I. Abstract of the Paper’s Core Research

This study employs a silanization reaction to perform surface functionalization on Ti₃C₂Tₓ MXene, preparing three types of MXene composite powders modified with amino and thiol groups. These powders are formulated into aerosol‑specific inks using a mixed solvent system of ethanol, tert‑butanol, and DMF, with no additional additives. The microstructure, chemical bonding, ink dispersion stability, and aerosol‑forming quality of the powders are systematically characterized. The key findings are as follows:

Three Types of Organosilane–Controlled Modification Systems for MXene

APTES (amino), MPTES, and MPTMS (thiol) are grafted onto MXene layers via siloxane covalent bonds, with successful grafting confirmed by FTIR, XRD, and Raman spectroscopy. The amino groups are well-suited for biomolecule immobilization, while the thiol groups enable metal targeting and click‑chemistry modifications, allowing functional switching as needed.

Aid-free long-lasting stable aerosol ink

Throughout the process, no binders or dispersants are added; MXene’s solvent compatibility is enhanced solely through silane modification. Stored under sealed conditions at room temperature for 18 months, it exhibits no sedimentation and no oxidation, thereby fully addressing the issue of rapid degradation inherent in pristine MXene aqueous solutions.

Stable atomization and high-precision 3D layer-by-layer fabrication

The ink is compatible with ultrasonic atomization aerosol‑generation equipment, and the carrier‑gas/ sheath‑gas flow rates and printing speed have been optimized. Single‑layer lines are uniform with no ink breakage, enabling the fabrication of three‑dimensional MXene conductive grids through multilayer stacking; the line morphology is smooth, free of pores or agglomeration.

The modified MXene structure retains its conductive properties intact.

Silane modification induces only surface grafting, without disrupting the layered crystalline structure of MXene; the resulting thin film retains its high‑conductivity two‑dimensional transport properties and exhibits no significant degradation in electrical performance.

General low-cost synthetic route

The silane-modification process operates under mild conditions, uses readily available raw materials, and is easy to scale up. It is compatible with a variety of substrates, including alumina and flexible polymers, and is well-suited for large-scale aerosol production.

II. Complete Preparation Procedure for Silane-Modified MXene Aerosol Ink

MAX phase Ti₃AlC₂ was etched with hydrofluoric acid, washed with water, and centrifuged to obtain multilayer Ti₃C₂ MXene powder.

MXene is dispersed in ethanol, and APTES, MPTES, or MPTMS silane reagents are added separately; the silanization grafting is completed by stirring at room temperature for 48 hours.

The water–alcohol mixture is used to wash away unreacted silane, and the material is dried to obtain functionalized MXene powder.

A ternary solvent system comprising ethanol, tert-butanol, and DMF was used, with only modified MXene added to formulate a 10 mg/mL additive-free ink.

Optomec AJ300 aerosol deposition system, featuring a 150 μm ceramic nozzle and a substrate‑mounted temperature controller set to 100°C, enables layered printing of two‑dimensional patterns and 3D‑stacked microstructures.

SEM, TEM, XRD, Raman, and infrared spectroscopy were used to perform a comprehensive characterization of both the powder and the printed thin films.

III. Core Competitive Advantages of the Three‑Five Aerosol Process (Comparison with Inkjet, Spin Coating, and Vacuum Deposition)

Maskless Digital 3D Stereolithography

MXene three-dimensional networks can be stacked layer by layer, spin-coating yields only planar films, inkjet printing suffers from insufficient resolution, and vacuum deposition is prohibitively expensive.

Contactless, long‑range spraying compatible with irregular and flexible substrates.

The nozzle–substrate gap is adjustable, enabling uniform MXene deposition on curved surfaces, thin films, and ceramic substrates without mechanical compression that could damage the layered structure.

Site-specific deposition significantly reduces the consumption of expensive MXene materials.

Only the functional areas are coated with ink, resulting in significant waste of coating material across the entire substrate; this approach is well suited for small‑batch R&D of two‑dimensional materials based on precious metals.

The ink is compatible with a wide process window, ensuring stable, long-term continuous printing.

Modified MXene with no agglomeration at the nozzle ensures consistently uniform line widths during hours of continuous printing, eliminating the need for frequent cleaning of the atomization chamber.

Low-temperature molding does not damage the substrate’s thermosensitive material.

Printing at only 100°C for substrate drying ensures that PI, PET, and biodegradable films do not deform or carbonize under high temperatures.

IV. Five Core Technological Innovations of This Study

Innovation 1: Covalent Silane Modification of MXene in an Additive-Free Aerosol Ink System

Amino- or thiol-functionalized silanes are employed to modify MXene aerosol inks, completely eliminating the need for binders and dispersants and thereby removing post‑printing impurity‑related defects.

Innovative MXene slurry with ultra-long ambient‑temperature storage stability of 18 months

Silane isolates oxygen and water, inhibiting the oxidation‑induced delamination of MXene, thereby overcoming the conventional limitation of ink losing efficacy within just a few days and significantly reducing consumable waste.

Innovation: Three bifunctional groups enable customizable modification strategies.

Amino groups facilitate the immobilization of biosensing molecules, while thiol groups enable metal‑catalyzed functionalization; a single MXene substrate can be reconfigured to support multiple device applications.

Innovation 4: Mild Silanization–Based Low-Cost Scale-Up Synthesis Route

Room-temperature liquid-phase reactions, requiring neither high temperature nor high pressure, feature low equipment requirements and facilitate seamless scale-up from laboratory to production.

Innovative 5‑Pure MXene‑Based 3D Aerosol Additive Manufacturing Paradigm

Free of carbon or metallic fillers, it fully preserves the intrinsic electrical conductivity, adsorption, and catalytic properties of two-dimensional materials, making it well suited for high‑precision functional microdevices.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: Native MXenes are prone to oxidation, leading to short-term sedimentation and degradation of the ink, which prevents long-term storage.

✅ Silane covalent coating effectively isolates moisture, ensuring the ink remains stable at room temperature for 18 months, with no oxidative agglomeration of the layered structure.

Challenge 2: Conventional MXene inks require the addition of large amounts of binders, resulting in high impurity levels in the films and reduced conductivity.

✅ Silane modification enhances solvent dispersibility, with zero additives throughout the process, yielding pristine printed films and superior electrical performance.

Challenge 3: MXene slurries tend to agglomerate during atomization, leading to nozzle clogging during prolonged printing.

✅ Surface modification weakens layer stacking, ensuring uniform aerosol ultrasonic atomization and continuous printing without nozzle clogging.

Challenge 4: MXene-based devices exhibit limited functionality, making it difficult to integrate biological and metallic active materials.

✅Both APTES and MPTES functional groups can be selectively modified to anchor enzymes or metal nanoparticles, thereby enhancing sensing and catalytic performance.

Challenge 5: Spin coating and inkjet printing can only fabricate planar MXene films, making it impossible to create three-dimensional structures.

✅ Aerosol‑based, layer‑by‑layer 3D stacking creates a three‑dimensional porous network with a high specific surface area, enhancing both energy storage and the number of catalytic active sites.

VI. Future Diversified Industrial Application Scenarios

1 Flexible, High-Sensitivity MXene Gas/Biosensor

Impurity-free conductive sensing circuitry, with amino‑functionalized immobilization of biorecognition molecules, for sweat‑ and environmental‑based trace‑level detection patches.

2 Microscale 3D MXene Supercapacitors

Aerosol‑printed three‑dimensional conductive mesh for enhanced specific capacity and scalable fabrication of ultra‑lightweight, wearable energy‑storage devices.

3 Electrochemical Catalytic Microarray Electrodes

Thiol‑anchored noble‑metal catalysts, low‑energy water treatment, and microreactor chips for CO₂ reduction.

4 Electromagnetic Shielding Flexible Circuit

Large-area aerosol direct-writing MXene shielding layers, lightweight anti-interference films for foldable displays and wearable devices.

5 High-Throughput R&D Platform of the Two-Dimensional Materials Laboratory

Rapidly switch between silane‑modified variants, enable low‑cost printing of multiple MXene‑based functional devices, and shorten the material‑screening cycle.

Image and Text Guide

Figure 1. Schematic illustration of the silanization synthesis route for Ti₃C₂ MXene.

The Ti₃AlC₂ MAX phase is subjected to HF etching to remove the Al layer, followed by exfoliation to obtain multilayer or few-layer Ti₃C₂Tₓ MXene. Subsequently, three organosilanes—APTES (bearing –NH₂ groups), MPTMS/MPTES (bearing –SH groups)—are covalently grafted onto the MXene surface via silanization reactions, yielding Ti₃C₂‑APTES, Ti₃C₂‑MPTMS, and Ti₃C₂‑MPTES, respectively. The surface–OH/–O/–F termini are thereby masked by these organosilanes, which suppress MXene oxidation in water while introducing reactive functional groups suitable for biochemical conjugation and click chemistry.

Figure 2. Morphological and Structural Characterization Before and After Functionalization

(a) Schematic illustration of the silanization process; (b) SEM image of the accordion‑like etched layered structure of pristine Ti₃C₂Tₓ; (c) Significant morphological changes upon surface coating with Ti₃C₂‑APTES; (d, e) TEM/HRTEM images of pristine Ti₃C₂Tₓ; (f, g) TEM/HRTEM images of Ti₃C₂‑APTES; (h) SEM image of Ti₃C₂‑APTES along with elemental mapping of C, Ti, O, and N, where the uniform distribution of N confirms successful APTES grafting; (i) XRD pattern matches the standard peak of Ti₃C₂ (JCPDS 052‑0875), with reduced intensity and a slight shift in the characteristic peaks after functionalization. The particle size of pristine Ti₃C₂ is 8.02 ± 5.9 nm, whereas after functionalization it decreases to 4.56 ± 3, 6.15 ± 4.1, and 20.56 ± 12.3 nm, respectively.

Figure 3. Comparison of XRD, Raman, and FTIR spectra

(a) High-resolution powder XRD: After functionalization, the (002) peak is significantly weakened and shifted, confirming the intercalation of silane molecules into the interlayer space; (b) Raman spectra: The A₁g(Ti–Tx) and A₁g(C) peaks of Ti₃C₂Tₓ exhibit pronounced changes in the APTES/MPTES samples, whereas the MPTMS sample shows only minor shifts due to steric hindrance from the –OCH₃ group. The upward shift of the A₁g(C) peak indicates an increase in the interlayer spacing of the Ti layers; (c, d) FTIR: New peaks appear at 1031 cm⁻¹ (Si–O–Si) and 2966 cm⁻¹ (CH₂) in the functionalized samples, confirming successful grafting of the organosilane.

Figure 4. Preparation of composite inks and 3D-AJP-printed structures

(a) Synthetic route from Ti₃AlC₂ MAX bulk to the Ti₃C₂–organosilane composite ink; (b) Photograph of the composite ink (10 mg/mL, dispersed in ethanol/tert-butanol/DMF); (c) Schematic of Optomec AJ300 AJP printing: 150 μm ceramic nozzle, stand-off distance of 3 mm, carrier gas flow rate of 20–25 sccm, sheath gas flow rate of 50–55 sccm, stage temperature of 100 °C, printing speed of 2 mm/s, and ultrasonic atomization current of 600 mA; (d, e) Optical images of the “International” logo and a cartoon pattern printed on an alumina substrate; (f–i) Low- to high-magnification SEM images of the corresponding patterns, revealing sharp line edges and dense packing, with direct forming possible without binders or additives. The ink remains stable at room temperature for 18 months, showing no sedimentation or oxidation.