Figure 1.

(a) Schematic of the microfluidic device with inlet (top), debris filter, constriction area surrounded by a bypass, and outlet (bottom). (b) Bright-field (top) and fluorescence (bottom) image of the constriction region with K562 leukemia cells stained with calcein. Images are contrast-enhanced. Scale bars, 20 μm. The SD of the brightness within each region of interest (indicated by a red square in front of a constriction) is used to calculate cell entry time. (c) t_entry versus ε_max/Δp of 19,991 K562 leukemia cells. Colors indicate the bivariate kernel density estimate of the data points. (Black line) Orthogonal least-squares fit of Eq. 1 to the data. (d) Strain evolution ε(t) of NIH 3T3 cells (black circles, mean ± SE of 59 cells) during entry into a constriction can be fitted by a power law (orange line). Time t and strain ε are normalized by t_entry and ε_max before averaging. The parameter t = 0 corresponds to the time point when the cell first encounters the constriction, and t = 1 corresponds to the time point when the cell has reached its maximum strain ε = ε_max and leaves the constriction. (Inset) Normalized strain versus normalized time of individual cells. To see this figure in color, go online.