how a smartwatch for non-invasive blood glucose?

Smartwatches achieve non-invasive blood glucose monitoring by integrating multiple sensors and advanced algorithms. Typically, they use optical sensors, such as near-infrared (NIR) spectroscopy, which emit specific wavelengths of light into the skin. These light waves penetrate the epidermis and dermis to reach the interstitial fluid, where glucose molecules absorb and scatter the light uniquely. The sensor then detects the reflected or transmitted light intensity changes, which correspond to glucose concentration variations.

Some models combine photoplethysmography (PPG) with electrochemical sensing. PPG sensors measure blood flow changes to assess physiological parameters, while microelectrodes in the watch detect subtle chemical signals from sweat or interstitial fluid without breaking the skin. Additionally, impedance spectroscopy may be used to analyze tissue properties, as glucose levels affect electrical conductivity.

Collected raw data is processed by machine learning algorithms to eliminate interference from factors like skin thickness, hydration, and temperature. By correlating sensor readings with reference data, the watch estimates real-time blood glucose trends, enabling continuous, painless monitoring for users, especially diabetics, to manage their health proactively.