Passive flow-rate regulators using pressure-dependent autonomous deflection of parallel membrane valves

Area of Science:

• Microfluidics
• Mechanical Engineering
• Materials Science

Background:

• Existing passive flow-rate regulators face challenges in integration with micropumps due to complex structures and high-pressure requirements.
• Micropumps often exhibit variable inlet pressures, necessitating precise flow control for microfluidic systems.

Purpose of the Study:

• To present novel passive flow-rate regulators with a simple structure and low threshold pressure for micropump integration.
• To demonstrate autonomous flow-rate regulation independent of inlet pressure variations.

Main Methods:

• Design and fabrication of four passive flow-rate regulator prototypes (W20, W30, W40, W50) using a single mask process.
• Utilizing autonomous deflection of parallel membrane valves to adjust flow resistance.
• Employing analytical and numerical models for flow-rate estimation, validated by experimental studies.

Main Results:

• Prototypes achieved constant flow-rates, e.g., 6.09 ± 0.32 µL/s (W20) at 20 kPa inlet pressure using 10:1 PolyDiMethylSiloxane (PDMS).
• Prototypes fabricated with lower Young's modulus 20:1 PDMS exhibited lower threshold pressures and higher regulated flow rates.
• The W40 prototype using 20:1 PDMS maintained a constant flow-rate of 14.53 ± 0.51 µL/s at a minimum inlet pressure of 15 kPa.

Conclusions:

• The developed passive flow-rate regulators offer a simple, effective solution for maintaining constant flow rates in microfluidic systems.
• These regulators demonstrate low threshold pressure operation and compatibility with integrated microfluidic systems.
• The use of different PDMS formulations allows tuning of performance characteristics for specific applications.