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DES Seminar Series: "Inkjet drop formation in complex rheological fluids - can rheology improve jetting performance?"

Date: Wed 1 Nov 2017, 14:00 - 15:00

Location: Seminar Room, SEMS

Abstract: Inkjet printing relies upon accurate delivery of drops generated in the jetting process. However the processes of jetting and drop formation is strongly affected by fluid rheology. Inks containing high loadings of colloidal particles will be shear-thinning and so may have a different characteristic viscosity within the nozzle compared to the ejected ligament. Moreover, even trace amounts of long chain polymers can cause substantially different breakup dynamics compared to that of an ordinary (Newtonian) fluid, influencing in-flight fragmentation and detachment from the nozzle. We have developed numerical simulations of drop on demand inkjet printing that allow the effects of different types of non-Newtonian behaviour (shear-thinning, viscoelasticity, thixotropy) to be consider, and compared with experiments on “model” inks. From these we are able to establish the parameter values controlling the break-up length and character of jet break-up, such as the production of small satellite droplets. In particular for appropriate choices of rheological parameters it is possible to obtain satellite-free drops at higher speeds than is possible with Newtonian fluids.

Bio-Sketch: Dr Oliver Harlen is a Reader in the School of Mathematics at the University of Leeds. His research interests lie in the fluid dynamics of complex fluids such as polymer solutions, polymer melts and suspensions.

Updated by: Jun Chen