  The lack of a simple operable method for longitudinal dynamic self-assembly
of particles in a microchannel is one of the main problems in applying this
technology to a wide range of researches, such as biomedical engineering,
material science, and computation. Herein, a viscoelasticity-induced trapping
microfluidic system for flowing particles is proposed to increase the
maneuverability of longitudinal dynamic self-assembly of particles and achieve
real-time control of the interparticle spacings and the frequency of particles
passing through the outlet. Two kinds of functional microstructures and a
side-channel were designed to preprocessing the randomly distributed particles
to make particles no aggregation and evenly distributed and realize real-time
control of the particle volume concentration. Randomly distributed particles
could be focused into a line and become equally spaced in the center axis of a
straight microchannel under the balance of the elastic force and the
viscoelasticity-induced effective repulsive force. Besides, a finite element
method model is established to analyze the processes of particles flowing in
each functional microstructure. Therefore, a step forward in this microfluidic
technology can provide significant promotion for a wide range of researches.

Fluid Dynamics;Soft Condensed Matter