Fig. 1. Experimental setup: the schematic diagram of the miniature wearable Raman spectroscopy system.

Fig. 2. (Color online) Raman spectra of glucose solutions with concentrations of 3.8–13.3 mmol/L. The area of 1372.7cm−1 and the concentration of glucose are directly related.

Fig. 3. (Color online) Difference between the relationship of the peak area and intensity with the concentration of the glucose solution.

Fig. 4. (Color online) Calculated result of the glucose solution, with a coefficient of determination of 98.1% and an MAE of 0.394 mmol/L.

Fig. 5. (Color online) Comparison between the spectrum of the rat skin and the spectrum of the glucose solution. The spectrum of the rat skin is more complicated.

Fig. 6. (Color online) Calculated results for one of the rat samples.

Fig. 7. (Color online) (A) Comparison between the spectrum of the human skin and the spectrum of the rat skin. (B) Comparison between the spectrum of the human skin and the spectrum of glucose. The spectrum of the human skin is similar to the spectrum of the rat skin.

Fig. 8. (A) Calculated result for one of the human volunteers without using a grin lens. (B) Calculated result for one of the human volunteers using a grin lens. The result when using a grin lens is obviously better.

Fig. 9. (Color online) Comparison between calculated results for all samples and one of the samples.