Nanotubes go with the flow to penetrate brain tissue

first_img Return to article. Long DescriptionFast-moving fluid pulls a fiber through a microfluidic device to be inserted into brain tissue. The device invented at Rice University could provide a gentler method to implant wires into patients with neurological diseases and help scientists explore cognitive processes and develop implants to help people to see, to hear and to control artificial limbs. Courtesy of the Robinson Lab“The electrode is like a cooked noodle that you’re trying to put into a bowl of Jell-O,” said Rice engineer Jacob Robinson, one of three project leaders. “By itself, it doesn’t work. But if you put that noodle under running water, the water pulls the noodle straight.”The wire moves slowly relative to the speed of the fluid. “The important thing is we’re not pushing on the end of the wire or at an individual location,” said co-author Caleb Kemere, a Rice electrical and computer engineer who specializes in neuroscience. “We’re pulling along the whole cross-section of the electrode and the force is completely distributed.”“It’s easier to pull things that are flexible than it is to push them,” Robinson said.“That’s why trains are pulled, not pushed,” said chemist Matteo Pasquali, a co-author. “That’s why you want to put the cart behind the horse.”The fiber moves through an aperture about three times its size but still small enough to let very little of the fluid through. Robinson said none of the fluid follows the wire into brain tissue (or, in experiments, the agarose gel that served as a brain stand-in).There’s a small gap between the device and the tissue, Robinson said. The small length of fiber in the gap stays on course like a whisker that remains stiff before it grows into a strand of hair. “We use this very short, unsupported length to allow us to penetrate into the brain and use the fluid flow on the back end to keep the electrode stiff as we move it down into the tissue,” he said.“Once the wire is in the tissue, it’s in an elastic matrix, supported all around by the gel material,” said Pasquali, a carbon nanotube fiber pioneer whose lab made a custom fiber for the project. “It’s supported laterally, so the wire can’t easily buckle.”Carbon nanotube fibers conduct electrons in every direction, but to communicate with neurons, they can be conductive at the tip only, Kemere said. “We take insulation for granted. But coating a nanotube thread with something that will maintain its integrity and block ions from coming in along the side is nontrivial,” he said.Sushma Sri Pamulapati, a graduate student in Pasquali’s lab, developed a method to coat a carbon nanotube fiber and still keep it between 15 to 30 microns wide, well below the width of a human hair. “Once we knew the size of the fiber, we fabricated the device to match it,” Robinson said. “It turned out we could make the exit channel two or three times the diameter of the electrode without having a lot of fluid come through.” https://www.youtube.com/watch?v=HC4QRypYPkc&feature=youtu.beRelated materials:Carbon nanotube fibers make superior links to brain: https://sp2.img.hsyaolu.com.cn/wp-shlf1314/2023/IMG10707.jpg” alt=”last_img” />

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