Figure 1 . QCL-GAP optical setup used for microorganism sample
acquisition.
2.3 Sample Preparation
Aliquots of 20 µL of neat and mixtures of bacteria samples were
deposited on the 2 X 2-in2(25.8-cm2) stainless-steel (SS) plates. Substrates
were cleaned with isopropyl alcohol and left to dry in a chemical hood
to avoid any sample contamination. Bacterial samples Sa, Se, andMl were used to create the following mixtures: Sa/Se ,Sa/Ml , and Se/Ml . A sample smearing technique using a
micropipette tip (~1 mm diameter) was used to deposit
the sample onto the substrate [20]. The smearing procedure accounts
for minimal sample loss during handling. The solutions deposited on the
substrate were left air-dry for 20 minutes until the solvent evaporated.
Each bacterial sample acquired twenty (20) replicas by moving the
optical stage in the QCL-GAP setup.