Extracellular needle-electrode with a diameter of only 5 μm mounted on a connector. Image Credit: Toyohashi University of Technology. All Rights Reserved.
Extracellular needle-electrode with a diameter of only 5 μm mounted on a connector. Image Credit: Toyohashi University of Technology. All Rights Reserved.
Nanotechnology Technology

The World’s Smallest Needle-Electrodes Have a Diameter of Only 5 μm

A recently developed tiny needle may facilitate the development of a brain-machine interface and help solve the mysteries of the brain.

The needles electrodes are manufactured on 1 mm × 1 mm block modules and have a diameter of only 5-μm. The research team is based at the Department of Electrical and Electronic Information Engineering and the Electronics-Inspired Interdisciplinary Research Institute (EIIRIS) at Toyohashi University of Technology.

The neuron networks in the human brain are tremendously complex. It was expected that electrical activities of the microscale neuronal circuits in the brain would be analyzed and recorded by micro fabricated silicon needle electrode devices. Smaller needle technologies with needle diameters of less than < 10 μm are however required to diminish damage to brain tissue.

Apart from the needle geometry, the device substrate should also be minimized to reduce the total amount of damage to tissue. The substrate should also be able to enhance the ease of access of the electrode to the brain. The new electrode technologies will enable new experimental neurophysiological concepts to be realized.

The block modules that individual microneedles are fabricated on are small enough to use in the narrow spaces present in brain tissue. The team demonstrated this by showing a recording using mouse cerebrum cortices. The block module also substantially improves the design variability in the packaging. This opens up the possibility of numerous in vivo recording applications.

Assistant Professor Hirohito Sawahata, the first author and co-author researcher Shota Yamagiwa note that in vivo neuronal recordings were done by placing the device on a mouse’s brain. This demonstrated the high design variability in the packaging of their electrode device. He adds that they were surprised that when the 5μm diameter needle was used, high quality signals of a single unit were recorded stably over a long period.

Associate Professor Takeshi Kawano, the leader of the research team, notes that the silicon needle technology provides novel methodologies for electrophysiology and offers low invasive neuronal recordings. He believes it therefore has the potential to enhance experimental neuroscience. The team expects that both brain-machine interfaces and applications to solve the mysteries of the brain will be developed because of this study.

The research results were published in journal Scientific Reports.