text: In 2004, Andre Geim and Konstantin Novoselov at the University of Manchester in England achieved a breakthrough when they isolated graphene for the first time. A flat form of carbon made up of a single layer of atoms, graphene is the thinnest known material—and one of the strongest. Hailed as a wonder material, it won Geim and Novoselov a Nobel Prize in physics in 2010.
  Twenty years later, graphene is finally making its way into batteries, sensors, semiconductors, air conditioners, and even headphones. And now, it’s being tested on people’s brains.
  This morning, surgeons at the University of Manchester temporarily placed a thin, Scotch-tape-like implant made of graphene on the patient’s cortex—the outermost layer of the brain. Made by Spanish company InBrain Neuroelectronics, the technology is a type of brain-computer interface, a device that collects and decodes brain signals. InBrain is among several companies, including Elon Musk’s Neuralink, developing BCIs.
  “We are aiming to have a commercial product that can do brain decoding and brain mapping and could be used in a variety of disorders,” says Carolina Aguilar, InBrain’s CEO and cofounder.
  Brain mapping is a technique used to help plan brain surgeries. When taking out a brain tumor, for instance, surgeons place electrodes on the brain to determine the location of motor and speech function in the brain so that they can safely remove the tumor without affecting the patient’s ability to move or speak.
  During today’s surgery, the implant was installed for 79 minutes. The patient was already undergoing brain surgery to have a tumor removed and consented to the experiment. In that time, researchers observed that the InBrain device was able to differentiate between healthy and cancerous brain tissue with micrometer-scale precision.
  The University of Manchester is the site of InBrain’s first-in-human study, which will test the graphene device in up to 10 patients who are already undergoing brain surgery for other reasons. The goal of the study, which is funded by the European Commission’s Graphene Flagship project, is to demonstrate the safety of graphene in direct contact with the human brain.
  David Coope, the neurosurgeon who performed the procedure, says the InBrain device is more flexible than a conventional electrode, allowing it to better conform to the surface of the brain. “From a surgical perspective, it means we can probably put it in places where we would find it difficult to put an electrode,” he says. The mainstay electrodes used for brain mapping are disks of platinum iridium set in silicon. “So they’re reasonably stiff,” Coope says.
  By contrast, the InBrain device is a transparent sheet that sits on the brain’s surface. Half the thickness of a human hair, it contains 48 tiny decoding graphene electrodes measuring just 25 micrometers each. The company is developing a second type of implant that penetrates the brain tissue and can deliver precise electrical stimulation.
  The surface device alone can be used for brain mapping, but Aguilar says the company is also integrating the two devices and plans to eventually test them together as a treatment for neurological disorders such as Parkinson’s disease.
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  GearDeep brain stimulation, or DBS, in which a needlelike metal electrode is placed into the brain tissue, is already an approved treatment for Parkinson’s, epilepsy, and a handful of other conditions. It involves delivering an electrical current to disrupt the irregular signals in the brain that cause tremors and other movement symptoms.
  Currently, most DBS systems stimulate constantly, whether or not a patient is experiencing any symptoms. Over time, the nervous system can adapt to this constant stimulation and its effects can wear off. InBrain is looking to improve on DBS by using its surface device to detect biomarkers related to motor function and then delivering stimulation only when it is needed with the penetrating device.
  Metals have traditionally been used for electrodes because they have high conductivity. That makes them good at capturing brain activity—essentially bursts of electricity emitted when neurons communicate with each other. Metal electrodes are routinely used for DBS, as well as for brain-computer interfaces to help people with paralysis use digital devices with their thoughts.
  But Christina Tringides, an assistant professor in materials science and nanoengineering at Rice University who isn’t involved with InBrain, says metal electrodes have their disadvantages. Notably, they’re brittle and rigid while the brain is soft and gel-like. “It’s like putting a spoon in a bowl of jello or a knife in a block of tofu,” she says.
  The brain pulsates with every breath, but metal electrodes stay in place. This mismatch means that when the brain shifts in the skull, electrodes can cause inflammation or scarring. Over time, these issues can hinder the ability to pick up neural signals. Metals also oxidize in the aqueous environment of the brain, which can lead them to degrade over time.
  Ideally, electrodes placed in the brain would last a long time to minimize repeat surgeries for patients. “That’s why there’s a push to use other materials,” Tringides says.
  Graphene is an excellent conductor and doesn’t oxidize. Plus, Aguilar says InBrain’s device can inject 200 times as much charge into the brain compared to current DBS systems. The surface array the company built also has 12 stimulating electrodes composed of 8,400 graphene micro-islands that can deliver focused stimulation, but in this initial human study, the stimulation won’t be turned on.
  Aguilar says the commercial version of the device will have close to 100 electrodes, and the company is also developing one with 1,024 electrodes. The more electrodes, the more data can be recorded from the brain. Because the graphene dots are so small, the device can also deliver very precise stimulation.
  Aguilar says the company’s interfaces may also have applications for treating stroke and epilepsy patients. For now, InBrain will have to pass its initial safety study.
  “This is the first time graphene is being placed in the brain of a human being,” Aguilar says. “So we are hoping for a great outcome.”