Electrokinetically induced concentration of diluted sample by liquid metal embedded microfluidic chip

Microfluidic devices have been demonstrated to be able to concentrate low-abundance analytes and to be integrated in point of care (POC) devices for the purpose of reducing equipment size and cost; however, the complications involved in the fabrication of microfluidic chips or microelectrodes can be challenging. Here, we present a simple and effective microfluidic device monolithically integrated with liquid metal-based microelectrodes for the transportation and concentration of molecules in dilute solutions. Numerical and experimental studies were combined to validate and optimize the performance of the presented co-designing microfluidic chip featured by a double T-shaped manifold microchannel, in which the electrokinetically induced pressure-driven flow and concentration process were fully characterized. The microfluidic chip was used in a fluorimetric assay based on fluorescence resonance energy transfer between the fluorophore labeled aptamer and molybdenum disulfide nanosheets for the detection of cortisol, a stress biomarker of humans. Both experimental and numerical results show that a concentration factor up to 83-fold can be achieved within 5 min. By avoiding cumbersome fabrication processes and mechanical equipment, the proposed co-designing concentrating strategy provides insights for the fabrication of compact microfluidic chips that facilitate the miniaturization of POC devices with enhanced detection limit and sensitivity.