Turning 3D printing’s biggest flaw into its smartest feature

Civil and systems engineers at Johns Hopkins University have turned a longstanding problem with 3D printers into a multifunctional feature: The team developed a new printing technique that solves the fundamental weakness between the layers created during 3D printing. This work, which appears in Advanced Materials, has the potential to customize the behavior of 3D-printed objects.

“In 3D printing, interfaces are notorious for creating vulnerabilities,” said Jochen Mueller, an assistant professor in Whiting School of Engineering’s Department of Civil and Systems Engineering. “The printed material either adheres too much or too little, resulting in structural weaknesses. It’s similar to the way spaghetti sticks together after cooking, but easily pulls apart. This creates flaws that limit the functionality of 3D-printed products.”

To combat this, the team members developed a new printing technique that allows them to precisely control interfaces between voxels, the three-dimensional counterparts to pixels, and how they function, including properties like adhesion—how well different layers or materials stick together.

Known as voxel interface 3D printing, or VI3DP, the technique uses a printhead equipped with a standard nozzle ringed by four additional nozzles. While the standard nozzle deposits material, these additional nozzles add a thin film of different material on top. This allows the interface between each 3D printed line to be controlled and customized in both single- and multi-material printing, eliminating the need for multiple printheads and unnecessary gaps or features in an object.

Beyond creating stronger prints, VI3DP also opens up a range of new applications for 3D-printed objects. In the study, the team demonstrates how they can integrate optical, mechanical, and electrical properties into the interfaces—all in a single print and without increasing weight, time, or cost.

Doctoral candidate Daniel Ames said that “adding mechanical, optical, or electrical properties is already possible using some 3D printing processes, including material extrusion and material jetting, but those processes require the properties to be added as entire voxels, rather than thin interfaces surrounding the voxels, significantly reducing throughput and resolution. Our method makes these properties feasible at a fraction of the voxel size, expanding the range and type of applications for soft materials.”

By embedding interfaces with physical properties, the new technology offers an unprecedented level of functional control in 3D printing, the researchers say.

“Interfaces are extremely crucial because of what they can enable,” said Mueller, the corresponding study author. “VI3DP has the potential to produce thinner interfaces, new material combinations, and integrated functions like complex 3D circuits, electromechanical devices, data-embedded composite structures, and print-in-place mechanisms with precise fittings.”

The team plans to investigate these potential improvements in future research.

“VI3DP is a strong foundation for future fabrication developments. We’ll be able to print complex structures that have never been possible before,” said Ames.

Study collaborators include Johns Hopkins University doctoral candidate Sarah Propst and visiting high school scholar Aadarsh Shah.