Laser processing of dry, wet and immersed polyamide nanofiber nonwovens with different laser sources

Electrospun nanofiber scaffolds of different polymers are used in tissue engineering to mimic the extracellular matrices with favourable conditions for cell growth and proliferation. Structures such as cavities, holes and cuts in the scaffolds can be used to optimize cell growth. We investigated the influence of different laser sources used for direct laser writing on the cutting and structuring quality of electrospun polyamide nonwovens. Ablation thresholds and rates were determined. Because of different approaches in cell colonization with scaffolds, the investigations were carried out on dry, wet and immersed nonwovens. The results show that femto- and picosecond lasers are very well suited for processing of dry nonwovens. Processing with green wavelengths is more effective and leads to similar minimum feature sizes than in the ultraviolet range. Ablation rates up to 8000 µm³/pulse were obtained which are about a factor of 100 higher than those for polyamide bulk material. Nanosecond UV lasers produced structures of reduced quality. Excimer lasers at 193 nm offer a possible alternative for large-area structures when operated at low fluences. Processing of wet and immersed nanofibers is possible with smaller processing speed and with a slightly degraded quality.