## 8 Conclusions  
We present a wearable device--Palprest--for breast self-examination based on tactile imaging. The device was modelled using FE analysis, and then designed, assembled, and tested using breast phantoms. It consists of a stretchy top which covers both breasts, with internal layers consisting of (a) wearable sensors (n.b., although the prototype is constructed using piezo resistive fabric, other pressure or displacement sensing materials (e.g., piezo capacitive) could also be used in the device); (b) a compartment containing sub-compartments which can be selectively inflated by applying a precise pressure to different zones of the breast. Alternate inflation of each subcompartment mimics the action of breast palpation and the resulting haptic feedback detected by the wearable sensors gives an indication of the difference in stiffness between the left and right breast, which are correlated to the  
Figure 14: 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.  
Figure 13: Example of textile pressure sensing matrix response after the application of different pressures in position (R0,C0).  
size and location of nodules; (c) an intelligent interface for analysis of differences in stiffness between the left and right breast giving appropriate alerts to users to consult a doctor.  
Results from the calibration of the system indicate that it is highly reproducible although we did observe some crosstalk between taxels. More sophisticated data analysis, using, for example, a neural network, could overcome this limitation and even take advantage of this crosstalk [25]. Despite this limit in resolution, the device in its current form is able detect the presence of a 2 cm nodule in a breast phantom.  
As Palprest can be classified as a Class I medical device according to Medical Device Regulation 2017/745 (low risk, not being a diagnostic tool), it does need to undergo clinical trials. However, further improvements on the FE analysis using reconstructed 3D images of real breasts would be useful to understand how non-symmetrical shapes of the breast or irregular contours of the nodule may influence the resolution of the system, and thus if a sensor pad with smaller and more densely packed taxels is required. In addition, miniaturization of the pneumatic system as well as preliminary tests on a number of volunteers is necessary for the device to be marketed as a support for personal screening in women.  
L.A. conceived the device. All authors contributed to its modeling, design, realization, and testing as well as to the preparation and editing of the manuscript.  
This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731053 UBORA.  
The authors would like to acknowledge the \"PhD+\" and \"Contamination Lab\" programs of the University of Pisa, and the Additive Manufacturing CrossLab of the Department of Information Engineering of the University of Pisa for the support in development of the idea of wearable device for breast self-examination. The device is named \"Palprest\" after the programs \"PhD+\" and \"Contamination Lab\" at the University of Pisa, devoted to the incubation of innovative ideas toward product development.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.