Objective: Continuous measurement of key physiological parameters, such as heart rate (HR), pulse oxygen saturation (SpO2), and sweat pH value, has very broad applications in healthcare, disease surveillance, and fitness and sports training. In this study, a stretchable optical sensing patch system was developed for real-time continuous noninvasive monitoring of the HR, SpO2, and sweat pH, and the sensing data were transmitted to a smartphone through Bluetooth.
Methods: The sensor patch system adopted serpentine stretchable interconnects between the optical sensor and microcontroller chip with wireless function on a flexible substrate. The pH sensing function was implemented by coating a pH sensitive organically modified silicate film on the surface of a commercial blood oxygen sensor, achieving simultaneous measurement of HR, SpO2, and sweat pH with a single sensor.
Results: Real-time on-body assessment was carried out to evaluate the sensor patch system, showing its excellent repeatability and applicability. The sensor patch system could withstand up to 35% extension and exhibited a pH sensitivity of 4.42 mV/pH from 4.0 to 8.0, while the accuracy of HR from 25 to 250 b/min and SpO2 from 70% to 100% sensing were ±1 b/min and ±2%, respectively.
Conclusion: The triple sensing functions was achieved through a single optical sensor on a flexible substrate while holding excellent contact with the body.
Significance: The sensor patch system can be used for fitness guidance, skin disease detection, and wound monitoring and management by replacing related sensitive films.