Biaxial tensile testing system for measuring mechanical properties of both sides of biological tissues

Jumpei Takada, Kohei Hamada, Xiaodong Zhu, Yusuke Tsuboko, Kiyotaka Iwasaki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The aortic wall exhibits a unique elastic behavior, periodically expanding in aortic diameter by approximately 10% during heartbeats. This elastic behavior of the aortic wall relies on the distinct yet interacting mechanical properties of its three layers: intima, media, and adventitia. Aortic aneurysms develop as a result of multifactorial remodeling influenced by mechanical vulnerability of the aortic wall. Therefore, investigating the mechanical response of the aneurysmal wall, in conjunction with changes in microstructural parameters on both the intimal and adventitial sides, may offer valuable insights into the mechanisms of aortic aneurysm development or rupture. This study aimed to develop a biaxial tensile testing system to measure the mechanical properties of both sides of the tissue to gain insights concerning the interactions in anisotropic layered tissue. The biaxial tensile test set-up consisted of four motors, four cameras, four load cells, and a toggle switch. Porcine ascending aortas were chosen as the test subject. Graphite particles with diameters of approximately 5–11 [μm] were randomly applied to both sides of the aorta. Strain measurements were obtained using the stereo digital-image correlation method. Because stretching a rectangular specimen with a thread inevitably concentrates and localizes stress, to reduce this effect the specimen's shape was investigated using finite element analysis. The finite element analysis showed that a cross-shaped specimen with diagonally cut edges would be suitable. Therefore, we prepared specimens with this novel shape. This test system showed that mechanical response of the aortic tissue was significantly different between the intimal and adventitial side in the high-strain range, due to the disruption of collagen fibers. The adventitia side exhibited a smaller elastic modulus than the intimal side, accompanied by disruption of collagen fibers in the adventitia, which were more pronounced in the longitudinal direction. In contrast, in the mid-strain range, the elastic modulus did not differ between the intimal and adventitial sides, irrespective of longitudinal or circumferential direction, and collagen fibers were not disrupted but elongated. A biaxial tensile test system, which measures the mechanical properties of both sides of biological tissues and the shape of the specimen for reducing the concentration of stress at the chuck region, was developed in this study. The biaxial tensile testing system developed here is useful for better understanding the influences of mechanical loads and tissue degeneration on anisotropic, layered biological tissues.

Original languageEnglish
Article number106028
JournalJournal of the Mechanical Behavior of Biomedical Materials
Volume146
DOIs
Publication statusPublished - 2023 Oct

Keywords

  • Biaxial tensile testing system
  • Biological tissue
  • Finite element analysis
  • Incremental elastic modulus
  • Porcine ascending thoracic aorta

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering
  • Mechanics of Materials

Fingerprint

Dive into the research topics of 'Biaxial tensile testing system for measuring mechanical properties of both sides of biological tissues'. Together they form a unique fingerprint.

Cite this