Flexible Neural Implants

Citation

Huang, Ray Kui-Jui (2011) Flexible Neural Implants. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/VMZB-0N20. https://resolver.caltech.edu/CaltechTHESIS:07092010-104142755

Abstract

Despite recent development in integration technologies for biomedical implantable devices, current state-of-the-art prosthetic platforms still lack a reliable and convenient packaging scheme to integrate high-density signal-driving chips, wireless telemetry circuitries and noise-canceling amplifiers, mainly due to the limitations in fabrication technology, material compatibility and interconnect reliability. In this dissertation, new packaging technologies are developed and presented to enable a new generation of flexible neural implants. These technologies can also house integrated circuit chips and provide high-density electrical connection to it.

This packaging scheme utilizes the parylene-metal-parylene skin structure and can be totally integrated and be monolithically fabricated with existing functional devices. The size and the electrode patterns can be modified to suit different chips and applications. Integration with flexible cable integrated silicon probes for neural prosthesis, implantable muscle stimulators and implantable RFID tagging technology are all successfully demonstrated in this dissertation. Other discrete components can also be integrated to achieve high level functionality.

In order to ensure the long-term stability of such packaging scheme, accelerated hot saline soaking test is conducted on the overall structure and its components. Detailed adhesion enhancement techniques are also presented to improve its performances. A physical model of the flexible retinal implant is then tested in vivo during the course of the experiment. Finally, the high-density squeegee bonding technique is introduced, which allows the integration of a 256-channel chip. Functionality of the chip has been demonstrated. As a result, this technology has the potential to achieve ultra high lead count connection and can facilitate future research in flexible implantable biodevices.

Thesis Files