New Chemical Tracing Technology Can Track 3D Printed “Ghost Guns” Raw Materials

In many countries, the threat of 3D printed firearms to public safety is escalating. The blueprints for manufacturing such weapons are easily accessible online, and the entry barrier is remarkably low. With just a relatively inexpensive 3D printer and a simple web search, anyone can produce their own unlicensed firearms.

The Threat of “Ghost Guns”

Last October, the Australian Border Force seized 281 3D printed firearms or their components during an operation. These 3D printed parts can be combined with standard hardware store components to create “hybrid” weapons, significantly enhancing their strength and durability. Whether fully 3D printed or hybrid, these firearms can be as lethal as factory-manufactured weapons. Recent incidents have prompted calls for retailers to assist in curbing the spread of 3D printed firearms. Suggestions include installing shielding technology on 3D printers or implementing purchase alerts for items that can be used to manufacture hybrid firearms.

However, how should authorities respond to the weapons already circulating in society?

3D printed guns are labeled “ghost guns” because tracing their origin using conventional firearm analysis methods is challenging. In the face of difficulties in tracking the sources of seized ghost guns, researchers are seeking alternative solutions. Analyzing the chemical composition of the materials used to print these weapons may be key to ending their “untraceable” status.

What Are 3D Printing Filaments?

3D printing filaments are made from various types of polymers (plastics). The most commonly used polymer for home 3D printing is polylactic acid (PLA), a biodegradable plastic that can be used to make compostable garbage bags. Other common filaments include:

• ABS: Known for its high strength, it is the primary material used for LEGO bricks.
• PETG: A flexible polymer commonly used for sports water bottles.

Some specialty filaments are made from a blend of different polymers. Many filaments also contain additives that enhance strength, flexibility, or appearance. Since 3D printing filaments are often patented to protect their unique formulations, product packaging generally does not disclose the additives and other trace components. It is these trace components that could be crucial for tracing ghost guns.

The combination of ingredients in 3D printing filaments gives each type a unique chemical fingerprint. These characteristics can be identified using infrared spectroscopy, a technique that records how filaments absorb infrared light. The absorption patterns (infrared spectra) change based on the molecular composition of the filament. The research, conducted in collaboration with the ChemCentre, a forensic laboratory in Western Australia, analyzed over 60 types of filaments available in the Australian retail market. The findings revealed that many filaments that appear identical to the naked eye can be differentiated using infrared spectroscopy.

• PLA, ABS, and PETG filaments: Due to significant differences in their chemical compositions, these can be easily distinguished.
• Even filaments made from the same polymer can be differentiated based on variations in infrared spectra caused by additives. For instance, a specific filament showed the presence of a compatibilizer (an additive that helps two polymers blend). This component was not found in other filaments made from the same base polymer, indicating it may be a unique part of that brand’s formulation. This suggests that although the packaging only lists one polymer, the filament may actually contain two different polymers.

These discoveries highlight that even though filaments are widely consumed products, conducting chemical analyses remains highly valuable.

Tracking the Untraceable

The ability to distinguish and identify different 3D printing filaments will enable forensic investigators to:

• Link seized firearms to the filaments used to create them.
• Connect firearms seized in different cases.

These connections can assist law enforcement in identifying the sources of firearms, ultimately severing supply chains and preventing further production. Although the research indicates that some 3D printing filaments can be differentiated, not all filaments may be traceable. Further studies are being conducted to utilize additional analytical techniques to gather complementary information, such as the types of elements contained within the filaments. By combining various techniques, it may be possible to fully reconstruct the chemical profile of each filament.

It is hoped that this information will help establish a triple connection: seized 3D printed firearms → the filaments used → the printers utilized. By locking in the chemical fingerprints of 3D printed firearms, criminals will no longer be able to hide behind the shield of being “untraceable.”