilities of using a standard cross-slot microchannel to develop a planar extensional flow by means of using two inmiscible fluids. Therefore the idea was very simple, i.e. two arms will be filled with core fluid (the one which will be undergone to a planar extensional flow) and the other two arms will be filled with the lubricant fluid. Once the system is under rest, we pull the core fluid with a constant flow rate (or ideally with a constant force) and the surface tension and the conservation of mass within the cross-chamber will show a "sheet-thinning process". 

 

This thinning process, ideally, will happen vertical and horizontal directions and, ideally at the same speed. The following picture shows the thinning of the sheet at the midplane (z=0), recalling the filament thinning process observed in the CaBER for a Newtonina fluid.

However, wen we look at the thinning process in the vertical plane (x=0), we see that the filament is not breaking at the midplane, but closer to the top wall, due to differences in the roughness between the end walls, which is consequence of the fabrication process. 

We are still trying to solve this problem, but we believe that this technique can be useful for quantifying the planar extensional properties of low viscosity fluids in microflduics.

Last update - 19/10/2014