Harbin Institute of Technology, Applied Physics Letters: Voronoi‑based metallic mesh combined with aerosol jet printing enables curved‑surface transparent electromagnetic shielding.
Product Introduction
Equipment Parameters
I. Core Research Summary
- The Voronoi mesh exhibits superior optical performance across the board compared to the conventional random quadrilateral mesh.
Natural, irregular polygonal topology; vertex‑edge counts are randomly distributed; diffraction intensity is discretized and homogenized. At the same transmittance level, the coefficient of variation of diffraction is significantly lower than that of conventional grids, yielding a pronounced stray‑light suppression effect; for 90% of samples with randomization, transmittance can reach 89.88%.
- Aerosol-based conformal printing of high-precision metallic silver meshes on curved surfaces
On a convex lens with a curvature of 3.7 mm, a uniform silver mesh pattern with an average linewidth of 12.5 μm has been stably fabricated on the curved surface, exhibiting no broken lines or filaments, thereby overcoming the bottleneck of lithography that is limited to planar processing. The planar sample measures 40 × 40 mm, while the curved‑surface lens fully covers the optical effective area.
- Ku-band stable and efficient electromagnetic shielding performance
12–18 GHz full‑band shielding performance with SE > 23 dB; the silver mesh provides a continuous conductive path that effectively attenuates RF electromagnetic radiation, meeting the shielding requirements of radar systems, vehicle‑mounted electro‑optical equipment, and communication optical windows.
- Image quality of the curved lens shows no significant degradation.
When a resolution target is imaged through a convex lens covered by a grid, the light intensity distribution is uniform, with no diffraction fringes or ghost images, and the optical imaging accuracy is virtually unaffected by the shielding layer.
- Digital Rapid Topology Iteration
CAD‑adjustable grid‑based random dithering parameters eliminate the need for photolithographic masks, enabling on‑the‑spot modification of the topology and same‑day printing of both planar and curved samples, thereby significantly shortening the development cycle for optical shielding films.
II. Process Flow and Core Technological Advantages of the Complete Set of Curved-Surface Shielding Meshes for Aerosol Spraying
(1) Complete Preparation Process for Voronoi Metal Shielding Mesh
- Plasma cleaning of flat glass and convex lens substrates to enhance the adhesion of silver films;
- NovaCentrix nano-silver ink is atomized by ultrasonic atomization, with an aerosol carrier gas flow rate of 23 sccm and a printing speed of 2 mm/s.
- A metal grid was directly written using a Voronoi‑based patterning scheme at a 90% randomization level, with a target line width of 10 μm and an average measured line width of 12.5 μm.
- Cured in a low-temperature oven, the silver layer is dense and resistant to alcohol and water washing.
- The optical diffraction platform and the vector network analyzer were used to calibrate transmittance and shielding effectiveness, respectively.
(II) Five Core Processes (Photolithography / Evaporation / Screen Printing Compared)
- Unique advantages of conformal printing on curved surfaces
A 3–5 mm tolerance in spray distance ensures safe operation; convex lenses and arc‑shaped optical components can be directly patterned into continuous conductive silver meshes on curved surfaces, whereas evaporation and photolithography cannot accommodate substrates with complex curvatures.
- Maskless Digital Topology Rapid Iteration
No custom metal photomasks are required; Voronoi randomness can be adjusted with a single click, and multiple versions of the optical mask can be prototyped in just a few hours, reducing the R&D cycle by 90%.
- Micron-level fine line formation ensures high light transmittance.
Precisely controls metal wires down to sub‑10‑micron dimensions, with low metal content and high visible‑light transmittance, simultaneously meeting both shielding and imaging requirements.
- Single-device adaptation plane + multi-curvature optical substrate
A single set of printing parameters is applicable to both soft and hard transparent substrates, such as glass and optical resins, ensuring high versatility across the production line.
- High consumable utilization, green and low-cost additive manufacturing.
Silver is deposited only in the optical window area, eliminating large‑area coating waste and photolithography etching effluents; for small‑batch samples, the cost is significantly lower than that of vacuum deposition.
III. Five Key Technological Innovations
Innovation 1: Voronoi topology addresses key pain points in the optical diffraction industry.
Innovation 2: Integrated Manufacturing of Aerosol Curved-Surface Conformal Metal Shielding
Innovation 3: A System for Quantitative Regulation of Optical Properties via Randomization
Innovative 4 Ku-band broadband curved-surface shielding molding process
Innovative 5-Optics – Electromagnetic Dual-Performance Synchronous Verification Platform
IV. Current Industry Challenges and Corresponding Solutions for Overcoming Them
Challenge 1: The regular metallic grating produces well-defined diffracted spots, but the resulting image exhibits striped artifacts.
Challenge 2: Lithography and evaporation deposition can only process flat surfaces, making it impossible to deposit shielding grids on curved optical lenses.
Challenge 3: In traditional random quadrilateral meshes, transmittance and diffraction‑suppression performance are mutually constrained.
Challenge 4: Vacuum coating equipment is expensive, mask fabrication takes a long time, and redesign costs are high.
Challenge 5: Curved-surface coating is prone to line breakage and conductive discontinuities, leading to a sharp drop in shielding performance.
V. Future Diversified Industrial Application Scenarios
1 In-vehicle AR-HUD / Curved optical shielding for in-vehicle cameras
2 AR/VR head-mounted optical lenses
3 Airborne Electro-Optical Detection Window
4 Infrared temperature measurement, machine vision lenses
5. University Optical-Electromagnetic Hybrid Laboratory
Figure 1. Voronoi diagram and random quadrilateral mesh. (a)–(d): Schematic illustrations of Voronoi diagram generation; (e) and (f): Random quadrilateral meshes with varying degrees of randomness, along with their corresponding Voronoi‑derived mesh structures.
Figure 2. Comparison between a random Voronoi diagram and a random grid. (a) Slope distribution; (b) Diffraction pattern.
Table I. Diffraction Uniformity Analysis of Voronoi Diagrams and Random Quadrilateral Meshes
Figure 3. Fabrication and experimental characterization of Voronoi metallic meshes. (a) Schematic illustration of the AJ printing process. (b) Photograph of a Voronoi metallic mesh. (c) Optical microscopy image of the Voronoi metallic mesh. (d) Schematic diagram of the optical diffraction experiment and the corresponding diffraction pattern. (e) Optical diffraction pattern. (f) and (g) Photographs of the Voronoi metallic mesh positioned in front of an object.
Figure 4. Curved‑surface Voronoi metallic mesh structure. (a) and (b) show schematic diagrams of the Voronoi metallic mesh fabricated on a plano‑convex lens. (c) Optical microscope image of the metallic mesh. (d) Photograph of the sample containing the metallic mesh, captured using the experimental setup. (e) Schematic illustration of the imaging principle for the plano‑convex lens. (f) Photograph of the experimental setup without the metallic mesh. (g) Schematic diagram of the experimental configuration, featuring a plano‑convex lens with a metallic mesh on its curved surface. (h) Normalized light intensity profiles along the marked line in the resolution target images shown in (d) and (f).
Figure 5. Electromagnetic shielding performance of the Voronoi metal mesh. (a) Schematic diagram of the experiment for measuring electromagnetic radiation (SE). (b) Simulated and measured electromagnetic radiation curves.
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