Totally transparent hydrogel-based subdural electrode with patterned salt bridge.

Area of Science:

• Biomedical Engineering
• Materials Science
• Neuroscience

Background:

• Developing advanced neural interfaces is crucial for understanding brain activity and improving neurosurgical outcomes.
• Existing subdural electrodes often lack transparency or optimal conformability for delicate brain surface applications.

Purpose of the Study:

• To develop a fully transparent, soft, and conformable subdural electrode for neural recording.
• To demonstrate the feasibility of a novel bonding technique for constructing such electrodes.
• To evaluate the electrode's performance in vivo for brain wave signal acquisition.

Main Methods:

• Fabrication of a transparent subdural electrode by embedding poly(vinyl alcohol) (PVA)-filled poly(dimethylsiloxane) (PDMS) microchannels into a PVA hydrogel substrate.
• Achieving tight bonding between PVA and PDMS via mechanical interlocking using microprotrusions (salt bridge).
• Conducting in vivo experiments on a porcine brain model to assess electrode contact and signal recording capabilities.

Main Results:

• A transparent subdural electrode with a total thickness of approximately 1.5 mm was successfully fabricated.
• The electrode exhibited excellent softness and shape conformability to the brain surface.
• In vivo measurements demonstrated close contact with the brain and successful recording of brain wave signals in the 1–15 Hz frequency range.
• The electrode's high transparency facilitated clear visualization of the brain surface.

Conclusions:

• The developed salt bridge electrode offers a promising, transparent, and conformable solution for subdural neural recording.
• The simple, additive-free bonding method is suitable for fabricating advanced biomedical devices.
• The electrode's properties support potential applications in neurosurgery and optogenetic research by enabling simultaneous recording and visualization.