Mechanics at the nanoscale has become important in both material science and biomedical applications. For example, mechanical properties of nanocomposites are defined by the properties of material at the nanoscale. Many devices have nowadays nanometer scale components. Mechanics of those is important to know the behavior of the devices. In biomedical area, the mechanics of tissue, cells, and even molecules has become an active area of research.

In our research, we are trying to understand the mechanical behavior of  soft materials, polymers, cells, molecules, and tissues (skin). The major tool of our research is atomic force microscopy (AFM). We also use nanoindenter.

One of the main difficulties is the actual measurements of the mechanical behavior of  soft materials at the nanoscale. For a regular nanoscopic contact, the load force is of the order of nanoNewtons, whereas the contact area is of the order of nanometers. It is trivial to estimate that mechanical stress corresponding to such a contact is rather high. Typically, it is way above the so-called proportionality limit (when stress is linear proportional to strain). This is the problem of non-linearity.

The other problem is connected to the interface. It is very rare to have the contact interface smooth at the nanoscale. An example is shown below. A spherical AFM probe is touching epithelial cell. One can see that the cell surface is far fro being smooth.

cells_Nature_Nano1

How to handle rough surfaces, what to do with the non- linearity, this is our research..

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