Gravity-driven preprogrammed microfluidic recirculation system for parallel biosensing of cell behaviors.

Area of Science:

• Microfluidics
• Organ-on-chip technology
• Biomedical engineering

Background:

• Fluid recirculation is crucial for organ-on-chip (OOC) and microfluidic systems.
• Simultaneous multi-flow conditions in parallel channels are essential for systematic analysis.
• Existing systems often rely on complex off-chip controllers, limiting device simplicity.

Purpose of the Study:

• To develop a simplified microfluidic recirculation system driven solely by water-head pressure.
• To enable preprogrammed, parallel flow control in microfluidic devices without external controllers.
• To demonstrate the system's utility for cell culture and biological studies.

Main Methods:

• A microfluidic system was designed using oscillator and cell culture modules.
• Water-head pressures from small reservoirs (<500 mL) were utilized to drive recirculation of cell culture media (<500 μL).
• The system was programmed to achieve both constant and pulsatile flow conditions in four parallel channels.

Main Results:

• The system successfully recirculated cell culture media in parallel channels with controlled flow rates (0.06-144 μL/min) and shear stress (0.004-9.6 dyn/cm²).
• Pulsatile flow periods were independent of flow rate, ranging from 0.7 to 13.0 s.
• Demonstrated utility through parallel analysis of endothelial cell elongation and successful myoblast culture for 8 days, achieving myotube formation.

Conclusions:

• A novel, controller-free microfluidic recirculation system driven by water-head pressure was successfully developed.
• The system offers precise control over flow rates and shear stress, enabling complex fluidic programming for parallel analyses.
• This technology simplifies OOC device operation and facilitates systematic studies of cellular responses to diverse fluidic environments.