2, Department of Engineering, School of Engineering and Mathematical Sciences, La Trobe University, Melbourne, Victoria, Australia
Advances in material science and engineering has bolstered technological advancements of the twenty first century. Nature constantly provides solutions to overcome materials and structures related obstacles. Cuticle of Mantis shrimp dactyl club, scarabaei, lobster, and epicarp of diplazium crenatoserratum and pollia condensata fruit, have inspired scientists to mimic their microstructure for enhanced optical and mechanical properties. The structural arrangement of the fiber layers plays crucial role in enhancement of toughness of the composite. In past, attempts have been made to design helicoidal structures at macroscopic levels. We have successfully fabricated helicoidally oriented fibers in microns range (20-25 microns) using near field electrospinning. For our first study, melt near field stage-controlled electrospinning was used to assemble dense Polycaprolactone (PCL) fibers (150-200μm) stacked helicoidally at 15° angle offsets. The toughness of the surface-treated helicoidal PCL was found to be two times higher than the surface-treated unidirectional sample and five times higher than the helicoidal sample without surface treatment. Alternatively, in our second study, near field solution electrospinning was used to fabricate much smaller (av. ~22μm) Polyvinylidene fluoride (PVDF) fibers fused together and oriented at angle offsets of 15°. Numerous interface changes between different planes and directions, arrests crack propagation in helicoidal layers, allowing material to absorb more energy before fracture. These fibers show superior tensile characteristics, impact resistance and toughness as compared to its bulk counterparts. Near field electrospinning provides a promising future pathway to fashion helicoidal architectures in nano range increasing the toughness and impact resistance of the materials furthermore.