3D printers are devices that create 3D objects using an additive process. Most use plastic, but some can print using metal, paper, and even liquid UV curable epoxy. 3D printing differs from most manufacturing processes (such as CNC milling, plasma cutters, and formers), as it builds up structures by placing material (additive) instead of taking material away (subtractive).
A typical desktop 3D printer utilizes a hot nozzle that melts plastic fed from reel, and three motors are used to move a target bed that places the nozzle just above the work piece. 3D models are sliced into thousands of layers in the horizontal plane, which are stacked on top of each other. Printing even the simplest object can take hours, and not all 3D objects can be 3D-printed. Any overhangs in a design require scaffolding to support the model during the printing process.
3D-printed electronics commonly refer to electronic components that are created using a 3D additive process. However, it should be noted that even if a printing technology prints only a single layer of components, it is still a 3D device. This is because additional layers can be printed on top of this layer if run through the same process as well as the fact that active components (such as transistors) require multiple layers printed on top of each other to function.
How could 3D-printed electronics benefit technology?
One major advantage of being able to print electronic circuits is that almost any design could be prototyped from scratch. Instead of needing to wait for a specific IC to be developed and manufactured (which can take years), a custom design could be quickly designed in CAD and then sent to a 3D printer.
The concept of 3D-printed electronics could be taken further and combined with standard 3D-printing technologies. A combined printer would not only be able to produce an enclosure, it would also be able to integrate the electronics into the design such that there is no need for screw mounting, gaskets for environmental sealing, or prototyping of the enclosure to ensure it works with a PCB.
3D-printed electronics also gives rise to the possibility of 3D electronics. Instead of being restricted to a single 2D plane, 3D electronics could be printed vertically, thereby allowing circuits to be oriented in any direction. Another advantage to stacking circuits is the ability to also stack processors and other advanced circuits. A stacked processor can double its capability by doubling its thickness, and considering that such circuits could be made in the microns, a 1-cm–thick device would provide 10,000 layers of active circuits.
What challenges do printed electronics face?
While there have been multiple examples of printed electronics (such as PragmatIC), most of these face some major challenges that prevents them from being used in commercial designs.
By far, the biggest challenge currently facing 3D-printed electronics is size. Anyone can make a 3D printer print out conductive plastic or conductive ink, and this can be used to create capacitors and resistors. But current technology does not allow for printing extremely small devices, and this leads to printed deigns that are extremely large. The same applies to printed transistors, and the result is that printed designs with active components are many orders of magnitude larger than their semiconductor counterparts.
The second biggest challenge is finding suitable materials that can create practical electronic components. Carbon-based inks are useful for scientific demonstration, but many such inks have resistances far too great to be made practical. Such high resistances can increase power consumption while also impeding transmission lines between devices.
Another major challenge facing printed electronics is developing complementary active devices. PragmatIC is an excellent example of why N- and P-type printed transistors are extremely important. Recently, PragmatIC developed a fully printed ARM microcontroller on a flexible substrate, which was able to operate at about 600 kHz and store several hundred bytes of memory.
While the device was functional, it had an energy efficiency of 1%, and this was directly caused by the use of NMOS-like technology. Simply put, PragmatIC’s processor was constructed using only N-type transistors with pull-up resistors, meaning that when a transistor is active, power is wasted through the pull-up resistor. Complementary logic allows for the implementation of CMOS logic, which is highly energy-efficient. As such, researchers continue to try and find methods for printing both P- and N-type transistors together.
Will 3D-printed electronics ever become practical?
There is no doubt that researchers will continue to explore 3D-printing methods for manufacturing electronic circuits, but it is unlikely that they will ever place day-to-day electronics. The first fact to consider is that integrated circuits allow for transistors to be fabricated with sizes close to a few atoms, and it is unlikely that any 3D printer will ever have the ability to print at this resolution. This means that off-the-shelf semiconductors will always be more powerful and capable than any printed electronics system.
However, not every application requires a 2-nm feature device with a billion transistors, and printed electronic systems could prove essential in remote locations. For example, settlers on Mars may find that they are unable to produce semiconductors on demand to replace failing equipment. Assuming that equipment needing repair is relatively simple (such as door controls), 3D-printed electronics could fill this need.
The use of 3D-printed electronics could also find its way into enclosure design. Custom-ordered 3D-printed enclosures could also integrate communication links and antennas by embedding such connections into the structure itself. This would decrease the need for loose wires while also reducing the weight. Such designs would also be more assembly-line–friendly, thereby reducing the cost of manufacture.
Another possible application for 3D printers is the combination of 3D printers with PCB technology. 3D-printing technology could be used to create highly advanced PCBs that integrate passive components inside signal layers such as resistors and capacitors. Furthermore, the move toward surface-mount devices would remove the need for through-hole components, and this would allow circuit boards to be far thicker than they currently are. The increased thickness would allow for more signal trace layers, enabling more complex designs.
Conclusion
Overall, 3D-printed electronics will not replace current manufacturing methods for most electronics, but their ability to work with flexible substrates and be remotely located does make them practical for a few applications. It is likely that maker communities will develop such technology alongside researchers in an attempt to combine all product development stages into a single manufacturing process.