Micromachining of polyurea aerogel using femtosecond laser pulses

We successfully sliced cylindrical polyurea aerogel samples of 10–15 mm in diameter into 1–3 mm disks using femtosecond laser. The experiments were performed using a Ti:sapphire laser with 800 nm wavelength in ambient air with a pulse duration of ~ 40 fs. We found that the laser fluence to breakdown this material is 1.3 J/cm2. The ablation rate at different energy levels was evaluated. The factors influencing the ablation surface quality were investigated. The proper fluence to slice the porous polyurea is 6.4– 8.9 J/cm2 with the beam linearly scanning the sample at a speed of 0.1 mm/s, or 5.1–7.6 J/cm2 with the beam circularly scanning the sample at a speed of 3.5–4°/s, and high quality machining surface was obtained under these conditions. The material removal mechanisms are proposed. Structural details of the machined area were characterized using a number of techniques such as optical microscopy and scanning electron microscopy. This work provides insights for micromachining nanostructured porous polymers using femtosecond lasers.