Active electronics, which include components capable of controlling electrical signals, typically rely on semiconductor devices to receive, store, and process information. These components require advanced manufacturing technologies and must be produced in clean rooms, facilities that are not widely available outside a few specialized manufacturing centers.
During the Covid-19 pandemic, the lack of large-scale semiconductor manufacturing facilities contributed to a global electronics shortage, driving up consumer costs and affecting everything from economic growth to national defense. The ability to 3D print a complete active electronic device without semiconductors could revolutionize electronics manufacturing, making it accessible to businesses, labs, and homes worldwide.
While this concept is still in its early stages, researchers at MIT have made significant progress by demonstrating fully 3D-printed resettable fuses. These fuses are essential components of active electronics, which typically require semiconductors.
The researchers created these semiconductor-free devices using standard 3D printing equipment and a biodegradable, cost-effective material. These devices can perform the same switching functions as semiconductor transistors used in active electronics processing operations.
Although they do not yet match the performance of semiconductor transistors, the 3D-printed devices could be used for basic control operations, such as regulating the speed of an electric motor.
"This technology has real potential. Even if we can’t compete with silicon as a semiconductor, our goal isn’t necessarily to replace existing technology but to explore new frontiers in 3D printing. In essence, it’s about democratizing technology. It could enable anyone to create smart hardware far from traditional manufacturing centers," says Luis Fernando Velásquez-García, a principal researcher at MIT’s Microsystems Technology Laboratories (MTL) and the lead author of a study describing the devices, published in Virtual and Physical Prototyping.
He co-authored the paper with Jorge Cañada, a graduate student in electrical engineering and computer science.
An Unexpected Project
Semiconductors, including silicon, are materials whose electrical properties can be tailored by adding certain impurities. A silicon device can have both conductive and insulating regions, depending on its design. These properties make silicon ideal for producing transistors, the building blocks of modern electronics.
However, the researchers did not initially set out to 3D print semiconductor-free devices that could mimic silicon-based transistors.
The project originated from another effort to create magnetic coils using extrusion printing, a process where the printer melts filament and extrudes the material through a nozzle, building an object layer by layer.
They observed an intriguing phenomenon in the material they were using—a polymer filament doped with copper nanoparticles.
When a large amount of electrical current was passed through the material, it exhibited a significant resistance spike but returned to its original level shortly after the current stopped.
This property allows engineers to create transistors that can function as switches, a role typically associated with silicon and other semiconductors. Transistors, which switch on and off to process binary data, are used to form logic gates that perform computations.
"We saw this as a way to elevate 3D printing hardware to the next level. It offers a clear path to bring some degree of intelligence to an electronic device," says Velásquez-García.
The researchers attempted to replicate the phenomenon with other 3D printing filaments, testing polymers doped with carbon, carbon nanotubes, and graphene. Ultimately, they could not find another printable material capable of functioning as a resettable fuse.
They hypothesize that the copper particles in the material disperse when heated by the electrical current, causing a resistance spike that decreases as the material cools and the copper particles come back together. They also believe that the polymer base of the material transitions from crystalline to amorphous when heated and returns to crystalline when cooled—a phenomenon known as the positive temperature coefficient of polymer.
"For now, this is our best explanation, but it’s not the complete answer because it doesn’t explain why this only occurred with this specific material combination. We need to conduct more research, but there’s no doubt that this phenomenon is real," he says.
3D Printing Active Electronics
The team leveraged this phenomenon to print switches in a single step, which can be used to form logic gates without semiconductors.
The devices are made from thin, 3D-printed traces of the copper-doped polymer. They contain conductive regions that intersect, allowing researchers to regulate resistance by controlling the voltage applied to the switch.
Although the devices do not perform as well as silicon-based transistors, they could be used for simpler control and processing functions, such as turning a motor on and off. Their experiments showed that even after 4,000 switching cycles, the devices showed no signs of degradation.
However, there are limitations to the size of changes researchers can make, based on the physics of extrusion printing and the material’s properties. They could print devices a few hundred microns in size, but cutting-edge electronic transistors are only a few nanometers in diameter.
"The reality is that many technical situations don’t require the best chips. Ultimately, all that matters is whether your device can perform the task. This technology can meet such a requirement," he says.
Unlike semiconductor manufacturing, their technique uses a biodegradable material, consumes less energy, and produces less waste. The polymer filament could also be doped with other materials, such as magnetic microparticles, to enable additional functionalities.
In the future, the researchers aim to use this technology to print fully functional electronic components. They are working on creating a functional magnetic motor using only extrusion 3D printing. They also plan to refine the process to build more complex circuits and explore the performance limits of these devices.
"This paper demonstrates that active electronic devices can be fabricated using extruded conductive polymer materials. This technology enables the integration of electronics into 3D-printed structures. An exciting application is the on-demand 3D printing of mechatronic components aboard spacecraft," says Roger Howe, William E. Ayer Professor Emeritus of Engineering at Stanford University, who was not involved in this work.
This research is partially funded by Empiriko Corporation.
