The human brain-inspired light-stimulated gelatin-biopolymer gated synaptic transistor for realizing cognitive activities

Abstract

In recent times, there has been a growing interest in the development of light-stimulated artificial synapses for applications related to artificial intelligence. Low operating voltage, low energy consumption, less noise, high transmission rate, and high operating speed make artificial synaptic organic field-effect transistors (OFET) suitable candidates for future artificial complex neural network development. In this work, we demonstrate human cognitive activities through the utilization of water-soluble gelatin biopolymer gated poly(2,5-bis(3-alkylthiophen-2-yl)) thieno [3,2-b] thiophene [PBTTT-C14] synaptic OFETs. The devices exhibit basic neurobiological phenomena including excitatory post-synaptic current (EPSC), pair-pulse facilitation (PPF), short-term plasticity (STP), long-term plasticity (LTP), STP to LTP conversion, and learning-forgetting-memorizing (LFM) nature similar to the human brain. The photo-response parameters such as photoresponsivity, detectivity, and the photo and dark current ratio are estimated for the better realization of the photo synapses. The OFETs exhibit commendable photoresponsivity of 11.10 mA W⁻¹, high detectivity of 8.55 × 10⁸ Jones, and the photo to dark current ratio of 654. Moreover, these photo synaptic OFETs imitate the human emotion-tuneable and the mood-swing-influencing (MSI) memory and learning behavior. Further, We also demonstrate the implementation of the ‘OR’ logic gate under the stimulation of two different wavelengths by utilizing these OFETs. Additionally, we replicate Pavlov's dog experiment to explain the associative learning nature of the OFETs. The OFETs exhibit a fairly low energy consumption of ∼89 nJ per optical event to perform basic neurobiological activities which facilitates the development of complex artificial neural networks with minimal energy consumption.