Now Printing: Electronic Components

Designers can functionalize a wide variety of parts and surfaces with embedded electronics

A 3D printed, 3.4 GhZ Wi-Fi antenna. Photo courtesy of Voxel8.

Mark Shortt
Editorial Director
Design-2-Part Magazine

What would you do if you could 3D print electronics?

Voxel8, a bold startup in Somerville, Massachusetts, is asking that question of design engineers everywhere via a video on its website (voxel8.com). The company, recognized as a 2016 Technology Pioneer by the World Economic Forum, has created a multi-material 3D printer for fabricating embedded electronics and other novel devices. Its first product, the Voxel8 Developer's Kit, is reported to simplify the development of electronics by enabling engineers to co-print thermoplastics and a highly conductive silver ink for circuits, right on their desktops.

Ultimately, Voxel8 aims to develop a technology pipeline to enable the mass customization of electronics and other finished products.

"At Voxel8, we're revolutionizing 3D printing by developing a full 3-dimensional electronics printing platform," says Jennifer Lewis, co-founder of Voxel8, in a company video. "Multi-material 3D printing holds the promise of mass customization of electronics and the ability to truly print your imagination."

If you're using Voxel8's Developer's Kit 3D printer, you might rapidly design a novel device with embedded 3D antennas, connectors, or transducers. If you're struggling with wire harnesses, you can replace them with 3D traces by using Voxel8's highly conductive silver ink. Maybe the best part is that you could design the electronics to fit your part, rather than designing the part around your electronics.

The Quadcopter is a fully functional UAV with a 3D printed exterior body, interior wiring, and embedded components. Photo courtesy of Voxel8.

"With our Developer's Kit printer, we will be able to integrate electronics into mechanical objects," says Michael Bell, co-founder and hardware lead, in the video. "You will be able to print devices, like quad copters and integrated electro-mechanical assemblies that typically have to be manufactured through multiple methods. Our conductive ink is specifically formulated for 3D printing. It prints and dries at room temperature, has excellent electrical properties, and has excellent adhesion to other matrix materials."

Highly conductive inks are necessary for 3D printing of electronics that have large operating currents, and Voxel8's silver ink, specifically formulated for 3D printing, is reported to be 20,000 times more conductive than conductive filled-thermoplastic filaments. It is also said to be 5000 times more conductive than carbon-based inks currently used in additive manufacturing, and to have excellent adhesion to other matrix materials. Bell describes Voxel8's team as "fundamentally materials experts" who have created a platform specifically designed to be upgraded with different materials as the company releases them.

Components Are Inserted During Printing

The Developer's Kit 3D Printer uses a pneumatically controlled, direct-write deposition method to print PLA (polylactic acid), a biodegradable plastic, and conductive silver ink that is reported to cure in five minutes. Users can insert electrical components into parts directly on the printer while it is printing. However, a kinematic coupling allows users to easily remove the build plate, or bed, if they need more room to insert components into parts during printing.

A 3D printed watch that houses an embedded microcontroller and LEDs in a free-form structure. A removable coin cell battery provides power. Photo courtesy of Voxel8.

"Our printer prints similarly to typical 3D printers–layer by layer. To place a part, the printer stops, allows you to remove the bed, place the part inside of the material, and then replace the bed on the printer. It will print right where it left off, knowing that there's a part inserted inside of it," Bell says.

The printer is a rugged machine, featuring a rigid machined aluminum chassis and a durable anodized coating. A Core XY motion stage, which the company says is precisely crafted and assembled, is mounted on top. "During assembly, all of our motion stages are electronically tested for accuracy so that they produce dimensionally accurate, consistent prints every time," Voxel8 states on its website. The printer offers a build volume of 150 x 150 x 100 mm, layer resolution of 200 microns, and conductive trace width of 250 microns.

A short video on the company's website offers a look at how the Developer's Kit 3D Printer is manufactured, showing glimpses of processes like machining, bending, and laser marking. Voxel8 says that it sources and manufactures many of the components locally before doing final assembly, calibration, and burn-in at its facility in Somerville, Massachusetts, just outside Cambridge. "From there, we ship to our customers around the world."

The Voxel8 Developer's kit was highlighted as "one of the 9 best ideas from CES 2015" by Fast Company and was selected as Gold Medal winner at the 2015 Edison Awards.

"The circuits of today are flat, two-dimensional circuit boards that are embedded into three-dimensional cases," says Karl Willis, research engineer at Voxel8, in a company video. "This whole paradigm is going to change because we're enabling designers to create circuitry and physical objects at the same time, using Voxel8's 3D printing technology."

In a video presentation for The World Economic Forum Technology Pioneer program, Voxel8 co-founder and Harvard materials scientist Jennifer Lewis talks about what makes Voxel8 innovative and unique. The company's mission, she says, is to create advanced materials that enable the integration of form and function in three-dimensionally printed products.

"Since its inception, three-dimensional printing has mainly focused on complex shapes or prototypes," says Lewis. "What makes Voxel8 unique is our proprietary functional materials that allow 3D parts to be fabricated with embedded electronics, antennae, and sensors."

The Quadcopter interfaces with an existing PCB embedded inside of a custom 3D model. Magnetic connections ensure contact between the PCB and printed silver interconnects. Photo courtesy of Voxel8.

An Embedded Watch and a Quadcopter

One product, the Embedded Watch, is a fully functional device in which electronic components are embedded into a 3D printed housing. During the printing process, a micro-controller, button, LEDs, magnets, and pogo pins are inserted into the watch and electrically connected to form a 3D circuit, Voxel8 states on its website. A coin battery, connected from a separate printed tray, powers the circuit. The watch is programmed to indicate the hours and minutes by blinking when the button is pressed. By illustrating how electrical and mechanical function can be closely integrated, the Embedded Watch shows how electronics can be designed to fit the part, the company says, rather than designing the part around the electronics.

"The end result is a free-form circuit deeply integrated into the design," the company says.

Another example is the Quadcopter, a fully functional UAV (unmanned aerial vehicle) with a 3D printed exterior body, internal wiring, and embedded components. Inside the thermoplastic exterior body, a circuit board, motors, and LEDs are connected via printed silver traces. Here's where the conductivity of the Voxel8 silver ink comes in handy–it's high enough to handle the current drawn by the four motors, the company says.

Voxel8 is collaborating with Autodesk, the developer of "Project Wire," a Spark powered design tool for 3D printed electronics. Autodesk's Project Wire creates an end-to-end pipeline in an effort to make it simple for users to create 3D printed parts with embedded functionality. It enables users to bring in their CAD models to place components and to route wires in 3D using the Autodesk Spark platform, said Willis. "That's really happening for the very first time. The software for this simply did not exist before."

Highly functional materials are the key enablers of Voxel8's core technology. The company is working to apply more than a decade of research, which has led to 17 patents (10 issued) on functional materials, print heads, and other processes for 3D printing, from the Harvard lab of co-founder and materials scientist Jennifer Lewis. Her work provides the foundation for Voxel8's efforts to revolutionize multi-material 3D printing, and is reported to have led to the development of advanced materials for the manufacturing of lithium-ion micro-batteries, stretchable electronics, sensors, and 3D antennas. Through its Developer's Kit and industrial partnerships, Voxel8 is working to bring these technologies to market.

To realize its vision, the company has recruited a multi-disciplinary team with expertise in advanced materials, precision hardware, intelligent software, and design.

"We are a group of passionate engineers and designers who are literally making the future," she says in Voxel8's video for the World Economic Forum's Technology Pioneers program. "Specifically, we are creating new functional materials for digital manufacturing, new software for product design, and new printing platforms that ensure the seamless integration of form and function."

Lewis believes that companies that fully embrace the growing convergence between materials, hardware, and software will emerge as the leaders of this digital revolution. "The opportunities are truly enormous, and Voxel8 is at the forefront as one of the 2016 Tech Pioneers," she said.

Taking 3D Printed Electronics to the Micron Scale

An Aerosol Jet 3D printed micro-structure showing a free-standing, millimeter-wave dipole antenna. Photo courtesy of Optomec.

As Voxel8 works to bring 3D printing of antennas, connectors, and other electronic components into the mainstream, a company in Albuquerque, New Mexico, is showing design engineers another possibility to consider. Optomec, a maker of production-grade equipment for 3D printing of electronics and metals, offers an Aerosol Jet Technology that can print sensors, circuits, interconnects, antennas, and other electronic components onto a variety of non-planar (non-flat), complex three-dimensional surfaces. Feature sizes from as small as 10 microns–including tiny polymer and composite micro-structures with electronic functionality–up to millimeters in size can be printed by the technology.

"Our technology is currently being used in production today–24 hours a day, seven days a week–by companies such as Lite-On Mobile and General Electric for printing antennas on smartphones, and sensors on turbine blades," said Optomec Director of Aerosol Jet Product Management, Mike O'Reilly, in a phone interview. "What makes us different in the marketplace is we have a high standoff distance between the nozzle tip and the surface of the substrate, which enables us to print on complex parts."

Optomec's process is based on a print engine that delivers tiny droplets of electronic ink, suspended in an aerosol mist, to the print head. There, an annular sheath gas surrounds the droplets so that they don't come into contact with the head and cause clogging. As the aerosol passes through the nozzle surrounded by the sheath gas, it is aerodynamically focused into a tight high-velocity stream that enables creation of high resolution features on the substrate. Because the high-velocity mist stream remains in focus at distances up to 5 millimeters, the Aerosol Jet process can maintain desired feature size and resolution while printing on non-uniform surfaces. If necessary, the print head can also be tilted to print on vertical surfaces, such as stacked dies.

"That type of process allows us to fly high over the surface," said Richard Plourde, Optomec business development manager, in an interview at Rapid 2016 earlier this year in Orlando, Florida. "So we can be 5 millimeters away from the surface and still maintain feature definition down to 10 microns. We can go from 10 microns up to 3 millimeters in width, and from about 100 nanometers to about 5 microns in thickness."

Optomec's Aerosol Jet Technology came out of the Defense Advanced Research Projects Agency's Mesoscopic Integrated Conformal Electronics (DARPA MICE) program, a 4-year, multimillion-dollar project aimed at developing a new tool for manufacturing electronic components ranging in size from 10 microns to several millimeters. The new tool, according to Optomec, had to be capable of rapidly producing electronics directly from CAD models. It also needed to "support processing of a wide variety of materials to produce robust, customized electronic components in a conformal manner on virtually any substrate, including low-temperature (below 200 degrees Celsius)."

Optomec (optomec.com), one of several companies that participated in the $45 million program, was awarded a $9 million contract to develop its direct-write techniques for manufacturing microelectronics. Its work resulted in what is now the Aerosol Jet Technology. "After that contract, we decided there was enough in the technology that we could commercialize it," said Plourde. "So we started commercializing in 2005, and we're into our 11^th year of commercializing."

The Aerosol Jet Technology can print various types of inks, ranging from conductive nanoparticle and polymer inks to dielectrics, semiconductors, etchants, dopants, and bio-materials. Virtually any materials that can be dispersed in a solution and atomized can be printed, according to Optomec.

"That material could be nanoparticle–silver, gold, platinum, palladium inks, copper inks–or it could be dielectric materials, insulating materials, or other types of materials with biological matter," O'Reilly told D2P. "So it doesn't matter, as long as it's in a liquid pool of material, and as long as it fits our droplet size."

This strain gauge illustrates how electronics can be 3D printed onto a non-planar (non-flat) surface. Photo courtesy of Optomec.

A key advantage of the technology is that instead of having to print everything on a flat surface, Aerosol Jet can print on conformal surfaces, allowing users to embed sensors, for example, directly onto the surface of the substrate. As a result, the process was used to print antennas on smartphones when the manufacturer wanted the antenna to be made by putting metal rings around the plastic substrate. Traditional electroplating wouldn't work, so the Aerosol Jet process was used to print capacitive sensors onto the inside covers of the smartphones.

O'Reilly called the ability to print onto complex shapes a key advantage of the technology that allows users to fully functionalize electronics onto plastic objects. Besides smartphone antennas, application examples include the printing of rear windscreens on polycarbonate to lighten the weight of a car, and printing onto three-dimensional objects to replace automotive cables and harnesses.

Another unique capability of Aerosol Jet is its ability to print around three-dimensional objects, Plourde said. "With our 5-axis system, we'll take a CAD file of the object and we create a zero, zero (0, 0) point based on feature recognition, and we can print around the object, which is very unique," he told D2P. "You can't do that with planar-type applications, like pump dispense syringe or an inkjet type of application."

Stacked Die Connectivity

Electronics packaging is another key area of application. As the density of parts increases and more and more functionality is designed into them, the traditional methodology of wire bonding may no longer work, O'Reilly said, because wires can sway as interconnections are being made. But the high standoff distance between the Aerosol Jet nozzle tip and the surface of the substrate enables a solution.

"If I have a bunch of interconnects very closely spaced to each other, and I have swaying of those wires as I'm putting in wire bonds, I'll get cross-talk, I'll get shorting, I'll get all sorts of issues," he said. "But if I can take a series of stacked dies, we can directly print up the sidewalls of those stacked dies–that's one of the advantages because of the high standoff distance–and eliminate that sway and those kinds of shorting. So we can help increase package density with our technology."

Plourde said that Aerosol Jet's capability to replace wire bonding on a stacked die offers a novel approach to designing electronic components.

"We're running into applications now where engineers can really think differently in terms of design because [Aerosol Jet] is a novel approach to be able to do something that they couldn't do before, such as replacing wire bonding on stacked die, in a cell phone," Plourde commented. "Packages are getting smaller and smaller, the wires are getting closer, and so they have to find a way in which they can provide stacked die connectivity. And they can do that with our technology."

A 3D printed dome is another example of the Aerosol Jet Technology's ability to print on curved surfaces. Photo courtesy of Optomec.

Tightly Packed Assemblies

Plourde offered a case study reporting that NASA technologists at the Goddard Space Flight Center in Greenbelt, Maryland, have begun to assess the use of Aerosol Jet printing to construct tightly packed electronic assemblies–novel detector assemblies that can't be created via conventional assembly methods.

According to Beth Paquette, a technologist at Goddard, the technology's ability to print carbon nanotubes and print around bends, on spheres, or on flexible surfaces make Aerosol Jet highly suitable for detector assemblies. That's especially true, she said in the case study, of "assemblies that require varying shapes or are very tiny yet dense, due to the large number of miniature parts that have to be electrically wired or connected together on a circuit board."

"We can make these wires microns in width," Paquette was quoted as saying. "These lines are very small, down to 10 microns wide. These sizes aren't possible using traditional circuit board manufacturing processes."

In another case, the Optomec Aerosol Jet 500 system was used at the Lawrence Livermore National Laboratory, opening the door for creating miniature circuits on surfaces and substances that couldn't be used before, according to an application summary from Optomec. The system was reported to have allowed engineers to manufacture conductors, semiconductors, and microcircuits "with an intricacy and flexibility not possible with the Lab's previous technology."

Optomec's Aerosol Jet 5X System was used to print creep sensors, antenna, and a strain gauge on this dome. Photo courtesy of Optomec.

"I can make electronics that are not only flat, but curved," said electronics technologist Julian Larregui, in the summary report.

The 260-square-foot Optomec system was also considered a potential replacement for an entire 2,700-square-foot electronics prototyping facility, which reportedly required a high volume of hazardous chemicals to operate. "We're in the process of moving toward a safer environment," said Chris Bishop, electronics managing supervisor in LLNL's Materials Engineering Division, in the report. "It's really cool to say we've eliminated the hazard and have the same capability, but to have more capability in less space is huge."

Laboratories still comprise a large percentage of Optomec's customer base. "Up until three years ago, 95 percent of our sales were into R&D facilities," O'Reilly said. But now, the company's focus is to help manufacturers get into a production environment, said Plourde. "It's not just R&D anymore. It's not just low-volume manufacturing; it's something that scales up," Plourde told D2P. "What's developed in the lab can be transferred into production, so our focus is production."

Plourde said that Optomec is always trying to find new materials with the type of functionality that can expand Aerosol Jet's application range. An example is a material for high-temperature strain gage applications, such as printing onto turbine blades in the hot section of an engine. He pointed to a display showing a sensor measuring creep on land-based turbines.

"It's ceramic, so it meets 1800 degrees Fahrenheit, and it's part of the Industrial Internet, where the sensors are being read," he said. "It's fed to a predictive modeling program, and it predicts when a part will fail before it fails. We can't do the same thing on high-temperature strain gages because the material doesn't exist. So we're always working with material vendors to find a good material that will meet the criterion."

When a customer defines a potential application, Optomec will do proof of concept testing at its application development center in St. Paul, Minnesota. So far, its customers don't include contract manufacturing companies, but that may change. "That's one thing we may want to look at–to expand the capability to contract manufacturers that are looking to bring our technology in, and do [application testing] for companies that want to contract manufacture."