Yes—but the “pencil” is a compressed carbon-nanotube material, not an ordinary graphite pencil, and the result was a laboratory ammonia sensor rather than a ready-to-use gas alarm. In a 2012 demonstration, researchers drew the material across electrodes on paper and measured how ammonia changed the device’s electrical current.
How does a nanotube pencil make a sensor?
The pencil-like material is made by compressing carbon nanotube powder into a form that can be rubbed or drawn across a surface. The research team deposited gold electrodes on paper, then drew the compressed material across the gaps between them. The carbon formed a conductive network connecting the electrodes.
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When the researchers flowed ammonia diluted with nitrogen past the device, the nanotube network’s electrical current changed. Measuring that change provided the sensor’s response. The fabrication process was solvent-free: sensing-material powders were mechanically abraded onto cellulose fibers.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11“Pencil” describes the material’s shape and the drawing action. Ordinary pencil graphite was not the sensing material in the demonstrated ammonia device.
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- MQ-2 gas sensor sensitive material used in the clean air low conductivity tin oxide (SnO2). When there is the environment in which the combustible gas sensor, conductivity sensor with increasing concentration of combustible gases in air increases.
- Quick response and recovery characteristics
- The dual signal output (analog output and TTL output)
- The analog output and increased with the increase of concentration, the higher the concentration higher voltage
- Has a very high sensitivity to sulfide, benzene vapor, smoke and other harmful gases
What gas did it detect, and how sensitive was it?
The reported demonstration tested ammonia (NH3). The 2012 paper reports detection at concentrations as low as 0.5 parts per million (ppm). For devices drawn on weighing paper, it reports a dynamic range of 0.5–5000 ppm and a theoretical detection limit of 0.36 ppm. These are distinct measures: 0.5 ppm was the lowest reported detected concentration, while 0.36 ppm was a theoretical limit, not a claim that this concentration was experimentally detected.
The study also reports a between-device coefficient of variance of 5 ± 1% for weighing-paper devices across ammonia concentrations of 0.5–80 ppm. That figure describes variability between devices in the reported study, not a guaranteed result for devices made elsewhere.
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- Double-sided panel design, with power supply indication and TTL signal output indication;
- With DO switching signal (TTL) output and AO analog signal output;
- The effective signal of TTL output is low level. (When the output low level signal light, can be directly connected to the microcontroller or relay module)
- Analog output voltage, the higher the concentration of the higher voltage.
Why did the choice of paper matter?
The researchers compared papers with different surface properties. Weighing paper performed best among the substrates they examined, based on signal-to-noise ratio, sensitivity, and theoretical detection limit. A contemporary account also noted better results on smoother paper than on rougher paper.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsThe substrate is part of the sensor, not just a convenient place to draw: its surface affects how the carbon material is deposited and how consistently the resulting network responds. The study also investigated single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes, and graphite. Its reported ammonia performance figures above are for the SWCNT devices; the fact that other carbon forms were examined does not establish equivalent performance for them.
Rank #3
- Working voltage: DC 5V; With signal output indicator light;
- With a long service life and reliable stability;Quick response and recovery characteristics;
- The analog output and increased with the increase of concentration, the higher the concentration higher voltage
- For harmful gas family, environment detection device, is suitable for the detection of the ammonia, aromatic compounds, sulfide, benzene vapor, smoke and other harmful gas, gas sensitive element concentration range: 10 to 1000ppm provides reference cases.
- Package Includes: MQ-2 Smoke Sensor,MQ-3 Alcohol Sensor,MQ-4 Methane Sensor,MQ-5 LPG Natural Gas City Gas Sensor,MQ-6 isobutane propane sensor,MQ-7 Carbon Monoxide Sensor Module,MQ-8 hydrogen sensor,MQ-9 Carbon Monoxide Combustible Gas Sensor,MQ-135 air quality detection sensor
Could the same approach detect other gases?
The paper and contemporary coverage discuss functionalizing sensing materials to adapt them to other analytes. That is a proposed extension, not a result established by the ammonia prototype. The demonstrated device should not be understood as detecting almost any gas, disease biomarkers, or chemical warfare agents.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is this a household gas alarm?
No. The study is a 2012 laboratory demonstration. It does not establish a certified household alarm, a consumer-ready product, or reliable performance in homes or other field conditions. Descriptions of the approach as potentially inexpensive, disposable, wearable, or adaptable refer to possible attributes or future uses—not proof that a tested product is available or safe for alarm use.
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- High Precision Performance - CO₂ accuracy of ±(40 ppm + 5% MV) and humidity accuracy of ±6%RH (typical) ensure reliable environmental data.
- Low Power Operation - Averages <0.4 mA at 5V with 1 measurement every 5 minutes, ideal for battery-powered or long-term monitoring applications.
- SCD41 CO2 Carbon Dioxide Gas Sensor Module Dual-Function Sensing - Simultaneously measures CO₂ (400–5000 ppm), temperature, and humidity for comprehensive indoor air quality monitoring.
- SCD41 CO2 Carbon Dioxide Gas Sensor Module Integrated I2C Interface - 2.54mm pitch pin interface (GND, VDD, SCL, SDA) enables easy connection to microcontrollers and development boards.
- SCD41 CO2 Carbon Dioxide Gas Sensor Gas Detect Module Temperature Humidity Sensor I2C Communication 2.4-5.5 V for Air Quality Monitoring
Lead author Katherine A. Mirica described the fabrication as simple enough not to require a clean room or highly trained technicians. That simplicity concerns making the sensor; it does not establish that the device is calibrated, certified, or suitable for protecting people from ammonia exposure.
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Quick Recap
Best Value
- MQ-8 module for hydrogen h2: SnO2 sensing element heated inside a metal mesh cap
- Analog output AO rises with gas concentration; digital output DO switches at a level you set
- 5V DC supply, 4-pin 2.54 mm header (VCC / GND / DO / AO), power and signal LEDs
- Onboard LM393 comparator and threshold potentiometer, so DO can drive a buzzer or LED with no extra code
- Two modules per pack; needs warm-up and your own calibration - a prototyping module, not a certified detector
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