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Open AccessFeature PaperArticle

A mm-Sized Free-Floating Wireless Implantable Opto-Electro Stimulation Device

1
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27606, USA
2
Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
3
Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
4
Bionic Sciences Inc., Atlanta, GA 30316, USA
*
Author to whom correspondence should be addressed.
Micromachines 2020, 11(6), 621; https://doi.org/10.3390/mi11060621
Received: 5 June 2020 / Revised: 23 June 2020 / Accepted: 24 June 2020 / Published: 25 June 2020
(This article belongs to the Special Issue Implantable Microdevices, Volume II)
Towards a distributed neural interface, consisting of multiple miniaturized implants, for interfacing with large-scale neuronal ensembles over large brain areas, this paper presents a mm-sized free-floating wirelessly-powered implantable opto-electro stimulation (FF-WIOS2) device equipped with 16-ch optical and 4-ch electrical stimulation for reconfigurable neuromodulation. The FF-WIOS2 is wirelessly powered and controlled through a 3-coil inductive link at 60 MHz. The FF-WIOS2 receives stimulation parameters via on-off keying (OOK) while sending its rectified voltage information to an external headstage for closed-loop power control (CLPC) via load-shift-keying (LSK). The FF-WIOS2 system-on-chip (SoC), fabricated in a 0.35-µm standard CMOS process, employs switched-capacitor-based stimulation (SCS) architecture to provide large instantaneous current needed for surpassing the optical stimulation threshold. The SCS charger charges an off-chip capacitor up to 5 V at 37% efficiency. At the onset of stimulation, the capacitor delivers charge with peak current in 1.7–12 mA range to a micro-LED (µLED) array for optical stimulation or 100–700 μA range to a micro-electrode array (MEA) for biphasic electrical stimulation. Active and passive charge balancing circuits are activated in electrical stimulation mode to ensure stimulation safety. In vivo experiments conducted on three anesthetized rats verified the efficacy of the two stimulation mechanisms. The proposed FF-WIOS2 is potentially a reconfigurable tool for performing untethered neuromodulation. View Full-Text
Keywords: free-floating implants; inductive link; switched-capacitor-based optical/electrical stimulation; charge balancing free-floating implants; inductive link; switched-capacitor-based optical/electrical stimulation; charge balancing
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MDPI and ACS Style

Jia, Y.; Gong, Y.; Weber, A.; Li, W.; Ghovanloo, M. A mm-Sized Free-Floating Wireless Implantable Opto-Electro Stimulation Device. Micromachines 2020, 11, 621.

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