Multilevel Reset Dependent Set of a Biodegradable Memristor with Physically Transient

Abstract

The electronic device, with its biocompatibility, biodegradability, and ease of fabrication process, shows great potential to embed into health monitoring and hardware data security systems. Herein, polyvinylpyrrolidone (PVP) biopolymer is presented as an active layer, electrochemically active magnesium (Mg) as a metal electrode, and chitosan-based substrate (CHS) to fabricate biocompatible and biodegradable physically transient neuromorphic device (W/Mg/PVP/Mg/CHS). The I-V curve of device is non-volatile bipolar in nature and shows a unique compliance-induced multilevel RESET-dependent-SET behavior while sweeping the compliance current from a few microamperes to milliamperes. Non-volatile and stable switching properties are demonstrated with a long endurance test (100 sweeps) and retention time of over 10⁴ s. The physically transient memristor (PTM) has remarkably high dynamic R_ON /R_OFF (ON/OFF state resistance) ratio (10⁶ Ω), and when placed in deionized (DI) water, the device is observed to completely dissolve within 10 min. The pulse transient measurements demonstrate the neuromorphic computation capabilities of the device in the form of excitatory post synaptic current (EPSC), potentiation, depression, and learning behavior, which resemble the biological function of neurons. The results demonstrate the potential of W/Mg/PVP/Mg/CHS device for use in future healthcare and physically transient electronics.

Keywords: biocompatible; multilevel memory; polyvinylpyrrolidone; resistive switching; transient memory.

Figure 1

Shows an atomic force microscopy (AFM) image of the topology and roughness of the PVP active layer. a) Dried at room temperature and atmospheric pressure. b) Dried in vacuum (10⁻³ mbar), having a root‐mean‐square (RMS) roughness value of 0.686 and 0.314 nm respectively, scanning area of 5 × 5 µm².

Figure 2

Reveals the W/Mg/PVP/Mg/CHS memristor. a) 3D structure schematics and inset image showing cross‐section view of same. b) Cross‐sectional scanning electron microscope (SEM) image depicting different layer thicknesses. c) Forming I–V sweep and schematic of cross‐section view for biasing the device. d) The endurance characteristics of the device were evaluated by running 99 consecutive I–V sweeps.

Figure 3

a) ON (LRS) and OFF (HRS) retention characteristics at I _CC = 10⁻⁵ A and a memory window of 10⁶. Cumulative Probability distribution for 100 sweeps of. b) resistance of LRS and HRS. c) SET and RESET voltage.

Figure 4

Represents a schematic of the electrochemical metallization (ECM) process in W/Mg/PVP/Mg/CHS memristor. a) The pristine state of the PTM. b) Oxidation, migration, and reduction of Mg²⁺ ions in the polymer matrix during the SET process. c) Reduction and accumulation of Mg atoms on the bottom electrode, which leads to the growth of highly conducting filament. d) Filament rupturing and Mg atom dissolution inside the polymer matrix during the RESET process.

Figure 5

Represents the complianceinduced multilevel RESET‐SET operation of the W/Mg/PVP/Mg/CHS memristor obtained by controlling the compliance current. a) I–V curve of Ic = 100 µA. b) I–V curve of Ic = 500 µA. c) I–V curve of Ic = 1 mA. Schematic representation of multilevel mechanism: d) Possible filament formation and its textures during the LRS. e) Possible filament rupturing point and depth of filament‐1 for multilevel HRS during the reset.

Figure 6

Shows the retention characteristics of PTM after each HRS and LRS. a) Real‐time retention of HRS1, HRS2, HRS3, HRS4, and HRS5. b) Real‐time retention of LRS1, LRS2, LRS3, LRS4, and LRS5. c) Real‐time degradation of multilevel memory from set to reset state.

Figure 7

a, b) Schematic representation of the biological synapse, illustrating the pre‐synaptic and post‐synaptic neurons. Neuromorphic behavior of the PTM device: c) EPSC by repetitive pulses of the same magnitude with constant time (V_pulse = 2 V, t_width = 100 µs, t_period = 180 µs). d) Variation of EPSC with dual sweep pulse mode, varying the magnitude (V_start = 0 V, V_stop = 2 V_step = 0.25 V, t_width = 1 ms, t_period = 1.6 ms). e) EPSC modulation by changing the amplitude of pulses (V_start = 0 V, V_stop = 2 V_step = 0.1 V, t_width = 120 ms, t_period = 250 ms). f, g) Potentiation and depression performance of the PTM device in response to a positive and negative stream of 2 V, 100 ms pulses applied. h) The schematic of the letter “S” consists of 8 pixels generated by a training pulse to show the learning process in the brain.

Figure 8

Shows photograph of a) W/Mg/PVP/Mg/CHS memristors on biocompatible and biodegradable substrate (Chitosan). b) Bio and wearable compatibility of W/Mg/PVP/Mg/CHS memristors. c) PTM biodegradability in deionized water at room temperature over various time intervals: 0, 30, 120, and 300 s.