We present the performance of a CMOS miniaturized (4mm x 3.2mm x 3.3mm) spectrometer for two specific wearable health applications: reflective medically-accurate SpO2 and dermal H2O measurement for preventive health and remote follow-up use cases. The spectrometer has been manufactured using a monolithically integrated filter process, enabling low-cost, low-power, miniature and mass-producible spectral sensors. Accurate biomarker models can be built using continuous on-skin hyperspectral tissue and PPG data. A deoxygenation trial on 17 healthy volunteers was conducted using the wrist-worn spectrometer in the 650-900nm wavelength range. Using partial least squares (PLS) modeling, a model was built to correlate the obtained spectral PPG data to SpO2 data from a reference finger clip (Nonin 8000A). In the tested range between 87% and 100% SpO2, an RMSEP of 1.86%SpO2 has been obtained on a separate test set, well within the 3.5% requirement of the FDA. For dermal skin hydration, a study on 29 volunteers (including 4 patients with congestive heart failure (CHF) and fluid retention in legs) was conducted with the spectrometer in the 750-1050 nm range. A spectroscopic model was compared with a lymph scanner as gold standard measuring localized percentage water content (PWC), yielding a decent prediction accuracy of 3.3% RMSE, while correctly identifying the patients with CHF. We demonstrated the viability of a miniaturized spectrometer for wearable skin biomarker measurements. This solution has the potential to detect other tissue biomarkers such as SpCO or StO2, or to read subdermal markers such as hydrogels for glucose or lactate detection.
A hyperspectral laser scatter imaging (HLSI) system based on a supercontinuum laser in combination with a
monochromator has been developed for contactless and non-destructive measuring the ripeness of Braeburn apples.
Reflectance images were obtained by a CCD camera at 91 different wavelengths ranging from 550 nm to 1000 nm and
transformed into reflectance profiles. A linear function was fitted to the logarithm (log10) of the extracted profiles,
resulting in an intercept and a slope. These two parameters were then correlated with apple ripeness parameters such as
firmness and soluble solids content (SSC) measured by the reference, destructive methods. Preliminary results showed
the potential of slope and intercept to be used as a ripeness indicator. Moreover, during fruit ripening, the new HLSI
measurement technique clearly showed the degradation of chlorophyll over time.
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