Fig. 1.

a Schematic illustration of AFM-based elasticity measurements carried out for soft samples. Young’s modulus is derived from force-versus-indentation curves being the subtraction results of reference (stiff; glass coverslip surface) and sample (soft; cells or polyacrylamide hydrogels) force curves. b Exemplary histogram showing Young’s modulus distribution obtained for (5% PA/0.4% bis-A) hydrogel sample probes over a squared scan area of 6 µm × 6 µm (n = 64 force curves; sampling interval ΔE = 0.5 kPa); measured with OTR4 probe. The final modulus value was obtained from a Gaussian fit (E = 4.82 ± 0.95 kPa). c The corresponding 2D elasticity map (force volume). d Indentation depth-dependent fitting of the Hertz model to raw data for 5% PA gels. e Young’s modulus dependence on indentation depth obtained by fitting a theoretical model assuming either cone or paraboloid shape of the AFM tip. Each point represents the fitted value of the modulus and standard error (from the fit). f Divergence calculated for the same data as in e