Liquid Bridge Cutting Valves for Microfluidic Passive Distribution and Sequential Reaction

In bioanalysis, precisely isolating liquid reactions in distinct systems or at different temporal sequences is vital for ensuring accurate results devoid of crosstalk. However, passive liquid isolation is unattainable through existing microfluidic valves. Here, liquid bridge cutting valves (LBCVs) are introduced to automatically segregate liquids by establishing airlocks, offering an innovative microfluidic structure for liquid distribution. The principle of liquid bridge breakup is studied and applied to the design of LBCVs. Additionally, monolithic chips connecting units with LBCVs in different topologies facilitate sequential sampling and reactions, achieving the detection of sweat glucose and lactate in wearable applications, as well as cortisol ELISA on the chips. As a missing puzzle piece of microfluidic elements in liquid separation, LBCVs can be seamlessly integrated with maturing microfluidic structures, creating a lab-on-a-chip device to enable complex fluid manipulation for individual healthcare monitoring and clinical scenarios.