I. Core Research Abstract

Aerosol-compatible wide-viscosity ink system (40–600 cP) It overcomes the viscosity limitations of inkjet printing, enabling stable deposition of two types of carbon-based materials—graphene and carbon nanotubes. The print head–substrate gap is adjustable from 1 to 5 mm, ensuring optimal compatibility with uneven, porous, and rough aluminum substrates.

The single-pass printing achieves a maximum precision of 40 μm (using SWCNT water-based ink). , with edge roughness below 5 μm; low-speed printing promotes better spreading, while high-speed printing yields sharper lines, and the optimal printing speed varies significantly among inks formulated with different solvents.

Rough Substrate Full-Coverage Micropore Solution: Single‑pass printing results in voids and coating gaps; ten successive depositions can fully encapsulate substrate pores ranging from 1 to 15 μm, yielding a continuous, intact conductive and thermally conductive thin film.

The performance of ink systems varies significantly: Low-viscosity aqueous‑based graphene ink exhibits the highest crystallinity (with a very low D/G ratio), a sheet resistance of only 11 Ω/□, and superior electrical performance; DMF‑based organic ink yields dense films with numerous defects and poor conductivity; carbon nanotube ink offers the strongest coating capability, but residual surfactants elevate its resistivity.

Establish a standardized process database: The influence of nozzle velocity, sheath‑gas focusing ratio, and ink solvent type on line uniformity, porosity coverage, and the crystallinity of carbon materials was systematically elucidated, thereby establishing a reusable process window for fabricating carbon‑based circuits on industrially rough substrates.

II. Complete Preparation Procedure for Carbon Film Aerosols on Rough Substrates

Substrate Pre-treatment: Hydraulic leveling of the aluminum alloy die-casting substrate, followed by plasma electrolytic oxidation to form a porous, rough AlₓOᵧ surface layer;

Ink Formulation: Water-based graphene (high and low viscosity), DMF-based graphene, and single-walled carbon nanotube water-based inks—subjected to prolonged ultrasonic dispersion to eliminate agglomeration of carbon materials.

Optomec AJ300 Aerosol Equipment , pneumatic atomization, nitrogen sheath gas focusing, and a constant‑temperature substrate at 50°C to facilitate solvent evaporation;

Single-channel accuracy test: 250 μm fine nozzle, printing speed 0.5–3 mm/s, used to fabricate gradient‑spacing test lines;

Multi-channel full-coverage process : 3 mm-wide nozzle, 10 reciprocating passes, fully coating the substrate’s micro‑pores and surface irregularities;

Then allow to air-dry at room temperature. , characterized by SEM, Raman spectroscopy, XRD, and four-point probe measurements to assess morphology, crystallinity, and electrical conductivity.

III. Core Process Advantages of Three- and Five‑Layer Aerosol Jetting (Compared with Inkjet, Vacuum Evaporation, and Lithography)

Adjustable spray distance for conforming to uneven, rough substrates.

The nozzle is adjustable over a wide range of 1–5 mm,不受平面限制, and can be directly molded onto a PEO aluminum heat sink with micron‑scale pores. Inkjet printing at short distances is prone to scratching and misregistration.

Compatible with ultra-wide viscosity carbon-based inks

It can stably print high-viscosity pastes ranging from 40 to 600 cP; graphene and carbon‑nanotube inks with high solid content can both be atomized, whereas inkjet printing only supports diluents below 20 cP and yields inks with extremely low solid content.

Multi‑channel stacking enables complete encapsulation of the porous substrate.

Layered deposition progressively fills the substrate’s micropores, and single‑pass missed areas can be fully sealed through multiple printing passes; vacuum coating, however, struggles to penetrate recessed features.

Maskless digital direct writing; rapid prototyping of custom‑designed heatsink circuits.

CAD allows for the freehand design of thermal‑interconnect patterns, eliminating the need to fabricate photomasks and significantly reducing prototyping costs for custom‑shaped heat‑dissipation structures in small batches.

Low-temperature solution processing, without damaging the aluminum oxide insulating layer.

The entire process operates at a substrate temperature of only 50°C, eliminating the need for high‑temperature sintering. The PEO alumina insulating layer remains intact—without delamination or cracking—while preserving the substrate’s insulating properties.

IV. Five Core Technological Innovations of This Study

Innovation 1 Carbon-Based Aerosol Printing System for Industrial Rough Heat-Sink Substrates

Quantitative Differentiation of the Formulation Mechanisms of Innovative Two-Phase Water/Organic Dual-System Inkjet Printers

Innovation: A Three‑Stage Multi‑Layer Deposition Process Enabling Full‑Coverage Micropores

Innovation: Criteria for Matching Crystallinity and Electrical Properties of Carbon Materials with Ink Formulations

Innovative Standardized Process Database for Carbon Nanomaterials with Five Viscosity Ranges

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: The surface of industrial aluminum heat sinks is uneven and porous, leading to traditional printing issues such as missed areas and broken lines.

Challenge 2: Inkjet printing uses only low-viscosity, dilute carbon inks, which have low solid content, thin film thickness, and poor thermal conductivity.

Challenge 3: Printing on uneven substrates can easily cause scratches, and contact-based processes may damage the oxide insulating layer.

Challenge 4: In DMF, organic inks exhibit severe low-speed spreading, making it impossible to fabricate fine micro‑circuits.

Challenge 5: The lack of standardized printing parameters for rough‑surface carbon substrates forces development to rely entirely on trial and error.

VI. Future Diversified Industrial Application Scenarios

1 LED, thermal interface circuit for power device heat sinks

2 High-Power Electrical Equipment Thermal Management Films

3 Flexible/Rigid Hybrid Microcircuit Carbon-Conductive Leads

4 Electrochemical Microfluidic Carbon Electrodes

5. A Universal R&D Platform for Carbon-Based Additive Manufacturing in Higher Education Institutions

Table 1. Overview of Ink Formulations and Properties

Figure 1: (a) Photograph; (b) Top-view SEM micrograph; (c) Three-dimensional AFM topography of the PEO–aluminum block‑copolymer substrate. The two-dimensional distribution of the AFM data in (c) is shown in Figure S1.

Figure 2. (a–e) Top-view photographs of the entire AJP single-pass test pattern on a PEO‑aluminum block substrate (left), and optical microscopy top-view images of selected single-pass AJP lines on the PEO‑aluminum block at different magnifications (right), covering all five inks.

Figure 3. (a–e) Top-view SEM micrographs of five types of ink on a PEO‑aluminum substrate, acquired at different magnifications for a single AJP line.

Figure 4. (a–e) Raman spectra of all five inks measured on a single AJP pass over a PEO‑aluminum substrate.

Figure 5 shows, for the PEO–Al-block substrate, a top‑view photograph of the AJP pattern after ten scans (left), SEM micrographs at different magnifications (center), and XRD patterns (right), corresponding respectively to: (a) a graphene aqueous solution (low viscosity); (b) graphene in DMF containing polymer; and (c) an aqueous SWCNT solution. The XRD patterns highlight the diffraction peaks of the dominant phases, with the peak attributable to sodium cholate in (c) marked by an asterisk. Note that the XRD intensities are plotted on a logarithmic scale to emphasize the scattering signals originating from the nanocarbon deposition layer—only a few micrometers thick—on the surface of the Al‑block substrate, which itself has a thickness on the order of millimeters.

Figure 6 shows SEM cross-sectional micrographs of ten deposition cycles at different magnifications: (a) graphene deposition in a low-viscosity aqueous solution; (b) co-deposition of graphene and a polymer in DMF; (c) SWCNT deposition on a glass slide. The glass slides were manually cut to expose the cross‑sectional fracture surfaces of the AJP‑deposited layers; corresponding top‑view images are provided in Figure S4.

Figure 7. Top-view TEM micrographs of single-deposition processes at different magnifications: (a) graphene deposition in a low-viscosity aqueous solution; (b) co-deposition of graphene and a polymer in DMF; (c) SWCNT deposition on an SiN TEM membrane.

Table 2. Measured sheet resistance values of AJP samples with ten through-holes on PEO aluminum substrates.