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Towards a Microfabricated Flexible Graphene-Based Active Implant for Tissue Monitoring During Optogenetic Spinal Cord Stimulation

: Velea, Andrada Iulia; Vollebregt, Sten; Hosman, Tim; Pak, Anna; Giagka, Vasiliki


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019 : Stockholm, Sweden, October 27-30, 2019
Piscataway, NJ: IEEE, 2019
ISBN: 978-1-7281-2637-1
ISBN: 978-1-7281-2638-8
Nanotechnology Materials and Devices Conference (NMDC) <14, 2019, Stockholm>
Conference Paper
Fraunhofer IZM ()

This work aims to develop a smart neural interface with transparent electrodes to allow for electrical monitoring of the site of interest during optogenetic stimulation of the spinal cord. In this paper, a microfabrication process for the wafer-level development of such a compact, active, transparent and flexible implant is presented. Graphene has been employed to form the transparent array of electrodes and tracks, on top of which chips have been bonded using flip-chip bonding techniques. To provide high flexibility, soft encapsulation, using polydimethylsiloxane (PDMS) has been used. Making use of the “Flex-to-Rigid” (F2R) technique, cm-size graphene-on-PDMS structures have been suspended and characterized using Raman spectroscopy to qualitatively evaluate the graphene layer, together with 2-point measurements to ensure the conductivity of the structure. In parallel, flip-chip bonding processes of chips on graphene structures were employed and the 2-point electrical measurement results have shown resistance values in the range of kΩ for the combined tracks and ball-bonds.