3D-printed active electronics

A fortunate discovery

The thing about science and engineering is that sometimes experiments can offer unexpected and welcome results – a phenomenon experienced by the MIT researchers.

When working on a project fabricating magnetic coils using extrusion printing, the team noticed that there was a spike in resistance when a large amount of electric current passed into the material they were using, which was a polymer filament doped with copper nanoparticles. This spike was then followed by a return to normal levels, which is a property that is typically seen in semiconductors.

This occurrence caught the attention of the researchers and prompted them to further explore the reason behind it. They soon realised the material exhibited behaviour similar to that of transistors – which are fundamental components for controlling electrical signals in active electronics. However, what was particularly intriguing about this discovery was that it did not involve the use of traditional semiconductors, instead, this material could be processed using standard 3D printing techniques.

Semiconductor-free electronics

The team began to explore this occurrence, and one of the scenarios they looked into was whether this effect could be harnessed to create other electronic components. To test this possibility, they began experimenting with different configurations, and they discovered that they were able to 3D print resettable fuses and logic gates.

These devices were created using copper-doped polylactic acid (PLA) that allowed for current control in a manner similar to semiconductor-based transistors, but without the need for silicon or cleanroom conditions.

The material operates through a effect called the polymeric positive temperature coefficient (PPTC), which means when the material heats up due to the flow of electrical current, its resistance increases dramatically, causing the current to stop. Once the material cools down, its resistance then returns to normal, allowing current to flow again.

3D printed active electronics

The ability to 3D print active electronics is an exciting step forward for the electronics industry whereby the traditional fabrication of components like transistors has required expensive and specialised equipment. However, by using 3D printing there is a real possibility to create these devices in a more accessible and decentralised manner which could open up new opportunities for businesses, labs, and even hobbyists – enabling them to manufacture electronics without the need for advanced fabrication facilities.

One of the key benefits of this discovery is that it could lead to more sustainable electronics manufacturing. Unlike traditional semiconductor production, which involves hazardous chemicals and generates a lot of waste, the 3D printing process used by the MIT team is far more environmentally friendly. The copper-doped PLA is biodegradable, and the process itself consumes less energy, which marks it out as a promising process to help reduce environmental impact.

While the performance of these 3D-printed components is not yet on par with silicon-based transistors, they are suitable for basic control operations, such as turning motors on and off. However, as the technology develops, it could enable custom electronics to be produced on-demand and on-site, even in remote or off-grid locations. For example, it could be valuable for space missions, where spare parts and electronic components could be printed directly on spacecrafts, which then reduces the need for large inventories.

The beginning of what is possible

While the devices demonstrated in this research serve as proof of concept, there are still challenges to overcome before 3D-printed active electronics can replace traditional semiconductors in more complex applications. To this end, the researchers are continuing to refine the process and explore new materials that could enhance the performance of these devices.

So, in the future, we could see fully functional, 3D-printed electronic systems that combine both mechanical and electronic components in a single manufacturing step. This would revolutionise how electronics are designed and produced, making the process faster, more sustainable, and more accessible to a wider range of users.