A Magnetically Assembled High-Aspect-Ratio Needle Electrode for Recording Neuronal Activity

Area of Science:

• Neuroscience
• Biomedical Engineering
• Materials Science

Background:

• Microelectrode devices are vital for neuroscience and brain-machine interfaces, enabling neuronal signal detection.
• Existing devices require further development to meet criteria for reduced tissue damage, increased length, and high spatial resolution.

Purpose of the Study:

• To report a novel magnetic assembly technique for fabricating high-aspect-ratio microneedles.
• To demonstrate the fabrication of microneedles meeting specific dimensional requirements for neural recording.

Main Methods:

• Utilized a magnet-assisted assembly technique to create high-aspect-ratio microneedles.
• Fabricated nickel wires (750 µm length, 25 µm diameter) on a silicon substrate.
• Performed in vivo neuronal signal recordings in mouse brains.

Main Results:

• Successfully assembled microneedles with a diameter <30 µm and length ≈750 µm.
• Achieved an impedance magnitude of 5.6 kΩ at 1 kHz with high signal amplitude transmission (96.7%).
• Demonstrated in vivo recording of local field potentials and action potentials in the mouse somatosensory cortex.

Conclusions:

• The magnetic assembly technique is effective for producing microneedles suitable for neural recording.
• The fabricated microneedle electrodes show promise for high-resolution in vivo neural signal acquisition.
• This advancement supports the development of next-generation neuroscience tools and brain-machine interfaces.