By manipulating the geometry and surface chemistry of microfluidic channels,capillary-driven microfluidics can move and stop fluids spontaneously without external instrumentation.Furthermore,complex microfluidic circu...By manipulating the geometry and surface chemistry of microfluidic channels,capillary-driven microfluidics can move and stop fluids spontaneously without external instrumentation.Furthermore,complex microfluidic circuits can be preprogrammed by synchronizing the capillary pressures and encoding the surface tensions of microfluidic chips.A key component of these systems is the capillary valve.However,the main concern for these valves is the presence of unwanted diffusion during the valve loading and activation steps that can cause cross-contamination.In this study,we design and validate a novel diffusion-free capillary valve:theπ-valve.This valve consists of a 3D structure and a void area.The void acts as a spacer between two fluids to avoid direct contact.When the valve is triggered,the air trapped within the void is displaced by pneumatic suction induced from the capillary flow downstream without introducing a gas bubble into the circuit.The proposed design eliminates diffusive mixing before valve activation.Numerical simulation is used to study the function and optimize the dimensions of theπ-valve,and 3D printing is used to fabricate either the mould or the microfluidic chip.A comparison with a conventional valve(based on a constrictionexpansion valve)demonstrates that theπ-valve eliminates possible backflow into the valve and reduces the mixing and diffusion during the loading and trigger steps.As a proof-of-concept,this valve is successfully implemented in a capillary-driven circuit for the determination of benzodiazepine,achieving the successive release of 3 solutions in a 3Dprinted microfluidic chip without external instrumentation.The results show a 40%increase in the fluorescence intensity using theπ-valve relative to the conventional value.Overall,theπ-valve prevents cross-contamination,minimizes sample use,and facilitates a sophisticated preprogrammed release of fluids,offering a promising tool for conducting automated immunoassays applicable at point-of-care testing.展开更多
基金This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no.813863This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 801342(Tecniospring INDUSTRY)All authors are joint inventors on a Patent Application PCT/ES2021/070720,which covers theπ-valve concept(international publication number WO 2023/057659 A1).
文摘By manipulating the geometry and surface chemistry of microfluidic channels,capillary-driven microfluidics can move and stop fluids spontaneously without external instrumentation.Furthermore,complex microfluidic circuits can be preprogrammed by synchronizing the capillary pressures and encoding the surface tensions of microfluidic chips.A key component of these systems is the capillary valve.However,the main concern for these valves is the presence of unwanted diffusion during the valve loading and activation steps that can cause cross-contamination.In this study,we design and validate a novel diffusion-free capillary valve:theπ-valve.This valve consists of a 3D structure and a void area.The void acts as a spacer between two fluids to avoid direct contact.When the valve is triggered,the air trapped within the void is displaced by pneumatic suction induced from the capillary flow downstream without introducing a gas bubble into the circuit.The proposed design eliminates diffusive mixing before valve activation.Numerical simulation is used to study the function and optimize the dimensions of theπ-valve,and 3D printing is used to fabricate either the mould or the microfluidic chip.A comparison with a conventional valve(based on a constrictionexpansion valve)demonstrates that theπ-valve eliminates possible backflow into the valve and reduces the mixing and diffusion during the loading and trigger steps.As a proof-of-concept,this valve is successfully implemented in a capillary-driven circuit for the determination of benzodiazepine,achieving the successive release of 3 solutions in a 3Dprinted microfluidic chip without external instrumentation.The results show a 40%increase in the fluorescence intensity using theπ-valve relative to the conventional value.Overall,theπ-valve prevents cross-contamination,minimizes sample use,and facilitates a sophisticated preprogrammed release of fluids,offering a promising tool for conducting automated immunoassays applicable at point-of-care testing.
