Authors: C. Aramphongphun, O. Hemminger, J.M. Castro and L.J. Lee
Affilation: The Ohio State University, United States
Pages: 633 - 636
Keywords: rheology, microfluidics, carbon black suspensions, fluidic device design and fabrication
Rheology and microfluidics are essential and challenging topics in designing microfluidic devices and materials processing. A study of rheological properties (e.g. viscosity) of complex fluids becomes more important in the flow at microscale due to the high rate-of-deformation. A carbon black dilute suspension – a material typically used in a coating process – was examined in this study. Continuum models of a pressure driven flow between two parallel plates with no-slip and slip boundary conditions were developed to determine the viscosity of the suspension fluid and the effect of the wall slip. Customized microslit rheometers were designed and used to test the suspension fluid at various channel thicknesses (approximately 25-125 µm) and temperatures (25˚C and 50˚C). The experimental results from the microslit rheometer were also compared with those from a conventional parallel plate rheometer. From both the mathematical models and experimental results, we can estimate the value of the slip parameter called the slip length. This slip length is then used in the flow prediction of the coating material in the process known as in-mold coating (IMC) where the final coating thickness is in the range of 75-125 µm. In addition, we will be employing high-speed confocal microscopy to obtain data that can be used for microscale confocal particle image velocimetry (µCPIV). This will allow us to measure thin optical slices that can be reconstructed to give three-dimensional velocity profiles of the flow at steady state. Furthermore, we will extend our study to nanofluidics and other complex fluids such as biofluids.