*2.6. Surface Analysis*

## 2.6.1. Epi-Fluorescence Microscopy

After the exposure test, samples were taken out and stained by a fluorescent dye to discriminate cells in active (green) or inactive (red) cells. Stained microbial cells were made visible by exciting the DNA/stain with ~490 nm blue light and observing the emitted green or red fluorescence under the microscope. In the case of no bacteria, no fluorescence will be detected.
