Solid-Phase microextraction on Self-Driven microfluidic chip using capillary micropump and microvalves for saliva electrochemical analysis

The real-time detection of biomarkers in saliva is of great significance for early non-invasive diagnostic of related diseases. In this work, molecular imprinting technology was used to prepare a lactic acid monolithic column, which could realize specific adsorption and elution of lactic acid, achieving solid phase microextraction (SPME) of lactic acid in samples, and purify the analytes. Lactic acid monolithic column was then embedded into the microfluidic channel, and passive microfluidic structures such as stop valve, retention valve, trigger valve and capillary pump were utilized to construct the SPME self-driven microfluidic chip. A series of complex operations such as lactic acid adsorption, rinse and elution on the monolithic column could be realized automatically without external power. Since the purification of the analytes was achieved by the monolithic column, the low-cost nano copper oxide modified electrode was used to achieve the specific electrochemical analysis of lactic acid. The screen-printed electrode was designed and fabricated, and the integrated electrochemical detection circuit was used to realize the portable analysis of Na+, K+ and lactic acid simultaneously. The microfluidic chip, screen-printed electrode and miniaturized detection circuit are integrated into a Point-of-care testing (POCT) device, which realizes the automatically real-time detection of saliva. By adjusting the template molecule in monolithic column polymerization, the application of this physiological fluid POCT device can be extended, and may provide some implications for the development of portable non-invasive health monitoring devices.