J. Mater. Sci.: A Highly Sensitive and Selective Aniline‑Based Ammonia Sensor Fabricated via All‑Aerosol Jet Printing: A New Pathway for Low‑Cost, Low‑Power Gas Sensing
Product Introduction
Equipment Parameters
I. Abstract of the Paper’s Core Research
- All‑in‑one AJP device, with no multi‑step lamination.
A single device sequentially prints 50-μm-wide silver fork‑finger interdigitated electrodes and a double‑layer polyaniline sensing film, with a thickness of approximately 100 nm. The thin film uniformly and completely covers the electrode gaps, eliminating the need for the complex fabrication process that combines screen printing and inkjet deposition.
- Ultra-high sensitivity and ultra-low detection limit
It can stably detect 5 ppm of ammonia at room temperature, with a theoretical detection limit as low as 24 ppb; within the 5–1000 ppm concentration range, the resistance response exhibits linear fitting with an R² of 0.99, making it well suited for early warning of trace leaks in industrial settings.
- Excellent ammonia specificity and strong resistance to hydrocarbon interference.
At equivalent high concentrations of propane and isobutane, the response is only 0.06%–0.09% of that for ammonia, with virtually no cross‑interference, making it suitable for specialized monitoring of refrigerant pipelines.
- The humidity response recovery is significantly accelerated.
In dry environments, equilibrium is achieved within several hours; at typical indoor humidity levels of 30% or 50%, response time is approximately 1 minute and recovery time about 5 minutes, significantly enhancing on-site real-time detection efficiency.
- Ultra-low power consumption + Exceptional long-term operational stability
The operating voltage is only 50–100 mV, and the power consumption is at the microwatt level; after 6 consecutive days of cycling, the baseline remains stable with no drift, and the sensor performance shows no degradation after three months of storage at room temperature.
- Wide-temperature stable operating range
It can perform normal detection across a temperature range of 23–80°C, with only a slight reduction in sensitivity at high temperatures, thereby meeting the diverse temperature requirements of cold storage facilities and industrial workshops.
II. Complete Sensor Fabrication Process and Core Advantages for Aerosol Spraying
(1) Complete Integrated Printing Workflow
- Polyimide (PI) film is cleaned and dried, followed by plasma activation to enhance ink adhesion.
- Silver nanoparticle ink aerosol direct‑print interdigitated electrodes (finger width 50 μm, gap 65 μm), dried and cured at 120 °C;
- Switch to DBSA-doped PANI aqueous ink and print a double-layer circular sensing film.
- No additional modifications are required; the gas‑path test platform can be set up directly to perform performance calibration.
(II) Five Major Process Advantages (Comparison with Screen Printing and Inkjet Printing)
- Single‑equipment, full‑component molding eliminates the need to switch between multiple printing machines.
Eliminating the need for two separate processes—screen-printed electrodes and inkjet-printed sensing layers—the production line can fabricate a conductive–gas‑sensitive bilayer structure in a single step, significantly reducing fabrication time.
- Higher graphic resolution, with a minimum line width of up to 10 μm.
Inkjet printing has a minimum feature size of 30 μm, and screen-printing suffers from lower precision; in contrast, AJP can fabricate micron‑scale, densely packed interdigitated electrodes, thereby increasing the effective sensing area of the electrode and amplifying the detection signal.
- Compatible with wide-viscosity aqueous conductive polymer inks
The aerosol atomization is compatible with low-viscosity polyaniline dispersions, eliminating nozzle clogging issues and delivering enhanced long-term printing stability.
- Non-contact flexible curved-surface adaptation
A safe printing distance of 3–5 mm allows for the fabrication of both PI and irregularly shaped curved substrates, enabling the production of adhesive‑compatible flexible sensor patches.
- Digital rapid iteration, no need for custom screens or masks.
With CAD, electrode dimensions and sensor‑area sizes can be modified with a single click, enabling the rapid fabrication of multiple concentration‑gradient samples on the same day and significantly reducing R&D costs.
III. Five Core Technological Innovations of This Study
Innovation 1: Innovative Preparation of an All-Aerosol Integrated Polyaniline Ammonia Sensor
Innovative 2 DBSA‑doped PANI‑specific aqueous aerosol ink system
Innovation: A Novel Mechanism for Synergistic Acceleration of Sensing Response via Humidity Coordination
Innovative 4‑Electrode Ultra‑Low‑Power Flexible Gas‑Sensing Architecture
Innovative 5 Long-Term Stable Reversible Room-Temperature Sensing System
IV. Current Industry Challenges and Corresponding Solutions for Overcoming Them
Challenge 1: The conventional process requires two separate steps—screen printing and inkjet printing—resulting in numerous pieces of equipment and a complicated workflow.
Challenge 2: Pure polyaniline devices exhibit extremely slow recovery from dry‑environment exposure, making real-time monitoring impossible.
Challenge 3: Refrigerants such as propane and isobutane are prone to cross‑signal interference, leading to inaccurate detection.
Challenge 4: Traditional printed devices have high power consumption and require an external high‑power supply.
Challenge 5: The screen-printed pattern is rough, the electrode gap is large, and the detection sensitivity is insufficient.
V. Future Diversified Industrial Application Scenarios
- Refrigerant Leak Monitoring Patch for Commercial Cold Storage
- Smart Packaging Label for Food Freshness
- Online Monitoring of Agricultural Livestock and Poultry Housing Environments
- Wearable non-invasive breath-based kidney disease detection patch
- Portable gas detector for industrial chemical workshops
- University-level gas-sensing materials research and development platform
Figure 1. a Schematic illustration of the sensing membrane on the spiked electrode; b The prepared PANI-based ammonia gas sensor; c SEM image of the PANI thin film on the sensing device.
Figure 2. Surface morphology of the Pani film, along with EDS elemental carbon and silver maps corresponding to the IDE regions in (a), (c), and (e), and in (b), (d), and (f). The elemental mapping data were acquired from the boxed areas indicated in Figures (a) and (b).
Figure 3. Dynamic resistance transient characteristics of the Pani sensor. The inset shows the response curves under ammonia exposure at 5 ppm and 10 ppm.
Figure 4. Sensitivity of the Pani-based sensor at different ammonia concentrations.
Figure 5. Selectivity of the Pani-based ammonia sensor toward selected hydrocarbon refrigerants. Note that the concentrations of isobutane and propane were both maintained at a relatively high level of 1% (i.e., 10,000 ppm) to ensure detection sensitivity. The figure also includes response data for lower ammonia concentrations for comparative purposes.
Figure 6. Repeatability of the Pani-based sensor under dry conditions after continuous exposure to a 20 ppm ammonia environment for 140 hours (indicated by the dashed line).
Figure 7. Comparison of the sensor response of a Pani-based device to ammonia at different concentrations under varying relative humidities.
Figure 8. Effect of operating temperature on the sensor response under a fixed ammonia concentration of 50 ppm. For clarity, the time zero lines at each temperature have been offset.
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