Artificial Synaptic Behavior of Aloe Polysaccharides-Based Device with Au as Top Electrode

Abstract

Formulated, processed, and dried Aloe polysaccharides thin film sandwiched between ITO as bottom electrode and Au as top electrode has been adopted as an artificial synapse to emulate behavior of neuromorphic computing. The synaptic plasticity or weight has been modulated with this simple metal-insulator-metal structure by applying voltage sweep and voltage pulse, with excitatory postsynaptic current being monitored. Synaptic potentiation and depression has been demonstrated by applying 6 consecutive sweeps of voltage in positive and negative polarity, respectively. By varying number (10 – 50) of voltage pulses, variable synaptic weight has been measured with paired pulse facilitation and post-tetanic potentiation indexes of 2.61x10-6and 1.45x10-4, respectively. The short-term plasticity and long-term potentiation can be clearly revealed when applying 40 pulses and beyond, with extracted time constants of approximately 28 s at 40 pulses and 90 s at 50 pulses.

Natural Organic Materials Based Memristors and Transistors for Artificial Synaptic Devices in Sustainable Neuromorphic Computing Systems

“…Similar to PPF, a post-tetanic potentiation (PTP) effect was reported by an aloe polysaccharide-memristor [ 10 ] and a lignin-memristor [ 24 ]. PTP represents the gradual increase in synaptic transmission when, instead of two stimulation spikes, multiple sequential stimulation spikes are applied within a short time.…”

“…Besides applying DC voltage sweeps to realize the continuous and gradual change in the current level, analog memristor behaviors were also investigated by transient electrical characterization by applying input voltage pulses to the device and recording the current response with time. Such pulse tests have been reported by memristors based on aloe polysaccharide [ 10 ], honey [ 17 ], lignin [ 24 ], dextran [ 30 ], chicken egg albumen [ 40 ], cellulose [ 54 ], bombyx mori silk [ 55 ], etc., as shown in Figure 2 f–m. When 10 consecutive pulses (±0.10 V, 30 ms) with opposite polarities were applied on a cellulose-memristor [ 54 ], the increase of current values upon five successive negative bias pulses demonstrated the potentiation of the conductance states, while the decrease of current values upon five successive positive bias pulses showed the depression of the conductance of the device.…”

“…A variety of natural organic materials, mainly protein and carbohydrates such as chitosan [ 3 , 4 , 5 , 6 ], Aloe Vera and polysaccharide [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ], zein from maize [ 14 ], gelatin [ 15 ], honey [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ], lignin [ 23 , 24 ], collagen [ 25 ], trypsin [ 26 ], ι-carrageenan [ 27 , 28 ], dextran [ 29 , 30 ] sodium alginate [ 31 ], wood-derived cellulose nanopapers [ 32 ], biomass-based hydrogel [ 33 ], casein [ 34 ], pectin [ 35 , 36 ], carotene [ 37 ], lipid [ 38 ], natural acidic polyelectrolyte [ 39 ], chicken albumen [ 40 , 41 ], etc., are currently under investigation for making memristor- and transistor-based artificial synaptic devices. These natural organic materials have the advantages of being renewable, sustainable, biodegradable, environmentally friendly, etc., making them an attractive alternative to other inorganic metal oxide and polymer materials [ 42 ] for artificial synaptic devices.…”