Ionic sensing using natural indigo molecules and its impact on inhibitory and excitatory postsynaptic currents in an artificial synaptic device

Neuromorphic devices designed to emulate brain function are expected to be highly efficient and require high-performance capabilities for diverse applications. This emulation begins at the fundamental level of synaptic transmission, where ionic interactions are crucial for signal excitation and inhibition. This study explores the role of sodium and chloride ions in enhancing synaptic functions within an indigo-based two terminal artificial synaptic device. Our findings reveal that the device demonstrates enhanced memory functions and mimics excitatory and inhibitory brain actions. Indigo based synaptic devices have very good sensitivity toward Na+ and Cl− ions with significant modifications to memristor characteristics with addition of ions. We establish that the detection limit of the fabricated device for NaCl is (0.05 ± 0.015) mM < x < (0.5 ± 0.015) mM. Notably, the presence of 0.1 mM NaCl ions resulted in a sixfold increase in the on–off ratio at 1.3 V, along with a 12-fold enhancement in both excitatory and inhibitory postsynaptic currents (EPSC and IPSC). These results effectively replicate the physiological functions of Na+ in EPSC and Cl− in IPSC, demonstrating the successful modulation of synaptic functions through optimized addition of NaCl. Significant improvements in memristor characteristics and synaptic responses highlight the potential for the development of advanced neuromorphic technologies that mimic brain-like behavior, paving the way for more efficient and scalable applications in artificial intelligence and cognitive computing based on molecular materials.