Need for safe, flexible bioelectronic devices

Implanted bioelectronic devices are playing a critical role in these treatments, but there are a number of challenges that have stalled their widespread adoption. These devices require specialized components for signal acquisition, processing, data transmission, and powering. Up to now, achieving these capabilities in an implanted device has entailed using numerous rigid and non-biocompatible components that can lead to tissue disruption and patient discomfort. Ideally, these devices need to be biocompatible, flexible, and stable in the long term in the body. They also must be fast and sensitive enough to record rapid, low-amplitude biosignals, while still being able to transmit data for external analysis.

Columbia researchers invent first stand-alone, flexible, fully organic bioelectronic device

Columbia Engineering researchers announced today that they have developed the first stand-alone, conformable, fully organic bioelectronic device that can not only acquire and transmit neurophysiologic brain signals, but can also provide power for device operation. This device, about 100 times smaller than a human hair, is based on an organic transistor architecture that incorporates a vertical channel and a miniaturized water conduit demonstrating long-term stability, high electrical performance, and low-voltage operation to prevent biological tissue damage. The findings are outlined in a new study, published today in Nature Materials.

Both researchers and clinicians knew there was a need for transistors that concurrently pose all of these features: low voltage of operation, biocompatibility, performance stability, conformability for in vivo operation; and high electrical performance, including fast temporal response, high transconductance, and crosstalk-free operation. Silicon-based transistors are the most established technologies, but they are not a perfect solution because they are hard, rigid, and unable to establish a very efficient ion interface with the body. ]

The team addressed these issues by introducing a scalable, self-contained, sub-micron IGT (internal-ion-gated organic electrochemical transistor) architecture, the vIGT. They incorporated a vertical channel arrangement that augments the intrinsic speed of the IGT architecture by optimizing channel geometry and permitting a high density arrangement of transistors next to each other — , 155,000of them per centimeter square.

Scalable vGITs are the fastest electrochemical transistors

The vIGTs are composed of biocompatible, commercially available materials that do not require encapsulation in biological environments and are not impaired by exposure to water or ions. The composite material of the channel can be reproducibly manufactured in large quantities and is solution-processible, making it more accessible to a broad range of fabrication processes. They are flexible and compatible with integration into a wide variety of conformable plastic substrates and have long-term stability, low inter-transistor crosstalk, and high-density integration capacity, allowing fabrication of efficient integrated circuits.

“Organic electronics are not known for their high performance and reliability,” said the study’s leader Dion Khodagholy, associate professor of electrical engineering. “But with our new vGIT architecture, we were able to incorporate a vertical channel that has its own supply of ions. This self-sufficiency of ions made the transistor to be particularly fast — in fact, they are currently the fastest electrochemical transistors.”

To push the speed of operation even further, the team used advanced nanofabrication techniques to miniaturize and densify these transistors at submicro-meter scales. Fabrication took place in the cleanroom of the Columbia Nano Initiative.

Collaborating with CUIMC clinicians

To develop the architecture, the researchers first needed to understand the challenges involved with diagnosis and treatment of patients with neurological disorders like epilepsy, as well as the methodologies currently used. They worked with colleagues at the Department of Neurology at Columbia University Irving Medical Center, in particular, with Jennifer Gelinas, assistant professor of neurology, electrical and biomedical engineering and director of the Epilepsy and Cognition Lab.

The combination of high-speed, flexibility. and low-voltage operation enables the transistors to not only be used for neural signal recording but also for data transmission as well as powering the device, leading to a fully conformable implant. The researchers used this feature to demonstrate fully soft and confirmable implants capable of recording and transmitting high resolution neural activity from both outside, on the surface of the brain, as well as inside, deep within the brain.

“This work will potentially open a wide range of translational opportunities and make medical implants accessible to a large patient demographic who are traditionally not qualified for implantable devices due to the complexity and high risks of such procedures,” said Gelinas.

“It’s amazing to think that our research and devices could help physicians with better diagnostics and could have a positive impact on patients’ quality of life,” added the study’s lead author Claudia Cea, who recently completed her PhD and will be a postdoctoral fellow at MIT this fall.

Next steps

The researchers plan next to join forces with neurosurgeons at CUIMC to validate the capabilities of vIGT-based implants in operating rooms. The team expects to develop soft and safe implants that can detect and identify various pathological brain waves caused by neurological disorders.

A research team from the Department of Energy’s Pacific Northwest National Laboratory reports that the flow battery, a design optimized for electrical grid energy storage, maintained its capacity to store and release energy for more than a year of continuous charge and discharge.

The study, just published in the journal Joule, details the first use of a dissolved simple sugar called β-cyclodextrin, a derivative of starch, to boost battery longevity and capacity. In a series of experiments, the scientists optimized the ratio of chemicals in the system until it achieved 60 percent more peak power. Then they cycled the battery over and over for more than a year, only stopping the experiment when the plastic tubing failed. During all that time, the flow battery barely lost any of its activity to recharge. This is the first laboratory-scale flow battery experiment to report more than a year of continuous use with minimal loss of capacity.

The β-cyclodextrin additive is also the first to speed the electrochemical reaction that stores and then releases the flow battery energy, in a process called homogeneous catalysis. This means the sugar does its work while dissolved in solution, rather than as a solid applied to a surface.

“This is a brand new approach to developing flow battery electrolyte,” said Wei Wang, a long-time PNNL battery researcher and the principal investigator of the study. “We showed that you can use a totally different type of catalyst designed to accelerate the energy conversion. And further, because it is dissolved in the liquid electrolyte it eliminates the possibility of a solid dislodging and fouling the system.”

What is a flow battery?

As their name suggests, flow batteries consist of two chambers, each filled with a different liquid. The batteries charge through an electrochemical reaction and store energy in chemical bonds. When connected to an external circuit, they release that energy, which can power electrical devices. Flow batteries differ from solid-state batteries in that they have two external supply tanks of liquid constantly circulating through them to supply the electrolyte, which is like the “blood supply” for the system. The larger the electrolyte supply tank, the more energy the flow battery can store.

If they are scaled up to the size of a football field or more, flow batteries can serve as backup generators for the electric grid. Flow batteries are one of the key pillars of a decarbonization strategy to store energy from renewable energy resources. Their advantage is that they can be built at any scale, from the lab-bench scale, as in the PNNL study, to the size of a city block.

Why do we need new kinds of flow batteries?

Large-scale energy storage provides a kind of insurance policy against disruption to our electrical grid. When severe weather or high demand hobble the ability to supply electricity to homes and businesses, energy stored in large-scale flow battery facilities can help minimize disruption or restore service. The need for these flow battery facilities is only expected to grow, as electricity generation increasingly comes from renewable energy sources, such as wind, solar and hydroelectric power. Intermittent power sources such as these require a place to store energy until it’s needed to meet consumer demand.

While there are many flow battery designs and some commercial installations, existing commercial facilities rely on mined minerals such as vanadium that are costly and difficult to obtain. That’s why research teams are seeking effective alternative technologies that use more common materials that are easily synthesized, stable and non-toxic.

“We cannot always dig the Earth for new materials,” said Imre Gyuk, director of energy storage research at DOE’s Office of Electricity. “We need to develop a sustainable approach with chemicals that we can synthesize in large amounts — just like the pharmaceutical and the food industries.”

The work on flow batteries is part of a large program at PNNL to develop and test new technologies for grid-scale energy storage that will be accelerated with the opening of PNNL’s Grid Storage Launchpad in 2024.

A benign ‘sugar water’ sweetens the pot for an effective flow battery

The PNNL research team that developed this new battery design includes researchers with backgrounds in organic and chemical synthesis. These skills came in handy when the team chose to work with materials that had not been used for battery research, but which are already produced for other industrial uses.

“We were looking for a simple way to dissolve more fluorenol in our water-based electrolyte,” said Ruozhu Feng, the first author of the new study. “The β-cyclodextrin helped do that, modestly, but it’s real benefit was this surprising catalytic ability.”

The researchers then worked with co-author Sharon Hammes-Schiffer of Yale University, a leading authority on the chemical reaction underlying the catalytic boost, to explain how it works.

As described in the research study, the sugar additive accepts positively charged protons, which helps balance out the movement of negative electrons as the battery discharges. The details are a bit more complicated, but it’s like the sugar sweetens the pot to allow the other chemicals to complete their chemical dance.

The study is the next generation of a PNNL-patented flow battery design first described in the journal Science in 2021. There, the researchers showed that another common chemical, called fluorenone, is an effective flow battery component. But that initial breakthrough needed improvement because the process was slow compared with commercialized flow battery technology. This new advance makes the battery design a candidate for scale up, the researchers say.

At the same time, the research team is working to further improve the system by experimenting with other compounds that are similar to β-cyclodextrin but smaller. Like honey, β-cyclodextrin addition also makes the liquid thicker, which is less than ideal for a flowing system. Nonetheless, the researchers found its benefits outweighed its drawbacks.

Understanding the complex chemistry happening inside the new flow battery design required the expertise of many scientists, including Ying Chen, Xin Zhang, Peiyuan Gao, Ping Chen, Sebastian Mergelsberg, Lirong Zhong, Aaron Hollas, Yangang Lian, Vijayakumar Murugesan, Qian Huang, Eric Walter and Yuyan Shao of PNNL, and Benjamin J. G. Rousseau and Hammes-Schiffer of Yale, in addition to Feng and Wang.

Researchers were peripherally aware of the fish’s existence, but “discovering” a new species requires scientific description based on specimens collected in their natural environment. Redtail garras appear to be restricted to a small stretch of river straddling the border between Thailand and Myanmar. The locality is isolated and difficult to reach, so wild redtail garras have existed in relative obscurity, despite their global appeal.

Larry Page, curator of ichthyology at the Florida Museum of Natural History, has surveyed fishes in Thailand every year since 2007. He recently encountered a few redtail garras while conducting fieldwork along the Kasat River, a tributary of the Ataran River in neighboring Myanmar.

“When we first collected specimens, we thought it must be widespread in Myanmar because of its popularity in the aquarium trade. But it turns out it’s not. It’s only in the Ataran River basin,” he said.

Page and his colleagues published the new species description in the journal Zootaxa. Redtails take their place among nearly 200 additional species in the genus Garra, one of the most diverse and widely distributed fish groups anywhere on Earth. Garra can be found in streams and rivers from the farthest reaches of western Africa through the Middle East, India and southern and eastern Asia, including parts of China. Yet their ubiquity has not resulted in a corresponding amount of research on the group.

“There’s surprisingly little information on their natural history,” Page said. There are few studies that broadly assess diversity in the genus, and little is known about relationships or how various groups within Garra have diversified.

According to Page, basic information about the fishes’ biology is available, but often in the form of studies on individual species or regions. “Most of them live in fast-moving water, and they have a disclike structure formed from a modification of the lower lip, which they use as an adhesive pad to cling to rocks and maintain their position in the water column as they feed,” he said.

Garra primarily subsist on algae and the occasional arthropod, which they eat by scraping detritus off rocks with specialized mouthparts. Like other species in the genus, redtails lack stomachs and have a snout encrusted with modified and hardened scales called tubercles. Similar structures in other fish groups are temporary; they’re used to defend nests but fall off after the breeding season has ended. Redtail tubercles are permanently attached and seem to be used as weapons, based on aggressive behavior observed in aquaria.

Redtail garra can be distinguished by their unique, elongated snout, covered in even more tubercles, which they can raise or lower, ostensibly as a means of intimidating opponents during combative encounters. And, as their common name suggests, their tails are emblazoned in red like a signal fire.

Their unique color pattern and their industrious ability to clear away algae have made them a coveted component of aquarium tanks, but their late addition to the roster of scientifically described species underscores a pressing need to take stock of biodiversity in understudied regions.

Page, who is working on a book describing the fishes of the Mae Klong River basin in Thailand, said the belated description of redtail garra is part of a larger recurring pattern. “Many of the fishes in Southeast Asia are referred to by names given to species discovered in India or Indonesia because they look similar.” People know particular species exist, Page said, but they are mistaken for those from other geographic areas, and their diversity has consequently been drastically underestimated.

Page and his colleagues named the new species Garra panitvongi after the author of another book on Thailand’s fishes, Nonn Panitvong. Lauded as a biodiversity hero by the Association of Southeast Asian Nations, Panitvong is both a businessman and an avid naturalist. He’s nurtured a passion for nature since his childhood days spent translating books about animals written in English with the help of his mom. He developed a special appreciation for Thailand’s aquatic life from his dad, who took him on fishing trips.

“Over the years, I found that in many of the places we went fishing, the environments were getting worse. There were fewer fish overall, and the fish assemblage changed for the worse, with a decreasing number of native species and more invasives,” he said.

Panitvong obtained a Master of Business Administration at the University of North Carolina Wilmington so he could effectively run his family’s sugarcane farm, but when it came time for a doctorate, he opted to study environmental science. After returning to Thailand, he created the website Siamensis.org, an open platform on which nature enthusiasts could share information about Thailand’s flora and fauna and plan excursions to wilderness areas.

In 2006, Panitvong and a friend discovered one of Thailand’s redtail garra populations and helped introduce the fish to the aquarium trade. Now, more than 15 years later, he said the official naming of redtail garra — and the discovery of species like it — help bring the world into clearer focus.

“I like to imagine humanity in a big room, painted in white. As we turned around, we would have no conception of which direction we were facing,” he said. “With each new discovery, a dot is added, a point made, and we know more and more about where we stand as a species.”