A 7.5 V window dual-functional planar micro-device based on a biopolymer ionogel electrolyte for charge storage and neuromorphic computing†

The increasing demand for miniaturized electronics arises from the need for compact, energy-efficient devices that can perform complex functions, enabling advancements in applications such as wearable technology, the Internet of Things (IoT), and high-performance computing systems. Current miniaturized electronics face challenges in integrating efficient energy storage with adaptive, synaptic-like behaviours, often requiring complex interfaces and additional protective coatings, which limit their scalability and performance. Conventional supercapacitors and neuromorphic devices are typically developed separately, hindering the development of compact, multifunctional systems. This work overcomes these limitations by introducing a dual-functional micro-device that combines charge storage with synaptic plasticity, eliminating the need for extra coatings and enabling the seamless integration of energy storage and neuromorphic functionality in miniaturized electronics. The device utilizes a lithium-ion conducting biopolymer ionogel electrolyte, composed of a chitosan/gelatin blend and 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid in an interdigitated microelectrode configuration, which enables a sufficiently high ionic conductivity (∼10⁻⁴ S cm⁻¹) and remarkable dielectric constant (∼1610). The device demonstrates an exceptionally wide electrochemical potential window of 7.5 V, showcasing exceptional supercapacitive performance with an areal capacitance of 5.78 F cm⁻², positioning it as a high-performance micro-supercapacitor. The same device also exhibits synaptic plasticity behaviour, with potentiation and depression phases driven by ion migration, charge accumulation, and redox reactions, demonstrating tunable behaviour through modulation of the pulse width and pulse number. This unique electrochemical response, coupled with ionic double layer formation at the electrode/ionogel interface, underscores the potential of the device for both energy storage and neuromorphic computing applications.