Toward improved auricle reconstruction: The role of FDM 3D printing with PCL and TPU materials.

Microtia, along with trauma, represents one of the main causes of external ear malformation. Different clinical techniques were developed for the reconstruction of the auricle, but they all have some drawbacks. This work is focused on the development of an innovative 3D porous scaffold, printed by Fused Deposition Modelling (FDM) and based on laser-scanned images of the healthy contralateral ear of the patient. The scaffold was printed using polycaprolactone (PCL) and thermoplastic polyether urethane (TPU) to mimic the components of the cartilage and adipose tissue, respectively. After the optimization of the printing parameters, the 3D surface obtained as an output of the laser scan was elaborated, sliced and used as input for printing the layered structure. Micro CT investigation confirmed the structure homogeneity and good pore interconnection. Mechanical compression and torsion tests were performed to verify that the mechanical properties of the 3D PCL/TPU structure were adequate. The 3D structure exhibited elastic moduluses comparable to those of the cartilaginous and adipose parts of the auricle. The torsion tests showed the adequacy of the structure without detachment between TPU and PCL printed layers. In vitro cell viability tests confirmed the absence of cytotoxicity in both materials. The PCL/TPU layered scaffold reproduced the anatomy of the patient's healthy contralateral ear, representing a good compromise between flexibility and strength. This, along with the other assessed properties, makes this scaffold a valid alternative for the reconstruction of the external ear.