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Neuromorphic atomic switch networks.

Avizienis AV, Sillin HO, Martin-Olmos C, Shieh HH, Aono M, Stieg AZ, Gimzewski JK - PLoS ONE (2012)

Bottom Line: However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks.Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks.These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

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Related in: MedlinePlus

Device Fabrication.(a) SEM image of complex Ag networks (scale bar = 10 µm) produced by reaction of aqueous AgNO3 (50 mM) with (inset) lithographically patterned Cu seed posts (scale bar = 1 µm). (b) High resolution image of the functionalized Ag network at the device electrode interface (Pt) showing wire widths ranging from 100 nm to 3 µm (average <1 µm) and lengths extending from a few microns to almost a millimeter (scale bar = 700 nm).
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pone-0042772-g001: Device Fabrication.(a) SEM image of complex Ag networks (scale bar = 10 µm) produced by reaction of aqueous AgNO3 (50 mM) with (inset) lithographically patterned Cu seed posts (scale bar = 1 µm). (b) High resolution image of the functionalized Ag network at the device electrode interface (Pt) showing wire widths ranging from 100 nm to 3 µm (average <1 µm) and lengths extending from a few microns to almost a millimeter (scale bar = 700 nm).

Mentions: Based on the view that recurrent connectivity is essential to brain-like function, we have built, characterized and operated devices using massively interconnected (109 junctions/cm2 according to analysis of SEM images), silver nanowire networks functionalized with interfacial Ag/Ag2S/Ag atomic switches. These nanowire networks were prepared through self-assembly without pre-patterning of the network topology using the electroless deposition of Ag from Cu inside the SU-8 reaction well of an I/O device platform [18], [47]. Specifically, spontaneous oxidization of metallic copper through reaction with dilute aqueous solutions of AgNO3 produces a metallic silver structures with variable morphologies depending on the concentration of Ag+ and distribution of Cu [48]–[50]. Dendritic silver nanowires with minimum feature sizes <100 nm seen in Figure 1b were produced by using lithographically patterned Cu posts shown in the inset of Figure 1a. Control over the size and distribution of Cu seeds increased device yield by ensuring the formation of conductive pathways between the Pt device I/O electrodes as seen in Figure 1b. Ag/Ag2S/Ag interfaces were formed spontaneously within the network during gas phase sulfurization [51]. Following optimization of fabrication protocols, a total of 96 networks were used for the device characterization described below.


Neuromorphic atomic switch networks.

Avizienis AV, Sillin HO, Martin-Olmos C, Shieh HH, Aono M, Stieg AZ, Gimzewski JK - PLoS ONE (2012)

Device Fabrication.(a) SEM image of complex Ag networks (scale bar = 10 µm) produced by reaction of aqueous AgNO3 (50 mM) with (inset) lithographically patterned Cu seed posts (scale bar = 1 µm). (b) High resolution image of the functionalized Ag network at the device electrode interface (Pt) showing wire widths ranging from 100 nm to 3 µm (average <1 µm) and lengths extending from a few microns to almost a millimeter (scale bar = 700 nm).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412809&req=5

pone-0042772-g001: Device Fabrication.(a) SEM image of complex Ag networks (scale bar = 10 µm) produced by reaction of aqueous AgNO3 (50 mM) with (inset) lithographically patterned Cu seed posts (scale bar = 1 µm). (b) High resolution image of the functionalized Ag network at the device electrode interface (Pt) showing wire widths ranging from 100 nm to 3 µm (average <1 µm) and lengths extending from a few microns to almost a millimeter (scale bar = 700 nm).
Mentions: Based on the view that recurrent connectivity is essential to brain-like function, we have built, characterized and operated devices using massively interconnected (109 junctions/cm2 according to analysis of SEM images), silver nanowire networks functionalized with interfacial Ag/Ag2S/Ag atomic switches. These nanowire networks were prepared through self-assembly without pre-patterning of the network topology using the electroless deposition of Ag from Cu inside the SU-8 reaction well of an I/O device platform [18], [47]. Specifically, spontaneous oxidization of metallic copper through reaction with dilute aqueous solutions of AgNO3 produces a metallic silver structures with variable morphologies depending on the concentration of Ag+ and distribution of Cu [48]–[50]. Dendritic silver nanowires with minimum feature sizes <100 nm seen in Figure 1b were produced by using lithographically patterned Cu posts shown in the inset of Figure 1a. Control over the size and distribution of Cu seeds increased device yield by ensuring the formation of conductive pathways between the Pt device I/O electrodes as seen in Figure 1b. Ag/Ag2S/Ag interfaces were formed spontaneously within the network during gas phase sulfurization [51]. Following optimization of fabrication protocols, a total of 96 networks were used for the device characterization described below.

Bottom Line: However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks.Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks.These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

Show MeSH
Related in: MedlinePlus