Shape Evolution of Sandwitched Droplet in Microconfined Shear Flow

Droplets confined in a microfluidic channel often exhibit intriguing shapes, primarily attributable to complex hydrodynamic interactions over small scales. We show that effect of varied substrate wettability conditions may further complicate these interactions remarkably, and often non-trivially. Our studies reveal that the combined influence of substrate wettability and fluidic confinement eventually culminates towards influencing the droplet transients, distortion of the local shear flow field, as well as drop stabilization against breakup or detachment, allowing one to develop different regimes of shapes evolution that are fascinatingly distinct from the ones reported in earlier studies on drop breakup in micro-confined shear flows. We further demonstrate that combined consequences of wall effects and interfacial wettability characteristics can be exploited to pattern microfluidic substrates with pre-designed patches, bearing far-ranging scientific and technological consequences in several scientific and technological applications of contemporary relevance.