Design and Mechanical Characterization Using Digital Image Correlation of Soft Tissue-Mimicking Polymers

Oliver Grimaldo Ruiz; Mariana Rodriguez Reinoso; Elena Ingrassia; Federico Vecchio; Filippo Maniero; Vito Burgio; Marco Civera; Ido Bitan; Giuseppe Lacidogna; Cecilia Surace

doi:10.3390/polym14132639

Design and Mechanical Characterization Using Digital Image Correlation of Soft Tissue-Mimicking Polymers

Polymers (Basel). 2022 Jun 28;14(13):2639. doi: 10.3390/polym14132639.

Authors

Oliver Grimaldo Ruiz^{1

2}, Mariana Rodriguez Reinoso^{1

2}, Elena Ingrassia^{1

2}, Federico Vecchio¹, Filippo Maniero^{1

2}, Vito Burgio^{1

2}, Marco Civera^{1

2}, Ido Bitan³, Giuseppe Lacidogna¹, Cecilia Surace^{1

2}

Affiliations

¹ Department of Structural, Geotechnical and Building Engineering (DISEG), Politecnico di Torino, Corso Duca Degli Abruzzi 24. P. C., 10129 Turin, Italy.
² Laboratory of Bio-Inspired Nanomechanics "Giuseppe Maria Pugno", Politecnico di Torino, Corso Duca Degli Abruzzi 24. P. C., 10129 Turin, Italy.
³ Stratasys Headquarters, 1 Holtzman St. Science Park, Rehovot P.O. Box 2496, Israel.

Abstract

Present and future anatomical models for biomedical applications will need bio-mimicking three-dimensional (3D)-printed tissues. These would enable, for example, the evaluation of the quality-performance of novel devices at an intermediate step between ex-vivo and in-vivo trials. Nowadays, PolyJet technology produces anatomical models with varying levels of realism and fidelity to replicate organic tissues. These include anatomical presets set with combinations of multiple materials, transitions, and colors that vary in hardness, flexibility, and density. This study aims to mechanically characterize multi-material specimens designed and fabricated to mimic various bio-inspired hierarchical structures targeted to mimic tendons and ligaments. A Stratasys^® J750™ 3D Printer was used, combining the Agilus30™ material at different hardness levels in the bio-mimicking configurations. Then, the mechanical properties of these different options were tested to evaluate their behavior under uni-axial tensile tests. Digital Image Correlation (DIC) was used to accurately quantify the specimens' large strains in a non-contact fashion. A difference in the mechanical properties according to pattern type, proposed hardness combinations, and matrix-to-fiber ratio were evidenced. The specimens V, J1, A1, and C were selected as the best for every type of pattern. Specimens V were chosen as the leading combination since they exhibited the best balance of mechanical properties with the higher values of Modulus of elasticity (2.21 ± 0.17 MPa), maximum strain (1.86 ± 0.05 mm/mm), and tensile strength at break (2.11 ± 0.13 MPa). The approach demonstrates the versatility of PolyJet technology that enables core materials to be tailored based on specific needs. These findings will allow the development of more accurate and realistic computational and 3D printed soft tissue anatomical solutions mimicking something much closer to real tissues.

Keywords: PolyJet technology; Shore A hardness; additive manufacturing; digital image correlation; finite element analysis; mechanical properties and standards; polymer; tendons and ligaments; uni-axial tensile test.

Grants and funding

This research received no external funding.