LLNL tunes light intensity for precise control of 3D printing

03 Feb 2026

Regulating crystallinity in thermoplastics opens new possibilities for advanced manufacturing.

A project at Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories has identified a new way to optimize the quality of 3D-printed thermoplastics.

Described in Science, the technique varies the intensity of the light used in an additive fabrication operation to influence the crystallinity of the printed material.

The approach has been named crystallinity regulation in additive fabrication of thermoplastics (CRAFT), and could have implications for advanced manufacturing, soft robotics and information storage, among other applications.

“A classic example of crystallinity is the difference between high-density polyethylene like a milk jug, and low-density polyethylene like plastic bags," said Johanna Schwartz from LLNL. "The bulk property difference in these two forms of polyethylene stems largely from differences in crystallinity."

However, contemporary manufacturing strategies, from injection molding to traditional 3D printing, result in monolithic objects unable to spatially encode crystallinity, noted the project in its paper.

The CRAFT approach aims to control the crystallinity within a thermoplastic spatially through variations in light intensity, making areas of increased and decreased crystallinity in order to produce parts controlled material properties throughout the whole geometry.

Light dosage governs stereochemistry of the photocured material, noted the project, giving access to a continuum of materials from strong rigid plastics to more extensible materials, all at the flick of a switch.

A key challenge, however, was translating this idea into practical manufacturing instructions that could be used on real 3D printers. LLNL identified a missing link: a way to convert any three-dimensional computer-aided design (CAD) into the detailed light patterns needed to print parts using the CRAFT method.

Energy dampening and metamaterial design

The answer drew on previous LLNL research into 3D printing of lattice structures, where the additive manufacturing process needs to produce areas of different material distribution. Creating the printing instructions to control this operation has traditionally been complex and time-consuming, but LLNL used parallel computing to reduce the time needed significantly.

Applying that same computational approach to CRAFT, LLNL researcher Hernán Villanueva adapted the workflow to encode changes in light, rather than changes in material. This meant that 3D CAD geometries could be converted directly into CRAFT printing instructions, cutting instruction-generation time from hours down to seconds and making rapid design iteration a practical prospect.

In use, lower light intensities favor more ordered crystalline regions, while higher intensities suppress crystallization, yielding softer, more transparent material. By projecting grayscale patterns during printing, the team produced parts with smoothly varying mechanical and optical properties, according to LLNL.

The researchers demonstrated the CRAFT technique on commercial 3D printers, fabricating bio-inspired structures that mimic bones, tendons and soft tissue, reproductions of famous paintings, as well as materials designed to absorb or redirect vibrational energy.

The ability to tune properties by changing a light’s intensity rather than swapping materials could significantly simplify additive manufacturing, commented Schwartz, and the technology could have broad and near-term impact.

"Energy dampening and metamaterial design are the most exciting use cases to me. From space to fusion to electronics, there are so many industries that rely on energy and vibrational dampening control. This CRAFT printing process can access all of them."