Speaker
Description
Microscale roughness can trigger local plastic rearrangements in soft glassy materials, effectively reducing their apparent viscosity and facilitating flow. Here we investigate how geometrically asymmetric, biomimetic surface patterns fabricated by 3D maskless photolithography can be used to control yielding and flow localization in microchannels. Two roughness geometries are considered: herringbone riblets and wedge-shaped ramps, introducing topological asymmetry along the flow direction. The flow of yield-stress emulsions is characterized using fluorescent tracer particles and particle tracking velocimetry (PTV), enabling spatially resolved velocity measurements across the channel cross-section. We show that asymmetric roughness enhances flow in distinct ways: herringbone patterns induce localized flow banding near the riblet tips, while wedge-shaped ramps promote directional flow enhancement across the channel. These results highlight the potential of combining maskless lithography and fluorescence-based velocimetry to design microstructured surfaces that actively control complex fluid flows