Flexible and Extensible Ribbon-Cable Interconnects for Implantable Electrical Neural Interfaces.

Area of Science:

• Biomedical Engineering
• Materials Science
• Neuroscience

Background:

• Implanted neural devices require reliable electrical interconnects.
• Existing interconnects often lack the flexibility and extensibility needed for optimal integration with microelectrode arrays.
• Thin-film technologies offer potential for miniaturized and flexible neural interfaces.

Purpose of the Study:

• To design and characterize novel thin-film ribbon cables for neural stimulation and recording devices.
• To develop flexible and extensible interconnects that integrate seamlessly with thin-film microelectrode arrays (MEAs).
• To investigate a lattice geometry for enhanced cable extensibility without compromising electrical function.

Main Methods:

• Fabrication of multichannel ribbon cables using amorphous silicon carbide (a-SiC), polyimide, and titanium/gold thin films.
• Investigation of linear, serpentine, and open lattice electrical trace designs via photolithography and thin-film processing.
• Characterization of cable flexibility, tensile elongation tolerance, and impedance changes.
• Development and testing of an electrical interconnect process using conductive epoxy for MEA integration.
• In vivo testing of the ribbon cable-MEA system for acute neuronal recording in rat cortex.

Main Results:

• Ribbon cables demonstrated tolerance to flexural bending (50 μm radius) without impedance change.
• Standard designs failed at <5% tensile elongation, while lattice designs achieved 300% elongation without failure.
• Lattice structure's out-of-plane displacement mechanism prevents fracture during high elongation.
• Extensible cables withstood 50,000 cycles of 45% tensile extension without failure.
• Successful acute neuronal recording was achieved using the ribbon cable connected to an a-SiC MEA in rat cortex.

Conclusions:

• Highly flexible and extensible thin-film ribbon cables were successfully designed and fabricated.
• The lattice geometry is crucial for achieving significant elongation tolerance in neural interconnects.
• These cables can accommodate large extensions, aiding surgical implantation and potentially reducing tethering forces on MEAs.
• The developed interconnects show promise for improving chronic neural recording performance and device longevity.