**6.2 Laser ablation of viscoelastic ultrathin spider silk fibers**

We estimated a single-shot response of spider silk fiber of about 2–3 μm in diameter (**Figure 17**) [20, 55]. It is positioned at the focus using 100 x objective (NA: 0.9) with an estimated beam spot size around 1 micron. SEM micrographs illustrate the singlepulse ablation of silk fiber at 0.1 μJ and 0.3 μJ pulse energies. The estimated ablation threshold (Fth) for spider silk is about 0.05 μJ (1 J/cm2 ). A slightly lower ablation threshold (0.6 J/cm2 ) for silkworm silk is reported for different laser parameters with 230 fs pulses at the central wavelength of 515 nm wavelength [56]. This could be due to differences in the laser parameters, as well as the material properties [19, 20, 57]. Fth is found to be significantly higher than the ablation threshold for the crystalline Si, it could be attributed to the nonabsorbing nature of silk sample for incident laser wavelength, that is, 800 nm [19, 41]. By compensating for the dispersion of the fs-pulse, it

*Ablation of Materials Using Femtosecond Lasers and Electron Beams DOI: http://dx.doi.org/10.5772/intechopen.106198*

### **Figure 17.**

*(a) Native spider silk. (b) Illustrating ablation of silk fiber at different pulse energies 0.3 and 0.1 μJ, and (c) magnified SEM micrograph illustrating nanoscale ablation of spider silk microfiber at 0.3 μJ [55].*

should be possible to further reduce the precision of ablation and may open a route to create nano-patterns on silk for various potential applications.
