  Fine manipulation of fluid flows at the microscale has a tremendous impact on
mass transport phenomena of chemical and biological processes inside
microfluidic platforms. Fluid mixing in the laminar flow regime at low Reynolds
is poorly effective due to the inherently slow diffusive mechanism. As a
strategy to enhance mixing and prompt mass transport, here, we focus on
polyelectrolyte multilayer capsules (PMCs) embodying a catalytic
polyoxometalate as microobjects to create elastic turbulence and as micromotors
to generate chaotic flows by fuel-fed propulsions. The effects of the elastic
turbolence and of the artificial propulsion on some basic flow parameters, such
as pressure and volumetric flow rate are studied by a microfluidic set-up
including pressure and flow sensors. Numerical-handling and physical models of
the experimental data are presented and discussed to explain the measured
dependence of the pressure drop on the flow rate in presence of the PMCs. As a
practical outcome of the study, a strong decrease of the mixing time in a
serpentine microreactor is demonstrated. Unlike our previous reports dealing
with capillarity flow studies, the present paper relies on hydrodynamic pumping
experiments, that allows us to both develop a theoretical model for the
understanding of the involved phenomena and demonstrate a successfully
microfluidic mixing application. All of this is relevant in the perspective of
developing microobject based methods to overcome microscale processes purely
dominated by diffusion with potential improvements of mass trasport in
microfluidic platforms.
