Transport of Microgels in a Microfluidic Constrictive Channel*

The transport of soft bodies in narrow channels are remarkably common in biological systems and industrial processes. During the transport process, the soft body deforms and blocks the channel, and thus induces a pressure drop across the channel. In this work, we study the motion and deformation of microgels in a constrictive channel with a circular cross-section. Employing elasticity theory with small deformation assumption, we find the correlation among the built-up pressure, the mechanical properties of microgels, and the geometry of the channel. An approximate method is applied to estimate stress distribution at the contact surface between the deformable microgel and the channel. We then conduct experiments in constrictive micro-channels using microgels with well controlled sizes and mechanical properties to validate the effectiveness of our analysis. Compared to previous studies on microgel transport through constrictive channels, our result features an optimal balance between simplicity and accuracy. The methodology can be easily extended to various natural and engineered processes involving transport of soft bodies in narrow channels.