title: Improved selectivity from a wavelength addressable device for wireless stimulation of neural tissue.
abstract: Electrical neural stimulation with micro electrodes is a promising technique for restoring lost functions in the central nervous system as a result of injury or disease. One of the problems related to current neural stimulators is the tissue response due to the connecting wires and the presence of a rigid electrode inside soft neural tissue. We have developed a novel, optically activated, microscale photovoltaic neurostimulator based on a custom layered compound semiconductor heterostructure that is both wireless and has a comparatively small volume (<0.01 mm(3)). Optical activation provides a wireless means of energy transfer to the neurostimulator, eliminating wires and the associated complications. This neurostimulator was shown to evoke action potentials and a functional motor response in the rat spinal cord. In this work, we extend our design to include wavelength selectivity and thus allowing independent activation of devices. As a proof of concept, we fabricated two different microscale devices with different spectral responsivities in the near-infrared region. We assessed the improved addressability of individual devices via wavelength selectivity as compared to spatial selectivity alone through on-bench optical measurements of the devices in combination with an in vivo light intensity profile in the rat cortex obtained in a previous study. We show that wavelength selectivity improves the individual addressability of the floating stimulators, thus increasing the number of devices that can be implanted in close proximity to each other.
authors.affiliation: Department of Biomedical Engineering, Boston University, Boston MA, USA.
authors.forename: Elif Ç
authors.initials: EÇ
authors.lastname: Seymour
authors.affiliation: Department of Electrical and Computer Engineering, Boston University, Boston MA, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Freedman
authors.affiliation: Nanotechnology Research Center, Bilkent University Ankara, Turkey.
authors.forename: Mutlu
authors.initials: M
authors.lastname: Gökkavas
authors.affiliation: Nanotechnology Research Center, Bilkent University Ankara, Turkey.
authors.forename: Ekmel
authors.initials: E
authors.lastname: Ozbay
authors.affiliation: Department of Biomedical Engineering, New Jersey Institute of Technology, Newark NJ, USA.
authors.forename: Mesut
authors.initials: M
authors.lastname: Sahin
authors.affiliation: Department of Biomedical Engineering, Boston University, Boston MA, USA ; Department of Electrical and Computer Engineering, Boston University, Boston MA, USA.
authors.forename: M Selim
authors.initials: MS
authors.lastname: Unlü
keywords: addressable stimulators; floating micro electrodes; neural prostheses; optical neural stimulation; optically powered; wireless