Development of a Thermoplastic Polyurethane gradient deformation monitoring system

Deformational Plagiocephaly (DP) is a common medical condition in children. The deformity can be corrected using good practices recommended by the medical staff, however, in more severe cases, physical therapy is required. In this sense, cranial orthoses are mostly used to correct the deformity. However, the standard solutions do not quantify the treatment and are mostly produced through manually-based fabrication processes. Our research teams explored the potential of flexible materials, namely thermoplastic polyurethane (TPU), for the construction of complex shapes. However, the current systems do not have any strategy to quantify the applied force and pressure. In this study, a new strategy to quantify the pressure in a TPU structure is proposed and evaluated. The strategy consisted in placing the TPU material between a magnetic sensor (bottom part) and a magnetic (top part). After the material was placed on these components, we applied known forces and displacements on the bottom part and recorded the magnetic field (as the magnet was moving towards the sensor) to create a calibration curve that allowed us to classify the variation of the magnetic field according to the displacement exerted. Compression experiments were performed with the TPU material. Our results demonstrated that for the same displacement, the applied force varied proportinally with the internal thickness of the material. Furthermore, we were able to obtain a linear model for the foams that characterizes the magnetic field obtained by the magnet as a function of displacement for 3 different types of internal thickness. Overall, the described solution has potential to be used as a monitoring system for the tretment of cranial deformaties.