The Brain-to-Machine Interface Just Became Better
Brainpower control of technology may be a step closer.
Electronic implants in the brain or other parts of the body may be more efficient and effective due to a recent breakthrough by researchers at the University of Delaware. The advance potentially offers a wide array of biotechnology benefits and could also allow humans to control unmanned vehicles and other technologies with the brain.
The development involves a type of polymer material known as PEDOT, which is a “short name for a long chemical structure that’s essentially a polythiophene,” according to David Martin, a professor of materials science and engineering and the associate dean, research and entrepreneurship, College of Engineering, University of Delaware. That long chemical structure is poly (3,4-ethylene dioxythiophene).
PEDOT materials have been around for years and can be chemically tailored for different purposes. New cars and trucks with mirrors that automatically shift to night mode use a form of PEDOT. The materials either are used now or show promise for solar cells, electronic displays, supercapacitors such as building bricks that also store energy and wearable electronics integrated into clothing for monitoring health or providing heat in winter.
Martin’s team at the University of Delaware uses PEDOT as a base to create coatings for electronic medical devices such as brain, ear, eye and heart implants. The American Chemical Society, which announced the most recent advance, hailed the achievement as another step toward the merger of the human brain and artificial intelligence (AI)—cyborgs, in other words. The headline on the American Chemical Society press release reads, “‘Cyborg’ technology could enable new diagnostics, merger of humans and AI.”
Martin even describes the materials in terms that may sound cyborg-like to the ear of a nonscientist. “They have mechanical properties, electrical properties, structures that are really in between these two extremes of the engineered abiotic, implantable device and the living, wet, biotic, salty solutions that make up biology.”
The new materials, which Martin describes as PEDOT Plus, dramatically enhance electronic implants in the body. “It’s based on PEDOT, but it’s plus something else on the side of the PEDOT that allows us to better fine-tune either the interactions with the device or the interaction with the tissue or the long-term stability or whatever,” Martin explains. “Just plain old baseline PEDOT, that’s so 20 years ago.”
While PEDOT Plus can improve virtually any implantable device, the implications for brain research are arguably the most mind-blowing. Interest in brain-computer interfaces has spawned a new area of research. Doctors use deep brain stimulators to treat Parkinson’s Disease. The U.S. military and others have invested heavily in robotic prosthetics that can be controlled with connections directly to the brain. Researchers at the University of Pennsylvania and Cornell University announced last year that they have created nanosized robots that can be injected into the brain or along the spinal column to gather medical data. Elon Musk’s company, Neuralink, is researching brain technologies to treat blindness, deafness, paralysis, memory loss and strokes.
“If we could communicate directly with the brain, you could potentially help people who are completely paralyzed control a computer or move their wheelchair around, turn the lights on and off in the room, send emails, play video games. There’s no reason technologically why this can’t be done,” Martin offers.
He mentions that researchers at the University of Pittsburgh are using brain implants to give a bionic hand a sense of touch. “That, to me, is really going to revolutionize next-generation prosthetic arms and legs. It’s one thing to be able to control the device, it’s another thing to actually be able to use the device for sensing. Once you’ve got sensation coming back to the operator, you could imagine a whole number of other things you could be sensing.”
For example, the fingers on the bionic arm could be used to smell—yes, smell—or even to sense chemical or biological agents on the battlefield. “If you have a prosthetic arm that has chemical sensors on it, you can imagine sticking your hand out the window to smell the air. It could even be remotely. You could have your sensors out on your lawn ready to sense anything that goes by,” Martin declares.
Controlling robots or unmanned vehicles with brainpower is another possibility. “If you can control a wheelchair, you can control something else. It can be any kind of mobile device you can imagine,” he adds.
The PEDOT Plus materials literally improve the interface between electronic implants and biological tissue. Biomedical devices, such as neural, cochlear or heart implants, carry an electronic charge in a solid state. Biological tissue, on the other hand, carries an ionic charge in the wet state. PEDOT Plus is chemically tailored to do both.
“These polymers are both electrically active and ionically active, so they can communicate—or exchange charge well—with both the device and with the tissue that you’re trying to talk to,” Martin explains.
Furthermore, the chemistry of the polymer can be adjusted so that it can adapt to either the specific type of device or the specific type of tissue. For example, common electrodes are often made of stainless steel, iridium, platinum, gold or silicon-based substrates. Whichever is used, PEDOT Plus materials can be chemically tuned to enhance such characteristics as the adhesion, strength or electrical charge.
“But then you can also tailor the polymer chemistry so that it’s designed to interface well with the type of tissue. Whether you’re going after the heart or the eye or the ear, there are specific chemical properties of each of those tissues that you can use to optimize the interaction of the polymer on the coating,” Martin elaborates. “These polymers allow you to change that organic chemistry and create something that’s much more similar to the natural tissue that it’s trying to talk to.”
And that opens new possibilities for using PEDOT materials. “That gives you a whole lot of flexibility both for promoting biointegration of the device into the tissue as well as for creating materials that might be used, say, as a chemical sensor. They can respond in a certain way if there was something in their environment that changes the interaction with the polymer. You can use that as a sensor of what’s going on either while it’s in tissue, or you can use it as a sensor for vapors or liquids or whatever.”
The PEDOT Plus materials also offer less electrical resistance or impedance. As electronic devices become smaller and smaller, impedance becomes a bigger and bigger issue. Smaller devices are desirable because they are more precise, but miniaturization comes at a price. “It turns out that if your electrode surface is flat and made of a metal, the impedance of the electrode is inversely proportional to the area, so as the area got smaller and smaller and smaller … the impedance got so high they couldn’t really work anymore,” Martin notes. “These [PEDOT Plus] materials, it turns out, are kind of open and porous, so they’re able to facilitate this charge exchange essentially all throughout their volume. The whole volume of the film is acting like a capacitor where you can do the charge exchange from the electron conduction to the ion conduction.”
A half micron coating of a PEDOT Plus material can lower the impedance of an electrode by 100 or even 1,000 times. “That totally changes the game. Impedance is all about signal. It’s all about power requirements. It’s all about battery lifetimes. It’s all about size and miniaturization. It really opens up a whole new realm of design possibilities for the biomedical device people to create very tiny, very precise and very highly integrated electronic coatings right at that interface.”
Ongoing research could help reduce the scarring that occurs when electronic devices are implanted. Brain electrodes, for example, are “extraordinarily sensitive to even a little tiny amount of scarring that might occur when you stick the electrode in the brain,” Martin offers. Martin’s team already has made some progress, but he says he hopes for further advances.
“One method we’ve been working on and that shows promise is instead of trying to coax the cell to come back to the electrode, we have found that we can actually deposit these PEDOT polymers after we insert the electrode into the device. And then we actually grow the polymer off of the metal electrode out and into the tissue,” he offers. “The idea is to insert the big metal electrode into the tissue and then you can grow chemically this electrically active polymer out from the metal electrode into the tissue so that it’s directly integrated into the tissue.”
Technically, PEDOT Plus materials could likely be used today. The only delay would be in conducting all the necessary tests and scaling up production, which requires commercial investment. “Really the only limitation would be scaling it up to ensure that it’s safe and effective and does what it needs to do. I don’t, at the moment, see any barriers to entry,” Martin offers. “The universities aren’t in the business of making these materials. They’re always interested in a conversation with somebody who would want to turn it from an idea into an actual product.”