Material jetting is the additive manufacturing process that most resembles a 2D inkjet printer scaled into the third dimension. Print heads with hundreds of nozzles deposit microscopic droplets of liquid photopolymer onto a build platform, and a UV lamp passing immediately behind cures each layer before the next one lands. Layer heights of 14–27 microns are routine, giving the smoothest surface finish and highest dimensional accuracy of any commercial 3D printing process — often ±20 μm over 100 mm.

The killer feature is multi-material printing in a single build. Because each nozzle can deposit a different photopolymer, a single part can transition from rigid clear plastic to rubber-like elastomer to opaque ABS-mimic — sometimes within the same millimeter. Stratasys PolyJet and 3D Systems MultiJet machines combine base resins in software-defined ratios to produce thousands of "digital materials" with tuned Shore hardness, color, and translucency. Overhangs use a separate support material — typically a wax or water-soluble gel — that is dissolved or melted away after the build.

Real-world example: Surgical planning models for complex cardiac procedures. A cardiothoracic surgeon needs to rehearse a septal defect repair on a patient-specific model where the myocardium feels like muscle (Shore A 40), the valve leaflets feel like leaflets (Shore A 27), and the calcified plaques print rigid and opaque. Material jetting prints all three in one build from CT segmentation data, in full color showing the pathology — something no other process can do without assembly.

Rule of thumb for cost: material jetting consumables run roughly $300–600 per kilogram of printed part, with support material often equal to or exceeding model material by volume. Budget total material cost as (part volume + 1.5 × support volume) × $0.50/cm³ for quick estimates. That's 10–20× the cost of FDM and 3–5× SLA, which is why material jetting lives in prototyping, medical models, and dental — not production runs.

Limitations engineers must respect:

• UV and thermal degradation: photopolymer parts yellow and embrittle within months of sunlight exposure; not for outdoor use.
• Low heat deflection: most resins soften by 50–60°C; useless for under-hood or near-motor applications.
• Anisotropy is mild but real: Z-axis tensile strength runs 10–15% below XY due to inter-layer adhesion.
• Wall thickness: minimum 0.6 mm for rigid resins, 1.0 mm for elastomeric — thinner walls tear during support removal.

The process shines when you need a part that looks and feels like the final product — overmolded grips, sealed enclosures with integrated gaskets, anatomical models — and you need it tomorrow.