Diffused reflectance infrared spectroscopy is well known as a compact, low-cost, and efficient handheld spectrometers. One of the spectrometer’s most important optical parameters is the effective collected spot profile from diffuse reflection samples not the simple illumination spot which determines the analyzed sample portion defining the spatial resolution. In this work, we present a novel method for characterizing the spot size based on the Knife-Edge technique. A sharp high scattering material such as PTFE is displaced into the spectrometer optical interface on a 1-dimensional moving stage while capturing the power at each step. Then by differentiating this cumulative power, the intensity spot profile is obtained and fitted to a Gaussian profile where the spot size is defined as the diameter that contains 90% of the reflected power. MEMS FT-IR spectrometers with different spot sizes measured as a demonstration of the technique. Moreover, this method quantifies different other parameters such as Goodness of Fit, spot lateral shift in addition to spot shape wavelength dependence that may occurs due to any non-ideality in the spectrometer system.
The conventional methods used for the diagnostics of viral infection are either expensive and time-consuming or not accurate enough and dependent on consumable reagents. In the presence of pandemics, a fast and reagent-free solution is needed for mass screening. Recently, the diagnosis of viral infections using infrared spectroscopy has been reported as a fast and low-cost method. In this work a fast and low-cost solution for corona viral detection using infrared spectroscopy based on a compact micro-electro-mechanical systems (MEMS) device and artificial intelligence (AI) suitable for mass deployment is presented. Among the different variants of the corona virus that can infect people, 229E is used in this study due to its low pathogeny. The MEMS ATR-FTIR device employs a 6 reflections ZnSe crystal interface working in the spectral range of 2200-7000 cm-1. The virus was propagated and maintained in a medium for long enough time then cell supernatant was collected and centrifuged. The supernatant was then transferred and titrated using plaque titration assay. Positive virus samples were prepared with a concentration of 105 PFU/mL. Positive and negative control samples were applied on the crystal surface, dried using a heating lamp and the spectrum was captured. Principal component analysis and logistic regression were used as simple AI techniques. A sensitivity of about 90 % and a specificity of about 80 % were obtained demonstrating the potential detection of the virus based on the MEMS FTIR device.
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