Fang and Koppes Receive $2.2M NIH Award Leading to State-of-the-Art Electrophysiological Capabilities

Hui Fang and Ryan Koppes

Soft and Transparent: Building Better Brain Implants

Your brain is almost constantly moving. Every time you breathe, every time you move, your brain moves, too. This usually isn’t an issue; your brain is flexible, it’s built to move. But when you bring brain implants into the equation, things get a bit tricky.

You see, traditional brain implants are rigid. This makes them less than ideal when our “squishy” — the technical term — brain moves. Over time, these implants can damage the soft brain tissue, and also become unstable and must be replaced, which means brain surgery.

The thing is, these traditional electrodes have been proven effective. They reliably gather information, provide therapy, and complete many other tasks. So, any advances to make them more compatible with the brain’s morphology need to keep that effectiveness.

A better, softer implant

ECE Assistant Professor Hui Fang and ChE Assistant Professor Ryan Koppes of Northeastern’s College of Engineering recently won a $2.2 million NIH award, in collaboration with UCLA and Boston Children’s Hospital, titled, “Novel transparent, ultra-soft neuroelectrode arrays based on nanomeshing conventional electrode materials,” to develop and optimize new electrode arrays to provide a better interface between the outside world and the brain. To accomplish this task, the team has two layers of goals.

The first is to develop a device that’s compatible with optical approaches. There are many different methods to interface with the brain, and they all come with advantages and disadvantages. Electrodes are known to be fast — they can pick up fast electrical signals around the brain — but you have to put them close to neurons in order to record their activity. This brings in a fundamental limitation in terms of spatial coverage.

This is where optical approaches shine: there’s no need to implant anything. Right now, however, light isn’t great at picking up the fast neurological activities that traditional electrodes can.

With this next generation of arrays, the goal is to be able to do what electrode arrays are supposed to do, which is marry the electrical signals from the brain, but also integrate them with optical methods.

The second goal is making these devices so that they’re chronically stable inside the body.

“Whenever you implant anything into the body, into your tissue, there’s going to be a lot of foreign body response,” Hui explains. “This creates issues coming from the tissue-implant interface.”

Ryan adds, “You have to make sure the brain stays happy.”

The brain is squishy, and feels almost like a gel. It makes sense, then, that research has shown softer implants, ones that can flex with the brain as it moves, lead to less inflammation and other negative side effects.

The teams are proposing to make implants both optically transparent and mechanically as close to the softness of brain tissue as possible through a unified technique called nanomeshing. They use conventional electrode materials — implantable metals, coatings, and other material — but use nanomeshing to make them transparent and ultra-soft.

The next logical question is, “What exactly is nanomeshing?” If you break down the words, it’s exactly what it sounds like: making a mesh out of these materials, but at the nanometer scale. So, where traditional electrodes can be like stiff fence posts, when they are nano-meshed they’re more like the chain-link fence. By interweaving these structures, they’re making a flexible mesh, that if it’s designed right can also be stretchable.

“Think about a candy wrapper,” Hui explains. “It’s flexible, you can crumple it and bend it, but it’s not stretchy. Skin, for example, is both flexible and stretchy.”

Great potential

Of course, any research being done on the brain requires years of proof and study before being applied to humans, so the teams will focus on animal models. But the potential for better understanding the human brain and providing treatments for neurological disorders is exceptional.

“We know so little about our brain, and part of that is because we have limited tools. People don’t have all the right tools to investigate all the questions we have about our brains,” Hui explains. “Developing softer devices — as soft as the brain — can be a game changer.”

Down the road there’s even great potential for improving patient care.

“My hope is that these devices can, someday, help us inform how our body creates minds,” Ryan explains. “In the clinic this could ultimately mean that this better understanding can lead to better, less-invasive, treatments.”

Abstract Source: NIH

There is a growing interest to effectively combine optical approaches with electrophysiology at large scale and with great precision to fully leverage the complementary spatial and temporal resolution advantages of both techniques. It is also widely recognized that device softness and compliance are important attributes to dramatically lower tissue injury and irritation and maintain signal quality over time. Our long-term goals are (i) to converge electrophysiology with optical brain recording/stimulation seamlessly at the large scale to achieve high-spatiotemporal-resolution brain activity mapping which captures both the finest spatial intricacies of the neuronal circuit and fastest temporal dynamics of neuronal communication and (ii) to integrate electrode arrays seamlessly with the brain tissue. The objective of this R01 application, which is the first step in achieving these goals, is to develop and validate a novel neuroelectronic tool which provides state-of-the-art electrophysiological capabilities while allowing at the same time, optical and chronic-bio- compatibilities, realized critically through the optical transparency and mechanical ultra-softness of the entire MEA, along with other engineering efforts. We are very ambitious about tackling both of these two big challenges because of a unified technical concept, nanomeshing conventional electrode materials. In our prior work, we have proposed this novel electrode concept, which has led to the demonstration of transparent, flexible electrodes with high performance of sizes down to 15×15µm2, and with the ability to record single-unit spikes. In this application, we aim to prove: this nanomeshing concept can lead to 100s-electrode- scale, high-density, transparent and ultra-soft electrode arrays that simultaneously allow both the capability of (i) effectively integrating electrical recordings/stimulation with optical imaging in vivo, and (ii) chronic stability of single-unit recordings. The proof of this concept will readily enable stable, concurrent electrical/optical investigations of the brain at the mm-to-cm scale with further scalability, while also providing unique opportunities for next-generation therapeutic interventions via sustainable neural prosthetics. In three inter- related aims, we will develop and validate proof-of-concept, nanomesh-microelectrode-based, transparent, ultra-soft, high-density (NANOMESH) array with at least 256 high-performance nanomesh microelectrodes and artifact rejecting wireless data link through an interdisciplinary 3-year plan integrating innovative technological developments with basic neuroscience testing. We will benchmark our devices to industry standards in vivo, and integrate neural engineering feedback throughout the design, testing and validation phases of the project. This project leverages a vibrant and successful collaboration between material scientists, neuro-engineers, electrical engineers, and neuroscientists at Northeastern University (NU), the University of California Los Angeles (UCLA), and Boston Children’s Hospital (BCH), to translate transparent nanomesh technology into large-scale brain-mapping tools and implantable devices.

Related Faculty: Ryan Koppes

Related Departments:Chemical Engineering, Electrical & Computer Engineering