Fig. 4: Monolayer MoS2 memtransistor-based “hunger neuron” and “appetite neuron”.
From: An all 2D bio-inspired gustatory circuit for mimicking physiology and psychology of feeding behavior
a Optical image and b circuit schematic of a representative comparator circuit composed of 8 MoS2 memtransistors (\({{{{{\rm{MT}}}}}}_1\)–\({{{{{\rm{MT}}}}}}_8\)) used as the “hunger neuron” and the “appetite neuron”. The comparator circuit is a 4-stage cascaded inverter as each memtransistor pair, \({{{{{\rm{MT}}}}}}_1-{{{{{\rm{MT}}}}}}_2\), \({{{{{\rm{MT}}}}}}_3-{{{{{\rm{MT}}}}}}_4\), \({{{{{\rm{MT}}}}}}_5-{{{{{\rm{MT}}}}}}_6\), and \({{{{{\rm{MT}}}}}}_7-{{{{{\rm{MT}}}}}}_8\) serve as an inverter. c \({{{{{{\rm{V}}}}}}}_{{{{{{\rm{N}}}}}}4}\) measured at node, \({{{{{\rm{N}}}}}}4\). d \({{V}}_{{{{{{\rm{N}}}}}}5}\) measured at node, \({{{{{\rm{N}}}}}}5\). e \({{V}}_{{{{{{\rm{N}}}}}}6}\) measured at node, \({{{{{\rm{N}}}}}}6\), and f \({{V}}_{{{{{{\rm{N}}}}}}7}\) measured at node, \({{{{{\rm{N}}}}}}7\), as a function of the input voltage, \({{V}}_{{{{{{\rm{N}}}}}}2}\), applied to node \({{{{{\rm{N}}}}}}2\). Peak gain for each inverter stage is mentioned in the inset. Highest gain of ~90 is observed for the output stage, which allows for the abrupt state transition for \({{V}}_{{{{{{\rm{N}}}}}}7}\) from 0 to \({{V}}_{{{{{{\rm{DD}}}}}}}\), i.e., logic “0” to logic “1”. The input voltage, \({{V}}_{{{{{{\rm{N}}}}}}2}\), at which this sharp state transition occurs is referred to as the comparator threshold (\({{V}}_{{{{{{\rm{TH}}}}}}-{{{{{\rm{C}}}}}}}\)). For the “hunger neuron” and the “appetite neuron”, \({{V}}_{{{{{{\rm{TH}}}}}}-{{{{{\rm{C}}}}}}}\) is represented by \({{V}}_{{{{{{\rm{HN}}}}}}}\) and \({{V}}_{{{{{{\rm{AN}}}}}}}\), respectively, and \({{V}}_{{{{{{\rm{N}}}}}}7}\) is represented by logic state variables \({{{{{\rm{H}}}}}}\) and \({{{{{\rm{A}}}}}}\), respectively. Temporal evolution of \({{V}}_{{{{{{\rm{H}}}}}}}\), i.e., logic state of \({{{{{\rm{H}}}}}}\) in response to g sweet and h bitter taste stimulants. Temporal evolution of \({{V}}_{{{{{{\rm{A}}}}}}}\), i.e., logic state of \({{{{{\rm{A}}}}}}\) in response to i sweet and j bitter taste stimulants. k Transfer curve for the “appetite neuron” for different \({{V}}_{{{{{{\rm{AN}}}}}}}\) obtained through non-volatile programming of MoS2 memtransistor, \({{{\rm{MT}}}}_{2}\). Corresponding temporal evolution of \({{V}}_{{{{{{\rm{A}}}}}}}\) or \({{{{{\rm{A}}}}}}\) in response to l sweet and m bitter taste stimulants.
