Direct measurements of velocity profiles in flows of polymer solutions through a rectangular microchannel with a PDMS surface

Velocity profiles of polymer solutions were directly measured in a microchannel with rectangular cross sections. The test fluids are 0.2 wt% aqueous solutions of polyacrylamide whose molecular weights are 6 x 10(6) (fluid A) and 1.5 x 10(7) (fluid B). The microchannel was made of PDMS and it was mounted on the glass plate. The velocity profile in the depth direction is discussed as a function of the flow rate and shear stress on the wall. Consequently, for the flows of fluid A, a symmetric profile is observed in the region between the PDMS wall and the glass wall in a low flow rate, but the velocity profile slightly becomes asymmetric with increasing flow rate: the velocity near the PDMS wall is larger than that near the glass wall. For the flows of fluid 13, a slightly asymmetric profile is observed even in the low flow rate and a largely asymmetric one in the large flow rate. The PDMS wall significantly affects the velocity profile in the flow of polymer solution through a PDMS microchannel.