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Improved selectivity from a wavelength addressable device for wireless stimulation of neural tissue.

Seymour EÇ, Freedman DS, Gökkavas M, Ozbay E, Sahin M, Unlü MS - Front Neuroeng (2014)

Bottom Line: Optical activation provides a wireless means of energy transfer to the neurostimulator, eliminating wires and the associated complications.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Boston University, Boston MA, USA.

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.

No MeSH data available.


Related in: MedlinePlus

Simulation of a class of wavelength selective devices. The optical block aluminum concentration was increased in 4% increments relative to the p-i-n diode, which was at lower aluminum concentrations.
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Figure 1: Simulation of a class of wavelength selective devices. The optical block aluminum concentration was increased in 4% increments relative to the p-i-n diode, which was at lower aluminum concentrations.

Mentions: In our custom layered AlxGa(1-x)As photodetector structures, wavelength selectivity is achieved by adjusting the proportional composition of aluminum and gallium in the GaAs/AlGaAs compound semiconductor system. The ability to modify the optical characteristics of compound semiconductor heterostructures by adjusting the compositional variation is known as bandgap engineering. A large bandgap layer is utilized as an optical block to filter shorter wavelengths and the active layer of the photodiode is engineered to limit responsivity to specific wavelengths. An example of using bandgap engineering to create a series of individually addressable devices is shown in Figure 1. As a proof of concept, we have designed two different custom layered GaAs/AlxGa(1-x)As heterostructures providing two different stimulation channels with their corresponding wavelengths in the NIR region. In this work, we present simulations of expected spatial and wavelength selectivity of our devices when they are activated by wavelength specific light inside the rat brain cortex.


Improved selectivity from a wavelength addressable device for wireless stimulation of neural tissue.

Seymour EÇ, Freedman DS, Gökkavas M, Ozbay E, Sahin M, Unlü MS - Front Neuroeng (2014)

Simulation of a class of wavelength selective devices. The optical block aluminum concentration was increased in 4% increments relative to the p-i-n diode, which was at lower aluminum concentrations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927122&req=5

Figure 1: Simulation of a class of wavelength selective devices. The optical block aluminum concentration was increased in 4% increments relative to the p-i-n diode, which was at lower aluminum concentrations.
Mentions: In our custom layered AlxGa(1-x)As photodetector structures, wavelength selectivity is achieved by adjusting the proportional composition of aluminum and gallium in the GaAs/AlGaAs compound semiconductor system. The ability to modify the optical characteristics of compound semiconductor heterostructures by adjusting the compositional variation is known as bandgap engineering. A large bandgap layer is utilized as an optical block to filter shorter wavelengths and the active layer of the photodiode is engineered to limit responsivity to specific wavelengths. An example of using bandgap engineering to create a series of individually addressable devices is shown in Figure 1. As a proof of concept, we have designed two different custom layered GaAs/AlxGa(1-x)As heterostructures providing two different stimulation channels with their corresponding wavelengths in the NIR region. In this work, we present simulations of expected spatial and wavelength selectivity of our devices when they are activated by wavelength specific light inside the rat brain cortex.

Bottom Line: Optical activation provides a wireless means of energy transfer to the neurostimulator, eliminating wires and the associated complications.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Boston University, Boston MA, USA.

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.

No MeSH data available.


Related in: MedlinePlus