Biomimetic 3D printed spicule-like structure composite of organic material/rigid resin cylinders with highly enhanced strength and toughness

Recently, the microstructure of Euplectella Aspergillum (EA) marine sponges, called spicule, has been recognized as one of the attractive biological microstructures with superior flexural strength and toughness. The lack of studies to mimic this structure motivated us to design rods with a spicule-inspired structure with improved mechanical properties. In this study, spicule-inspired structures were produced by the stereolithography (SLA) method. Different adhesives were infiltrated between the layers to evaluate the effect of organic materials on their mechanical properties. The effect of the curing process on the mechanical properties of spicule-inspired structures with and without organic (adhesive) interlayers was evaluated. Also, the effects of various adhesives, different spaces between the cylinders, and ultraviolet (UV) curing on mechanical properties were evaluated. The results showed that the flexural strength of spicule-inspired structures was improved by about 71 % after curing the samples at 60 °C and under UV light for 30 min and aging in the air for 30 days. Samples including Titebond adhesive (SP1-1.1) showed a higher amount of peak load (129.5 ± 17.21 N) and extension (22.3 ± 3.12 mm) compared to those counterparts without any organic layers (SP-1.1) with a peak load of 101.5 ± 13.34 N and extension of 19.1 ± 1.32 mm. Adding the adhesive layers between the rigid cylinders enhanced the flexibility and strength of the structures. It was found that the curing time by UV after 30 days of aging did not affect the mechanical properties of the samples.