Citation: Brognara, L.; Fantini, M.; Morellato, K.; Graziani, G.; Baldini, N.; Cauli, O. Foot Orthosis and Sensorized House Slipper by 3D Printing. Materials 2022, 15, 4064. https://doi.org/10.3390/ ma15124064 Received: 7 May 2022 Accepted: 4 June 2022 Published: 8 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Foot Orthosis and Sensorized House Slipper by 3D Printing Lorenzo Brognara 1 , Massimiliano Fantini 2 , Kavin Morellato 3 , Gabriela Graziani 4 , Nicola Baldini 5 and Omar Cauli 6,7, * 1 Department of Biomedical and Neuromotor Sciences (DIBINEM), Alma Mater Studiorum University of Bologna, 40123 Bologna, Italy; lorenzo.brognara2@unibo.it 2 Romagna Tech s.c.p.a., 47121 Forli, Italy; msm.fantini@gmail.com 3 Department of Industrial Engineering, Alma Mater Studiorum, University of Bologna, Via Terracini 28, 40131 Bologna, Italy; morellato.kavin@gmail.com 4 Laboratory of Nanobiotechnology, IRCCS Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy; gabriela.graziani@ior.it 5 Biomedical Science and Technologies Lab, IRCCS Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy; nicola.baldini@ior.it 6 Nursing Department, University of Valencia, Avda Menendez Pelayo 19, 46010 Valencia, Spain 7 Frailty Research Organizad Group, University of Valencia, Avda Menendez Pelayo 19, 46010 Valencia, Spain * Correspondence: omar.cauli@uv.es Abstract: Background: In clinical practice, specific customization is needed to address foot pathology, which must be disease and patient-specific. To date, the traditional methods for manufacturing custom functional Foot Orthoses (FO) are based on plaster casting and manual manufacturing, hence orthotic therapy depends entirely on the skills and expertise of individual practitioners. This makes the procedures difficult to standardize and replicate, as well as expensive, time-consuming and material-wasting, as well as difficult to standardize and replicate. 3D printing offers new perspectives in the development of patient-specific orthoses, as it permits addressing all the limitations of currently available technologies, but has been so far scarcely explored for the podiatric field, so many aspects remain unmet, especially for what regards customization, which requires the definition of a protocol that entails all stages from patient scanning to manufacturing. Methods: A feasibility study was carried out involving interdisciplinary cooperation between industrial engineers and podiatrists. To that end: (i) For patient-specific data acquisition, 3D scanning of the foot is compared to traditional casting. (ii) a modelling GD workflow is first created to design a process permitting easy creations of customized shapes, enabling the end user (the podiatrist) to interactively customize the orthoses. Then, (iii) a comparison is made between different printing materials, in order to reproduce the same mechanical behavior shown by standard orthoses. To do this, the mechanical properties of standard materials (Polycarbonate sheets), cut and hand-shaped, are compared with four groups of 3D printed samples: poly(ethylene glycol) (PETG), poly(acrylonitrile-butadiene.styrene) (ABS), polycarbonate (PC) and poly(lactic acid) (PLA) obtained by Fused Filament Fabrication (FFF). Results: Differences found between the foot plaster model obtained with the plaster slipper cast in a neutral position and the model of the real foot obtained with 3D scanning in the same position can be ascribed to the non-stationarity of the patient during the acquisition process, and were limited by a locking system with which no substantial differences in the almost entire sole of the foot scan were observed. Conclusions: Using the designed GD workflow, podiatrists with limited CAD skills can easily design and interactively customize foot orthoses to adapt them to the patients’ clinical needs. 3D printing enables the complex shape of the orthoses to be reproduced easily and quickly. Compared to Polycarbonate sheets (gold standard), all the printed materials were less deformable and reached lower yield stress for comparable deformation. No modifications in any of the materials as a result of printing process were observed. Keywords: gait; foot care; foot orthosis; mechanical properties; polymers Materials 2022, 15, 4064. https://doi.org/10.3390/ma15124064 https://www.mdpi.com/journal/materials