Structuring electrospun polycaprolactone nanofiber tissue scaffolds by femtosecond laser ablation

Meshes of electrospun (ES) polycaprolactone (PCL) and polyethylene terephthalate nanofiber meshes were structured by ablation of linear grooves with a scanned femtosecond laser. Focus spot size, pulse energy, and scanning speed were varied to determine their affects on groove size and the characteristics of the electrospun fiber at the edges of these grooves. The femtosecond laser was seen to be an effective means for flexibly structuring the surface of ES PCL scaffolds. Femtosecond ablation resulted in much more uniformly ablated patterns compared to Q-switched nanosecond pulse laser ablation. Also, the width of the ablated grooves was well controlled by laser energy and focus spot size, although the grooves were significantly larger than the spot size. Also, some melting of fibers was observed at the edges of grooves. These affects were attributed to optical radiation from laser-induced plasma at higher pulse energies and melting of fibers at laser fluences lower than the ablation threshold. The ablation threshold for the PCL mesh was estimated to be significantly larger than that of bulk (solid) PCL, a result attributed to multiple scattering of the laser energy within the volume of the nanofiber mesh.