The models used to calculate Young's moduli from atomic force microscopy (AFM) force curves consider the shape of the indentation. It is then assumed that the geometry of the indentation is identical to the geometry of the indenter, which has been verified for hard materials (E > 1 MPa). Based on this assumption, the force curves calculated by these models, for the same object with a given Young's modulus, are different if the indenter geometry is different. On the contrary, we observe experimentally that the force curves recorded on soft living cells, with pyramidal, spherical, or tipless indenters, are almost similar. This indicates that this basic assumption on the indentation geometry does not work for soft materials (E of the order of 5 kPa or less). This means that, in this case, the shape of the indentation is therefore different from the shape of the indenter. Indentation of living cells by AFM is not what we thought!

用于根据原子力显微镜 (AFM) 力曲线计算杨氏模量的模型考虑了压痕的形状。然后假设压痕的几何形状与压头的几何形状相同，这已针对硬质材料 ( E  > 1 MPa) 进行了验证。基于这一假设，对于具有给定杨氏模量的同一物体，如果压头几何形状不同，则由这些模型计算的力曲线是不同的。相反，我们通过实验观察到，使用锥体、球形或无尖头压头在软活细胞上记录的力曲线几乎相似。这表明这种关于压痕几何形状的基本假设不适用于软材料（E量级为 5 kPa 或更小）。这意味着，在这种情况下，压痕的形状因此不同于压头的形状。AFM 对活细胞的压痕并不是我们想象的那样！