Lab-on-Chip for In Situ Analysis of Nutrients in the Deep Sea

Area of Science:

• Oceanography
• Environmental Science
• Sensor Technology

Background:

• Ocean chemistry is undersampled globally, particularly in deep-sea environments.
• Existing nutrient sensors often lack the capability for deep-sea deployment (>200 m).
• Microfluidic sensors offer potential for in situ oceanographic measurements.

Purpose of the Study:

• To develop and validate miniaturized lab-on-chip (LOC) colorimetric analyzers for in situ deep-sea nitrate and phosphate measurements.
• To demonstrate the capability of these sensors for accurate chemical analysis in hyperbaric environments.
• To provide a low-cost, high-performance tool for ocean chemistry research.

Main Methods:

• Development of miniaturized LOC colorimetric analyzers for nitrate and phosphate.
• Incorporation of a novel inertial-flow mixer for improved efficiency and reduced back pressure.
• Laboratory calibration and field-based testing, including deployment on CTD rosettes and profiling floats.
• Validation of in situ measurements against laboratory-based analyses.

Main Results:

• Analyzers successfully performed in situ nitrate and phosphate measurements from surface to >4800 m depth.
• Average limits of detection were 0.03 μM for nitrate and 0.016 μM for phosphate.
• Sensors exhibited a large linear range suitable for both ocean and freshwater environments.
• Field tests confirmed in situ measurements comparable to laboratory analyses.

Conclusions:

• The developed LOC analyzers represent a significant advancement for deep-sea ocean chemistry monitoring.
• This technology offers a low-cost, high-performance solution for in situ nutrient measurements in hyperbaric conditions.
• The sensors enable high-resolution spatial and temporal data collection, addressing the global undersampling of ocean chemistry.