A Magnetically Tunable Check Valve Applied to a Lab-on-Chip Nitrite Sensor.

Area of Science:

• Microfluidics
• Materials Science
• Environmental Sensing

Background:

• Accurate marine nutrient sensing is crucial for understanding oceanographic processes.
• Existing microfluidic valves often lack tunability or require active control.
• Development of passive, low-cost microfluidic components is needed for portable sensing platforms.

Purpose of the Study:

• To design, fabricate, and characterize a tunable microfluidic check valve.
• To demonstrate the valve's integration into a lab-on-chip device for marine nitrite detection.
• To provide a passively sealed, customizable valve solution for microfluidic systems.

Main Methods:

• Fabrication of a ball-style microfluidic check valve using micro-milling.
• Integration of a rare-earth permanent magnet for tunable sealing force.
• Characterization of valve performance, including cracking pressure and leakage rates.
• Assembly into a poly(methyl methacrylate) (PMMA) lab-on-chip device with optical absorbance detection.

Main Results:

• The magnetic check valve demonstrated tunable cracking pressure via magnet positioning.
• Low leakage rates (<2 µL min⁻¹ at ~350 kPa) were observed at high back pressures.
• The valve was successfully integrated into a PMMA lab-on-chip device for nitrite detection.
• The valve operates passively, requires no power, and is low-cost.

Conclusions:

• A passively sealed, tunable microfluidic check valve was successfully developed.
• The valve's customizable nature and low leakage make it suitable for marine nutrient sensing.
• This technology offers a cost-effective and easily implementable solution for microfluidic sensing platforms.