Wearable Sweat Sensor for Health Monitoring




Wearable devices and sensors provide a convenient and non-invasive way for continuous health monitoring. Such devices are commonly used for monitoring vital body signs such as heart rate, blood oxygen level, sleep patterns, electrocardiograms, and have been gaining popularity in the form of fitness trackers/watches (e.g. from Fitbit, Garmin and Apple). However, the current existing devices have limited capability as they are unable to track health indicators at the molecular level. To expand the functionality of existing wearable devices, we have designed a wearable prototype that allows real-time monitoring of the pH of sweat. Sweat is a biofluid that is readily available and contains rich amount of biomarkers such as sodium, chloride, pH, glucose – many of which are potential indicators for diseases, hydration level and health monitoring. In our prototype, a flexible pH sensor (developed in-house) was mounted onto the pulse oximeter of existing fitness trackers, which allows the real-time measurement of sweat pH. The pH readings were obtained readily with an accuracy of over 90%. Further, the integration of the pH sensor does not hinder the measurement of heart rate and oxygen saturation level of existing devices. This technology can potentially be extended to detect other biomarkers in sweat.


This technology uses a pH-responsive polymeric material (polyaniline, PANI) to monitor pH variations in sweat. The optical spectra of PANI show significant changes in the visible to near-infrared (NIR) regions in relation to changes in pH. Utilising the NIR and red light of existing pulse oximeter in a typical wearable device, the relative transmission of light at 660 nm (red light) and 880 nm (NIR) can be determined which correlates to the pH of sweat. Advantages: Low cost and only requires low power to operate. Highly reusable and accurate, and provides real-time and continuous sensing. Easily incorporated into current wearable devices with pulse oximeters. Allows the simultaneous monitoring of pH, heart rate and oxygen saturation level. Sensing platform can be modified to detect other biomarkers.


For monitoring the pH of sweat – particularly useful for athletes, and persons involved in strenuous/outdoor activities (as the pH level provides an indication on the hydration level etc). Can potentially be extended to monitor a wide range of biomarkers other than pH (e.g. glucose, cortisol).  Can be used independently and/or integrated into existing fitness trackers.


This invention expands the functionalities of existing wearable technology to provide comprehensive health monitoring for users. With our technology, users are able to obtain real-time information of their health (i.e. chronic diseases, hydration level etc) simply based on the analyses of their sweat.