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The article titled "Enhanced aerosol-jet printing using annular acoustic field for high resolution and minimal overspray" presents a novel approach to improve aerosol jet printing by employing an annular acoustic focusing technique. This method addresses the challenges of overspray and instability that typically hinder the precision of aerosol jet printing, particularly at high resolutions. By optimizing the focusing frequency for silver nanoparticles and modifying the nozzle geometry, the researchers achieved ultrafine traces with a line width of less than 6 μm and minimal overspray of 0.1 μm. The study demonstrates that this technique not only enhances the printing resolution but also significantly improves the electrical conductivity of the printed materials, making it a promising solution for the fabrication of high-performance conformal electronics
Acoustic Focusing Frequency Optimization:
The research team determined the optimal focusing frequency for precise control of silver nanoparticles to be 5.8 MHz using a particle ejection model.
Improvement of Nozzle Geometry:
A modified nozzle design was proposed, featuring two conical focusing zones to create an annular acoustic field, effectively concentrating aerosol particles toward the nozzle center and reducing droplet drift and overspray.
Experimental Validation:
Experiments successfully achieved ultrafine printed lines (line width < 6 μm, overspray < 0.1 μm), with results showing a 60% reduction in line width and a 180% increase in conductivity compared to prints without acoustic focusing technology.
Long-Term Stability Testing:
An 8-hour printing experiment was conducted to assess stability during the printing process, demonstrating effective consistency in the printed traces.
Fluid Dynamics Model Analysis:
A three-dimensional computational fluid dynamics model was utilized to analyze the behavior of aerosol particles within the nozzle, revealing the interaction between the annular acoustic field and the flow field.
Illustrated Explanation
Figure 1 illustrates the overall concept and design of the annular acoustic focusing (AF) technology in aerosol jet printing (AJP), along with its impact on the behavior of aerosolized particles (APS). Specifically, Figure 1 includes the following components:
1. Nozzle Design: The schematic shows an additional piezoelectric tube integrated with the AJP nozzle. The piezoelectric tube is excited by a signal generator and power amplifier to create an annular acoustic field. This design allows for effective focusing of aerosol particles within the nozzle.
2. Gas Flow Dynamics: The figure depicts how aerosol particles are propelled into the print head by the carrier gas and further focused by sheath gas. The acoustic focusing technology, generated by the piezoelectric tube, enables more precise jetting of aerosol particles onto the target surface.
3. Focusing Behavior: Part of Figure 1 demonstrates the change in aerosol flow diameter. Under the influence of acoustic focusing, the diameter of the aerosol flow decreases from an initial diameter D0D0 to a focused diameter DADA, indicating that acoustic focusing effectively reduces droplet size, thereby enhancing printing precision.
4. Force Distribution During Printing: The figure also illustrates various forces acting on aerosol particles during ejection, including Stokes drag force and acoustic radiation force. These forces collectively cause aerosol particles to converge toward the central axis within the nozzle channel, achieving better focusing.
5. Printing Trace Schematic: Finally, the figure presents a schematic of the traces printed during the acoustic focusing process, highlighting the more detailed and consistent printing results achieved with this technology.
Figure 2 illustrates the impact of the acoustic field (AF) on the geometry of printed lines: (a) shows the original geometric form of printed lines before acoustic focusing (AF);
(b) depicts the geometry of lines continuously printed with the acoustic field (AF) ON, where the line width (LW) is significantly reduced and overspray is suppressed to a lesser extent;
(c) illustrates the geometry of lines printed continuously with (b) after turning OFF AF, where both LW and overspray have returned to their original states;
(d) provides an overview of the three continuous states of the printed lines: AF OFF, ON, and OFF;
(e,f) depict the convergence and divergence processes of AJ printed lines during AF intervention and dispersion, where VP is represents the printing speed and IP is denotes the length of the transition zone.
Figure 3 validates the multi-width, stability, omnidirectionality, and feasibility of printing assisted by acoustic focusing (AF).
(a-d) Cross-sectional profiles of aerosol jet (AJ) printed traces with different line widths (LW): (a) ~10 μm, (b) ~30 μm, (c) ~50 μm, and (d) ~80 μm, with AF ON/OFF.
(e) Two-dimensional orthogonal continuous AJ printing with intermittent switching of AF to verify the omnidirectional focusing capability.VpVp represents the printing speed. (f) A high-density array printed with AF-assisted AJ, with length-width and spacing ranges approximately 6 μm.
(g) Variation of LW in continuous AJ printing traces with multiple AF ON/OFF states in different directions
Original text link：Enhanced aerosol-jet printing using annular acoustic field for high resolution and minimal overspray | Nature Communications
