An Intra-Oral Optical Sensor for the Real-Time Identification and Assessment of Wine Intake

Abstract

Saliva has gained considerable attention as a diagnostics alternative to blood analyses. A wide spectrum of salivary compounds is correlated to blood concentrations of biomarkers, providing informative and discriminative data regarding the state of health. Intra-oral detection and assessment of food and beverage intake can be correlated and provides valuable information to forecast the formation and modification of salivary biomarkers. In this context, the present work proposes a novel intra-oral optical fiber sensor, developed around an optical coupler topology, and exemplified on the detection and assessment of wine intake, which is accounted for example for the formation of N^ε-carboxymethyllysine Advanced Glycation End-products. A laboratory proof of concept validates the proposed solution on four white and four red wine samples. The novel optical sensor geometry shows good spectral properties, accounting for selectivity with respect to grape-based soft drinks. This enables intra-oral detection and objective quality assessment of wine. Moreover, its implementation exploits the advantages of fiber-optics sensing and facilitates integration into a mouthguard, holding considerable potential for real-time biomedical applications to investigate Advanced Glycation End-products in the saliva and their connection with consumption of wine, for the evaluation of risk factors in diet-related diseases.

Keywords: intra-oral sensors; optical coupler; optical fiber sensors; side-emitting fiber; wearable sensors; wine color analysis.; wine spectroscopy.

Figure 1

Implementation concept of the proposed intra-oral optical sensor, consisting of an LED source and a D-shaped side-polished optical fiber deployed in a vertical coupler topology, implementing point sensing.

Figure 2

Implementation concept of the extended sensing area intra-oral sensor, consisting of an LED source, a side-emitting fiber, and an end-emitting fiber. Sensing is achieved by having the end-emitting fiber incident illumination applied via a side-emitting fiber, which distributes the incident LED source onto the entire sensing surface.

Figure 3

A macrobending of an optical fiber, with the illustration of the input source intensity I_in, intensity of the light, which leaves the fiber through the bending I_out, the propagation parameters: incidence angle θ_i, and length variable d, and the bending parameters: bending radius R and bending angle θ.

Figure 4

Practical realization of the point intra-oral sensor laboratory proof of concept, which has the LED source and the optical fiber from the sensor structure integrated into a lateral mouthguard.

Figure 5

Practical realization of the extended sensing area intra-oral sensor laboratory proof of concept, which has the side emitting fiber and the end-emitting fiber deployed in parallel and integrated into a frontal mouthguard. The source, which feeds light axially into the side-emitting fiber, is external to the sensor.

Figure 6

The intra-oral optical sensor test setup for wine color analysis: (a) point sensor test setup, and (b) extended sensing area sensor test setup.

Figure 7

Qualitative plot of a typical absorption spectrum for: (a) white wines, and (b) red wines.

Figure 8

Test setup for the assessment of the point intra-oral sensor spectral attenuation measures: (a) schematic diagram, (b) practical realization with external LED supply and optical filter foils.

Figure 9

Spectral attenuation measures of the point intra-oral optical sensor expressed in terms of: (a) insertion loss, (b) coupling ratio, (c) excess loss.

Figure 9

Spectral attenuation measures of the point intra-oral optical sensor expressed in terms of: (a) insertion loss, (b) coupling ratio, (c) excess loss.

Figure 10

Test setup for the assessment of the wavelength dependent coupling loss of the extended sensing area intra-oral sensor.

Figure 11

Wavelength dependent coupling loss of the extended sensing area intra-oral sensor.

Figure 12

Test setup, consisting of a TH 2100 Tungsten Halogen source and SV 2100 spectrometer, for the acquisition of the reference absorption spectra of the wine samples in plastic cuvettes.

Figure 13

Illustration of the intra-oral optical sensor test procedure for wine color analysis, which assumes having the sensor integrated into a mouthguard and mounted onto a custom jaw mold.

Figure 14

Spectrum of the blank system, i.e., in the absence of the analyte, with a blue line for the point sensor (with white LED source), orange for the extended sensing area sensor (with white LED source), and green line for the reference system (with Tungsten Halogen source).

Figure 15

White wine absorption spectra, acquired via the proposed intra-oral sensor implementations, with a blue line for the point sensor, orange line for the extended sensing area sensor, and green line for standard spectroscopic method, respectively: (a) blended dry, (b) blended medium dry, (c) Yellow of Transylvania, (d) Sauvignon Blanc.

Figure 16

Red wine absorption spectra, acquired via the proposed intra-oral sensor implementations, with the blue line for the point sensor, orange line for the extended sensing area sensor, and green line for standard spectroscopic method, respectively: (a) blended medium dry, (b) blended medium sweet, (c) Fetească Neagră, (d) Cabernet Sauvignon.

Figure 17

Fetească Neagră red wine absorption spectra, acquired with the point sensor, for different dilutions of wine in saliva.

Figure 18

Grape-based drink absorption spectra, acquired via the proposed intra-oral point sensor: (a) white grape (5%) and aloe vera, (b) white grape (11%) and raspberry, and (c) red grape (0.1%) fizzy drink.

Figure 18

Grape-based drink absorption spectra, acquired via the proposed intra-oral point sensor: (a) white grape (5%) and aloe vera, (b) white grape (11%) and raspberry, and (c) red grape (0.1%) fizzy drink.