Fabrication and Assembly Techniques for Sub-mm Battery-Free Epicortical Implants

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Wireless implantable medical devices (IMDs) have advanced significantly over 30 years.
• Improving stability, safety, and distribution of neural interfaces is crucial.
• A new generation of single-channel, sub-millimeter wireless microelectronic devices is under development.

Purpose of the Study:

• To present a novel and straightforward fabrication and assembly technique for a sub-millimeter, wirelessly powered stimulating implant.
• To characterize the performance of this ultra-small implant.

Main Methods:

• Fabrication of a sub-mm implant integrating an ASIC (900 × 450 × 80 µm³), PEDOT-coated microelectrodes, an SMD inductor, and SU-8 coating.
• Wireless power transfer using near-field electromagnetic (EM) waves via a two-coil inductive link.
• In vivo testing on an anesthetized rat to verify stimulation efficacy.

Main Results:

• The implant's components (microelectrodes, SMD) were directly mounted onto the ASIC.
• A maximum power transfer efficiency (PTE) of 0.17% was achieved in air with a 0.5 cm coil separation.
• Successful verification of stimulation efficiency in vivo.

Conclusions:

• The developed technique enables the creation of ultra-small, wirelessly powered implants.
• The device demonstrates potential for effective neural stimulation.
• This technology contributes to the advancement of stable, safe, and distributed neural interfaces.