Fig. 4: AFM force curve and material deformation schematic diagrams, Young’s moduli histograms and corresponding images for three corneocytes.

a Graphical representation of the load as a function of the indenter displacement showing the quantities used in the analysis and b a schematic interpretation of these quantities, adapted from Ref. ²³. \(a\) is the contact radius; \({h}_{\max }\) is the maximum indentation depth; \({h}_{c}\) is the contact depth; \({h}_{s}\) is the surface elastic deflection at the perimeter of the contact; \({h}_{f}\) is the final depth of the residual hardness impression; \({h}_{e}\) is the elastic component of the displacement. TM-AFM images of corneocytes and histograms showing values of Young’s modulus calculated from 64 force curves in that region for c and d Cell 1 of P1, e and f Cell 3 of P2 and g and h Cell 4 of P3. The cells were fixed on a glass slide, and the maximum force setpoint was 2 µN. Scale bars = 1 µm.