Green Fabrication of Ionic Liquid‑Enhanced Geopolymer Synapses via Solvent‑Free Curing

Abstract

We report a sustainable, solvent-free route to fabricate ionic liquid–enhanced geopolymer synapses for low-power neuromorphic applications. Metakaolin-based geopolymer precursors were dry-mixed with 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM·BF₄) at 10 wt % and cured at ambient conditions without added solvents or high-temperature firing. SEM and EDX mapping confirm homogeneous IL confinement within the geopolymer’s interconnected pore network. Thermal analysis reveals stable IL retention up to 120 °C, while FTIR spectra verify chemical integrity post-curing. Au/geopolymer–IL/Au crossbar devices exhibit forming-free bipolar resistive switching with set/reset voltages of +0.50 V/–0.45 V and on/off ratios exceeding 10². Key synaptic behaviors—paired-pulse facilitation/depression and spike-timing-dependent plasticity—are emulated with energy consumption below 8 pJ per event. Devices maintain >10³ switching cycles and >10⁴ s retention without performance loss. Life-cycle assessment indicates a >60 % reduction in processing energy and solvent emissions compared to conventional solvent-based composites. This green fabrication strategy paves the way for scalable, eco-friendly neuromorphic hardware based on geopolymer–ionic liquid composites.