Understanding the Brain with Super-Small Needles

The 5-µm-diameter needle-electrode mounted on a connector. The needle is 160 µm long. (Image courtesy of Toyohashi University of Technology.)

Engineers have developed extremely small needle-electrodes able to probe the complex circuits of the brain. The 5-µm-diameter needle-electrodes allow in vivo recording of brain signals; and the technology could help expedite the development of a brain-machine interface.

Analyzing the Brain

The complex networks of neurons in the human brain necessitate a certain amount of finesse. That’s why needle technology with diameters under 10 µm are necessary, as larger needles risk damaging the brain tissue. The device substrate should also be minimized, both to reduce damage as well as to enhance accessibility of the electrode in the brain.

The individual 5-µm needles are fabricated on 1-mm x 1-mm silicon block modules, which can be assembled into a number of device packages such as rigid or flexible printed circuit boards (PCBs). The researchers tested the needle-electrodes on mice and achieved better-than-expected results.

"We demonstrated the high design variability in the packaging of our electrode device and in vivo neuronal recordings were performed by simply placing the device on a mouse's brain. We were very surprised that high-quality signals of a single unit were stably recorded over a long period using the 5-μm-diameter needle," said researchers Hirohito Sawahata and Shota Yamagiwa.

Photographs and schematics of the needle electrode before (left) and after (right) insertion into the mouse cortex. See full paper for details. (Image courtesy of Nature.)

The Mysteries of the Brain

The researchers are optimistic about their results and believe similar electrode concepts will help realize new neurophysiological concepts.

"Our silicon needle technology offers low-invasive neuronal recordings and provides novel methodologies for electrophysiology; therefore, it has the potential to enhance experimental neuroscience," said research lead Takeshi Kawano. "We expect the development of applications to solve the mysteries of the brain and the development of brain-machine interfaces."

For more about the mysteries of the brain, read Are Brain Prosthetics on Their Way to Market?