I. Abstract of the Paper’s Core Research

This study uses micron‑scale commercial TiH₂ powder as the raw material, employing octylamine surface modification combined with wet ball milling to prepare a 56 nm‑stable TiH₂ nanoparticle dispersion. A conductive ink tailored for ultrasonic aerosol jet printing was then formulated by blending this dispersion with a low‑volatility cosolvent. High‑precision circuit patterning was achieved on glass and PI flexible substrates, with pulsed‑light instantaneous curing replacing high‑temperature furnace sintering. The ink’s atomization behavior, pattern resolution, thin‑film microstructure, and electrical properties were systematically characterized. The key findings are as follows:

Complete Process for the Preparation of TiH₂ Nanopowder

Commercial-grade coarse TiH₂ particles with a particle size of 1–10 μm were surface-modified with octylamine at 180°C, followed by wet ball milling in the presence of a polymeric dispersant, yielding nanoscale particles with an average hydrodynamic diameter of 56 nm. The resulting dispersion exhibits only slight settling upon prolonged standing and can be readily redispersed with gentle shaking, thereby meeting the stability requirements for ultrasonic atomization.

Aerosol Ink Formulation Optimization

Xylene serves as the primary solvent, with tetralin as a low‑volatility co‑solvent, blended at a 4:1 ratio to suppress droplet flight and prevent premature drying. The system is compatible with multiple nozzle sizes—110, 160, and 233 μm—and, under optimal process conditions, achieves a minimum feature width of 20 μm while maintaining continuous, stable printing for up to 5 hours with only minimal film‑thickness degradation.

High-temperature-free pulsed-light low-temperature curing technology

Single-pulse irradiation with xenon light at 1–10 J/cm² induces millisecond‑scale localized heating while keeping the overall substrate at low temperature, leaving the PI film undeformed. In the 7–9 J/cm² energy range, the film develops a continuous conductive network, with a sheet resistance stabilized at approximately 150 Ω/□. Multi‑pulse treatment densifies the film, further reducing its resistivity.

Microscopic and Chemical Properties of Thin Films

After photocuring, the TiH₂ particles sinter and interconnect, forming a highly porous structure. FTIR confirms the complete decomposition of the organic dispersant, while XRD retains the titanium hydride phase, eliminating the need for full dehydrogenation and metallization, thereby balancing electrical conductivity with the corrosion‑resistant properties of the titanium matrix.

Core Competitive Advantage Through Material Differentiation

Compared with silver inks: superior resistance to sulfidation and chloride‑ion corrosion, and enhanced biocompatibility; compared with copper inks: no rapid oxidation in ambient air; compared with high‑temperature titanium pastes: can be low‑temperature processed on flexible plastic substrates, making it well suited for wearable and implantable devices.

II. Complete Preparation and Printing Process of TiH₂ Aerosol Ink

Powder modification: Under argon atmosphere, TiH₂ powder is modified by heating with octylamine at 180°C, followed by centrifugal washing to remove free ligands.

Wet ball milling: Modified powders, Solsperse dispersants, and dimethylsolvent are subjected to high-energy ball milling to achieve nanoscale particle sizes.

Ink formulation: The ball-milled dispersion is mixed with tetralin at a ratio of 4:1 to formulate an ultrasonic‑atomized, low‑viscosity nano‑ink.

Aerosol printing: Ultrasonic atomization at 30–33 V, with a carrier gas flow of 5–15 sccm and a sheath gas flow of 5–80 sccm; the substrate is maintained at a constant temperature of 60°C. Multi‑specification nozzles are used to fabricate 20 μm‑wide precision lines.

Pulsed Light Curing: Vacuum, air, or hydrogen atmospheres are all compatible; a single-pulse gradient energy irradiation of 1 ms is employed, with multi-pulse processing to optimize film densification.

Complete characterization: DLS, SEM, XRD, and FTIR were used to analyze the powders and thin films; four‑probe measurements determined the sheet resistance, while an optical profilometer was employed to characterize the line width and film thickness.

III. Five Core Process Advantages of TiH₂ Line Fabrication via Aerosol Jet Printing

Ultra-high micrographic precision of 20 μm, compatible with miniature MEMS electrodes.

The airflow‑focused beam delivers a stable output of ultra‑fine lines, meeting the precision wiring requirements of biochips and microelectrochemical sensors.

Gentle, all‑process manufacturing ensures non‑destructive processing of flexible PI film.

No prolonged thermal curing above 200°C is required; millisecond pulsed light raises the temperature only locally in the thin film, ensuring compatibility with a wide range of flexible polymer substrates.

Expansion of material systems, breaking free from reliance on precious metals.

TiH₂ is abundant and significantly cheaper than silver and gold, while also possessing the intrinsic corrosion resistance and biocompatibility of titanium.

Long-term stable atomization with excellent production‑line consistency.

The ink exhibits excellent dispersion stability; during 5 hours of continuous printing, the film thickness shows only a slight reduction, thereby decreasing the frequency of production-line shutdowns for maintenance.

Non-contact conformal deposition, direct writing of curved-surface bio-devices

Adjustable spray distance enables integrated molding of irregular-shaped flexible patches and curved surfaces of miniature implantable devices.

IV. Five Core Technological Innovations of This Study

Innovation 1: A complete preparation process for octylamine-modified, ball-milled nano TiH₂.

Addressing the challenges of poor atomization and particle agglomeration associated with micron-sized titanium hydride, we have obtained an air-stable, nano-dispersed feedstock.

Innovative 2‑component low‑volatility dual‑solvent aerosol ink system

The tetrahydronaphthalene blend inhibits droplet evaporation during flight, significantly enhancing long-term print uniformity.

Innovative Three-Pulse Light–Driven Transient Curing of Titanium-Based Thin Films: A Novel Approach

It replaces conventional high‑temperature vacuum sintering above 800°C, enabling the fabrication of titanium conductive patterns on plastic substrates.

Innovative Controllable Fabrication Method for High-Porosity Ti Conductive Thin Films

Single-pulse porous and multi-pulse dense dual morphologies are tunable, each tailored to meet the distinct requirements of catalysis and sensing.

Innovation: A New Paradigm of Non‑Precious Metal–Based Titanium‑Based Aerosol Conductivity

Break the monopoly on silver and copper inks, and pioneer a new frontier in corrosion-resistant, biocompatible printed conductive materials.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: Conventional titanium powder particles are coarse, making ultrasonic aerosol atomization impossible.

✅ Surface modification with octylamine combined with high-energy wet ball milling yields nanoparticles as small as 56 nm, enabling continuous atomization without nozzle clogging.

Challenge 2: Titanium-based materials require sintering at ultra-high temperatures, while flexible substrates are highly susceptible to carbonization and deformation.

✅ Millisecond pulsed light local irradiation with overall substrate cooling; compatible with both PI and PET.

Challenge 3: Commercial silver inks are prone to corrosion and failure due to halide ions in seawater and sweat.

✅TiH₂ thin films exhibit strong chemical inertness on titanium substrates, resisting corrosion by acids, bases, and halogens, making them well-suited for humid biological environments.

Challenge 4: Copper nanoparticle ink undergoes rapid oxidation when stored in ambient air, leading to degradation of device performance.

✅ The titanium hydride system is air-stable, eliminating the need for inert encapsulation and reducing device packaging costs.

Challenge 5: Conventional titanium-based pastes can only be extruded into thick films and cannot achieve micron‑scale precision printing.

✅ Aerosol airflow focusing enables 20 μm ultra-fine lines, suitable for high-precision fabrication of microchips.

VI. Future Diversified Industrial Application Scenarios

1 Implantable/Wearable Biosensing Electrodes

Titanium-based materials exhibit no cytotoxicity and are suitable for flexible circuits subjected to sweat exposure and in vivo microelectrochemical sensing.

2 Miniature Sensors for Marine Corrosion Environments

Marine water quality monitoring; corrosion-resistant conductive microelectrodes for underwater micro‑sensors.

3 Porous Functional Electrodes for Electrocatalytic Reactions

A high‑specific‑surface‑area porous conductive layer in photo/electrocatalytic devices enhances the number of catalytic active sites.

4 Low-Cost Flexible Electrochemical Detection Chip

A disposable microfluidic electrode for rapid in vitro biochemical screening, replacing expensive silver paste.

5 High-Temperature, Corrosive-Environment MEMS Microdevices

Miniature conductive interconnects for industrial high-temperature gases and corrosive environments.

Image and Text Guide

• (a) pXRD : After treatment with octylamine (ON), the diffraction peak matches the TiH₂ reference (PDF 00-025-0982) with no significant change; following wet ball milling, the peak broadens—indicating grain refinement—and Scherrer analysis of the peak at 2θ = 34.9° yields an average crystallite size of approximately   157±20 nm 。
• (b) DLS : The average hydrated diameter of the ball-milled dispersion is approximately  56 nm The polydispersity index (PDI) is 0.17, indicating a narrow unimodal distribution; the particle sizes before and after ON treatment are similar.
• Explanation of Differences : pXRD provides the crystallite size, while DLS fits the hydrated particle size assuming a spherical shape; the discrepancy between the two values is normal.

• (a) Raw TiH₂ powder : Commercial powder, with a typical particle size of approximately 2–10 μm.
• (b) Powder treated with octylamine (ON) : The surface is pre-functionalized with an active surfactant, and its morphology remains largely unchanged.
• (c) TiH₂ nanoparticles after wet ball milling : Size reduced to approximately   50–400 nm (Lamellar, <100 nm), with a significant reduction in particle size.
• Key property The resulting nanoparticles are air-stable, easily dispersible, and resistant to agglomeration; after prolonged storage, they exhibit slight sedimentation, which can be readily redispersed with gentle shaking.

• (a)   Photograph of the printing nozzle during the patterning process (carrier/sheath gas: dry air; cartridge temperature maintained at 17 °C; ultrasonic atomization at 30–33 V).
• (b)   Dense lines on a polyimide substrate (optical microscopy) — can serve as conductive traces.
• (c)   High-resolution lines on a glass substrate—resolution can be as fine as   20 μm (110 μm nozzle).
• Ink formulation The dispersion is mixed with the low-volatility co-solvent tetralin at a 4:1 v/v ratio to slow down droplet evaporation within the print head.

• (a)   At a fixed focusing ratio, the film thickness increases approximately linearly with the aerosol flow rate, and the deposition rate is about…   4.7×10³ μm³/s/sccm ; there exists approximately   6 sccm deposition threshold , below this flow rate, deposition is virtually nonexistent.
• (b)   Under three nozzle diameters (233/160/110 μm), the line resolution varies with the focusing ratio (sheath gas:carrier gas); the solid line represents the theoretical estimate. The 110‑μm nozzle achieves the finest line width on both glass and polyimide substrates.   20 μm   Resolution.
• Consistency : After 5 hours of continuous printing, the film thickness decreases by approximately 50% (due to reduced ink volume and diminished atomization), but a continuous printing duration of 5 hours is already excellent for AJP.

• (a,b) As-printed : Black appearance, with a uniform microstructure composed of TiH₂ nanoparticles and a polymer binder.
• (c,d) After photon curing (IPL cured) : It transforms into a gray film with a metallic luster; SEM reveals Porous, with a high specific surface area Microstructure: primary particles are sintered into a continuous network.
• Causes and Significance : The porosity arises from the escape of gases generated by the decomposition of dispersants, ligands, and TiH₂ upon rapid photon heating; this high‑specific‑surface‑area morphology, in turn, is advantageous for the electrochemical stability and biocompatibility of titanium‑based materials in applications such as energy storage, catalysis, sensing, and biomedicine.

• (a) FTIR : Before curing, distinct stretching and bending peaks of the dispersant are observed at 2800–3000 cm⁻¹; after curing, these peaks disappear (leaving only weak peaks attributable to the polyimide substrate)—indicating that the organic components have been removed.
• (b) pXRD : After curing, the characteristic peak of TiH₂ (PDF 00-025-0982) remains but has weakened—indicating that some TiH₂ persists.
• (c) Electrical Engineering : In the pulse energy range of 3–7 J/cm², the initially non-conductive printed state transitions to a conductive state; 7–9 J/cm²   Time slice constraint   200 Ω/□ ; Multi-pulse curing can further reduce it to approximately   150 Ω/□   and form a denser thin film.
• Comparison Thermal curing requires 800 °C (in N₂) to achieve comparable performance, whereas photonic curing can be carried out on flexible polyimide and is independent of the curing atmosphere (H₂/N₂, vacuum, or air).