I. Abstract of the Paper’s Core Research

• Aerosol-based one-step fabrication of a complete three-electrode integrated system, with no manual modifications throughout the process.

Silver chloride layer, carbon substrate, and nano-functional layer are fabricated via sequential aerosol direct writing, replacing the conventional manual drop‑coating process. This approach yields electrodes with uniform thickness and strong film adhesion; cross‑hatch friction tests reveal no delamination, and batch‑to‑batch device variability is significantly reduced.

• The performance of CNT- and graphene-modified electrodes differs significantly.

The CNT-modified electrode exhibits a 105-fold increase in active surface area, with a detection sensitivity of 20 μA·mM⁻¹; the graphene electrode achieves a signal-to-noise ratio of 51.2 dB, demonstrating superior anti-interference performance; the respective limits of detection for the two are 7.3 μM and 8.8 μM, and their response times are both 2.5–3 s.

• Stable, broad-line quantitative detection of hydrogen peroxide

In the 0–500 μM concentration range, the current exhibits a linear fit with an R² greater than 0.9, and the long-term cyclic voltammetry signals show minimal drift, making it suitable for continuous monitoring of aqueous environments and biological fluids.

• Flexible substrate–compatible conformal printing on curved surfaces

Kapton film is thin, lightweight, and flexible; its aerosol‑free mist can be used to fabricate sensing arrays on complex curved surfaces, making it well suited for wearable, non‑invasive sweat‑based biosensors.

• Digitally Rapidly Iterated Multi-Material Sensing Chip

CAD enables one-click switching between CNT and graphene printing layouts, with a single system compatible with conductive silver ink, carbon ink, and carbon‑nanotube ink, allowing rapid completion of parallel comparative experiments on two types of nano‑electrodes.

II. Complete Electrochemical Sensor Fabrication Process for Aerosol Spraying and Its Core Technological Advantages

(1) Complete three-electrode sensor fabrication process

• Kapton film is ultrasonically cleaned with ethanol to activate the surface and enhance ink adhesion.
• Aerosol-printed Ag/AgCl ink, cured at 125°C, was used to fabricate the working and reference electrodes.
• Print the carbon ink onto the substrate, then anneal at 175°C to form the working electrode and the counter electrode substrate.
• Switch between CNT-based aqueous ink and self‑prepared graphene‑composite ink to precisely modify the surface of the working electrode via aerosol deposition.
• Nano-modified layer, dried at a low temperature of 200°C;
• Cyclic voltammetry and chronoamperometric calibration tests for hydrogen peroxide were performed on the electrochemical workstation in PBS buffer.

(II) Five Core Process Advantages (Comparison of Spin Coating, Lithography, and Screen Printing)

• Fully automated, integrated multi-layer deposition—eliminating manual drop coating.

Nano‑modified layers enable precise, site‑specific aerosol direct writing, depositing functional materials exclusively on the working electrode area while eliminating human‑induced operational errors and significantly enhancing batch-to-batch consistency.

• Dual-carbon nano‑ink is universally applicable; a single production line is compared against two types of sensing solutions.

The device enables rapid switching between CNT and graphene suspensions, simultaneously fabricating two types of electrodes with high sensitivity and a high signal-to-noise ratio, thereby significantly enhancing material‑screening efficiency.

• Micron-scale precision patterning, with electrode dimensions digitally controllable.

Aerosol beam focusing and shaping on a 495 μm standard circuit, with the capability to scale down miniature sensing pixels as needed, enabling integration with microfluidic chips.

• Flexible curved-surface compatibility enables mass production of wearable biochemical test strips.

Non-contact spray distance of 3–5 mm; direct printing onto PI films and curved substrates, ideal for skin‑conforming, non‑invasive monitoring patches.

• Maskless green additive manufacturing eliminates the photolithography and etching steps.

No custom masks or chemical waste are required; sensor development can be carried out on a desktop‑level platform, lowering the barriers to entry for SMEs and research labs.

III. Five Core Technological Innovations of This Study

Innovation 1: A complete solution for aerosol-based all-printed three-electrode nano-modified electrochemical sensing.

A quantitative comparative framework for the differentiated sensing performance of CNTs and graphene

Innovation 3: In-situ Formation Mechanism of High-Specific-Surface-Area Nanolayers

Innovative Paradigm for the Fabrication of Flexible, Integrated Biochemical Sensing Test Strips

Innovative High-Throughput Testing Method for Continuous Multi-Ink Switching

IV. Existing Process Challenges and Corresponding Solutions

Challenge 1: The conventional drop-casting method results in uneven distribution of nanomaterials, leading to significant variability among individual sensors.

Challenge 2: Lithography is a complex process that can only be applied to rigid, planar substrates, making it impossible to fabricate flexible wearable electrodes.

Challenge 3: A single nanomaterial cannot simultaneously achieve both high sensitivity and robust noise resistance.

Challenge 4: The stepwise fabrication process for multilayer electrodes is cumbersome, and the coordinated operation of multiple pieces of equipment incurs high costs.

Challenge 5: Comparative testing of laboratory materials is time-consuming, and preparing multiple sets of samples is cumbersome.

V. Future Diversified Industrial Application Scenarios

• Wearable non-invasive sweat biochemical patch

• Rapid Test Strip for Field Water Quality Assessment

• Rapid quality inspection at food processing sites

• Microfluidic chip–integrated microsensor array

• High School Biochemical Sensing R&D Platform

Table I: AJP Process Parameters

Figure 1. (a) Rendered design of the sensor (using pseudocolors for enhanced visibility), illustrating the layered structure: A: Substrate; B: Silver–silver chloride traces and rare earth elements (RE); C: Tungsten (WE) and carbon (CE) layers; D: Nanofunctionalization of tungsten. (b) Shows the printed device architecture at different scales.

Figure 2. Experimental setup for detecting hydrogen peroxide. The sensor (orange) is housed in a carrier filled with PBS buffer, and the assembly is positioned above a stirrer. The Palmsens3 device acquires sensor data and transmits it to a laptop, where the data are subsequently stored and analyzed.

Figure 3. Electrode profiles measured at position p2 using a mechanical profilometer (from left to right: CE, WE, and RE). The figure shows the four measurement positions from which profile data were acquired (inset).

Table II Selected Potential Windows

Figure 4. Optical images (a) and (b) of the sacrificial electrode after scratch testing, obtained using the magnetic electrode (CE) and the resistive electrode (RE), respectively.

Figure 5. Potential window characterization tests for (a) a bare carbon electrode, (b) carbon nanotubes (CNTs), and (c) graphene-functionalized materials.

Figure 6. Voltammograms obtained using ferrous/ferricyanide for (a) a bare carbon electrode, (b) a carbon nanotube electrode, and (c) a graphene electrode.

Figure 7. Cyclic voltammograms (CV) normalized peak currents recorded every 2 minutes in a 6 mM ferrocyanide/ferricyanide solution (scan rate = 0.2 V/s), corresponding to the carbon nanotube‑functionalized electrode (blue), the graphene‑functionalized electrode (red), and the commercial SPE electrode (yellow, on the secondary y‑axis).

Figure 8. (a) CA response curves of graphene‑functionalized sensors upon the injection of 100 μM hydrogen peroxide at the time point indicated by the red arrow. The calibration curves obtained from each sensor are shown in (b), where the dashed lines represent the average fitting lines for carbon nanotube‑(blue) and graphene‑(red) functionalized electrodes, respectively.

Figure 9. Noise power spectral density (PSD) of carbon nanotube–functionalized sensors within a single concentration range.

Table III: Comparison of Different Studies in the Literature with the Detection Limit (LOD) and Sensitivity Values of This Device