High shear rate viscosity measurements of inks by visual microfluidic rheometer

 
Understanding inks' rheological behavior improves printing quality and limits process issues (bleeding, clogging, etc.). We propose a novel instrument which measures simply and quickly a wide range of products (water-like to thick formulations) and of temperatures (4-80°C), even for high shear rates (up to 10 5 s-1)relevant for inks. A sample and a viscosity standard are pushed through a microfluidic Y-junction. Images of the resulting laminar co-flow are acquired and the position of the interface is measured. The position is related to the viscosity and the flow rates ratio, allowing to determine the sample viscosity. Several formulations of ceramic inks were measured at high shear rates, representative of the application. Fluidicam not only discriminated the low viscosity formulations with a high accuracy, but also highlighted shear thinning behaviors occurring at high shear-rates.