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3D Printed Electronics: Next Phase of the Additive Manufacturing Revolution?

By Mark Solomon| Business Development Media

3D Printed Electronics: Next Phase of the Additive Manufacturing Revolution?

The numbers do not lie: 3D printer company revenues have grown at a compound annual growth rate (CAGR) of 16% for the past decade, according to Wohlers Associates. With that kind of steamrolling growth, all of the early hype about 3D printing turned out to be well founded.

Now we know similar expectations are emerging for the next phase of 3D printing development: functional circuits “built” or “grown” in layers using variants on basic 3D printing principles and platforms.

From Korea’s nano-sized 3D printed graphene for flexible electrical circuits to the Keck Center’s 3D printed dice with embedded circuitry, advances are coming from both government and industry. Korea’s Ministry of Science KERI center announced its nano-graphene conductive 3D printing capability in December 2014, while University of Texas-El Paso’s Keck Center has demonstrated embedding conductive materials in 3D objects online.

Keeping track of the variety of 3D technologies and progress from prototype to direct part production can be a challenge. With over 30 3D printing companies traded on North American stock exchanges plus start-ups, universities and government research centers all pushing 3D capabilities, every month brings new advances. 

Difference between 2D Printing and 3D printing of Electronics

2D circuit printing technologies include everything from screen printing, automatic conductive paste deposition systems on a flat surface, laser printing, thin film deposition, and solution coated OLED (Organic Light Emitting Diode) fabrication. All of these processes operate on flat surfaces for the most part, and cannot be applied to substrates with contours or multi-axis dimensions.

2D electronic fabrication methods have advantages compared to current 3D electronic / conductive material printing methods. With decades of development behind them, 2D electronic fabrication systems are reliable, fast, and potentially inexpensive depending on the process and the number of circuits produced. Generally, their limitation is that they can deposit conductive material only on flat substrates, though flexible circuits are also possible by later deforming the flat substrate. The resulting electronic circuit becomes a separate component from the structure of the final product.
(While Optomec using aerosol jets can apply conductive material to 3d objects of limited geometry like simple curves post fabrication, it is a considered hybrid system that is not full 3D printing of electronics.)

3D electronic printing can function much like 2D printing, with the added advantage of being able to produce 3D objects with the wires and circuitry embedded within the structural material. 3D electronic printing allow designers to create products that are smaller, lighter, more efficient, and more customized. Many 3D printed electronics are almost impossible to create with standard 2D electronic fabrication methods.

The reality thus far is far not quite at the anticipated level of easy electronic to structural integration.

Trends in 3D Printing for Electronics

Mechanical 3D printing technology is well established. Design studios easily produce prototypes with 3D printers in plastic or metal, depending on need. Home hobbyists can create almost any small envelope 3D shape their imagination and budget can handle. 3D printing for electrical circuits or components, however, has not moved as quickly from concept into practical use in either industry or prototype labs.

Broadly speaking, the 3D conductive/electrical printing technologies vying for commercial success are, in no particular order:

  1. Filament base with inkjet applied conductive inks;
  2. Filament base with syringe applied conductive gels;
  3. Filament base with embedded copper conductors, a system developed by the Keck Center of Univ. of Texas at El Paso, a version of Fused Filament Fabrication or FFF;
  4. Graphene substrate and conductor as demonstrated by Korea’s KERI center;
  5. Filament base with conductive aerogel applicator.

Researchers are focused more on the materials than the applicators, with the exception of the copper embedding system. A variety of materials including silver pastes, silver based gels, and nano-particle graphene substrates are all possibilities for reducing cost, increasing conductivity, and increasing reliability for 3D printing of Electronics.

According to Dr. Chris Spadaccini, Director of Additive Manufacturing Initiatives at Lawrence Livermore National Laboratory, two companies have prototyping machines ready, with one already shipping. Both Optomec with an aerosol jet spraying conductive liquids typically loaded with particles, and Voxel8 which extrudes conductive, 3D printable inks, are delivering machines for industrial-level prototyping and functional components. As Dr. Spadaccini explained, “Optomec’s aerosol jet print head does not create a 3D structural part, but rather coats an existing 3D substrate using an aerosol jet to apply conductive media. The conductive media itself is not self-supporting. Voxel8’s machine uses extrusion techniques and 3D printable inks for integration of electrical components into 3D structures. Voxel8’s machine is more in-line with the general concept of 3D printing.” Regarding Korea’s recent announcement about successfully creating nano-graphene based flexible circuits, Dr. Spadaccini noted, “3D graphene printing is at the cutting edge of conductive materials development. Any advancements in this area, especially with flexible circuits, would be quite interesting.”

stretchableattena

(Photo courtesy of Lawrence Livermore National Laboratory)

“A flexible and stretchable antenna printed with conductive ink at Lawrence Livermore National Laboratory."

2-D Electronics are Common While 3-D Printed Electronics Have Challenges Ahead

According to researchers including Dr. Elena Polyakova of Graphene 3d Lab, “The key challenge in 3D printing electronics is developing material suitable to be used in a desktop 3D printer. To do this, you must incorporate conductive material (such as graphene) with a standard 3D printing material, but not so much that the filament loses processability. The advantages of 3D printing are that it has the ability to truly integrate electronics with objects, and the fact that 3D printing allows for distributed manufacturing.”

Another key hurdle appears to matching the current level of reliability, functionality, and low cost of readily available 2D electronic fabrication techniques.

Professor Eric MacDonald, Associate Director of the Keck Center-UTEP, and one half of a world renowned 3D conductive printing duo with Professor Ryan Wicker, has confronted many of the challenges mentioned by Dr. Polyakova. MacDonald speaks about the center’s R&D with the excitement of a pioneer who has discovered a land filled with gold. In his case, it is a technology filled with copper. The team’s R&D has shifted from the prevalent silver paste injection method of 3D printing, to a new approach embedding copper wire through unique processes. MacDonald explains: “We worked with silver based inks for 10 years, but moved away because they were inferior to copper boards.” In a case of borrowing from old technology to create the future, the team changed approaches: “Now we 3D print with thermoplastics then imbed wires into the thermoplastic with ultrasound resulting in a circuit that is far more conductive than printed inks, they are at least 100% more conductive, and the wires improve structural integrity of the end product.” Professors MacDonald and Wicker are spearheading a $2.5 million grant from the U.S. government for developing additive manufacturing to build the factory of the future. According to  MacDonald, the future of additive manufacturing will include their copper embedding system.

Directors of Keck Center

Prof. Eric MacDonald (left), Ph.D., Associate

Director of W.M.Keck Center for 3-D Innovation with Keck Center Director Prof. Ryan Wicker (right) and Frank Medina (center), former Manager, now with Arcam at Oak Ridge National Labs. Prof. MacDonald is holding a 3d printed piece that was launched into space. The machine behind the group is called Fortus 900mc from Stratasys used for prototyping electronics today.

The advantages of 3D printing of electronics are multifold according to MacDonald, “advantages include: complex geometries, aerospace parts can have radiation shielding plastics embedded, mass customization for biomedical companies making perfect copies of anatomy, the lack molds needed, CAD based software, building structures that could not be built with other processes. Eventually even the cost of high volume parts could be lowered with their system to surpass current 2D electronics printing.” There are other, possibly more critical advantages to the wire embedding technology. “We are 10-20X more conductive than inks, at the same conductivity of PCBs, and the wires improve the mechanical properties of the structure which is interesting as anisotropy can affect Z strength in some 3D printed technologies.”

An example of the Keck Center’s 3D conductive printing prowess using the standard silver past method is shown below in the glowing dice demonstration:

(YouTube video  http://youtu.be/IrCDKWmqgcs)

Prof. MacDonald also pointed to the University of Nottingham’s leadership role developing conductive inkjet 3d printing technology. Nottingham’s Additive Manufacturing EPSRC Center is developing jetting technologies based on the FujiFilm Dimatix DMP2831 and two PixDro LP50 systems. These systems allow for depositing particulate inks containing conductive materials like silver, as well as dual ink deposition for the PixDro version. According to the center’s site, the focus is on integrating the advanced depositing systems with existing additive manufacturing substrates.

Dr. Polyakova believes the future lies in Fused Filament Fabrication, much like the Keck Center is pursuing: “Fused Filament Fabrication (FFF) is the 3D printing technology which is most versatile for 3D printing electronics. This is because the process of FFF 3D printing is highly suited for multi-material printing. With that being said, 3D printing technology is still developing and I would say that it is future generations of 3D printers which will be widely used by industries such as automotive and medical; this is where our company, Graphene 3DLabs, is focused.”

While the Keck Center and Professors MacDonald and Wicker are producing prototype 3D electronics, industry analysts remain somewhat skeptical about the ability to scale and produce reliable components.

Anthony Vicari is a Research Associate leading 3D analysis for the Advanced Materials team at Lux Research Inc.  Lux Research provides strategic advice and ongoing intelligence for emerging technologies to business, finance, and government.  Vicari pointed out, “Everything is in the lab in prototype stage.” Over nearly an hour of discussing the state of the 3D printing electronic and conductive materials industry, Vicari detailed many significant industry developments and the chances of the technology making it to market. “Some of the technology leaders from R&D include Princeton developing a 3D printed quantum dot LED, and Lewis’ group at Harvard creating electrically active biomedical devices and batteries.”

3D Electronic Printing Technologies Close to Market Viability

Vicari further explained: “The fastest way to market now for 3D electronic printing is by combining current technologies into one platform. For example, 2012 Stratasys and Optomec began working on an aerosol jet to combine 3D printers or depositing conductive traces. Another leader in this combined approach is 3-Spark, a spinout from Northeastern University, using filament printing of thermoplastics with syringe printing of conductive elastomeric gels. Instead of attempting a difficult technical leap by creating completely new 3D printing methods for electronics, companies are building up from known technologies. This approach will bring new 3D electronic printers to market much faster.”

As with many exciting technologies, often the promises can exceed the reality. Despite the R&D nature of all 3D electronic and conductive materials printing, some companies have already gone public without complete, saleable products. The hope is to gain funding for completing the long R&D process resulting in a viable product.

One area that these development stage public companies are pursing involves a carbon based material called Graphene created by the University of Manchester in 2004. Graphene is a form of graphite that is exceptionally strong, light, and conducts heat and electricity very efficiently. Being able to 3D print graphene would open the door to a wide variety of flexible electronics applications.

While Korea’s KERI center has demonstrated a 3d printed Graphene nano circuit, Graphene 3d Lab has also created 3d printed Graphene components, including a battery. Dr. Polyakova explains: “...3D printable battery technology is one advancement of ours which I am personally excited about. The graphene-enhanced materials that have been developed by Graphene 3DLabs allow the 3D printing process to be used to fabricate a functioning battery which may be incorporated into a 3D printed object during the build process. “

Even though Voxel8 and other 3d printed electronics companies have no deliverable product just yet (Voxel8 plans machine shipments possibly by March according to their site), Vicari believes, “new 3D electronic printing companies will be able to get products to market faster than ever. They will use multiple printing heads for combining a plastic filament dispenser with perhaps a conductive gel dispenser or a conductive inkjet. The integration is not easy, but much easier than attempting to perform all functions with one material.”

The main limitations for 3D electronics printing relate to materials availability, reliability of the final product, repeatability, speed, and yield. Vicari explained: “The materials selection for 3D electronics printing is severely limited. Also, reliability and repeatability for high volume manufacturing in the auto industry is not there. For aerospace and biomedical applications, 3D electronics printing is much closer to being able to satisfy the low volume, high-material cost environment, high customization needs.”

Another challenge for 3D printing in general, according to Vicari, is the low quality of most 3D printed final products: “Surface finishes are just not at the level that consumer product manufacturers demand.” The most likely area for near-term, production-ready 3D electronic printers is for “antennas, micro batteries, and sensors.” Telling the difference between a 2D electronics fabrication produced antenna and 3D printed antennas and sensors may be a challenge because many of them are 2D objects. Initially at least, Vicari believes these are the only components suitable for early 3D electronics methods.

The 3D Electronics Printing Future is Around the Corner

MacDonald and the team at the Keck Center have already produced several fully integrated 3D electronic components using the unique wire-embedding methods. “With our mandate to lead the additive manufacturing center in providing factory ready 3D electronic printing systems in the near future, we think we have the technology approach and systems in place to fulfill our mission on schedule.” Based on their rapid progress in 3D electronics printing, proof of concept, and multiple patents from Professors MacDonald  and Wicker, it appears that additive manufacturing systems using the copper wire embedding technology from the Keck Center is headed to factory floors world-wide in the very near future.