Controlling the mechanical behavior of dual-material 3D printed meta-materials for patient-specific tissue-mimicking phantoms

Significance Statement

Mimicking the dynamic mechanical properties of the human aorta in 3D printed models is challenging because of the inherent difference between mechanical behaviors of polymeric materials and human tissues (Fig. A). We sought to print the aortic root using materials which achieved the strain-stiffening behavior of the human aortic tissues using commercial polymer printing materials. The mechanical behavior of aortic tissue is mimicked by a 3D printed meta-material, in which sinusoidal wave-shaped stiff fibers were embedded in a soft polymeric matrix (Fig. B). The wavelength, amplitude, and fiber diameter of the embedded sinusoidal fiber were tuned to study the meta-material’s stress-strain relationship. Then, fibers of ideal configurations were embedded in a 3D printed aortic root phantom (Fig. D). The designed meta-material demonstrated strain-stiffening behavior similar to the human aortic tissues. The stress-strain curve of the meta-materials was controlled by the design of the embedded fibers (Fig. C). As a follow-up to the study in this paper, a CoreValve prosthesis was deployed to simulate TAVR. The model was connected to a flow loop, and CMR images were acquired to visualize the in-vitro anatomy, and characterize and quantify the flow velocity field (Fig. E). 3D printed tissue-mimicking aortic root may enable predictions of post-TAVR root strain and distribution and aortic flow pattern, for pre-TAVR planning.

About the author

Kan Wang received the B.S. degree in Theoretical and Applied Mechanics from Peking University, Beijing, China, in 2005, the M.S. degree in Aircraft Design from Beihang University, Beijing, China, in 2007, and the Ph.D. degree in Industrial and Manufacturing Engineering from Florida State University, Tallahassee, USA in 2013. Currently, he is a post-doctoral fellow at the H. Milton Stewart School of Industrial and Systems Engineering and Georgia Tech Manufacturing Institute, Georgia Institute of Technology, Atlanta, USA. His research interest include nanomanufacturing, additive manufacturing, printed electronics technologies and their applications in smart materials and biomedical devices.

Journal Reference

Materials & Design, Volume 90, 15 January 2016, Pages 704–712.

Kan Wang^1,2, Yuanshuo Zhao¹ , Yung-Hang Chang^1,2^, ,Zhen Qian⁴, Chuck Zhang^1,2, Ben Wang^1,2,3, Mani A. Vannan⁴, Mao-Jiun Wang⁵

[expand title=”Show Affiliations”]

Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
Georgia Tech Manufacturing Institute, Georgia Institute of Technology, Atlanta, GA 30332, USA
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
Department of Cardiovascular Imaging, Piedmont Heart Institute, 95 Collier Road, Atlanta, GA 30309, USA
Department of Industrial Engineering and Engineering Management, National Tsing-Hua University, Hsinchu, Taiwan[/expand]

Abstract

Patient-specific tissue-mimicking phantoms are becoming available with the advent of additive manufacturing. Phantoms currently in use are focused on the geometrical accuracy and mechanical properties under small deformation. Mimicking the mechanical properties at large deformation is challenging because of the inherent difference between the mechanical behaviors of polymeric materials and that of human tissues. In this study, the mechanical behavior of soft tissues under a uniaxial tension is mimicked by dual-material 3D printed meta-materials with stiff micro-structured fibers embedded in a soft polymeric matrix. Although the two base materials are strain-softening polymers, some of the designed meta-materials demonstrate certain degree of strain-stiffening behavior. Further investigation shows how the stress–strain curve of the meta-materials can be controlled by the design parameters. Sensitivity analysis is used to study the effects of each parameter. General design guidelines are proposed based on the results of the experiments. Dual-material 3D printed meta-materials have great potential in fabricating patient-specific phantoms with accurate mechanical properties that are associated with the gender, age, ethnicity, and other physiological/pathological characteristics. Mechanically accurate phantoms can play an important role in a variety of biomedical applications, including validation of computational models, testing of medical devices, surgery planning, medical education and training, and doctor-patient interaction.

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