A breast phantom was purposely developed for testing the device’s ability to detect a stiffer inclusion within a healthy tissue. A healthy phantom (Figure 1a, 1b) was fabricated by casting silicone Ecoflex 00-10 (Smooth-on, Inc, Macungie, PA, USA) with the addition of three parts of Slacker additive (Smooth-on, Inc, Macungie, PA, USA) into a custom-made open mold of the breast. The design of the mold was based on a realistic model of the human breast developed with the 3D computer graphics software MakeHuman (www.makehumancommunity.org). Silicone was prepared according to the manufacturer’s instructions to have a final Young’s modulus of 7 kPa, corresponding to healthy tissue. The diseased breast phantom (Figure 1c, 1d) was prepared with the same protocol as the healthy one with the addition of a stiffer inclusion (irregular shape, approximately spherical, with a Feret diameter of 2 cm), separately prepared with the silicone Dragon Skin 10 (Smooth-on, Inc, Macungie, PA, USA), which has a Young’s modulus of 180 kPa. The inclusion was inserted into the mold containing Ecoflex during its polymerization.

_{Figure 1 - Breast phantom: (a),(b) show a healthy breast; (c),(d) show a diseased breast.}

To verify the ability of the pressure sensor matrix to identify the presence of a nodule inside the breast, the healthy and abnormal breast phantoms were pressed with an increasing load onto the sensor matrix, which was suspended on a rigid frame. Phantoms were placed in different positions and different loads were applied. Signals from all taxels were acquired for 10 s with a sampling rate of 0.5 Hz, and the median value was calculated. Between two different measurements, the rest value (absence of phantom) was acquired for excluding possible displacement of the fabric layers.

The ability of the device to identify the presence of a stiffer inclusion in the breast phantom is demonstrated in Figure 2, where the results of pressing the phantoms with a fixed load against the matrix is shown: the difference between healthy and abnormal breast gives different values of the acquired signals. Similar behavior was observed for other positions of the phantoms.

_{Figure 2 - Palpreast ability to detect inclusions in the breast}

Ability of the textile pressure sensing matrix to detect the presence of a stiffer inclusion at R1,C0-R1,C1 in the breast phantom. The phantoms were pressed with a load of 672 Pa against the matrix. (a) Differences (in %) between healthy–abnormal acquisition; (b) differences (in %) of two acquisitions with two healthy phantoms; and (c) position of the inclusion during the registration.