Material jetting

1.            Definition

    Material Jetting is a 3D printing technology that uses printheads to precisely jet liquid photopolymer resin onto a build platform, then cures it layer by layer with UV light. Its manufacturing principle is similar to inkjet printers, but it can stack materials layer by layer in three-dimensional space to form solid objects. This technology can jet multiple materials and colors simultaneously, offering extremely high resolution and excellent surface quality, and is commonly used for high-precision aesthetic models and full-color prototype production.

Figure 1. Schematic diagram of Material Jetting (MJ) process[1].

2.            Principle

    The basic principle of Material Jetting is to precisely jet liquid photopolymer resin in tiny droplets onto a build platform using an inkjet printhead, and then immediately cure it with ultraviolet (UV) light, stacking layers to form a three-dimensional model. The specific steps are as follows:

1.         Liquid Material Heating and Feeding:

Photopolymer resin is stored in heated cartridges to maintain appropriate viscosity for jetting.

2.         Droplet Jetting:

The printhead precisely jets droplets to the designated locations according to the sliced data of the CAD model. Resolution can typically reach several hundred dots per inch (DPI).

3.         UV Light Curing:

Immediately after each layer is jetted, it is exposed to a UV light source, causing the resin to polymerize and solidify instantly.

4.         Layer-by-Layer Stacking:

The cured layer serves as the base, and the jetting and curing steps are repeated until the entire model is complete.

5.         Support Material Removal:

After printing is complete, support structures (usually soluble photopolymer resin) are removed to obtain the finished product.

This technology enables multi-material simultaneous printing, color mixing, and high surface smoothness, making it commonly used for aesthetic display models and high-precision prototype production.

3.            Detailed Technical Explanation

1.         Core Architecture and Process

(1)      Material Feeding and Temperature Control: Photopolymer resin is stored in heated cartridges to maintain viscosity within the printable range (typically 8–40 mPa·s, depending on the model).

(2)      Printhead and Spreading: Uses a piezoelectric Drop-on-Demand printhead to scan the XY plane according to the sliced path, depositing micro-droplets line by line.

(3)      UV Immediate Curing: After each line (or layer) is deposited, it is immediately exposed to 365–405 nm UV-LED light to polymerize and cure the droplets.

(4)      Layer-by-Layer Stacking: The Z-axis is elevated by tens of micrometers, and the deposition/curing steps are repeated until completion.

(5)      Support Removal: Supports are removed by water washing, high-pressure water jet, dissolution, or thermal melting, depending on the model.

Figure 2. X, Y, and Z axes in Material Jetting (MJ) [1].

2.         Key Physics of Droplet Formation

(1)      Jetting Method: Piezoelectric actuation causes instantaneous changes in the ink chamber volume, ejecting droplets through the nozzle (typical volume 10-several tens of picoliters (pL), common nozzle aperture 20–50 µm).

(2)      Rheological Conditions: The material needs appropriate viscosity, surface tension, and wettability at working temperature to prevent stringing, satellite drops, and splashing. Dimensionless indices commonly used in engineering are:
Re = ρva/μ, We = ρv²a/σ, Oh = μ/√(ρσa), and Z = 1/Oh usually falls within 1–10 for stable jetting (range varies depending on the printhead).

(3)      Droplet Landing and Spreading: After landing, droplets are affected by the wetting angle, substrate surface energy, and viscoelasticity, spreading to form "dots"; the dot pitch and droplet volume determine the filling overlap and surface smoothness.

Figure. Schematic Diagram of PolyJet 3D Printing Mechanism [5].

3.         UV Curing and Voxel Control

(1)      Real-time photopolymerization: Resins containing photoinitiators generate free radicals under UV irradiation, promoting chain polymerization, completing the conversion from "dots" to "lines/surfaces" in milliseconds to seconds.

(2)      Penetration and Inhibition: UV penetration depth is affected by absorption coefficient and formulation; oxygen inhibition reduces surface conversion, thus high intensity, short distance, and segmented curing are often used to mitigate this effect.

(3)      Voxel Material Mixing: Multiple printheads can achieve hard/soft gradients, transparency gradients, and CMYK (+White/Clear) full color at the single pixel/voxel level through dithering or proportional jetting.

4.         Multi-Material and Full-Color Mechanism

(1)      Multiple Ink Paths in Parallel: Multiple printheads are arranged in the same row or staggered, each supplying different resins (rigid, flexible, transparent, colored, support).

(2)      Formulation Compatibility: Ensure co-curing compatibility and adhesion, avoiding brittle interfaces or long-term delamination between resins of different hardness.

(3)      Color Management: Use ICC/device characteristic curves for color translation; transparent and white inks are used to control brightness, saturation, and surface gloss.

5.         Support, Leveling, and Post-Processing

(1)      Support Material:
Gel-like soluble: water-soluble or alkali-soluble, easy to clean complex internal cavities;
Wax-like fusible: melted in a heated bath, providing an extremely fine surface finish.

(2)      Interlayer Leveling: Some systems use a squeegee/roller to gently brush away particles and micro-protrusions, maintaining consistent layer thickness.

(3)      Post-curing: Secondary UV or heat treatment can be chosen to improve conversion rate and dimensional stability. Polishing, clear coat for transparent parts, or dyeing are also common.

([1],[2])

IV.            Materials

1.         Material Overview

Material Jetting primarily uses liquid photopolymer resins, which solidify through UV light exposure that initiates a free-radical polymerization reaction. These materials are typically acrylic or epoxy-based, and their optical, mechanical, and elastic properties can vary based on their formulation. Similar toSLA, both use photopolymer resins, but forMaterial Jetting, "jetting behavior" must be specifically considered. Therefore, rheological properties (viscosity, surface tension) and photoreaction rates require precise control.

2.           Material Classification and Properties

[1],[2]

V.            Application Cases

1.         Appearance Prototypes and Product Display

(1)      Material jetting technology excels at printing models with extremely high resolution, smooth surfaces, and multi-color or translucent properties, making it highly suitable for appearance verification prototypes during the product development phase.

(2)      For instance, consumer electronics, appliance housings, or automotive interior panels can be quickly produced with the final appearance and texture using this technology.

(3)      These models can be used for market displays, visual evaluation, engineering verification, or packaging design checks.

(4)      The capability for multi-material or full-color printing further allows for simulating different material areas (e.g., hard plastics, soft cushioning, transparent mirrors) within a single print, reducing iteration time.

2.         Medical/Anatomical Models and Dental Applications

(1)      In the medical field, material jetting technology is often used to produce anatomical models, models for surgical planning, and dental models and guides.

(2)      For example, it can print detailed structures such as blood vessels, bones, soft tissues, and tumors, with differentiation by realistic colors, which aids doctors in pre-surgical simulation, patient communication, and teaching.

(3)      Advantages include high precision, smooth surfaces, and the ability to be transparent or colored, thus accurately reflecting human anatomy – an effect difficult to achieve with traditional molding or carving methods.

MJT 3D-printed anatomical model for surgical planning of complex chest wall and diaphragm hernia repair.
Segmented anatomical structures include: spine (green), ribs (yellow), costal cartilage (magenta), sternum and manubrium (white), inferior vena cava (cyan), right diaphragm (blue), metal plate (red), and herniated adipose tissue (orange).
(A) Transverse CT image with segmentation masks;
(B) 3D visualization model of segmented structures;
(C) Digital 3D model created using Materialise 3-Matic 18 CAD software;
(D) Final full-color 3D physical model printed with MJT technology, scaled down to 33%.[4]

References

[1]      O. Gülcan, K. Günaydın, and A. Tamer, “The State of the Art of Material Jetting—A Critical Review,” Polymers, vol. 13, no. 16, art. 2829, Aug. 2021, doi: 10.3390/polym13162829.

[2]      A. Elkaseer et al., “Material jetting for advanced applications: A state‐of‐the‐art review,” Additive Manufacturing, vol. 53, Jan. 2022, pp. 102603, doi: 10.1016/j.addma.2022.102603.

[3]      “Material Jetting: A New Era in 3D Printing,” Unionfab Blog, Oct. 20 2024. [Online]. Available: https://www.unionfab.com/blog/2024/10/material-jetting. [Accessed: Oct. 30 2025].

[4]      S. Chokshi, “Medical 3D Printing Using Material Jetting,” Bioengineering, vol. 12, no. 3, art. 249, 2025. [Online]. Available: https://www.mdpi.com/2306-5354/12/3/249?utm_source=chatgpt.com.

[5]      A. Pugalendhi, R. Ranganathan and M. Chandrasekaran, “Effect of process parameters on mechanical properties of VeroBlue material and their optimal selection in PolyJet technology,” The International Journal of Advanced Manufacturing Technology, vol. 108, pp. 1049-1059, 2020. [Online]. Available: https://www.researchgate.net/publication/337996957_Effect_of_process_parameters_on_mechanical_properties_of_VeroBlue_material_and_their_optimal_selection_in_PolyJet_technology.