Each of the fluorophore-labelled DNA oligonucleotides formed high-resolution arrays (Figure ). As expected, differences in intensity were observed between the different fluorophores, which was attributed to the varying properties of each fluorescent label and their compatibility with contact printing. With consideration towards the baseline fluorescence noise produced by the polyethylene substrate, signal-to-noise ratios (SNR) were used to quantify the intensity of each array (Figure ). SNRs of 17.3, 11.3, 21.0, and 13.2 were derived for the Pacific Blue, FAM, Cy3, and Cy5 arrays, respectively. Subsequent visualization with overlaid food products employed romaine lettuce, ground beef, and whole chicken, given that all evaluated products showed fluorescence profiles comparable to one of these three products (Figure ). SNR values were used to quantify reductions in array visibility induced by food (Figure ). Microcontact-printed arrays fabricated using the four respective fluorescence labels produced SNR values of 14.9, 4.1, 9.4, and 0, respectively when overlaid with romaine lettuce. This corresponded with 13.9%, 63.7%, 55.2%, and 100% reductions in SNR, respectively, relative to baseline SNR values. Accordingly, Pacific Blue was identified as an excellent candidate label, due to both its high baseline SNR and limited SNR reduction with lettuce. Opposingly, the FAMlabelled oligonucleotide lost significant visibility -an outcome driven by both a low baseline SNR and significant lettuce-induced fluorescence impedance. While the Cy3-labelled microarray also experienced significant fluorescence interference from overlaid lettuce, high visibility was still retained, owing to a very high baseline SNR. Lastly, the Cy5 microarray was completely unobservable given the high fluorescence background produce exhibits at this wavelength. Pacific Blue, FAM, Cy3, and Cy5 DNA microarrays imaged with underlying ground beef exhibited SNR values of 13.7, 4.2, 12.0, and 7.4, respectively. SNR was resultantly noted to have decreased by 20.8%, 62.8%, 42.9%, and 43.3% with the respective labels. Similar to romaine lettuce samples, the presence of a ground beef background slightly reduced the SNR of the Pacific Blue-labelled microarray, but to a comparatively limited degree. The reduction in the visibility of the FAM-labelled DNA microarray when imaged with a beef background was identical to what was observed with produce -a finding substantiated by the similar fluorescence profiles both foods exhibit at this wavelength. Cy3-labelled microarrays also behaved similarly between the two products, with a high SNR being maintained despite fluorescence interference from the overlaid food sample. The most notable difference with beef samples was observed with the Cy5-labelled microarray, as the significantly lower background fluorescence of meat at this wavelength allowed for successful visualization of the printed arrays. Nonetheless, the Pacific Blue and Cy3-labelled DNA microarrays offered higher visibility, owing to the lower baseline SNR of the Cy5-labelled microarray. Finally, the four respective microarrays exhibited SNR values of 10.2, 3.9, 9.9, and 6.1, respectively, when overlaid with chicken samples. This correlated with SNR reductions of 41.0%, 65.5%, 52.9%, and 53.8% relative to the baseline arrays. Again, Pacific Blue and Cy3labelled microarrays offered the highest SNR values, despite significant fluorescence interference from overlaid food samples. Similar to what was observed with beef, the FAM-labelled microarray offered considerably low visibility and the Cy5-labelled microarray offered moderate visibility.