There are a lot of interesting advances in the field of flexible hybrid electronics (FHE). To keep the FHE community in the loop, this year’s four-day virtual FLEX 2021 conference highlighted new FHE technologies, materials and equipment advances, sensors, power sources and much more.
The first two days covered flexible hybrid electronics (FHE) and materials; the report can be found here. Feb. 24’s session focused on Sensors and MEMS, while Feb. 25 covered Sustainability and Power.
On-demand content will be available through March 26.
Sensors and MEMS
The Feb. 24 session focused on Sensors and MEMS (microelectromechanical systems), beginning with the keynote talk, “Electronics on the Brain,” given by George Malliaras of the University of Cambridge.
Malliaras reported that the emergence of bioelectronic medicine is an accelerating trend.
“This is great news,” he said. “There are some limitations. First and foremost, we do not understand how the brain works – there are 80 million neurons in the brain. The current technology is also limiting as signals are small and diverse and the environment is hostile to electronics. This can also be highly invasive. New technologies are needed to address these limitations.”
One challenge is getting medicine into the brain. Malliaras mentioned some options, including shape-shifting implants, as devices that can change shape decrease invasiveness. An electrophoretic drug delivery device includes an ion exchange membrane and a microfluidic channel.
“Mapping the brain is used before surgery, and the electrodes placed on the cortex are fairly large. We can improve this by enhancing the couplings,” said Malliaras. “We need to make the electronics dynamic. Implants often require highly invasive surgery. We are combining bioelectronics with soft robotics, such as expandable implants.
“Implantable electronics hold considerable promise for understanding the brain and addressing its pathologies,” added Malliaras. “Microfluidics allows expandable implants that minimize the invasiveness of neurosurgery. Wearables that are much less invasive are much easier to deploy in scale. Flexible electronics does not have a predefined shape – this can be very fruitful.”
Malliaras’ talk was followed by a panel discussion on Sensors and MEMS, co-moderated by session chairs Doyle Edwards of Brewer Science and Eisuke Tsuyuzaki of Bayflex Solutions. The panel included Matthew Dyson of IDTechEx; Hadi Hosseini of Stanford University; Michael Brothers of UES Inc./711th Human Performance Wing, US Air Force Research Labs (AFRL); Erin Ratcliff of the University of Arizona; Michael Crump of the University of Washington; and Moran Amit of University of California, San Diego.
Dyson discussed the opportunities of printing stretchable electronics but noted that some of these systems may require rigid chips.
“That can be challenging,” Dyson noted. “Flexible hybrid electronics (FHE) has an awful lot of promise as it is a pragmatic approach to printing logic and transistors, but it is can’t compete with a silicon chip . There are a lot of benefits, including flexibility and being lightweight.
“In the near term, there will be applications in wearables like skin patches,” Dyson added. “The medical field and wearable/fitness/wellness are where the money and investment in flexible electronics is. These medical projects will take longer to trial. Every year more of these will come to commercialization. There is a lot of growth there. Also, we expect high volumes in smart packaging , and there is a lot of progress in PE being commercialized in cars and wearables, with orders in the hundreds of thousands.”
Ratcliff discussed developing wearables for sweat sensing.
“Sweat is a direct indication from the nervous system,” Ratcliff reported. “One of biggest challenges in wearables is what you benchmark it to. You have to benchmark it to something that isn’t even capable of measuring the same information. I think a big need is that we need bigger efforts – there is a variety of different sensing arenas. There needs to be a more targeted focus.”
Hosseini talked of the potential of sensors to improve the diagnosis of mental illnesses, such as finding biomarkers for mental illness.
“We want to accelerate this by developing a wearable system that can be used at home that can sample brain activity,” said Hosseini. “I am really amazed by all of the technologies and how underdeveloped these technologies are for mental health. We need to advance the field of mental health.”
Amit talked about research being done on wearable devices for point-of-use applications.
“Your temperature is being taken everywhere,” Amit noted. “We want to have a thermometer for every possible assessment. We are looking at muscle stiffness for children with spasticity.”
Crump focused on printed micro-electrical devices, structural 3D printable strain sensors for dermatological surgeries and all-printed devices.
“We intend to display high throughput of all-printed sensors on roll-to-roll printing,” said Crump. “One of the coolest things we are looking at is R2R electrophoretic inkjet printing – we have to print multiple layers for the conductive silver trace.”
Crump discussed the importance of sustainability in sensors.
“Sustainability is pervasive throughout our research; organic nanogels are biocompatible feedstocks. If you can reduce medical errors, you can conserve resources in the operating room and per medical patient,” Crump said.
Brothers observed that there is a need for wearable sensors that can be worn by soldiers and also monitor the environment.
“We need very minimalistic sensors,” said Brothers. “We do a lot of sensor development as well as sensor testing and evaluation – atmospheric testing to allow us to control oxygen, temperature and humidity levels, and look at them in mixtures to do reliability testing. Biomarker study is critical, but how do you create sensors that can detect change. These technologies take time to develop. One is a wearable gas sensor that is about to begin.”
Sustainability & Power
One of the challenges facing flexible and hybrid electronics is power sources. For some applications, such as the Internet of Things (IoT), a low cost, high production and flexible battery system are essential. A coin cell battery won’t allow the sensor to be wrapped around an item, and if you scale up to hundreds of billions of items, the cost will be critical.
Christine Ho of Imprint Energy, Inc. covered these issues in her talk, “Safe, High Performance, Green Batteries for Blending Electronics Into Our Lives.”
Ho noted that there is an urgency to deploy more than 100 billion IoT devices by 2030 to eliminate greater than 15% of our GHG emissions, and the IoT will be critical to reaching these goals.
“The transformation proposed is every necessary and very achievable,” Ho reported. “All sectors must transfer in parallel. IoT and digital technology have the potential to reduce fossil fuel emissions. It can also allow us to monitor and protect our most precious resources.”
Ho noted that connected devices are already rapidly deploying. One area of great interest is monitoring transportation and the supply chain.
“This ruins a lot of pharma shipped, and more than one-third of our food produced is lost in our supply chain. The inefficiency has enormous CO2 impact,” Ho said.
Ho suggested that a smart label consisting of a wireless chip, sensor and battery that is flexible is a simple yet powerful tool to monitoring supply chain processes.
“Smart tags are made possible that they can now be flexible and produced in high volumes,” Ho pointed out. “The battery is by far the largest real estate item, up to 50% of the smart label footprint.”
Ho noted that innovations in flexible power have been developed by the NextFlex community.
“Imprint screenprints thin flexible zinc-based batteries on roll-to-roll lines,” Ho said. “Imagine what a trillion thin flexible batteries can accomplish. There is a unique opportunity for us to build sustainable energy for devices. The lion's share of the carbon footprint for batteries is the mining of battery chemistry.
“We see benefits of printing batteries as well as their components,” added Ho. “Many of these batteries are disposed of. Our batteries are disposable. We have designed a sustainable and high-performance battery to blend electronics into our lives. We need to bring much more attention to reusing and recycling batteries. We are looking to partner to create a Circular Economy.”
“There are a lot of innovations that need to happen for IoT to take off,” Ho concluded. “The infrastructure such as the network is not all there yet. Lowering the power of wireless technologies would be enabling. One of the key pieces of the technology is executing more power in less material. How do we increase run times? Wrap around a pipe? Our battery is very flexible and bending and flexing contribute to performance being degraded.”
Ho’s presentation was followed by a panel discussion co-moderated by session chairs Bob Praino, Chasm Advanced Materials, and Eric Forsythe of CCDC Army Research Laboratory. The panel included Pradeep Lall of Auburn University; Dr. Joseph C. Bush of Battery Resourcers; Zachary A. Combs of Birla Carbon; Brian Berland of ITN Energy Systems; Andrew Manning of Lithium Battery Engineering; and Brian Zahnstecher of PowerRox LLC.
Berland talked about findings from two NextFlex sponsored programs on batteries. “How the battery properties match the duty cycle is a big matter,” said Berland. “When we go to highest energy density materials, you have to have energy management systems, and that involves capacitors and inductors.
“We can make a big impact by using very little material, like medical devices, which use millimeter-sized batteries that are only microns thick. What we are trying to do is enable form factors that don’t use a lot of materials,” Berland said.
Zahnstecher said that it is important to analyze and harmonize stakeholders and pay-back periods.
“The key concept here is a power value chain, from source to load, and power cost factor,” added Zahnstecher. “One of the key things is education. It’s not cynicism. It’s reality. The battery is a perfect example – people don’t see how to calculate for those. There are many factors that degrade performance.”
Lall talked about Auburn’s research looking at thin flexible power sources, which are different than batteries which typically have hard shells.
“We are looking at mechanical loads and how they impact the batteries’ health and storage life,” Lall said. “The most commonly used form factor are coin cells. Now we are using pouch batteries, as they will be flexible to install and can be folded or twisted. Less is known about the dynamic loads being impacted because of these dynamic loads, and how do you test for it.”
Dr. Bush reported that he is seeing an “incredible rate of innovation” driven by electric vehicles.
“We are going to see evolution in the EV market – Tesla has become a high-performance vehicle. We need to create a closed-loop so that we can harvest materials from old batteries and reuse them in new batteries,” Dr. Bush observed. “We see immense opportunity to reduce our footprint and drive down cost.”
Combs talked about the supply chain challenges faced in the battery market.
“Supplying raw material into a market that is very capital intensive means you have to consider if it is usable in existing processes as well as end of life,” said Combs. “We also have insecurity in our battery supply chain. Those supply chains are not sustainable from a mining or environmental standard. It’s important to consider new processes and how we can make materials more efficiently.”
Manning urged caution to the idea that new battery technologies will supplant incumbent technologies.
“I want to address overhyped headlines, and give people the tools to step back and see what the overall impact is on change,” Manning observed. “Don’t overinflate your breakthroughs.
“We worked on flexible batteries and very small batteries, and one of the biggest challenges is economic,” said Manning. “The costs of producing a battery are very high, including the amount of money to set up a production line. The average cost of a smart card battery is 80 cents. It is very hard to make any profit at that price. Where are we going to get all the energy to charge all these batteries and EV?”
Zahnstecher said that it is important to analyze and harmonize stakeholders and pay-back periods.
“The key concept here is a power value chain, from source to load, and power cost factor,” added Zahnstecher. “One of the key things is education. It’s not cynicism. It’s reality. The battery is a perfect example – people don’t see how to calculate for those. There are many factors that degrade performance.”
According to Dr. Bush, the challenge is to design the battery for reuse and recycling.
“What is consumer behavior at end of life? Pouches aren’t the easy recycling process that parents think of,” he added. “How can we design it for the end in mind? We don’t want to see this leach into the water. We are actually recycling over 95% of the battery, with 28% being able to go directly into the new battery."
