The human brain-the three pounds of spongy gray matter in our skulls -stores more information than a supercomputer and feeds our imaginations. But neurological illnesses affect more than 50 million Americans annually and cost more than $500 billion to treat. ECE Assistant Professor Xiaoting Jia is developing flexible, multifunctional brain implants that can be manufactured at a low cost and may herald the next generation of technology for treating Parkinson's disease, depression, stress, or other neurological disorders.

Current neural interface devices-sensors that can be implanted in a brain-have been used to alleviate some of these symptoms, but they are bulky, hard and rigid, made from metal or silicon. The brain's soft, fragile tissue is easily damaged by unyielding devices, which can also fail after long term implant.

Jia, with help from students and faculty collaborators, has been working on devices that seamlessly integrate into the brain's architecture-a flexible, multifunctional fiber that can not only read the electrical signals from neurons inside the brain, but also send optical, chemical, and electrical stimulation into the nervous system.

"Our flexible fiber devices mimic the compliances of brain tissue, causing less damage," said Jia. "They are an ideal platform for long term implant."

Although she's still in the early stages of research, Jia envisions a deep brain neural interface device that can interact naturally and gently with the human nervous system.

Active neurons transmit electrical signals, which can be recorded by an electrode placed nearby. Jia and her team can thread a single fiber with thousands of nanoscale electrodes or micro-scale drug delivery channels, which allow them to track the signals and interact with the brain at different locations.

"Most of our fibers are on the order of tens to hundreds of microns-comparable to a human hair-and they can be smaller," Jia said, selecting a translucent strand from a nest of fibers.

Using macroscale machining, they fabricate a large template of the fiber, called the macroscopic preform. The preform is a small block of polymer studded with electrodes, channels, or other features made from composite materials and metal with a low melting point. The template is carefully heated and stretched from a fiber draw tower.

The final product transforms a one-foot by one-inch block into a thin fiber hundreds of meters long.

"We end up with exactly the same cross-sectional features-which can include some complex geometries like electrodes, optical wave guides, or drug delivery channels-shrunk down by a factor of 200," said Jia.

Jia held up the preform, an amber slab tapering off into a long thread, like a Hershey's kiss. Consecutive drawing steps, she explained, can reduce the features' dimensions even further.

Because one device requires only a centimeter of fiber, each drawing can create hundreds of thousands of devices. The process generates a scalable, low-cost product that could eventually save lives.

Jia and her team are still in the beginning phases of the trials. Currently, the device is being tested at Virginia Tech Carillion Research Institute, where the group has inserted centimeter-long fibers into the prefrontal cortex of mouse brains.

"By sending certain stimulation, it's possible to affect the movement of the mouse," said Jia. "The device can also be implanted in other areas, like the regions that control memory or fear."

They are injecting dyes through the drug delivery channels to observe how they diffuse. This is laying the groundwork for research on drug delivery for people who are suffering from epilepsy or tumors. A neural interface device like the one Jia is developing would allow for more control over where and when drugs are released in the brain, and could minimize dangerous side effects.

This two-way interaction could also be used to pinpoint where neurons are malfunctioning, and then prompt the device to send stimulation to modify the activity.

"A device like this would bridge the gap between engineering and biology, harnessing the strengths of both to improve quality of life," Jia said.