Inkjet-printed fNAP arrays. A print solution containing 3 μM nucleic acid probe, EDC, and NHS was prepared in MES buffer at a pH of 4.5. A GeSIM Nanoplotter 2.0 was used to deposit 12 nL droplets onto carbon dioxide plasma-treated polyethylene substrates. Each array was composed of 36 spots arranged in a 6 ´ 6 configuration. Each slide contained four arrays, ensuring replicates with all subsequent assays. Printed arrays were incubated at 70% humidity for 2 h for mediate covalent attachment. The slides were then immersed in deionized water and washed for 30 mins at 220 RPM using a shaker set to 40 °C.