A Self-Powered Microfluidic-Based Flexible Triboelectric Sensor for Noninvasive Sweat Analysis

Abstract

Sweat, an abundant biofluid containing rich source of physiological and metabolic information regarding the health of an individual, with the potential for noninvasive extraction. Health monitoring via quantitative sweat analysis could potentially preclude the need for periodic blood sample assessments. Continuous monitoring of key electrolytes such as sodium can provide a wide range of information from electrolyte imbalance to diagnosis of cystic fibrosis. This makes the quantification of sodium ions important since the loss of sodium could lead to hyponatremia. About 5% of the adults and about 35% of hospitalized patients suffer from hyponatremia which makes it one of the most common electrolyte disorder. Therefore, developing a robust sensing platform is indispensable. A flexible, thin class of microfluidic device has been introduced of late, that can be used for sweat extraction and quantifiable monitoring of the sweat analytes. However, these devices operate with high cost, complex design, and an active power source. Therefore, in our study, we address such challenges by developing a triboelectric nanogenerator (TENG) based self-powered microfluidic device that works on contact electrification. The wearable microfluidic device monitors the sodium levels in the sweat of the individual extracted in a non-invasive manner. The flexible microfluidic channel utilizes the capillary action generated with the periodic finger tapping to transport the sweat from skin to the sensing area. The transported sweat is used in the liquid - solid interaction between the sweat and microfluidic channels with electrode coated with ion selective membrane (ISM) to obtain triboelectric output. The ISM coating on the electrode is able to selectively detect the target analyte which results in a significant difference in output. This study demonstrates a flexible microfluidic based self-powered noninvasive sweat sensor which has potential applications in analysis of electrolyte loss through sweat.