The evaluation of tissue mechanical properties, such as stiffness, is an important parameter to differentiate normal and diseased conditions in order to detect encapsulations. Normal tissue (7kPa) has a Young's modulus lower than the modulus of the breast cancers (>70kPa), that have different elastic properties. (Egorov V, Sarvazyan AP. Mechanical Imaging of the Breast. IEEE transactions on medical imaging. 2008;27(9):1275-1287)

In oder to evaluate the different mechanical properties, the working principle of the device is based on the sensor's capability to distinguish the stiffness of underlying tissue.

Healthy and abnormal conditions can be detect because the elastic modulus of the nodule increases with the malignancy of tumour.

Figure 1 shows the mechanical model of the prototype; it is characterized by two springs in series where the first one represents the sensor instead the second one the tissue's stiffness.

_{Figure 1 - Mechanical model of Palpreast}