Ultra-compact dual-channel integrated CO₂ infrared gas sensor.

Area of Science:

• Sensor Technology
• Biomedical Engineering
• Respiratory Monitoring

Background:

• Expiratory CO2 concentrations are vital indicators of physiological status, crucial for critically ill patients.
• Current respiratory gas analyzers are bulky and power-intensive, hindering wearable applications for active individuals.
• Existing CO2 sensors face challenges with interference, sensitivity, size, and power consumption for wearable use.

Purpose of the Study:

• To develop an ultra-compact and low-power carbon dioxide (CO2) sensor for wearable respiratory monitoring.
• To overcome limitations of existing sensors, including size, power consumption, interference, and sensitivity.
• To enhance sensor performance for reliable real-time tracking of physiological conditions.

Main Methods:

• Integrated a microelectromechanical system emitter and thermopile detectors within an optical gas chamber.
• Implemented heat transfer control to reduce power consumption and ambient temperature effects.
• Utilized a dual-channel design for improved humidity resistance and optimized optical coupling with an amplitude trimming network for enhanced sensitivity.

Main Results:

• Developed an ultra-compact sensor measuring 12mm x 6mm x 4mm.
• Achieved a reading error of <4% across a wide temperature range (-20°C to 50°C) with minimal power consumption (~33mW).
• Demonstrated rapid response (10s @1Hz), recovery times, and excellent humidity resistance, stability, and repeatability.

Conclusions:

• The developed ultra-compact CO2 sensor meets key requirements for wearable respiratory monitoring.
• The sensor's small size, low power, and robust performance make it suitable for tracking active individuals.
• This technology holds significant potential for advancing non-invasive, real-time physiological monitoring.