Dependence of the optical trapping efficiency of a biconcave red blood cell flowing in a rectangular microchannel on the sphericity index and the channel geometry

Today's optical trapping techniques have been frequently used in severe blood-disease-related studies using plastic microfluidic devices. Most fabrication methods provide several types of rectangular microchannels for these devices. However, most existing optical trapping models tend to reflect only a few geometric properties of these microchannels and only some morphological shapes of the targets effectively. In this article, a new model for the optical trapping efficiency of a biconcave red blood cell (RBC) flowing in a rectangular microchannel is presented. The hydrodynamic drag force is theoretically corrected using the concept of the sphericity index of the RBC. The effect of the channel geometry on the optical trapping efficiency is numerically simulated and compared with that of the existing model. Furthermore, an implication of this correction for clinical applications in a disposable plastic microfluidic device is discussed.