I. Core Research Summary

• The corrosion failure mechanism of silver electrodes has been fully elucidated.

The cations and anions of the ionic liquid undergo complexation reactions with silver under positive and negative bias, respectively: at the anode, [Ag(TFSI)]–complex salts are formed, while at the cathode, adsorption of EMIM⁺ ions disrupts the silver film’s structure. With continued polarization, the silver electrode gradually dissolves, causing a sharp increase in the device’s off-state current and the rupture of conductive pathways, thereby rendering both the linear and saturation operating regions completely inoperative. Moreover, high-humidity conditions accelerate silver migration, further increasing the risk of short circuits.

• Single-layer insulation protection scheme

A thin insulating layer of Parylene‑C or crosslinked PVP is deposited on the silver electrode, preventing direct contact between the ionic gel and the metal and tripling the device’s corrosion‑resistance lifetime; however, the insulating layer reduces the gate capacitance, slightly diminishing the modulation capability.

• Structural Optimization Root-Cause Solution (Optimal Route)

The device layout was redesigned so that the aerosol is deposited only in the channel region, with the ionic gel patterned exclusively there, thereby completely avoiding the silver source and drain electrodes. Meanwhile, the silver-side gate was replaced with a PEDOT:PSS conductive polymer gate, entirely eliminating metal corrosion sources and precluding any electrochemical side reactions.

• High-performance, stable bipolar transistor

The optimized device exhibits an on/off ratio of 10⁵–10⁶, a subthreshold swing as low as 70 mV/decade, and negligible voltage hysteresis. Within the gate‑bias range of −0.5 to 1.2 V, it stably supports both electron and hole conduction. Moreover, after a continuous 2‑hour bias‑stress test, no performance degradation was observed, thereby addressing the limitations of conventional p‑type devices, which typically operate unipolarly and suffer from poor stability.

• Complete integrated aerosol manufacturing process

Carbon nanotubes and ionic gel dielectrics are both deposited layer by layer using a single aerosol‑based deposition system, with the entire process carried out in ambient air. The approach is compatible with both glass and flexible PI substrates and enables the scalable fabrication of logic gates and sensor arrays.

II. Core Technological Advantages of Device Fabrication via Aerosol Jet Printing

(1) Complete Aerosol Layered Preparation Procedure

• Substrate pretreatment and ALD deposition of a 10-nm hafnium oxide adhesion layer;
• Silver source–drain and side-gate electrodes fabricated by inkjet printing, followed by low-temperature sintering;
• Aerosol jet printing (PFIID) sorts semiconductor carbon nanotube channels, followed by toluene washing to remove the dispersant.
• There are two fabrication processes: (1) full‑coverage ionogel; and (2) localized channel‑printing ionogel (without contacting the silver electrode).
• An optional PEDOT:PSS layer can replace the silver-side gate, enabling fully printed transistors.

(II) Five Unique Process Advantages

• Direct Writing of Multilayer Functional Materials in a Single Step

Both carbon nanotube semiconductors and ion‑gel high‑capacitance dielectrics can be atomized and deposited using a single aerosol‑based deposition system, eliminating the need to switch between multiple printing platforms and thereby simplifying the configuration of flexible production lines.

• Graphical height is fully controllable, with support for layout customization and optimization.

The ion‑gel printing area can be precisely controlled, enabling an improved structure that “covers only the channel while isolating the silver electrodes,” thereby eliminating corrosion risks at the device‑design level.

• Wide ink compatibility, compatible with high-viscosity ion‑liquid gels.

Conventional inkjet printing is prone to clogging, whereas aerosol‑assisted ultrasonic atomization is well suited to high‑boiling ionic gel systems, eliminating nozzle drying and blockage and making it ideal for long‑term, large‑scale fabrication.

• Room-temperature air processing, no glove box required.

The entire printing process is carried out under ambient atmospheric pressure, eliminating the need for an inert, sealed chamber and significantly reducing the capital costs of building a pilot‑scale production line.

• Compatible with flexible substrates; low-temperature processing does not damage plastics.

The maximum processing temperature throughout the entire process is 150°C, ensuring that PI and PET flexible films do not undergo thermal deformation, making them suitable for the large-scale production of wearable and textile‑based electronic circuits.

III. Key Technological Innovations of This Study

Innovation 1: A comprehensive elucidation of the dual anodic–cathodic corrosion mechanism of silver electrodes in ionic gels.

Innovation 2: “Structural Isolation” – A Root-Cause-Oriented Architectural Optimization

Innovation: A Corrosion-Free Gate Alternative to PEDOT:PSS

Innovation 4: Achieving Highly Uniform, Fully Printed Ambipolar Carbon Nanotube Transistors

Innovation: Two parallel, industrially viable solutions

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: Direct contact between the silver electrode and the ionic gel leads to galvanic corrosion upon application of an electric current, resulting in rapid device failure.

Challenge 2: All‑coverage ionogel devices exhibit only unipolar p‑type transport, making it impossible to implement complementary logic.

Challenge 3: The insulating protective layer reduces the gate‑oxide capacitance, degrading subthreshold characteristics.

Challenge 4: In high-humidity environments, silver electro-migration is severe, leading to microshorts in the devices.

Challenge 5: Large-area aerosol printing often leads to gel edge misalignment, and occasional contact with the silver electrode.

V. Future Diversified Industrial Application Scenarios

1. Flexible wearable sensor array

2. All-Printed Flexible CMOS Logic Circuits

3. Smart Electronic Textiles

4. Low-Power Passive IoT Chip

5. Aerospace / Special Radiation-Resistant Flexible Circuitry

Figure 1. a) Absorption spectrum of PFIID‑sorted sc‑SWCNT ink; b) Schematic and optical image of an all‑printed side‑gate SWCNT thin‑film transistor with a dielectric layer made of printed ionogel, channel dimensions L = 30 µm and W = 600 µm; c) SEM image of the SWCNT network within the device channel; d) A set of transfer characteristics for the printed side‑gate SWCNT thin‑film transistor, measured at VDS = −0.1 V using an ionogel gate dielectric; e) Typical output characteristics as a function of VGS over the voltage range from +0.6 V to −0.8 V, in steps of −0.2 V.

Table 1. Average electrical parameters and standard deviations extracted from transfer‑characteristic data in the linear region (based on 10 devices): At VDS = −0.1 V, VTH, VON, SS, ΔVHYST, and µFE represent the threshold voltage, turn‑on voltage, subthreshold swing, hysteresis effect, and linear‑field-effect mobility, respectively; [a] The intrinsic mobility (µ0) and contact resistance (RC) were determined using the Y‑function method.

Figure 2. a) Normalized drain current as a function of time under continuous bias stress conditions (VGS = −0.8 V, VDS = −0.1 V), with a measurement duration of 30 minutes. The three red arrows indicate the moments at which optical images of the source/drain electrodes were acquired; b), c), and d) show optical images of the source/drain electrodes under bias stress at 0 s, 1200 s, and 1500 s, respectively.

Figure 3. Optical images of printed silver electrodes after 20 seconds of polarization at V = 2 V in a) ionic gel, b) pure ionic liquid, and c) pure PS–PMMA copolymer—where the anode and cathode correspond to the bottom and top electrodes, respectively; (d) Ag 3d XPS spectrum of the printed silver electrode, (e) N 1s XPS spectrum, and (f) F 1s XPS spectrum: (1) shows the pre‑polarization state; (2) shows the state after 20 seconds of polarization at 2 V in the pure ionic liquid (for the anode in case (2) and for the cathode in case (3)).

Figure 4. a) Linear polarization states at various VGS values under VDS = −0.1 V; b) Optical images corresponding to continuous polarization at VDS = −0.1 V and VGS = −1 V; c) Saturation polarization states at VGS = −0.4 V for different VDS values; d) Optical images corresponding to continuous polarization at VGS = −0.4 V and VDS = −1 V. The black-and-white markers on the electrodes indicate cathodic corrosion and anodic corrosion, respectively.

Figure 5. a) Continuous polarization characteristics in the linear region at VDS = −0.1 V and VGS = −0.9 V; b) Transfer characteristics at different time points (points 1 to 4) during continuous polarization under VDS = −0.1 V; c) Transfer characteristics at different time points (points 4 to 7) during continuous polarization under VDS = −0.1 V.

Figure 6. a) Schematic of a printed-side-gate SWCNT thin-film transistor employing parylene‑C as the protective layer (black arrows indicate ion migration into the parylene‑C layer); b) Transfer characteristics under VDS = −0.1 V for parylene‑C layers of varying thicknesses (thickness L = 30 µm, width W = 600 µm); c) Continuous polarization characteristics in the linear operating region at VDS = −0.1 V and VGS = −1.15 V, corresponding to different parylene‑C layer thicknesses.

Figure 7. a) Optical image of a fully printed side-gated SWCNT thin-film transistor, in which a single ion‑gel line partially covers the channel (length L = 190 µm, width W = 600 µm); b) Transfer characteristics of 20 devices at VDS = −0.2 V, for three channel lengths: L = 125 µm (7 devices), L = 165 µm (7 devices), and L = 190 µm (6 devices); c) Schematic cross-sectional view of the printed SWCNT thin-film transistor—where the effective channel length (LE) corresponds to the portion of the channel covered by the ion gel; RS/RD, RCNT, and RChannel denote the contact resistance between the source/drain electrodes and the single-walled carbon nanotube layer, the access resistance from the SWCNTs to the channel, and the channel resistance, respectively; d) Optical image of the printed SWCNT thin-film transistor after continuous polarization of gate G1 for 2 hours; e) Transfer characteristics after applying continuous polarization to gate G1 (VDS = −0.1 V, VG1S = −1.15 V); f) Transfer characteristics at VDS = −0.2 V, using two gates (G1 and G2), with and without continuous polarization (G1R and G2R).

Table 2. Average intrinsic mobilities (µ0) and contact resistances (RC) of the n‑type and p‑type branches in the transfer curves, extracted using the Y‑function method. LCNT (referred to as the carbon nanotube access resistance length) corresponds to the portion of the channel that is not covered by the ionic gel.

Figure 8. a) Optical image of a fully printed side-gate SWCNT thin-film transistor, in which a single ion‑gel line partially covers the channel; and a PEDOT device fabricated by inkjet printing, with PSS serving as the side‑gate electrode. b) Transfer characteristics of a PEDOT device (PSS side‑gate SWCNT thin‑film transistor) with channel dimensions L = 190 µm and W = 600 µm, measured at VDS = −0.2 V (including 10 devices). c) Typical output characteristics of a fully printed bipolar SWCNT thin‑film transistor employing PEDOT (with PSS as the side‑gate electrode). d) Characteristics of a PEDOT (PSS side‑gate) device under continuous polarization conditions (VDS = −0.1 V, VG1S = −1.15 V). e) Transfer characteristics at VDS = −0.2 V before (black curve) and after (2 hours post‑polarization) continuous polarization.