Solid State Carbon Dioxide (CO2) Sensor

sensors

Solid State Carbon Dioxide (CO2) Sensor (TOP2-292)

Miniaturized, chip size solid state CO2 sensor

Overview

Detection of Carbon Dioxide (CO2) is very important for environmental, health, safety and space applications. CO2 is a harmful pollutant at higher concentrations due to its ability to displace oxygen in large concentrations. Current commercial sensors for CO2 have issues and shortcomings particular with precision at different temperatures, pressures and high humidity levels. NASA Ames has developed a novel solid state, CO2 sensor configured for sensitive detection of CO2 having a concentration within the range of about 100 Parts Per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO2 increases. The CO2 sensor can be easily integrated into existing electronic circuitry and hardware configurations, including the hardware of a mobile computing device, such as a smart phone or tablet device.

The Technology

The technology is a solid state, Carbon Dioxide (CO2) sensor configured for sensitive detection of CO2 having a concentration within the range of about 100 Parts per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions (e.g., > 80% relative humidity). The solid state CO2 sensor achieves detection of high concentrations of CO2 without saturation and in both dynamic flow mode and static diffusion mode conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide, for example O-MWCNT and iron oxide (Fe2O3) nanoparticles. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO2 increases. The CO2 gas molecules absorbed into the carbon nanotube composites cause charge-transfer and changes in the conductive pathway such that the conductivity of the composite sensing material is changed. This change in conductivity provides a sensor response for the CO2 detection. The solid state CO2 sensor is well suited for automated manufacturing using robotics and software controlled operations. The solid state CO2 sensor does not utilize consumable components or materials and does not require calibration as often as conventional CO2 sensors. Since the technology can be easily integrated into existing programmable electronic systems or hardware systems, the calibration of the CO2 sensor can be automated.

FE-SEM images for (A) oxidized MWCNTs deposited onto a silicon substrate, (B) iron oxide nanoparticles and (C), oxidized MWCNT/ iron oxide composite material.

Benefits

Accurate and rapid response - quickly provides accurate readings (in seconds) at different temperatures and pressures
High CO2 sensitivity: CO2 can be measured in the 100-10,000 ppm range
Operates at room temperature: Unlike standard metal oxide sensors which must operate at ~300 Celsius or higher, these sensors operate at room temperature (~25 Celsius)
Small footprint: Chips can be made 0.5 cm x 0.5 cm x 3 mm size with multiple sensors per chip
Light weight: Sensor only weighs a few grams
Low cost and low power: Less than 50 microwatts are required for power, and the sensor functions on a change in resistivity
Easy to integrate: Can be easily coupled with existing programmable electronic or hardware systems
Sensor is solid state; so extra materials are required to maintain operation
Provides in-situ monitoring; and calibration of the CO2 sensor that can be automated

Applications

Wearable sensor for environmental monitoring
Astronaut atmospheric monitoring; CO2 in a space suit, particularly within the astronauts' helmets
Modified atmospheres or closed crew cabin to continuously monitor real-time CO2 concentrations for permissible exposure limit levels; space-medicine
Determining the catalyzing efficiency of the CO2 splitting process; in-situ resource utilization of CO2 on Mars
Aerospace industry - for cabin air monitoring on the airplane
Medical diagnosis and monitoring
Indoor air quality
Stowaway detection
Monitoring landfill gas
Confined spaces; Cryogenics; Ventilation management, Mining industry
Rebreathers (SCUBA)
Cellar and gas stores; Marine vessels, and Greenhouses
Food industry
Monitoring global warming
CO2 scrubber industry

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Technology Details

Category sensors

Reference Number TOP2-292

Case Number(s) ARC-18097-1

Patent(s) 11,719,660

Papers https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6767332/

Tags:

solid state CO2 Sensors Carbon Nanotube composites metal oxide composites life support systems in-situ resource utilization high concentration sensitive detection gas sensor room temperature gas sensing functionalized nanotubes smartphone sensor chemiresistive sensor nanocomposite scrubber

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