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ref: -2012 tags: phase change materials neuromorphic computing synapses STDP date: 06-13-2019 21:19 gmt revision:3 [2] [1] [0] [head]

Nanoelectronic Programmable Synapses Based on Phase Change Materials for Brain-Inspired Computing

  • Here, we report a new nanoscale electronic synapse based on technologically mature phase change materials employed in optical data storage and nonvolatile memory applications.
  • We utilize continuous resistance transitions in phase change materials to mimic the analog nature of biological synapses, enabling the implementation of a synaptic learning rule.
  • We demonstrate different forms of spike-timing-dependent plasticity using the same nanoscale synapse with picojoule level energy consumption.
  • Again uses GST germanium-antimony-tellurium alloy.
  • 50pJ to reset (depress) the synapse, 0.675pJ to potentiate.
    • Reducing the size will linearly decrease this current.
  • Synapse resistance changes from 200k to 2M approx.

See also: Experimental Demonstration and Tolerancing of a Large-Scale Neural Network (165 000 Synapses) Using Phase-Change Memory as the Synaptic Weight Element

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ref: -2019 tags: optical neural networks spiking phase change material learning date: 06-01-2019 19:00 gmt revision:4 [3] [2] [1] [0] [head]

All-optical spiking neurosynaptic networks with self-learning capabilities

  • J. Feldmann, N. Youngblood, C. D. Wright, H. Bhaskaran & W. H. P. Pernice
  • Idea: use phase-change material to either block or pass the light in waveguides.
    • In this case, they used GST -- germanium-antimony-tellurium. This material is less reflective in the amorphous phase, which can be reached by heating to ~150C and rapidly quenching. It is more reflective in the crystalline phase, which occurs on annealing.
  • This is used for both plastic synapses (phase change driven by the intensity of the light) and the nonlinear output of optical neurons (via a ring resonator).
  • Uses optical resonators with very high Q factors to couple different wavelengths of light into the 'dendrite'.
  • Ring resonator on the output: to match the polarity of the phase-change material. Is this for reset? Storing light until trigger?
  • Were able to get correlative-like or hebbian learning (which I suppose is not dissimilar from really slow photographic film, just re-branded, and most importantly with nonlinear feedback.)
  • Issue: every weight needs a different source wavelength! Hence they have not demonstrated a multi-layer network.
  • Previous paper: All-optical nonlinear activation function for photonic neural networks
    • Only 3db and 7db extinction ratios for induced transparency and inverse saturation

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ref: -0 tags: Courtine PDMS soft biomaterials spinal cord e-dura date: 12-22-2017 01:29 gmt revision:0 [head]

Materials and technologies for soft implantable neuroprostheses

  • Quote: In humans, both the spinal cord and its meningeal protective membranes can experience as much as 10–20% tensile strain and
displacement (relative to the spinal canal) during normal postural movements. This motion corresponds to displacements on the order of centimetres17. The deformations relative to the spinal cord in animal models, such as rodents or non-human primates, are likely to be even larger.

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ref: -0 tags: parylene PDMS material properties gold compliant date: 02-08-2013 22:38 gmt revision:2 [1] [0] [head]

PMID-21240559 Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS

  • he microcable electrodes were also electromechanically tested, with measurable conductivity (220 kΩ) at an average 8% strain (n = 2) after the application of 200% strain.