I. Core Research Summary

• In-situ self-reduced MXene/Ag composite filler, enabling the construction of a multi‑interface microwave absorption system.

MXene flakes are uniformly coated with silver nanoparticles approximately 21 nm in size. After aerosol‑based layer-by-layer deposition, the resulting composite film develops a large number of heterojunctions within its structure, significantly enhancing electromagnetic wave absorption through multiple reflections and losses, thereby overcoming the limitation of pure silver films that rely solely on reflection for shielding.

• Micron-level, high-precision, ultra-thin conformal printing with a minimum film thickness of 500 nm.

Aerosol printing achieves a resolution of up to 10 μm, with precise control over the number of printed layers to enable thicknesses ranging from 0.5 to 7 μm. A mere 500-nm‑thick film delivers electromagnetic shielding efficiency exceeding 99%, with a shielding effectiveness per unit mass (SSE/t) as high as 52,591.4 dB·cm²/g, while adding only 0.9 mg of weight—demonstrating an unprecedented level of lightweight design.

• Excellent bend-resistant mechanical stability

The PI‑based printed circuit exhibits a resistance increase of only 4.8% after 1,000 180° flexural cycles; MXene flakes serve as a stress‑buffering scaffold, suppressing crack formation in the silver film and enabling robust performance under the long‑term deformation typical of wearable and sports‑related devices.

• Uniform deposition over the entire surface of complex curved shapes

Aerosol technology offers a safe spray distance of 1–5 mm, eliminating the need for substrate alignment. It can form a continuous, seamless coating on hemispherical, corrugated, eggshell‑shaped, and other complex curved surfaces, with no gaps and uniform thickness—addressing the key limitation of electroplating and sputtering, which are restricted to planar processing.

• Empirically validated electromagnetic shielding across multiple scenarios

The thin film can block wireless‑charging coupling radiation, shield NFC access‑control signals, and significantly reduce the electric‑field radiation intensity of chargers—from 660 V/m to 68 V/m—making it highly valuable for applications in drones, flexible circuits, and portable electronics.

II. Complete Preparation Process Flow and Core Technological Advantages of Aerosol Spraying

(1) Complete AJP Preparation Process for the Shielding Film

• LiF/HCl etching of MAX phases yields few-layer MXenes, while in-situ reduction in silver nitrate solution produces MXene/Ag composite powders.
• A ternary mixed solvent system of isopropyl alcohol, water, and ethylene glycol is used to disperse composite fillers; this dispersion is then blended with commercial silver ink to yield a stable aerosol ink.
• Anomalous-base ultrasonic cleaning, decontamination, and drying, equipped with a three-axis aerosol‑printing platform;
• Ultrasonic atomization of mixed inks, sheath‑gas focusing of a micro‑mist beam, and CNC‑controlled conformal deposition of shielding circuits along curved surfaces;
• At 200°C under vacuum, the solvent is completely evaporated, yielding a dense yet porous MXene/Ag–Ag composite shielding film.

(II) Five Core Processes (Comparison of Electroplating, Magnetron Sputtering, and Screen Printing)

• Conformal, dead‑zone‑free deposition on curved surfaces

Non-contact mist‑beam spraying maintains an adjustable, safe distance between the nozzle and the substrate, enabling complete film formation on complex structures such as concave–convex surfaces, curved shapes, and tubular components. In contrast, vacuum coating and electroplating are constrained by chamber geometry and cannot process irregularly shaped parts.

• Ultra-thin, high-precision, controllable forming

The deposition thickness of a single layer is at the nanoscale, and the film thickness can be precisely controlled by adjusting the number of printed layers. The thinnest shielding layer achievable is 500 nm, with line resolution down to 10 μm, while screen printing can achieve a minimum line width exceeding 100 μm.

• The ternary solvent system suppresses coffee-ring formation and overspray.

Ethylene glycol modulates the solvent evaporation rate, ensuring uniform spreading of the atomized droplets, with no edge bleeding or annular particle buildup. The resulting film is dense and smooth, exhibiting excellent consistency in shielding performance.

• Low-temperature, mild sintering; flexible substrates remain undamaged.

At 200°C under vacuum sintering, PI, PET, and various polymeric flexible substrates do not deform at high temperatures, making them suitable for wearable applications and shielding processes in flexible printed circuit boards.

• On-demand localized deposition, significantly reducing precious metal consumption.

Only the device’s shielded areas require ink coating, eliminating the need for full‑area plating. This significantly improves the utilization of silver and MXene consumables, enabling low‑cost, rapid prototyping for small batches.

III. Five Core Technological Innovations of This Study

Innovation 1: Aerosol-compatible formulation for in-situ self-reduced silver–MXene composite ink

Innovation 2: Aerosol Direct Writing for Constructing Multi‑Heterogeneous Microwave Absorbing Structures

Innovative 3‑layer ultra-thin, lightweight system with high specific shielding effectiveness

Innovative 4-MXene Stress-Buffering, Bend-Resistant Composite Film Structure

Innovation 5: Fully Digital Integrated Shielding Manufacturing for Complex Curved Surfaces

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: MXene nanosheets tend to agglomerate easily, leading to nozzle clogging during ink atomization and resulting in rough printed surfaces.

Challenge 2: Bending of the pure silver printed film induces microcracks, leading to degradation in both conductivity and shielding performance.

Challenge 3: Conventional coating processes are limited to planar substrates; they cannot achieve uniform film deposition on irregular curved surfaces.

Challenge 4: Ultra-thin metallic films rely solely on reflection for electromagnetic wave absorption, resulting in poor absorption performance and weak low-frequency shielding.

Challenge 5: Vacuum plating equipment is expensive, and small‑batch R&D entails high costs and long lead times.

V. Future Diversified Industrial Application Scenarios

• Lightweight Electromagnetic Protection for Drones

• 5G Wearable Flexible Electronics

• Portable medical diagnostic device

• Consumer Electronics Wireless Charging Module

• Precision Sensors and RF Components

Figure 1. Preparation strategy for MXene/Ag–Ag conformal thin films. (a) Schematic illustration of the synthesis of MXene and MXene/Ag. (b) Schematic diagram of the reaction mechanism for fabricating MXene/Ag–Ag conformal thin films via AJP.

Figure 2. Morphological and structural characterization of MXene/Ag. (a) XRD patterns of MXene and MXene/Ag; (b) XPS spectra of MXene/Ag; (c) Ag 3d spectrum; (d–e) TEM images of MXene/Ag; (f) EDS map of MXene/Ag.

Figure 3. Influence of the solvent system on AJP performance. (a) Schematic illustration of the solvent‑system effect. Optical microscopy images of AJP lines formed on a silica surface using MXene/Ag dispersions with and without ethylene glycol are shown in (b, c) and (e, f), respectively; (d, g) present SEM images of the printed inks with and without ethylene glycol, respectively.

Figure 4. (a) Traces of varying line widths printed using silver (Ag), MXene–Ag, and MXene/Ag–Ag inks. (b) External morphology and cross-sectional profile of an MXene/Ag–Ag thin film. (c) Surface roughness of films with different thicknesses prepared using silver, MXene–Ag, and MXene/Ag–Ag inks. (d) Resistance‑change curves for traces printed with silver, MXene, and MXene/Ag–Ag inks after 1,000 cycles at a bending angle of 180°.

Figure 5. SEM cross-sectional images of films with different thicknesses prepared using silver, MXene–Ag, and MXene/Ag–Ag inks.

Figure 6. (a) Silver film, (b) MXene–Ag composite film, and (c) MXene/Ag–Ag composite film: electromagnetic interference shielding performance across the entire X-band; (d) average electromagnetic interference shielding effectiveness (SE) for films of different thicknesses; (e) surface electrical conductivity (SEA) and surface resistivity (SER) of the films; (f) shielding effectiveness-to-thickness ratio (SE/t) and surface impedance-to-thickness ratio (SSE/t); (h) a comparison between the shielding effectiveness-to-thickness ratio of the films prepared in this study and that of previously reported materials; (i) a conformal MXene/Ag–Ag composite film deposited on complex surfaces.

Figure 7. (a) High-magnification surface micrographs of the silver thin film, (b) the MXene–Ag thin film, and (c) the MXene/Ag–Ag thin film; (d) high-magnification cross-sectional micrographs of the silver thin film, (e) the MXene–Ag thin film, and (f) the MXene/Ag–Ag thin film.

Figure 8. Schematic illustration of the electromagnetic interference shielding mechanism of MXene/Ag-Ag isodense films.

Figure 9. (a) Shielding performance of the MXene/Ag–Ag film against electromagnetic interference (EMI) between a wireless charger and a smartphone; (b) Digital images showing the change in EMI intensity before and after using the MXene/Ag–Ag film.