David Savastano, Editor02.24.21
For the present time, the COVID-19 pandemic has changed how conferences are organized. This has led to a lot of new approaches. But what doesn’t change is the need to present new information to attendees.
When it comes to flexible hybrid electronics (FHE), the FLEX shows are ideal. Typically held in the early part of the year, FLEX showcases new FHE technologies, material and equipment advances and more. Last year’s show was just at the beginning edges of COVID-19, and this year’s conference was forced to go virtual.
As a result, FLEX 2021 is being held over four days, with each day featuring a keynote speaker and a panel of speakers whose talks are being offered on-demand later that afternoon. Also, there are TechTALKS, poster and networking sessions.
The first day was Monday, Feb. 22, with the focus on FHE systems. The second day featured discussions on materials. The speakers offered insights into the future of FHE technology, which continues to look promising.
The conference continues today, Feb. 24, covering Sensors and MEMS, and Thursday, Feb. 25 (Sustainability and Power). There are also concurrent sessions on Flexible Technology from Asia on Feb. 23-24. On demand content will be available through March 26. Here are some of the highlights so far:
The Possibilities of FHE
Flexible hybrid electronics are finding new applications. In her keynote talk, “FHE Systems,” Ana Claudia Arias of the University of California Berkeley’s Electrical Engineering and Computer Sciences Department, said that form factor is a key advantage.
“The form factor is something we care a lot about – it can be conformable to the human body,” Arias said. “Flexibility has to do with form factor.”
Arias discussed the hybrid nature of FHE allows the device to combine the best of both worlds.
“The flexible part cannot do all the work that is designed for the system, such as communication of data,” Arias continued. “Hybrid allows us to take the flexible part and adds conventional electronic components, maybe something as simple as a discrete component. We have worked on systems where we needed to add a battery holder. Electronics come from the need to have an active system, such as wireless communications.”
“An FHE system is a complex system,” said Arias. “If you think about wearables, no wires are allowed in that space.”
“In order to be successful, it requires a lot of collaboration,” Arias said. “FHE also requires long-term funding. My team works on printing on flexible substrates, whether it is blade coating, inkjet, 3D printing and screenprinting.”
“Much of what we do comes out of the vision of the Human Intranet, which needs a lot of sensing to know the baseline of every individual human,” Arias said. “We started by looking at the bias signals we need to measure for electromyography and blood oximetry projects.
“EMG monitors muscle activity, used for gesture recognition and impact in rehab. The electrodes are bulky and connected by wires to computers. The accuracy is not very high and resolution is limited by the number of electrodes you can put on the body. In 2016 we started working with NovaCentrix on a system that could perform EMG as a wearable. The form factor part – two layers printed were easy – electrodes printed using silver nanoparticle ink. With that, we were able to control robotic arms.
“Blood oximetry can compute oxygenation, not just of blood but also tissue,” Arias added. “It was very complex printing – we wanted very close contact with the body. Accuracy was comparable to commercial sensors, but it still wasn’t wearable. We came up with a new sensor design.”
Arias’ talk was followed by a panel discussion co-moderated by session chairs Ben Leever of US Air Force Research Labs and Scott Miller of NextFlex. The panel featured Kris Erickson of HP Labs; Robert Street of PARC; Arsalan Alam of UCLA; Azar Alizadeh of GE Research; Regina Shia of US Air Force Research Labs (AFRL); and Kiarash Vakhshouri of Google Hardware.
Erickson talked about HP’s work on 3D printing.
“Instead of a color agent, we have a conductive agent,” Erickson noted. “We can define where we want to put conductive voxels, and can integrate pick and place, add conventional components, or print in components. Form factors can provide extra value.”
“We are still early stage on these,” Erickson added. “We haven’t looked at reliability testing on specific applications. It has to have all of the advantages of standard electronics while being able to go into a new manufacturing approach.”
Street noted that PARC is developing FHE for asset tracking, tracking temperature, humidity, impact and air leaks, while doing this as much as possible using printed electronics techniques.
“Some of the sensors are fairly conventional and some are quite new,” said Street. “Asset tracking is data logging, determining if something happened to a package. Multiple sensors can give you more data.”
“We’ve used carbon nanotubes for gas sensors and printed resistors,” Street reported. “Liquid metals are quite interesting for 3D structures and stretchable materials.”
“Delivering low-cost FHE devices is a challenge,” said Street. “One of big challenges has been finding that large application. It is clear costs can come down, but getting the application that will need roll-to-roll is important.”
Alam reported that his group has developed a highly flexible, very lightweight system that has up to 20 channels and integrates it all on a flexible substrate, such as for spine surgery and rehabilitation.
“FHE systems require a lot of teamwork, but there are definitely a lot of solutions,” Alam said. “In our work, we were able to show we can integrate high-performance electronics on flexible substrates. The bottleneck is power delivery; we still have to integrate bulky battery systems to bring more processing power and recharging.”
Alizadeh said that GE is working on low-cost wearable systems for health and performance monitoring.
“We do a lot of printing on flexible substrates and deliver functionalities at higher levels,” Alizadeh noted. “Real-time analysis is one of our most recent focuses. We are focusing on analytics; devices are a tool. We have capabilities to spend the data to our mobile app and the clouds.”
Alizadeh talked about the difference between the lab and fabrication.
“Working in the lab is really different from integrating into production,” said Alizadeh. “Sustainability is a very important question. The whole point is to improve workflow for nurses but it creates waste.”
Shia discussed materials for cognitive enhancement in an aerospace environment.
“We work with larger groups within AFRL on materials while other AFRL groups work on open architecture,” Shia said. “We have to sense fatigue in real-time. The cockpit environment is very difficult. We have to make sure devices are compatible with Air Force equipment such as helmets. We also have to make sure electrodes don’t dry out and function at higher altitudes.”
Vakhshouri said that Google Hardware is focusing on flexible displays for foldable phones.
“There is a need for global standards for these devices,” Vakhshouri observed. “It would be great if these device makers were all part of a global standards system.”
Vakhshouri noted that flexible displays are still based on plastic OLEDs, which require protection.
“In order for us to protect those layers, we need to wrap them around a certain shock absorbing layers to ensure they don’t get damaged,” Vakhshouri reported. “We need bending radius, and we do need advanced design.”
Materials Processing
Of course, to have flexible hybrid electronics, you also have to have cutting-edge materials. Keynote speaker Christopher Tabor, materials research scientist at Air Force Research Laboratory (AFRL), discussed some intriguing new opportunities for liquid metals in his talk, “Liquid Electronics for Stretchable Conductors .”
Tabor noted that the AFRL’s mission is to serve the needs of the Air Force and now the Space Force.
“We partner with a lot of entities, from academic to industrial, as well as institutions like SEMI and NextFlex,” said Tabor.
Tabor noted that stretchable electronics is one level above flexible electronic systems.
“I look at it as a continuum,” Tabor noted. “We are looking for adaptable systems, that are self-healing in a way and will repair themselves. Ultimately, we want a fully adaptable system that is intelligent.”
Tabor grouped materials in two categories – geometric, using known materials like silicon or thinning down materials, and intrinsic stretching, through the use of new materials. Tabor noted that these materials can be printable and elongated.
One of these intrinsic materials is liquid metals; Tabor cited Michael Dickey’s research with gallium alloys at North Carolina State University as an example where one can put bulk fluids in pre-fabricated microchannels.
“With liquid metal nanoparticles, sonication or shear mixing generates a suspension of microns to nanoparticles in solution,” Tabor added. “You can change the intrinsic nature of the shell by adding other materials like zinc, which can then change its mechanics. It gives us a processible ink that we can print down on a number of substrates that can be stretchable.”
One challenge is to make it stretchable, and adding a monomer helps in that regard.
“Adding a monomer crosslinks the polymer into a network, and the resistance of the trace doesn’t change even when it is being stretched up to 700%,” Tabor said. “These can be airbrushed, screen printed or ink-jetted. Ultimately, we would like to put these materials into textiles, creating smart flight suits with these circuits being built in.”
Tabor’s talk was followed by a panel discussion co-moderated by session chairs Mark Poliks, Empire Innovation Professor Binghamton University, and Stephen Farias, chief science officer for Materic. The panel featured Ricardo Prada Silvy of CHASM Advanced Materials; Mohammed Zulqarnain of Eindhoven University of Technology; Ben Plattner of NextFlex; Andy Behr of Panasonic; Ian Tevis of SAFI-Tech; and Cinzia Casiraghi of the University of Manchester.
Silvy noted that CHASM is working on new carbon nanotube (CNT) materials.
“It is scalable - we are working on commercialization,” Silvy added. “Our target is to produce 50 tons a year of this material.”
Silvy pointed to possible safety issues for carbon nanotubes. “CNT’s need to be very well controlled to prevent exposure for health issues,” Silvy reported.
Zulqarnain noted that the Eindhoven University of Technology is working on health care transistors on foil that features NFC compatibility.
Zulqarnain observed that working with new technology is a real challenge. “It can get really messy if you go to higher complexities,” he added.
“Sustainability is ultimately the goal,” said Zulqarnain. “We try to use materials and processes that do not have a negative impact on the environment.”
Ben Plattner of NextFlex spoke about the importance of finding practical solutions to manufacture FHE solutions.
“We had sheets of printed devices with components attached, but we needed to program the devices,” Platter said. “ We came up with a 6-axis robot that could help us finish off the devices.”
“To get material from the lab to manufacturing takes a lot of collaboration and our partners in our equipment space,” said Plattner. “It’s a back and forth process when working with suppliers, making tweaks.”
Panasonic’s Andy Behr discussed his company’s work on a novel stretchable thermosetting film that offers very high-temperature resistance and is biocompatible.
“Manufacturers are reluctant to spend capital on new manufacturing infrastructure on unproven technology,” said Behr. “We look to lower the barrier on entry cost.
“We’re slowly creating an ecosystem,” Behr noted. “As an emerging industry, we can learn from the past and design for scalability. We need to have scalable, robust supply chains and manufacturing.”
Behr said that recyclable FHE materials are “a bit further down the line.
“Designing flexible and conformable materials is a lot of work, and making them recyclable will be herculean,” Behr said. “As an emerging industry, we can learn from the past and design for scalability. We need to have scalable, robust supply chains and manufacturing.”
Ian Tevis of Safi-Tech discussed Safi-Tech’s supercooled liquid metal microcapsules, a tin bismuth-based alloy and a lead-free solder alloy.
“These are new materials that can make a full metal solder interconnect,” Tevis said. “We work exclusively with lead-free solders and are working on lowering temperatures for processing.”
“When you are bringing new material that no one has ever seen, you get a lot of questions,” Tevis observed. “We are competing with rigid electronics, but manufacturers want to produce the same way but better. This can create a barrier to bringing new materials to market.”
University of Manchester’s Cinzia Casiraghi is working on 2D materials including graphene, and how to make printable water-based inks for inkjet printing solutions.
“These are optimized for inkjet printing of capacitors and transistors,” Casiraghi said. “We wanted to make vertical structures so inkjet was the key technology. There wasn’t much choice there.”
“From an academic point of view, we are really good, but working toward commercialization, you have to find the killer application,” said Casiraghi. “You have to have clear discussions.”
“Sustainability is a big topic in Europe, and we are working with experts in life cycle analysis,” Casiraghi noted. “Graphene is made of carbon, which is a big advantage for the environment.”
