Researchers have successfully created 3D-printed logic gates that do not use semiconductors but still carry out computations in electronic devices. By eliminating the need for semiconductor materials, this advancement paves the way for the potential 3D printing of complete active electronic devices.
Active electronics are components that manage electrical signals and typically rely on semiconductor devices to receive, store, and process information. These semiconductors are manufactured in clean rooms and require advanced technology that is often limited to specialized facilities.
The Covid-19 pandemic highlighted the vulnerabilities in the global electronics supply chain, as the scarcity of semiconductor fabrication facilities led to a widespread electronics shortage. This situation escalated consumer costs and affected several sectors, including economic growth and national security. The ability to 3D print an entire active electronic device without semiconductor materials could democratize electronics manufacturing, making it accessible to businesses, labs, and households around the world.
While this concept is still a work in progress, researchers at MIT have made significant strides by demonstrating fully 3D-printed resettable fuses. These fuses are essential components in active electronic devices and typically rely on semiconductors.
Their devices, made with standard 3D printing equipment and a cost-effective, biodegradable material, can perform basic switching functions similar to those of semiconductor-based transistors found in active electronics.
Although these 3D-printed devices do not yet match the performance of semiconductor transistors, they can serve fundamental control tasks, like managing the speed of an electric motor. As Luis Fernando Velásquez-García, the lead research scientist at MIT’s Microsystems Technology Laboratories, explains, “While we can’t compete with silicon semiconductors directly, our intention is not to replace existing technologies but to explore new possibilities in 3D printing. Ultimately, this is about making technology accessible, allowing anyone to create smart hardware outside traditional manufacturing hubs.” He co-authored a paper detailing these developments, which is published in Virtual and Physical Prototyping.
Jorge Cañada, a graduate student in electrical engineering and computer science, is the lead author of the paper.
An unexpected project
Semiconductors like silicon can be engineered to have specific electrical properties by introducing certain impurities, resulting in conductive and insulating regions. This ability makes silicon ideal for fabricating transistors, which are foundational to modern electronics.
However, the researchers did not initially aim to create 3D-printed devices that mimic the behavior of silicon-based transistors.
The project originated from an experiment involving the production of magnetic coils using an extrusion printing technique. This technique involves melting filament and layer-by-layer deposition to form the object.
While experimenting with a polymer filament combined with copper nanoparticles, the researchers noticed a unique phenomenon. When a significant electric current was applied, the resistance in the material surged dramatically but reverted to its baseline level soon after the current stopped.
This property enables the creation of transistors that function as switches, a role typically reserved for silicon and other semiconductors. Transistors rapidly switch on and off to process binary data, forming logic gates that facilitate computation.
“We recognized this as a chance to advance the capabilities of 3D printing hardware, offering a pathway to impart some ‘intelligence’ to electronic devices,” Velásquez-García adds.
The team also explored whether other 3D printing materials could replicate this phenomenon, testing various polymers infused with carbon, carbon nanotubes, and graphene. Ultimately, no other material produced the desired resettable fuse effect.
The researchers believe that when heated by electric current, the copper particles in the polymer disperse, leading to the spike in resistance, which diminishes as the material cools and the particles return closer together. They also suspect that the polymer’s structure shifts from crystalline to amorphous when heated and reverts to crystalline as it cools—a change known as the polymeric positive temperature coefficient.
“Right now, that’s our best explanation, but it doesn’t fully address why this occurs in this specific combination of materials. Further research is necessary, but it is clear that the phenomenon is real,” he says.
3D-printing active electronics
The team capitalized on this phenomenon to create switches in a single step, paving the way for the development of semiconductor-free logic gates.
The devices consist of thin, 3D-printed traces made from the copper-doped polymer, with intersecting conductive areas that allow them to control resistance through the voltage applied to the switch.
Even though these devices do not match the efficiency of silicon-based transistors, they are suitable for simpler tasks, like turning a motor on and off. Experiments showed they remained functional after 4,000 switching cycles without any signs of wear.
However, there are limitations regarding the size of the switches, dictated by the physics of extrusion printing and the material properties. The researchers can create devices a few hundred microns in size, while cutting-edge transistors can be just a few nanometers wide.
“Many engineering scenarios do not demand the most advanced chips. Ultimately, functionality is what matters,” he states. “This technology is capable of meeting specific needs in those situations.”
Additionally, unlike traditional semiconductor manufacturing, the team’s method utilizes biodegradable materials, consumes less energy, and generates less waste. The polymer can also be enhanced with various materials, such as magnetic microparticles, to provide further functionalities.
Looking ahead, the team aims to leverage this technology to manufacture fully functional electronics. They aspire to produce a working magnetic motor using solely extrusion 3D printing and refine the technique to create more complex circuits.
This research has received partial funding from Empiriko Corporation.
