Of all manufacturing and prototyping methods in existence, 3D printing technology has by far been the most talked about in the media, seen the most online projects, and is the most accessible to anyone. While the technology may appear to be new, 3D printing dates back to the 1980s, when a company called 3D Systems filed for a patent regarding 3D construction of models using stereolithography.
The reason why 3D printers have been available for home users only recently comes down to the use of such patents that prevented their development, manufacture, and distribution. This is also a prime example of how patents can hold technology back, making an argument against the use of patents. Thus, the technology has been available since the 1980s, but it took three decades for anyone to develop it further.
How does 3D printing work?
Most 3D printers operate by splicing a 3D design into many small horizontal 2D slices and then printing each 2D slice atop one other. The most common 3D printers use a thermoplastic that is wound on a reel that is then extruded out of a hot nozzle. Some 3D printers can build such models using paper, with each layer cut out from the paper and then glued to the next layer, and some more exotic systems can use laser sintering of metallic dust.
What are 3D printed electronics?
3D printed electronics are electronic components manufactured using an additive process via a printer. However, the term “3D printed electronics” can be easily misunderstood, as some may see 2D printed electronics as not being 3D printed.
The truth is that most (if not all) 2D printed electronics are 3D, and this comes down to the need for multiple layers placed on top of each other. The same applies to transistors on semiconductors; while transistors are considered 2D, they are, in fact, 3D structures that require additive and subtractive processes to build up (such as the gate, source, and insulation layers).
To date, most printed electronics have little practical application and are seldom used in the real world. This is because traditional electronics are easier, cheaper, and more reliable to manufacture. However, there is a significant amount of research being done to try and create practical devices. Researchers have already created resistors, capacitors, diodes, and transistors using 3D printing methods, and while there are many different materials used, they are generally based either on graphene or an organic polymer. Graphene provides researchers with the ability to create narrow gates and channels while also enabling doping (critical for changing the conduction of graphene). Organic polymers can be easily dispensed in solution form (thus making it ideal for inkjet printers) as well as provide flexibility.
Examples of 3D printed electronics
While there is plenty of research in printed electronics, commercial application is rarely found, as printed electronic capabilities are nowhere close to standard electronics systems. Furthermore, printed electronics are still in their infancy and, as such, are found either in the research lab or on prototypes. When it comes to 3D printing technologies that are most likely going to become practical, two in particular stand out: PragmatIC and Duke University.
PragmatIC printed electronic solutions
PragmatIC is a U.K.-based company that produces printed electronic solutions for one-time applications and disposable electronics like RFID tags. One of the significant features behind PragmatIC devices is that PragmatIC uses a flexible substrate, making the resulting devices fully flexible. Furthermore, the company’s flexible electronic technology covers all the essential components, including resistors, capacitors, and transistors. While a functional device was not fully demonstrated, PragmatIC produced a sheet of ARM core processes using its process and claims that each device consumed 21 mW with an energy efficiency of only 1%.
What makes PragmatIC different from standard semiconductor construction methods is that the devices are printed instead of using intensive processing steps like those found in semiconductor foundries. Additionally, while PragmatIC electronics are built layer by layer, the use of organic chemicals and thin-film transistors pave the way for fully functional devices that could be constructed using equipment similar to a standard 3D printer.
Printed electronics at Duke University
Duke University presents one of the strongest examples of practical printed electronics that exceeds the typical life cycle of a product. In 2021, Duke University demonstrated a new method for creating printed electronic components, including resistors, capacitors, and transistors, using an additive method similar to 3D printers. Components are carbon-based and constructed using an aerosol spraying system (i.e., similar to inkjet technology), and insulating layers are built using cellulose.
The researchers are not just able to print components on a piece of flexible substrate; they can also add insulating layers, which may lead to adding more devices on top in order to create a truly 3D circuit. While the transistors developed by the team are extremely large (millimeters instead of micrometers), they are fully functional and continue to operate even when mechanically manipulated.
The most prominent feature of the printed circuits is that the designs are fully recyclable. The use of organic compounds and graphene allows researchers to dissolve old circuits and recover the inks for reprinting. This could enable future printed electronics to be fully recyclable and not require the use of landfills when old electronics are replaced with new devices.
Practical applications for 3D printed electronics
To understand what applications 3D printed electronics would provide, we first need to recognize their advantages:
- Enable fast prototyping of circuits
- Enable complete customization of the final design
- Potentially allow for designs to be stacked (i.e., creating active parts in all dimensions)
- Remove the need for highly complex processes
- Potentially fully recyclable
The first potential application for 3D printed electronics is the ability to create custom designs in remote locations. For example, 3D printers could be key to future space missions that aim to colonize extraterrestrial bodies such as Mars and the moon. Such systems would enable colonizers to create their own electronic products without the need to rely on Earth to produce ICs and other components.
The ability to rapidly create designs may make 3D printed electronics ideal for emergency repairs and replacements. For example, naval vessels and military base camps may utilize 3D printer systems for replacing and repairing defects in key equipment. As military environments can be both hostile and difficult to reach, the ability to send in replacement parts may be compromised; thus, any military installation or platform equipped with 3D printers could have an advantage over hostile environments.
As technology advances, older electronic components that are no longer in widespread use are discontinued by their manufacturers. While this does not affect modern designs, aging systems that are still needed (such as power plants and critical infrastructure) can be vulnerable to the discontinuation of components. The use of 3D printed electronics could allow the printing of such parts, thereby ensuring that aging systems can continue their operation while alternatives are sourced.
One major potential that printed electronics has is the ability to combine with typical 3D printers. A multi-nozzle design could simultaneously print structural plastic and components at the same time, essentially allowing for an entire design to be built in a single step. Electronics could be easily integrated into any part of a 3D printed structure, including components and wires, creating designs that are currently too difficult to manufacture. This could also lead to the possibility of printing components vertically on walls and allowing engineers to utilize all three dimensions instead of just two on a PCB.
Realistic expectations for 3D printed electronics
While the idea of 3D printed electronics sounds fascinating and promising, it is important that expectations are managed. Of all the challenges faced with 3D printed electronics, the biggest by far is that 3D printed electronics have a very small transistor density. This means that their data-processing capabilities are significantly smaller than modern processors and thus cannot be considered practical for commercial devices.
As such, it is unlikely that 3D printed electronics will ever replace silicon devices. Current manufacturing processes are extremely efficient at producing electronics at ultra-low prices. Modern processors may sell for several hundreds of dollars, but most microcontrollers sell for less than a dollar. As time progresses, such modern processors fall in price and eventually become cheap enough to use in everyday equipment.
Another challenge faced with 3D printed electronics may be what plagues 3D printers in general: Their designs are structurally weak. It is true that 3D printed parts can be made from metal, and plastic-printed parts are far stronger than they look, but fundamentally, these parts are prototypes. A plastic-injected moulded part will always win against a 3D printer simply due to the need for layers by the 3D printing system. For example, plastic on any single layer is very strong, but plastic on adjacent layers are not fully melted together, which creates grain boundaries. Thus, any force along the layers of a 3D printed design can cause it to shear with ease. The same effects may plague 3D printed electronics, especially those that are built using layers.
Future of 3D printing technologies
3D printed electronics are still in their infancy, but there is no doubt that what researchers have been developing is anything less than exciting. However, it is unlikely for such technology to begin replacing electronics commercially for the next decade or two. It is more likely that 3D printed electronics will be used in niche applications such as printed antennas in smartphones or RFID tags on products, as these applications are far less demanding than processors or memory.
