When the aircraft maintenance crew at Warner Robins Air Force Base asked for better safety monitoring when they work in fuel tanks, they got a Bluetooth-equipped, flexible, conformal armband that monitors volatile organic compound (VOC) concentrations, oxygen levels, temperature and humidity. The safety device was developed by NextFlex, using an emerging technology called flexible hybrid electronics (FHE)—in collaboration with the Air Force Research Laboratory’s Materials and Manufacturing Directorate and 711th Human Performance Wing.
“It’s a new way of integrating electronics into things,” said Janos Veres, director of engineering at NextFlex, the Manufacturing USA innovation institute focused on FHE. “Obviously the lead applications are in defense and aerospace, but this technology will migrate ... everywhere.”
Overall, Veres’ prediction is bolstered by analysis of the FHE market.
“In the past five years, the global market revenue of printed electronics has increased rapidly, for a combined annual growth rate of 22 percent, according to the market research report of Prescient & Strategic Intelligence,” Yuepeng Zhang, principal materials scientist at Argonne National Laboratory, said in a webinar on making materials for FHE. “With this rate, overall revenue is projected to grow from $36 billion in 2019 to $360 billion by 2030.”
In addition to environmental monitoring like that done at Warner Robins, applications for FHE in aerospace and defense exist in biomedical assessment, security, communications, energy generation and storage, computation, supply chain management and asset sustainment.
It’s easy to see why the aircraft maintenance team at the base favors its new armbands over traditional means of monitoring their safety.
“Current methods of monitoring worker health and safety in confined spaces rely on bulky atmospheric monitors and continuous visual observation,” according to a story posted on the NextFlex website. “These methods are labor intensive and inaccurate, as they cannot monitor the atmosphere directly around the workers or indicate when workers are in a dangerous situation.”
Just like at Warner Robins, the use of FHE over traditional semiconductor integrated circuits is popular because they are flexible, smaller and lighter.
For example, the NextFlex Flexible Microcontroller weighs 70 percent less than the Arduino Mini microcontroller board.
In addition to those parameters, FHE also satisfy the global demand for electronic devices that are less expensive and more energy efficient, Zhang said.
Despite the advantages, there are issues to overcome.
“One key concern for the U.S. electronics industry, and for defense electronics in particular, is that while significant research and development in electronics occurs domestically, much of the manufacturing strength for electronics products resides overseas,” according to a 2016 report from the Air Force Research Laboratory (AFRL). “This tendency for stronger foreign manufacturing of electronics implies that U.S. defense organizations must actively work to ensure the availability of domestic suppliers and improve their capability to meet the demand for increasingly sophisticated defense electronics.”
An official with AFRL confirmed this statement still rings true in 2021.
Globally, growth of the emerging technology is hampered by the need for more materials, processes and machine tools, said NextFlex Executive Director Malcolm Thompson.
In the United States, the manufacturing sector is well positioned in the FHE industry because of its knack for innovation, he said, and because of the bright minds who work in it.
“Talent?” Thompson said. “In the main, yes, we have it.”
Some of that talent resides within NextFlex, where engineers used FHE to create a wearable device that can be used instead of a smartcard by Department of Defense (DoD) personnel for secure access to military systems.
Adding order to chaos
In an office or other controlled environment, use of a smartcard and PIN to gain access is not only secure but the process is easily managed.
That’s not the case in a tactical situation or in combat, however.
For those chaotic situations, NextFlex collaborated with the U.S. Army Combat Capabilities Development Command to make a flexible, wireless FHE device that can be worn in the cuff of a shirt. The technology is in the pre-production, pilot stage.
“Instead of having a rigid card or puck that you normally have, you can imagine the ultimate goal of this project would be to create a device that’s embedded into a cufflink or the user’s textiles, something that you don’t notice,” said Sean Nachnani, a hardware systems engineer who led the project for NextFlex. “It’s just part of your clothing or uniform and it doesn’t have that weight constraint. That’s the beauty of FHE: It’s so thin, it’s conformal, it bends with you. You don’t notice it.”
Part of the manufacturing process for FHE is slicing silicon chips to a thickness of just tens of microns.
“That’s what’s exciting about the technology that we’re doing, because at that point silicon is bendable,” Veres said. “So, we’re making the overall circuitry together with the silicon potentially bendable.”
The DoD security device’s power and communications are wireless, so there are no ports for moisture and dust to enter.
The entire device is encased in a soft silicon resin achieved via an over molding process, which also offers protection against humidity, moisture and mechanical impact.
NextFlex hasn’t completed ingress protection testing. But other devices shielded in the same way easily are rated at IP68, said Rob McManus, engineering manager for software and testing.
Use of a similar wearable device could be applied to access secure locations in industrial settings, hospitals and even homes.
While FHE are critical for making better security devices for the DoD, Lockheed Martin is using them to make small, unmanned aerial systems (SUAS) like its Condor eXtended Endurance & Payload (XEP) see around corners.
Lockheed developed the Condor XEP in conjunction with the AFRL for intelligence, surveillance, reconnaissance/search and rescue operations.
It has a 143-inch wingspan and 68-inch fuselage, and a communication range of about 9.3 miles. The Condor XEP is designed to mimic a larger vehicle at a significantly lower cost, be portable and hand launchable.
The SUAS is equipped with a camera and night vision, but Steve Gonya, a research fellow in Lockheed’s advanced manufacturing technology group is leading efforts to add solar power and real-time, high-definition video streaming. The team is also upgrading the Condor XEP’s satellite communications (SATCOM) capability.
In general, all of these features have been included using conventional circuit boards but “what this is doing is looking at taking out the rigid components and putting more and more of the circuit function on flexible circuit cables alone, eliminating those bulkier, heavier-weight structures,” said Gonya’s co-collaborator Mark Poliks, engineering professor and director of the Center for Advanced Microelectronics Manufacturing at Binghamton University.
Gonya said they’ve already replaced a “big rat’s nest” wiring harness with FHE and added new circuit boards for power management.
To capture power from the sun, he’s using flexible, high-efficiency, triple-junction gallium arsenide solar panels on the SUAS’ wings. The team’s doing flight testing now.
“It doesn’t appear to affect the aerodynamic characteristics of the aircraft but we’re measuring how much power it generates,” Gonya said. “On a nice, sunny day, a full complement of solar cells on a wing should generate over 100 watts of power.”
One hundred watts is enough or close to the power needed for sustained flight, he said. In comparison, the lithium-ion batteries currently used to power the Condor XEP support about four hours of flight time.
Also in testing is a dual-band, minimal input-minimal output communications (MIMO-COMM) data link for real-time, high-definition video streaming from the SUAS’ camera.
The flexible, conformal antenna was designed by a team from the University of Massachusetts, Lowell. It looks like a patch stuck to the bottom of the SUAS’ wing. The MIMO-COMM replaces a blade antenna that is attached perpendicular to the wings.
“It can basically bounce around corners,” Gonya said. “Normally that’s a bad thing but for MIMO they can handle those multiple inputs. So, you can get a little better than line of sight.
“Plus, we wanted a nice, spherical antenna pattern with no nulls,” he said, contrasting the MIMO antenna’s radiation pattern with the doughnut-shaped pattern of an omnidirectional antenna. Omni antennas’ radiation pattern has loss of signal at the middle-top and middle-bottom.
Yet to be added to the aircraft for testing are FHE for SATCOM capability for beyond-line-of-sight video uplink.
Most SATCOM communication apertures are big and bulky, about the size of a breadbox. None of the commercially available apertures fits on an SUAS the size of the Condor.
“That was the most ambitious goal, the satellite communication,” Gonya said.
Though a partnership with the Georgia Institute of Technology, Lockheed developed a flexible aperture with electronics, circuitry, antenna elements and phase shifters all integrated to do a true phased array with beam steering.
“The electronics are integrated with the antenna to do the beam steering as the aircraft flies around and tries to follow the satellite,” said Gonya. “This is cutting-edge stuff here. We developed an aperture that’s sufficiently small and flexible with sufficient gain that we can now integrate it with this Group 1 aircraft.”
The team is still doing testing on communication range.
While Lockheed Martin’s technology is state of the art, today’s cutting edge in flexible, conformal hybrid electronics may lead to tomorrow’s innovation that incorporates sensing and functions even more closely with devices.
“I think that’s really the opportunity that’s pending in the future,” Poliks said. “We’ll see electronic skins for objects.”