Fig. 1.
The idea of the Young’s modulus E estimation for cell walls. a Top view image showing the AFM cantilever and a fragment of the cell wall material (CWM) in water. Dots denote a grid of points set for the force curve collection. b Schematic presentation of how the indentation is determined on a soft sample. Dashed line is sensitivity calibration curve recorded on a glass slide (an infinite hard surface). c Example of 3D topography of CWM used in experiment which showed that thickness of cell walls in pears is about 1 µm. d Screenshot from the proprietary code used to fit the Hertz–Sneddon model to the experimental data within the indentation depths of 0–100 nm. The goodness of the fit R 2 > 0.8 was set to be an acceptance threshold for the fitting quality