FIG. 4.

(Left) SEM image of an area of $0.5\times 0.5{\text{mm}}^2$ ablated on the surface of thick biofilm ($\sim 100\mu \text{m}$ thick). Laser was focused to a spot diameter of $200\mu \text{m}$ and ablation was done by rastering laser beam across the surface with $10\mu \text{m}$ spacing between shots. Magnification was 80×. (Right) Top right corner of the ablated region shown on the left image. Magnification was 3000×. The depth penetration was estimated by counting layers of cells from the top to the bottom, as the diameter of an individual S. epidermidis cell is $\sim 0.7\mu \text{m}$.