Highly conformable chip-in-foil implants for neural applications.

Area of Science:

• Biomedical Engineering
• Materials Science
• Neuroscience

Background:

• Increasing demands for high-resolution, long-lasting neural interfaces require advanced materials and designs.
• Sophisticated silicon-based integrated circuits are crucial for meeting these functional requirements.
• Flexible polymer substrates enhance the biocompatibility and coverage of neural implants.

Purpose of the Study:

• To address challenges in developing hybrid chip-in-foil neural implants.
• To optimize mechanical compliance for long-term tissue integration.
• To enable scalable and modular designs for neural interface systems.

Main Methods:

• Finite element modeling (FEM) to establish design rules for die geometry, interconnect routing, and contact pad placement.
• Development of a microfabrication process for transferring, aligning, and interconnecting multiple dice onto polyimide substrates.
• Assessment of mechanical compliance and structural integrity of the hybrid implant.

Main Results:

• Edge fillets in die bases improve die-substrate integrity and expand contact pad areas.
• Avoiding interconnect routing near die corners mitigates substrate stress concentration.
• Strategic placement of contact pads prevents delamination during implant conformance.

Conclusions:

• The developed hybrid chip-in-foil technology offers a promising approach for advanced neural interfaces.
• Design guidelines derived from FEM studies are critical for robust and scalable implantable systems.
• The microfabrication process allows for flexible arrangement of diverse chip types on conformable substrates.