Autonomous Seeding of Microparticles on the Inner Surface of Polymer Hollow Microfibers Using Hydrodynamic Forces

Lateral displacement of microparticles suspended in a viscoelastic fluid flowing through a microfluidic channel occurs due to an imbalance in the first (N1) and second (N2) normal stress differences. Here, the lateral displacement of fluorescent microparticles suspended in a polyethylene glycol (PEG) solution in a two-phase flow with aqueous sodium alginate, flowing through a unique microfluidic device that manufactures microparticles seeded alginate-based hollow microfibers is studied. Parameters such as concentration of the aqueous sodium alginate and flow rate ratios are optimized to enhance microparticle seeding density and minimize their loss to the collection bath. 4% w/v aqueous sodium alginate is observed to confine the suspended microparticles within the hollow region of microfibers as compared to 2% w/v. Moreover, the higher flow rate ratio of the core fluid, 250 µL min⁻¹ results in about 192% increase in the microparticle seeding density as compared to its lower flow rate of 100 µL min⁻¹. The shear thinning index (m) is measured to be 0.91 for 2% w/v and 0.75 for 4% w/v sodium alginate solutions. These results provide insights into understanding microparticle displacement within a viscoelastic polymer solution flowing through a microfluidic channel, motivating further studies in biofabrication, and cellular seeding and sorting.