Transient flow of microcapsules through convergent–divergent microchannels

Abstract

The study deals with a microfluidic method to investigate the transient behavior of microcapsules in flow. The technique consists of investigating ovalbumin microcapsules passing through a convergent–divergent microchannel made of PolyDiMethylSiloxane. We work with three types of square microchannel with, respectively, cross section values of h × h = 30 × 30, 50 × 50 and 70 × 70 μm. The microchannels length is L = 3h. We analyze the kinetics of deformation of the microcapsules in the microchannels for velocity ranging from 2 to 5 cm/s and for microcapsule size ratio d/h ranging from 0.9 to 2.5. The relaxation process at the pore outlet is modeled using an exponential relaxation law. We show that that the relaxation time at the divergent outlet depends on the microcapsule size ratio d/h. Thanks to the analytical expression of the relaxation, we extract a shear modulus of the membrane equal to 0.04 N/m. This value is consistent with the value of 0.07 N/m that we found using the steady state analysis performed in cylindrical glass capillaries. Thus, it is interesting to notice that the microcapsule behavior based on a simple analytical model can be successfully described despite the complex flow situation consisting of deformable microcapsule in confined square microchannels.