An Integrated Electrochemical Sensor with Flexible Microfluidic Structures for Human Sweat Analysis

Human sweat serves as a viable signal source for continuous monitoring of physiological indicators. Sweat sensors with flexible microfluidic structures offer the advantages of operational convenience and quantifiability, making them suitable for integration with electrochemical detection. The utilization of flexible polymer materials as substrates enhances the ability to manipulate sweat, necessitating exploration into highly integrated and controllable structural designs for fluid chambers in microfluidic structures. This study presents simulations and designs aimed at optimizing the layout of microfluidic structures and two-dimensional channel shapes. A flexible polyethylene glycol terephthalate substrate is employed to fabricate the microfluidic sensing device using laser cutting, screen printing, and layer-by-layer assembly techniques. The resulting microfluidic structure enables precise control over artificial sweat flow velocities and facilitates verification of Na⁺ detection. The optimal parameters of the length of 7 mm, width of 110 μm, and diffusion angle of 15°, ensure stable flow velocity under precise control. The response of the Na⁺ sensor exhibits near-Nernstian behavior that varies with the flow velocity. The integration of an electrochemical sensor with flexible microfluidic structures demonstrates high sensitivity and accuracy, and on-body quantitative analysis in human sweat is achieved.