Fig. 2

Results of ferrule-top nanoindentation experiments on a homogeneous gel. a Picture of the experimental setup, showing the Chiaro nanoindenter with the cantilever holder and optical fiber (white) attached to the z-Piezo (black). The probe with a microbead (transparent) is positioned above the gel and immersed in buffer solution (pink). b Histograms of the Young’s modulus as calculated either with the standard Hertzian fit approach (blue) or based on the average elasticity spectrum (red). Gaussian fit of the histogram values provides (peak position ± SEM) \(E=5.2\pm 0.2\) kPa for the Hertz approach and \(E=5.6\pm 0.1\) kPa for ES. c Force-indentation results, showing the average force-indentation curve \(\left\langle F(\delta ) \right\rangle\) (blue) and Hertzian fit (red dashed) from a set of 97 nanoindentation experiments. (d) Elasticity spectra analysis corresponding to the curves in c, showing the average elasticity spectrum \(\left\langle E(\delta ) \right\rangle\) (blue) and its mean value (red dashed)