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Stretchable organic optoelectronic sensorimotor synapse

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Science Advances  23 Nov 2018:
Vol. 4, no. 11, eaat7387
DOI: 10.1126/sciadv.aat7387
  • Fig. 1 Biological and organic optoelectronic synapse and neuromuscular electronic system.

    (A to D) In a biological system, (A) light stimulates a biological motor neuron that has photosensitive protein expression, and an action potential is thus generated. (B and C) A chemical synapse of a neuromuscular junction transmits the potentials to a muscle fiber, (D) which causes the muscle to contract. Analogously, (E to I) in an organic artificial system, (E) light triggers a photodetector to generate output voltage spikes. (H and G) The voltage spikes produce electrical postsynaptic signals from an s-ONWST to activate an artificial muscle actuator, (I) which the artificial muscle then contracts. (F) Optical wireless communication via organic optoelectronic synapse with patterned light signals representing the International Morse code of “ABC.”

  • Fig. 2 Fabrication and electrical characteristics of s-ONWST.

    (A) Fabrication procedure of s-ONWST based on a single ONW. An electrospun single ONW was first transferred onto prestretched rubbery SEBS substrate and subsequently buckled when the film contracted after the strain was released. (B) Optical microscopy image of a wavy NW stretched from 0 to 100% strain. (C) I-V characteristics of s-ONWST at 0, 50, and 100% strains. Blue arrows: clockwise hysteresis. (D) Maximum drain current and mobility as a function of various strains along the channel length and width directions.

  • Fig. 3 Synaptic characteristics of s-ONWST.

    (A) Neural signal transmission from preneuron to postneuron through a biological synapse (top) and an artificial synapse (bottom). (B) EPSCs triggered by single and double spikes (each spike: −1 V, 120 ms). A1 and A2 are EPSCs of the first and second spikes, respectively, separated by Δt = 120 ms. (C to E) Postsynaptic characteristics of stretched artificial synapse from 0 to 100% strains; (C) PPF (A2/A1) as a function of 120 ≤ Δt ≤ 920 ms, (D) spike voltage–dependent plasticity (SVDP) with various gate voltages from −0.3 to −1 V, and (E) spike number–dependent plasticity (SNDP) with 1 to 50 spikes. (F and G) Spike frequency–dependent plasticity (SFDP) characteristics with spike frequency from 0.3 to 5 Hz; (F) maximum EPSCs and (G) EPSC gain (A10/A1) of stretched artificial synapse from 0 to 100% strains.

  • Fig. 4 Organic optoelectronic synapse and neuromuscular electronic system.

    (A) Photograph of organic optoelectronic synapse on an internal human structure model. (B) Configuration of organic optoelectronic synapse (photodetector and artificial synapse) and neuromuscular electronic system (artificial synapse, transimpedance circuit, and artificial muscle actuator). (C) EPSCs triggered by single and double visible light spikes (each spike generated presynaptic voltage of −1.1 V for 120 ms). PPF (A2/A1) = 1.42. (D and E) Visible light–triggered EPSC amplitudes of s-ONWST from 0 to 100% strains; (D) SDDP from 120 to 960 ms and (E) SNDP with 1 to 30 spikes. (F) Visible light–triggered EPSC amplitudes of s-ONWST with the International Morse code of “SOS,” which is the most common distress signal. (G) Infrared (IR) and ultraviolet (UV) light–triggered EPSC amplitudes of s-ONWST with the International Morse code of “HELLO UNIVERSE.” (H) Maximum δ of polymer actuator and output voltage generated by s-ONWST according to 0 ≤ nSPIKE ≤ 60 and (I) digital images of the polymer actuator according to 0 ≤ nSPIKE ≤ 100 with 0 or 100% strain.

  • Table 1 Comparison of biological and optical neuromuscular electronic systems.
    Biological systemArtificial system
    Sensorimotor neuronPresynaptic membraneGate electrode
    Presynaptic potentialGate voltage
    Photosensitive proteinPhotodetector
    Neuromuscular
    junction
    Synaptic cleftIon gel electrolyte
    NeurotransmitterAnion
    Skeletal musclePostsynaptic membraneONW
    Postsynaptic potentialDrain current
    Muscle fiberPolymer actuator

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/11/eaat7387/DC1

    Additional supporting information

    Fig. S1. Working mechanism of s-ONWST.

    Fig. S2. Fabrication and morphology of ONW.

    Fig. S3. Electrical characteristics of s-ONWST.

    Fig. S4. SFDP of s-ONWST.

    Fig. S5. Current density-voltage (J-V) characteristics of organic photodetector.

    Fig. S6. Output characteristics of the photodetectors with different light spike frequency.

    Fig. S7. Frequency-dependent biological muscle contraction and EPSCs of s-ONWST.

    Fig. S8. A novel optical wireless communication method of human-machine interface.

    Fig. S9. Correlation between EPSC amplitude response and the International Morse code of English letters.

    Fig. S10. Full circuit diagram of transimpedance circuit.

    Fig. S11. Operating voltage shift of s-ONWST to connect the transimpedance circuit.

    Table S1. Summary of electrical characteristics of s-ONWST as function of strain in channel length and width directions.

    Table S2. Summary of electrical characteristics of s-ONWST after stretching cycles at 100% strain in channel length and width directions.

    Table S3. Maximum δ of polymer actuator and output voltage generated by s-ONWST according to the number of light spikes.

    Movie S1. Operation of an artificial muscle actuator by an optical sensory neuromuscular electronic system.

  • Supplementary Materials

    The PDF file includes:

    • Additional supporting information
    • Fig. S1. Working mechanism of s-ONWST.
    • Fig. S2. Fabrication and morphology of ONW.
    • Fig. S3. Electrical characteristics of s-ONWST.
    • Fig. S4. SFDP of s-ONWST.
    • Fig. S5. Current density-voltage (J-V) characteristics of organic photodetector.
    • Fig. S6. Output characteristics of the photodetectors with different light spike frequency.
    • Fig. S7. Frequency-dependent biological muscle contraction and EPSCs of s-ONWST.
    • Fig. S8. A novel optical wireless communication method of human-machine interface.
    • Fig. S9. Correlation between EPSC amplitude response and the International Morse code of English letters.
    • Fig. S10. Full circuit diagram of transimpedance circuit.
    • Fig. S11. Operating voltage shift of s-ONWST to connect the transimpedance circuit.
    • Table S1. Summary of electrical characteristics of s-ONWST as function of strain in channel length and width directions.
    • Table S2. Summary of electrical characteristics of s-ONWST after stretching cycles at 100% strain in channel length and width directions.
    • Table S3. Maximum δ of polymer actuator and output voltage generated by s-ONWST according to the number of light spikes.
    • Legend for movie S1

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Operation of an artificial muscle actuator by an optical sensory neuromuscular electronic system.

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