Concentration Profiles of Platelet‐Sized Latex Beads for Conditions Relevant to Hollow‐Fiber Hemodialyzers

Abstract: A freeze‐capture method was used to obtain the concentration profiles of platelet‐sized latex beads (2.5 μm diameter) in saline‐based red cell suspensions flowing through tubes with inner diameters of 135 and 200 μm. Without red cells the concentration profile exhibited a slight deficit near the wall. For hematocrits from 15 through 52%, the concentration profile exhibited a near‐wall excess of beads, from two to eight times the central concentration. Near‐wall excesses were small or nonexistent in the first half centimeter of the tube. For hematocrits of 15 and 30%, the profile and near‐wall excess were equal at stations 2 cm or more from the entrance. These results suggest that there is a flow‐driven mechanism that moves platelet‐sized beads toward, but not to, the wall.