MicroSynapse: A brain-inspired coplanar micro-supercapacitor for bridging capacitive energy storage and neuromorphic functionality

Abstract

This study investigates the interplay between capacitive and synaptic characteristics of MXene-NiO micro-supercapacitors (M-SCs), highlighting their potential for technological advancements. While most research focuses on resistive switching and memristive behavior, the ability of capacitors to emulate brain-inspired synaptic functions remains largely unexplored. An M-SC synapse is introduced, leveraging nonlinear ion transport in MXene-NiO composites to achieve synaptic behavior. A high-performance M-SC was fabricated using a cost-effective 3D stamping method with MXene-NiO composite ink. The device exhibits an impressive areal capacitance of 3053 mF/cm2 at a current density of 10 μA/cm2, achieving a maximum energy density of 152 Wh/kg and a power density of 600 W/kg. It maintains 77 % stability over 10,000 cycles at 40 μA/cm2, demonstrating excellent electrochemical durability. Notably, the device exhibits nonlinear, brain-inspired learning and forgetting behaviors, achieving highly reliable and reproducible synaptic performance for over 25,000 cycles. Furthermore, the biocompatibility of the MXene–NiO composite material was evaluated through in vitro (hemolysis and cell viability) and in ovo (angiogenesis) studies. These results not only advance supercapacitor technology but also provide a basis for exploring all-capacitive synaptic features, paving the way for innovations in neuromorphic computing and energy storage. © 2025 Elsevier B.V., All rights reserved.