FIGURE 1

Polyacrylamide gel characterization by AFM. (A) Representative curve of cantilever deflection as a function of tip indentation into a 5-kPa PA gel (circles) and the fit to the data with the Hertz model (bold line). (B) PA gel stiffness as a function of bis-acrylamide cross-linker concentration (open squares/dashed line, AFM 7.5% acrylamide; solid squares/solid line, macroscopic rheology 7.5% acrylamide; open circles/dashed line, AFM 5% acrylamide (8); solid circles/solid line, macroscopic rheology 5% acrylamide). (C) Topographical map of the surface of a 5-kPa PA gel. Scale, 30 μm × 30 μm. (D) Stiffness map of the surface of a 5-kPa PA gel. Scale, 30 μm × 30 μm.