Figure 4.

Spiking characteristics of artificial olfactory neuron modules. a,b) Spiking characteristics (V _out–t) of the artificial olfactory neuron modules composed of the SnO₂ gas sensor and the 1T‐neuron. Spiking was activated when the gas concentration of NH₃ was increased (ON‐type response) and was depressed as the gas concentration of NO₂ was increased (OFF‐type response). c,d) V _out–t of the artificial olfactory neuron modules comprising WO₃ gas sensor and the 1T‐neuron. Like the SnO₂‐based neuron module, spiking was activated as the gas concentration of NH₃ was increased (ON‐type response) and depressed when the gas concentration of NO₂ was increased (OFF‐type response). e,h) Ratio (f _gas/f _air) for various concentrations of NH₃, CO, acetone, and NO₂, where the spiking frequency to gas species is f _gas and that to air is f _air. Spiking frequency of the artificial olfactory neuron modules was increased in the NH₃, CO, and acetone environments (ON‐type response), while it was decreased in the NO₂ environment (OFF‐type response).