Recent theoretical and experimental work suggests a frictionless-frictional transition with increasing inter-particle pressure explains the extreme solid-like response of discontinuous shear thickening suspensions. However, analysis of macroscopic discontinuous shear thickening flow in geometries other than the standard rheometry tools remain scarce. Here we use a Hele-Shaw cell geometry to visualise gas-driven invasion patterns in discontinuous shear thickening cornstarch suspensions. We plot quantitative results from pattern analysis in a volume fraction-pressure phase diagram and explain them in context of rheological measurements. We observe three distinct pattern morphologies: viscous fingering, dendritic fracturing, and system-wide fracturing, which correspond to the same packing fraction ranges as weak shear thickening, discontinuous shear thickening, and shear-jammed regimes.

Model elastic inks were formulated, rheologically characterised in shear and extension, and printed via flexography to assess the impact of ink elasticity on print uniformity. Flexography is a roll-to-roll printing process with great potential in the mass production of printed electronics for which understanding layer uniformity and the influence of rheology is of critical importance. A new set of flexo-printable Boger fluids was formulated by blending polyvinyl alcohol and high molecular weight polyacrylamide to provide inks of varying elasticity. During print trials, the phenomenon of viscous fingering was observed in all prints, with those of the Newtonian ink exhibiting a continuous striping in the printing direction. Increasing elasticity significantly influenced this continuity, disrupting it and leading to a quantifiable decrease in the overall relative size of the printed finger features. As such, ink elasticity was seen to have a profound effect on flexographic printing uniformity, showing the rheological tuning of inks may be a route to obtaining specific printed features.

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Confined fluid-driven granular flows are present in a plethora of natural and industrial settings yet even the most fundamental of these are not completely understood. While widely-studied grain flows such as bed load and density-matched Poiseuille flow have been observed to exhibit exponential and Bingham style velocity profiles respectively, this work finds that a fluid-driven bed of non-buoyant grains filling a narrow horizontal channel -confined both from the sides and above -exhibits self-similar Gaussian velocity profiles. As the imposed flow rate is increased and the grain velocity increases, the Gaussian flow profiles penetrate deeper into the packing of the channel. Filling fractions were observed to also be self-similar and qualitatively consistent with granular theory relating to the viscous number I, which at a given position on the self-similar Gaussian curve is found to be generally constant regardless of imposed flow rate or velocity magnitude. An empirical description of the flow is proposed, and local velocity and filling fraction measurements were used to obtain local grain flux and accurately recover a total grain flow rate.