3D-printed bioinspired spicules: Strengthening and toughening via stereolithography

Fariborz Tavangarian; Sorour Sadeghzade; Niloofar Fani; Dariush Khezrimotlagh; Keivan Davami

doi:10.1016/j.jmbbm.2024.106555

3D-printed bioinspired spicules: Strengthening and toughening via stereolithography

J Mech Behav Biomed Mater. 2024 Apr 17:155:106555. doi: 10.1016/j.jmbbm.2024.106555. Online ahead of print.

Authors

Fariborz Tavangarian¹, Sorour Sadeghzade², Niloofar Fani³, Dariush Khezrimotlagh⁴, Keivan Davami⁵

Affiliations

¹ Mechanical Engineering Program, School of Science, Engineering and Technology, Penn State Harrisburg, Middletown, PA, 17057, United States; Department of Biomedical Engineering, Pennsylvania State University, University Park, State College, PA, 16802, United States. Electronic address: f.tavangarian@gmail.com.
² Mechanical Engineering Program, School of Science, Engineering and Technology, Penn State Harrisburg, Middletown, PA, 17057, United States; Shenzhen Key Laboratory of Soft Mechanics & Smart Manufacturing, Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
³ Mechanical Engineering Program, School of Science, Engineering and Technology, Penn State Harrisburg, Middletown, PA, 17057, United States.
⁴ Mathematical Sciences Program, School of Science, Engineering and Technology, Penn State Harrisburg, Middletown, PA, 17057, United States.
⁵ Department of Mechanical Engineering, University of Alabama, Tuscaloosa, AL, 35487, United States.

PMID: 38640693
DOI: 10.1016/j.jmbbm.2024.106555

Abstract

Recently, the replication of biological microstructures has garnered significant attention due to their superior flexural strength and toughness, coupled with lightweight structures. Among the most intriguing biological microstructures renowned for their flexural strength are those found in the Euplectella Aspergillum (EA) marine sponges. The remarkable strength of this sponge is attributed to its complex microstructure, which consists of concentric cylindrical layers known as spicules with organic interlayers. These features effectively impede large crack propagation, imparting extraordinary mechanical properties. However, there have been limited studies aimed at mimicking the spicule microstructure. In this study, structures inspired by spicules were designed and fabricated using the stereolithography (SLA) 3D printing technique. The mechanical properties of concentric cylindrical structures (CCSs) inspired by the spicule microstructure were evaluated, considering factors such as the wall thickness of the cylinders, the number of layers, and core diameter, all of which significantly affect the mechanical response. These results were compared with those obtained from solid rods used as solid samples. The findings indicated that CCSs with five layers or fewer exhibited a flexural strength close to or higher than that of solid rods. Particularly, samples with 4 and 5 cylindrical layers displayed architecture similar to natural spicules. Moreover, in all CCSs, the absorbed energy was at least 3-4 times higher than solid rods. Conversely, CCSs with a cylinder wall thickness of 0.65 mm exhibited a more brittle behavior under the 3-point bending test than those with 0.35 mm and 0.5 mm wall thicknesses. CCSs demonstrated greater resistance to failure, displaying different crack propagation patterns and shear stress distributions under the bending test compared to solid rods. These results underscore that replicating the structure of spicules and producing structures with concentric cylindrical layers can transform a brittle structure into a more flexible one, particularly in load-bearing applications.

Keywords: Biomimetic structures; Euplectella aspergillum sponge; Lightweight materials; Rigid resin; Spicule-inspired structure; Stereolithography.