Mechanical testing and comparison of porcine tissue, silicones and 3D-printed materials for cardiovascular phantoms

Joël Illi; Marc Ilic; Anselm Walter Stark; Cornelia Amstutz; Juergen Burger; Philippe Zysset; Andreas Haeberlin; Christoph Gräni

doi:10.3389/fbioe.2023.1274673

Mechanical testing and comparison of porcine tissue, silicones and 3D-printed materials for cardiovascular phantoms

Front Bioeng Biotechnol. 2023 Dec 1:11:1274673. doi: 10.3389/fbioe.2023.1274673. eCollection 2023.

Authors

Joël Illi¹, Marc Ilic¹, Anselm Walter Stark¹, Cornelia Amstutz², Juergen Burger², Philippe Zysset³, Andreas Haeberlin^{1

3

4}, Christoph Gräni^{1

4}

Affiliations

¹ Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
² School of Biomedical and Precision Engineering, University of Bern, Bern, Switzerland.
³ ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
⁴ Translational Imaging Center, Sitem Center, University of Bern, Bern, Switzerland.

Abstract

Background: Cardiovascular phantoms for patient education, pre-operative planning, surgical training, haemodynamic simulation, and device testing may help improve patient care. However, currently used materials may have different mechanical properties compared to biological tissue. Methods/Aim: The aim of this study was to investigate the mechanical properties of 3D-printing and silicone materials in comparison to biological cardiovascular tissues. Uniaxial cyclic tension testing was performed using dumbbell samples from porcine tissue (aorta, pulmonary artery, right and left ventricle). Flexible testing materials included 15 silicone (mixtures) and three 3D-printing materials. The modulus of elasticity was calculated for different deformation ranges. Results: The modulus of elasticity (0%-60%) for the aorta ranged from 0.16 to 0.18 N/mm², for the pulmonary artery from 0.07 to 0.09 N/mm², and for the right ventricle as well as the left ventricle short-axis from 0.1 to 0.16 N/mm². For silicones the range of modulus of elasticity was 0.02-1.16 N/mm², and for the 3D-printed materials from 0.85 to 1.02 N/mm². The stress-strain curves of all tissues showed a non-linear behaviour in the cyclic tensile testing, with a distinct toe region, followed by exponential strain hardening behaviour towards the peak elongation. The vessel samples showed a more linear behaviour comparted to myocardial samples. The silicones and 3D printing materials exhibited near-linearity at higher strain ranges, with a decrease in stiffness following the initial deformation. All samples showed a deviation between the loading and unloading curves (hysteresis), and a reduction in peak force over the first few cycles (adaptation effect) at constant deformation. Conclusion: The modulus of elasticity of silicone mixtures is more in agreement to porcine cardiovascular tissues than 3D-printed materials. All synthetic materials showed an almost linear behaviour in the mechanical testing compared to the non-linear behaviour of the biological tissues, probably due to fibre recruitment mechanism in the latter.

Keywords: 3D-printing; additive manufacturing; biomechanical testing; cardiovascular phantoms; cardiovascular tissue; patient-specific phantoms; tissue properties; uniaxial tensile test.

Grants and funding

The authors declare financial support was received for the research, authorship, and/or publication of this article. CG received funding from Swiss National Science foundation, Innosuisse, CAIM foundation and GAMBIT foundations, outside of the submitted work. AH has received travel fees/educational grants from Medtronic, Biotronik, Abbott, and Philips/Spectranetics without impact on his personal remuneration. He serves as a proctor for Medtronic. He has received research grants from the Swiss National Science Foundation, the Swiss Innovation agency Innosuisse, the Swiss Heart Foundation, the University of Bern, the University Hospital Bern, the Velux Foundation, the Hasler Foundation, the Swiss Heart Rhythm Foundation, and the Novartis Research Foundation outside the submitted study. He is Co-founder and CEO of Act-Inno AG. The other authors report that they have no relationships relevant to the contents of this paper to disclose.