#3DStartup: Kupros’ Cu29: A Conductive Copper Filament for FDM Electronics an Expert Said Would “Never Be 3D Printed”

When Ian Ramsdell, founder of Kupros, started asking electronics specialists about 3D printing solid copper, he faced plenty of skepticism. One expert, in Ramsdell’s recollection, insisted it could not be done and never would be: “Copper can’t be 3D printed, it’ll never be 3D printed.” What that expert did not know was that Ramsdell was already working from a confirmed laboratory experiment, one the US military had run and validated years earlier.

That distance between “impossible” and “already proven in a lab” is the founding story of Kupros and its flagship product, Cu29: a fully metallic, conductive filament engineered to print on standard fused deposition modeling (FDM) machines, the desktop hardware already sitting in most workshops. The ambition reaches past printed circuits. Because the conductor is extruded alongside structural plastic in the same build, Cu29 is aimed at integrated sensors, embedded signal routing, and conformal antennas and conductive paths that follow a part’s geometry rather than sitting on a flat board. In aerospace and defense, where Kupros sees its strongest early demand, the pitch is concrete: fewer wiring harnesses, connectors and interconnects, structural-health sensing built into load-bearing parts, and faster iteration as electrical and mechanical design evolve together. “Just because somebody has been told that something is impossible, doesn’t mean it can’t be done,” Ramsdell said.

Cu29 can be used to develop embedded electronics.

NASA, Northrop and Boeing Pre-Ordered Cu29 Before It Existed

The market committed before the material was finished. Accepted as an Army xTech finalist at the 2022 DMC conference in Tampa, Ramsdell left with prepaid orders from NASA, Northrop and Boeing. More pre-sales followed, from KBR, US Army DEVCOM and several universities. Buyers put money down while the material science was still in development. “They were willing to prepay me for first access to the material as soon as it came off production,” he says. It is an unusual level of confidence for a pre-revenue materials startup.

The Navy-Lab Origin

The underlying technology came out of a US Navy lab, credited by Ramsdell to scientist Carson Holmes, then a technician working on additive electronics systems from Optomec, Nano Dimension and nScript. Those seven-figure machines relied on silver inkjet chemistry with real limits: “As a result of the porosity in the traces, they’re sometimes restricted to only low voltage and low amperage usage,” Ramsdell explained. Holmes’ proposal for a better route was named top paper of 2017 under the Office of Naval Research Design Innovation Award, then sat unused until Ramsdell licensed it in 2021 through a US Department of Defense startup studio.

That route is why he pursued a material others had dismissed: rather than gamble on unproven science, he took on technology a national lab had already de-risked. The failure he set out to beat was long-standing, not niche. “One very, very large electronics manufacturer told us that they were trying to manufacture material similar to this since the 1990s and they’ve been unsuccessful.”

Why Copper Is Hard to 3D Print

The difficulty is intrinsic to the metal. “Copper is highly reflective and it transfers heat in a very efficient manner and then it oxidizes at the slightest temperature change,” Ramsdell says, a combination that has frustrated copper printing across process families for decades. Solving it, he argues, opened a door well beyond conductive traces. The team can now dope the material for properties such as radiation shielding and anti-tamper structures, “so people can’t x-ray components to reverse engineer.”

Conductive filament printing allows users to build embedded signal routing, integrated sensors, conformal conductive paths, embedded antennas, and more.

Built for Hardware You Already Own

The commercial case rests on access. Additive electronics has historically meant six- and seven-figure machines. Cu29 is built to drop into equipment already on the bench: Ramsdell has run it on sub-$300 desktop printers and on a Bambu Lab A1 Mini with its automated material system, and is qualifying the Prusa XL as a recommended platform. It needs no printer modifications beyond a steel hotend, and Kupros claims that a printed conductor is functional straight off the bed, with no sintering, plating, curing or chemical cleanup, a pointed contrast with silver inkjet’s maintenance overhead.

Notably, Cu29 is not meant to build bulk metal parts the way PLA builds plastic ones. Ramsdell says the team has printed only “five or six layer heights” in the Z axis, mainly to test self-adhesion, and is “not trying to build in the third dimension currently.” Rather, the focus is on embedded electronics. The filament functions as a conductor laid into and onto polymer structures, which is why the workflow is multi-material: structural plastic and Cu29 printed together, often on a dual-extruder or IDEX machine, so the electrical path is embedded as the part is built. “Instead of putting traditional components directly on the PCB, you’re gonna actually put them directly at that point of need.”

The Performance Claims

Kupros’ performance figures, which Ramsdell is careful to label preliminary, are the headline. In early high-voltage testing the company pushed 12,500 volts through the material without destroying it, then kept raising the current. “We kept blowing up power supplies and couldn’t get enough current to actually do destructive testing,” he said. A supercapacitor bank later drove what he estimates at well over 600 amps through a short sample, still without failure. Against silver inkjet, the only comparable additive material, Ramsdell claims Cu29 is 48,000% more conductive. Those numbers are company-stated and await independent verification, but the positioning is clear: a single material for both high- and low-power applications, which the incumbent chemistry cannot serve. Kupros also took the TCT Materials Award at RAPID this year.

A Space-Grade Variant in Development

Currently, Kupros is developing Cu29 Space, a variant of the base material which will target tin whiskering. Tin whiskering happens when tin conductors grow tiny metallic filaments that can bridge adjacent traces, shorting a circuit. This is risky especially for spacecraft, where hardware cannot be serviced and a single short can end a mission. According to Kupros, the Space variant is formulated to eliminate whiskering while printing traces from 0.2mm to 1.2mm on typical FDM hardware. The filament could be used for power-grade conductors, non-planar and modular electronics, and embedded sensors and antennas. 

What Cu29 Means for Additive Electronics

The name reaches back to the metal’s oldest history. “Kupros is Greek for copper,” Ramsdell notes, and “the Greeks were the very first human civilization to enter the copper age.” The framing is deliberate for a founder repeatedly told his core idea was impossible.

For an AM sector still waiting on the promise of functional, multi-material parts straight off the print bed, a conductive metal filament that runs on commodity hardware, with a space-grade line already in the pipeline, is a genuine step, provided the performance figures hold up. If you want to learn more about Kurpos, visit its website HERE.

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*All Photo Credits: Kupros