Shape Evolution of Sandwitched Droplet in Microconfined Shear Flow

TL;DR

This paper investigates how substrate wettability and confinement influence droplet shape evolution in microfluidic shear flows, revealing new regimes and potential for substrate patterning with scientific and technological implications.

Contribution

It introduces a comprehensive analysis of the combined effects of wettability and confinement on droplet dynamics, highlighting novel shape regimes and applications in microfluidic patterning.

Findings

Wettability and confinement significantly alter droplet shape evolution.

Distinct regimes of droplet shapes are identified under different conditions.

Potential for designing microfluidic substrates with tailored wettability patterns.

Abstract

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.