title: Laboratory investigation of microelectronics-based stimulators for large-scale suprachoroidal transretinal stimulation (STS).
abstract: This paper describes the technological developments underlying the realization of a reliable and reproducible microchip-based stimulator with a large number of stimulus electrodes. A microchip-based stimulator with over 500 electrodes for suprachoroidal transretinal stimulation (STS) is proposed in this paper, and an example is presented. To enhance reliability and reproducibility for such a large array, we introduce a flip-chip bonding technique and place microchips on the reverse side of a substrate. A square microchip of size 600 microm was fabricated using 0.35 microm standard CMOS process technology. Twelve microchips were flip-chip bonded on a polyimide substrate through Au bumps. To evaluate the feasibility of the proposed device, we successfully fabricated a stimulator with 12 microchips and 118 electrodes made of Pt/Au bumps, and demonstrated their operation in a saline solution for 2 weeks. Also, to evaluate the device operation in vivo, a stimulator with one active IrO(x) electrode was implanted into the scleral pocket of a rabbit and electrical evoked potential (EEP) signals with a threshold of 100 microA were obtained. We also fabricated a simulator with 64 microchips that has 576 electrodes (9 electrodes in a microchip times 64 microchips).
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan. ohta@ms.naist.jp
authors.forename: J
authors.initials: J
authors.lastname: Ohta
authors.forename: T
authors.initials: T
authors.lastname: Tokuda
authors.forename: K
authors.initials: K
authors.lastname: Kagawa
authors.forename: S
authors.initials: S
authors.lastname: Sugitani
authors.forename: M
authors.initials: M
authors.lastname: Taniyama
authors.forename: A
authors.initials: A
authors.lastname: Uehara
authors.forename: Y
authors.initials: Y
authors.lastname: Terasawa
authors.forename: K
authors.initials: K
authors.lastname: Nakauchi
authors.forename: T
authors.initials: T
authors.lastname: Fujikado
authors.forename: Y
authors.initials: Y
authors.lastname: Tano
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002829:Choroid / Q000502:physiology* / Q000601:surgery; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D004582:Electronics, Medical / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008904:Miniaturization; D011817:Rabbits; D012160:Retina / Q000502:physiology / Q000601:surgery; D012164:Retinal Diseases / Q000534:rehabilitation; D012165:Retinal Ganglion Cells / Q000502:physiology*; D013813:Therapy, Computer-Assisted / Q000295:instrumentation* / Q000379:methods