The authors of this study developed the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR) combined with machine learning as a point-of-care (POC) diagnostic platform, considering neonatal respiratory distress syndrome (nRDS), for which no POC currently exists, as an example. nRDS can be diagnosed by a ratio of less than 2.2 of two nRDS biomarkers, lecithin and sphingomyelin (L/S ratio), and in this study, ATR–FTIR spectra were recorded from L/S ratios of between 1.0 and 3.4, which were generated using purified reagents. The calibration of principal component (PCR) and partial least squares (PLSR) regression models was performed using 155 raw baselined and second derivative spectra prior to predicting the concentration of a further 104 spectra. A three-factor PLSR model of second derivative spectra best predicted L/S ratios across the full range (R2: 0.967; MSE: 0.014). The L/S ratios from 1.0 to 3.4 were predicted with a prediction interval of +0.29, −0.37 when using a second derivative spectra PLSR model and had a mean prediction interval of +0.26, −0.34 around the L/S 2.2 region. These results support the validity of combining ATR–FTIR with machine learning to develop a point-of-care device for detecting and quantifying any biomarker with an interpretable mid-infrared spectrum.

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Multi-layered tungsten disulfide (WS2) coated silicon/silica (Si/SiO2) substrate and SiO2 micro-bottle resonators (MBRs) have been prepared by van der Waals epitaxy method. Raman spectra of WS2-coated MBR show that the out-of-plane Raman mode is sensitive to the polarization of the excitation laser. The quality factor (Q) values of the whispering gallery modes (WGMs) in the transmission spectrum of an MBR decrease by 2 orders of magnitude on coating with WS2. On coating, a cleaner spectrum is obtained along with a concomitant effect of decrease in the number of lossy modes. Fano resonances as well as Autler-Townes splitting (ATS) was observed for the WGMs in the cleaned transmission spectrum. From the simulations it has been verified that the scattered electric field of the WS2 flakes contributes to the observation of the Fano resonances and ATS in the coated MBR spectra.