Aerosol Jet Printing (AJP) CAM Vector Prepress Guide

Comprehensive engineering guide to aerodynamic sheath focusing, nanoparticle ink deposition, and conformal 3D vector toolpath generation for printed electronics.

1. Aerosol Jet Printing Technology Overview

Aerosol Jet Printing (AJP) is a non-contact, additive manufacturing process designed for high-resolution direct-write deposition of functional electronic inks. Developed by Optomec, AJP atomizes functional liquid inks containing metallic nanoparticles (silver, gold, platinum, copper), conductive polymers (PEDOT:PSS), carbon nanomaterials, or dielectric polymers into a fine mist of 1–5 µm droplets.

Unlike conventional inkjet printing which requires low viscosity (< 20 cP) and short standoff distances (< 1 mm), AJP accommodates ink viscosities from 1 to 1,000 cP and maintains high stream collimation across standoff gaps of 1 to 5 mm. This enables conformal metallization over complex 3D topographies, cavity sidewalls, and curved medical catheters.

2. Governing Aerodynamic Focusing Equations

The aerodynamic collimation of the aerosol stream is achieved by introducing a coaxial annular flow of inert sheath gas (typically high-purity Nitrogen $N_2$). The sheath flow envelops and compresses the core aerosol beam as it accelerates through the convergent nozzle orifice.

2.1 Sheath Focusing Ratio

The primary control parameter is the dimensionless sheath-to-aerosol flow ratio $s$:

s = Q_sheath / Q_aerosol

Where:

• Q_sheath = Annular nitrogen sheath flow (sccm)
• Q_aerosol = Carrier gas flow through ultrasonic or pneumatic atomizer (sccm)

2.2 Focused Beam Width

Under laminar flow conditions within the deposition nozzle, the focused core beam width $W_{\text{beam}}$ is derived from mass continuity:

W_beam ≈ D_nozzle / √(1 + s)

Where $D_{\text{nozzle}}$ is the tip internal exit diameter (100 µm, 150 µm, 200 µm, or 300 µm). At a standoff distance $z$, slight beam divergence occurs:

W_line = W_beam · [1 + C_div · (z - z_0)]

3. CAM Vector Toolpath Optimization Rules

To ensure uniform trace geometry, low electrical resistivity, and prevent droplet pooling, vector toolpaths must strictly adhere to the following CAM rules:

4. Vector Prepress & Gerber/DXF Preparation Workflow

1. Trace Single-Stroke Centerline Vectorization: Extract exact centerlines from raster schematics. Convert stroke line widths to match the calibrated aerodynamic spot size ($W_{\text{line}}$).
2. Z-Surface Conformal Mapping: Project 2D planar vector paths onto 3D STL surface meshes using conformal NURBS projection to maintain constant normal standoff height.
3. Sintering Window Accommodation: Account for thermal shrinkage ($10\% - 25\%$) during photonic or thermal sintering at 150°C - 250°C.