Precise laser ablation processing of black widow spider silk

Abstract

Contact-free precise laser processing of black widow spider (Latrodectus hesperus) dragline silk by laser ablation at λ=157 nm is achieved. At this wavelength, the small optical penetration depth, below 100 nm, allows efficient and gentle material removal above the ablation threshold of Φth=29 mJ/cm2. The ablation rate in nm/pulse is measured against laser fluence Φ and simultaneously calibrated with ultrapure polymethylmethacrylate (PMMA). Ripple formation in fiber ablation can be overcome by a suitable combination of ablation removal and laser polishing steps using exposure sequences at different irradiation angles α, such as vertical at 0° followed by oblique irradiation at 70°. In this way ripples are destroyed until the fiber is automatically smoothed over the entire laser-exposed length. This allows precise laser ablation processing of spider silk fibers and other highly absorbing materials without affecting the bulk mechanical, and other material, properties.