Polymer flows over substrate with an array of high aspect-ratio microwells (µWells)*

Shear-stress and pressure measurement carry significant interest for various wall flows. However, obtaining both stresses simultaneously with adequate resolutions remains a challenge. Here, we propose wall stress measurement technique by creating arrays of µWells embedded with deformable mirrors and a digital holographic microscopic interferometry. We have developed a method to successfully fabricate a wrinkle free thin film mirror over a soft substrate by suppressing instability with a nm-layer of nanoparticles. Fabrication of thin film embedded in µWells requires flow highly viscous polymer into high aspect ratio µWells (e.g., depth of ~200 mm and diameter of 50-500mm) To understand the polymer flows in confinement, we use SU-8 µWell array fabricated by photolithography and a mixture of polydimethylsiloxane (PDMS) and hexane as model polymer system. By varying PDMS in hexane, we can tune the viscosity and surface tension of the mixture. Measurements will be performed to examine the flow in the µWells experimentally. Scaling of polymeric flow on Re and We will be established and validated via numerical simulations