I. Abstract of the Paper’s Core Research

This study has established a 3D aerosol jet printing system tailored for oxide ceramics, developed low‑binder ceramic nano‑inks, and systematically investigated the effects of substrate temperature, droplet spacing, and ink solid content on the formation mechanisms of three‑dimensional self‑supporting structures. We successfully fabricated single‑material, dual‑material, and hybrid ceramic microarchitectures, and validated their functionality in two key applications: photocatalysis and biosensing. The core findings are as follows:

Low-Binder-Specific Ceramic Aerosol Ink System

Commercial ZnO/ZrO₂/TiO₂/Al₂O₃ nanodispersions contain less than 0.86 wt% organic additives, significantly lower than the 7–10 wt% binder content typically found in metal inks. The solvent evaporates rapidly upon droplet formation, resulting in a densely packed green‑body microstructure and substantially reducing sintering shrinkage at its source.

Support-free freeform fabrication mechanism

Aerosol micrometer‑scale droplets are precisely focused by a sheath gas; upon impact with a high‑temperature substrate, the solvent evaporates instantaneously, and surface tension drives layer‑by‑layer self‑assembly, enabling the fabrication of tilted trusses, high aspect‑ratio microcolumns, and helical spirals without any external support. The minimum feature size achievable is 20 μm, while individual components can reach centimeter scale, with controllability spanning five orders of magnitude in size.

Extremely low sintering dimensional deviation

After sintering at 950°C, the linear shrinkage is only 3.8±1.0%, the area shrinkage is 8.0±2.2%, and the volumetric shrinkage is 11.5±2.4%—all significantly lower than the 20%–50% shrinkage typically observed in photopolymerization and extrusion‑based additive manufacturing. Moreover, the CAD‑designed geometry exhibits excellent dimensional accuracy, closely matching the physical part.

Multi-material integrated molding capability

Supports partitioned printing of ZnO–ZrO₂ and ZnO–TiO₂ bimaterial micro-pyramids, and can also fabricate homogeneous composite lattices by blending three ceramic materials, with seamless interfacial transitions and clearly defined EDX elemental distribution profiles.

Validation of Two Major High-Performance Functional Components

① Three-dimensional ZnO micro‑lattice photocatalysis: under identical mass conditions, the degradation efficiency of methyl orange is enhanced by 400%, while its large specific surface area and porous structure facilitate the adsorption and decomposition of pollutants.

②3D ceramic biosensing electrode: achieves a detection limit as low as 0.0193 fM for the Her2 breast cancer biomarker, delivers rapid signal response within 22 seconds, and enables stable identification of samples at extremely low concentrations.

II. Complete Preparation Process for 3D-AJP Ceramics

Ink formulation: The ceramic nano‑water dispersion is diluted as needed to solid contents of 8, 13, or 20 wt%; the composite ink undergoes multiple centrifugation steps to replace the solvent and eliminate precipitates.

Plasma cleaning of the alumina substrate; print platform temperature control range: 25–100°C.

Optomec AJ300 aerosol deposition system, featuring a 150 μm ceramic nozzle, with nitrogen as both carrier and sheath gas for synergistic focusing; supports CAD‑imported point‑array, spiral, and pyramidal 3D trajectories.

Layer-by-layer additive manufacturing without support structures, with the tilt angle of microcolumns controlled by the droplet spacing.

The green body was sintered in a tube furnace at 950°C for 6 hours under isothermal conditions, yielding a porous ceramic skeleton with nanoparticle neck‑to‑neck bonding.

SEM, FIB, XRD, an electrochemical workstation, and a photocatalytic system were employed to perform comprehensive characterization of morphology and performance.

III. Core Advantages of 3D Ceramic Technology for Three- and Five‑Axis Applications (Comparison of Extrusion, Photocuring, and 2PP)

Ultra-low sintering shrinkage, with precise and controllable dimensions.

With an extremely low binder content, the sintered parts exhibit only 2–6% shrinkage, eliminating the need for repeated dimensional compensation and significantly reducing prototyping and rework costs.

Fully unsupported freeform fabrication, with complex microstructures manufactured at the touch of a button.

Tilted trusses, interwoven spirals, and multi‑level lattice structures eliminate the need for sacrificial layers, thereby obviating post‑processing steps such as demolding, cleaning, and support removal.

Cross-scale compatibility, micrometer-level detail + Centimeter-scale components are integrally formed.

With minimum feature sizes of 20 μm, the overall structure can reach centimeter-scale dimensions, bridging the dimensional gap inherent in conventional ceramic fabrication techniques.

Seamless multi-material integration on a single device

Different functional ceramics can be printed within the same microstructural zone without retooling, enabling rapid prototyping of composite catalytic and sensing devices.

Lower equipment barriers and high cost-effectiveness for small-batch R&D.

No need for expensive, integrated equipment such as UV lasers or high-temperature sintering; a desktop‑level aerosol system can readily fabricate ceramic three‑dimensional microstructures.

IV. Five Core Technological Innovations of This Study

Innovation 1: Complete Formulation for Low-Binder Ceramic Aerosol Ink

Significantly reduces the proportion of organic additives, addressing the issues of substantial shrinkage and cracking during sintering in conventional ceramic printing, while simultaneously ensuring both atomization stability and green‑body density.

Innovation 2: A Novel Mechanism for Self-Assembled Formation of Fog Droplet Surface Tension

The study reveals the synergistic stacking mechanism of rapid evaporation on high-temperature substrates and droplet surface interactions, and establishes a quantitative process window that correlates droplet spacing, temperature, and micropillar tilt angle.

Innovative 3D additive manufacturing paradigm for low-shrinkage, high-precision ceramics

Overcoming the major challenge of high deformation in conventional ceramic printing, this approach achieves near‑perfect dimensional consistency between design and final part, enabling standardized, large‑scale fabrication of precision microarrays.

Innovative 4-Partition Heterogeneous Ceramic Integrated Direct-Writing Technology

Single‑process, stepwise deposition of multiple oxides yields interfaces free of delamination and doping, enabling the fabrication of custom catalytic–sensing integrated microdevices.

Innovation: Dual-Scenario Engineering Validation of a Multi-Functional Ceramic Device

3D-AJP ceramic lattices are simultaneously applied to photocatalytic degradation of wastewater and ultrasensitive tumor biomarker detection, thereby bridging the gap between materials development and practical applications.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: The extruded, photocurable ceramic slurry has a high binder content, resulting in significant shrinkage during sintering and cracking of the components.

✅ Specialized low‑additive ceramic ink; the green body exhibits dense particle packing, with sintering linear shrinkage kept below 6% and no visible cracks.

Challenge 2: Complex inclined and helical 3D ceramics require support structures during printing, and post-processing can easily damage the microstructure.

✅ Aerosol droplets solidify instantaneously, self‑supporting layer by layer through surface tension, enabling support‑free fabrication across all material categories.

Challenge 3: Current ceramic 3D printing is limited to single-material fabrication, and the production of composite components requires multiple processing steps.

✅ Time‑resolved switching of ceramic inks enables the deposition of functional materials such as ZnO and ZrO₂ within the same lattice‑defined regions, resulting in strong interfacial bonding.

Challenge 4: The scale of forming is highly polarized—either only nanoscale thin films or centimeter‑scale bulk components—with no cross‑scale microstructural solutions.

✅20 μm micro‑struts to centimeter‑scale monolithic integration, with multi‑level porous lattices fabricated in a single step.

Challenge 5: The fabrication process for ceramic micro‑catalysts and sensing elements is lengthy, leading to slow R&D iteration.

✅ Digital maskless direct writing allows for rapid prototyping by simply modifying the CAD design, significantly shortening the material‑screening cycle.

VI. Future Diversified Industrial Application Scenarios

1 Photocatalytic Microreactor for Industrial Wastewater

High‑surface‑area three‑dimensional ZnO lattice, a compact modular system for degrading organic dyes and heavy‑metal‑contaminated wastewater.

2 Biosensing chip for early tumor screening

3D porous ceramic electrodes, ultra‑trace tumor biomarker rapid detection, and in vitro diagnostic microchips.

3 MEMS micro gas and humidity sensors

ZrO₂/Al₂O₃ composite micro-lattice, a miniature sensing element with stable performance under high-temperature operating conditions.

4 Chip thermal barrier and thermally insulating micro-packaging structure

Lightweight porous ceramic three-dimensional scaffolds, AI chips, and lightweight thermal‑insulating substrates for power devices.

5 Tissue-engineered bioceramic scaffolds

Customizable multi-level porous three-dimensional architecture, suitable for cell proliferation and in vitro organoid culture.

Image and Text Guide

Figure 1. 3D-AJP process principle: (A) ZnO nanoparticle ink (particle size ~20 nm) is atomized by ultrasonic nebulization, yielding droplets of ~2–5 μm; (B) the aerosol is conveyed through a delivery line to the print head, where a sheath gas focuses it into a concentrated jet for deposition; (C) layer-by-layer freeform fabrication is achieved drop by drop, without the need for supports, with linear shrinkage upon sintering of only 2–6%; (D) compared with extrusion (20–40% shrinkage), two-photon polymerization (20–50%), and DLS (low resolution); (E) this method employs an extremely low binder content (0.86 wt%), significantly lower than the high binder levels typical of conventional additive manufacturing.

Figure 2. Controllable Growth of Tilted ZnO Micropillars: (A) SEM images and magnified views of printed micropillars at room temperature (22 °C, left) and 50 °C (right); (B, C) Side-view SEMs show that as the droplet spacing δ decreases from 13 μm to 9 μm, the pillar–horizontal angle θ increases from 28° to 54° at 22 °C, or from 51° to 62° at 50 °C, without any supporting structure; (D) θ decreases linearly with δ, with the overall value at 50 °C approximately 20° higher than at 22 °C; (E) The effect of ink concentration (8/13/20 wt%) on θ, with 13 wt% yielding θ ≈ 28° at 22 °C.

Table 1. Comparison of ceramic additive manufacturing methods: In this work, 3D-AJP (ZnO/ZrO₂) employs only 0.86 wt% binder, achieves feature sizes ranging from 10 μm to 1 cm, offers a resolution of 10 μm, exhibits sintering shrinkage of 2–5%, and yields a porosity of 9%—significantly outperforming conventional approaches such as DLP-SLA (35.26%), SLA (20–25%), 2PP (19–40%), DIW (20%), and extrusion (4.5–37%) in terms of both shrinkage rate and binder content.

Figure 3. Printability and Sintering Shrinkage: (A) Relationship between the CAD centerline diameter d and the actual diameter D; the actual D is approximately 1.3–1.5 times d, with a slight reduction in D as the chamber temperature increases (RT → 100 °C); (B) Linear shrinkage of 3.8 ± 1.0%, and area shrinkage of 8.0 ± 2.2%, both significantly lower than those observed in conventional ceramic additive manufacturing; (C) FIB cross-section reveals an average pore size of 214 nm after sintering; (D) Comparison between the CAD model and the physical 8×8×3‑unit ZnO micro‑lattice; (E) High aspect‑ratio micro‑lattice (1 cm tall, 600 μm wide); (F) Top‑view and side‑view SEM images of a ZrO₂ micro‑lattice.

Figure 4. Complex single- and dual-material ceramic microstructures: (A) multi-helical architecture, (B) pyramidal microlattice, (C) wavy microwalls—CAD (top) and SEM (bottom); (D) ZnO/ZrO₂ dual-material pyramid, with EDX elemental mapping confirming distinct layering of Zn (green) and Zr (blue); (E) TiO₂/ZnO and TiO₂/ZrO₂ dual-material cross‑lattices; (F) Al₂O₃/TiO₂/ZnO tri‑material hybrid lattice, with Ti (red), Al (green), and Zn (blue) uniformly distributed.

Figure 6. Photocatalytic demonstration: (A) ZnO micro‑lattices exposed to UV light degrade methyl orange (MO) dye; (B) The dye color fades progressively over 0, 24, 48, and 72 hours; (C) Degradation kinetics—within 20 hours, the 3D ZnO micro‑lattice degrades 72.8% of the initial concentration, outperforming bulk ZnO of the same mass (37.5%) and bulk ZnO of the same volume (57.5%), while the bare substrate shows no degradation; (D) Normalized projected‑area degradation efficiency: the 3D micro‑lattice achieves approximately 0.21 ΔC/min/mm², more than four times that of bulk ZnO (~0.05).

Figure 7. Her2 breast cancer biosensor: (A) Physical images of the ZnO wave‑shaped wall before (left) and after gold sputtering (right); (B) SEM and optical micrographs of the sintered ZnO wave‑shaped wall; (C) Equivalent circuit of the sensor (R_s/R_ct/C_dl) and impedance responses with and without the biomarker; (D) Nyquist plots at different Her2 concentrations (1 fM–10 nM); (E) R_ct exhibits a logarithmic–linear response to concentration (r² = 0.963), with a detection limit of ~0.0193 fM; (F) At a concentration of 1 nM, 85.1% response is achieved in 22.1 s, and at 1 pM, 98.0% response is attained.