Femtosecond laser structuring of PCL and PET electrospun nanofiber mesh

Electrospun polycaprolactone (PCL) and polyethylene terephthalate (PET) were structured by ablation of linear channels with a scanned femtosecond laser. Focus spot size, pulse energy and scanning speed were varied to determine affects on channel size and the characteristics of the electrospun fiber found at the edges of these channels. Femtosecond lasers provided an effective means of flexibly structuring the surface of these scaffolds to produce specific microenvironments that can influence cellular growth patterns during tissue engineering. Femtosecond ablation resulted in much more uniformly ablated patterns and less fiber melting compared to Q-switched laser ablation. The width of the ablated channels was well-controlled by laser energy and focus spot size although some melting of fibers was observed at the edges. The squared ablation diameter versus fluence relationship for the PCL mesh was non-logarithmic and the ablation threshold for the material could not be estimated. This was attributed to thermal affects due to radiation originating from plasma formed below the level of the mesh surface during channel ablation. When used properly, femtosecond lasers provide an excellent means of micro-patterning electrospun polymeric scaffolds at high levels of precision and complexity.