MEMS micro-coils for magnetic neurostimulation

Area of Science:

• Neuroscience
• Materials Science
• Electrical Engineering

Background:

• Micro-coil magnetic stimulation probes are crucial for brain tissue research.
• Existing MEMS fabrication methods face challenges in power efficiency, current leakage, and adaptability.
• The dynamic nature of neuroscience research demands agile fabrication processes for micro-coils.

Purpose of the Study:

• To present a novel MEMS fabrication process for micro-coil magnetic stimulation probes.
• To address the challenges of low coil resistance, high leak current, and adaptive fabrication.
• To enable efficient and reliable in vivo brain tissue stimulation.

Main Methods:

• Utilized a multilayer resist lift-off process for patterning thick metal films (up to 1800 nm) with high conductivity.
• Employed Atomic Layer Deposition (ALD) alumina and parylene C encapsulation for high leak resistance (>210 GΩ).
• Combined multi-step Deep Reactive Ion Etching (DRIE) and maskless photolithography for adaptive design and fabrication, avoiding SOI wafers and mask costs.

Main Results:

• Achieved high conductivity thin-film micro-coils with enhanced power efficiency.
• Demonstrated significantly high leak resistance (>210 GΩ) through effective encapsulation.
• Fabricated compact probes (4-mm long, 60-μm thick, 150-μm wide) with reduced design-to-device time.
• Successfully validated MEMS coil devices in vivo using mice.

Conclusions:

• The developed MEMS fabrication process effectively overcomes key challenges in micro-coil probe design.
• The process enables the creation of efficient, reliable, and adaptable micro-coil probes for neuroscience research.
• This advancement facilitates faster design iterations and reduces fabrication costs for micro-coil devices.