Microfluidic tesla valve sweat patch integrated smartwatch for optical continuous monitoring of glucose, oxygen, and heart rate

Abstract

Noninvasive continuous glucose monitoring (CGM) offers a promising alternative to conventional blood-based approaches for diabetes management. Among various body fluids, sweat is an attractive medium to reflect the blood glucose levels in the body. However, technical challenges for the sweat analysis persist due to the low analyte concentrations, potential contamination, and inefficient sampling. Here, we develop a microfluidic Tesla valve sweat patch integrated smartwatch for real-time optical continuous monitoring of glucose as well as oxygen and heart rate. The self-driven, unidirectional Tesla valve microchannel enables efficient and continuous sweat collection with minimal backflow. The optical hydrogel sensor is composed of glucose oxidase, catalase, and an oxygen-sensitive dye. The glucose oxidation and the following catalase reaction can be monitored by the oxygen-sensitive dye, producing optical signals reversibly proportional to glucose concentrations. The integrated smartwatch platform, equipped with micro-LEDs and a photodetector, provides optical readout and wireless data transmission for noninvasive continuous monitoring of glucose, oxygen and heart rate. On-body tests validate reliable CGM within the physiological sweat glucose range from 0.01 mM to 0.1 mM, showing the statistically significant correlation with blood glucose levels. Taken together, this smartwatch would be successfully used as a promising wearable healthcare system for personalized diabetes management.

Keywords: Continuous glucose monitoring; Diabetes management; Microfluidic Tesla valve; Optical sensor; Smartwatch.