Figure 1.

Results of the elastic layer model, the brush model, and Hertz model fits for a representative force-indentation curve. (A) Shown is the entire range of interaction from 0 to a maximum of 5 nN indentation force. (B) Shown is a portion of the indentation curve from 0 to 0.5 nN to focus on the initial interaction between the bead and the surface. Note that the dots represent a small fraction (∼1/30) of the measured data pairs, which follow the thin black line connecting the dots. The single modulus Hertz indentation theory matches the data well in the high-force regime where the cantilever has compressed the soft EGL layer and the slope of the indentation curve is dominated by the modulus of the cell body. The elastic-layer model fits the raw indentation curve data with high fidelity throughout the range of indentation forces as compared to the other two models. To see this figure in color, go online.