Efficient Proton Rectification in Quasi-Solid-State Nanofluidic Diode Membrane for Ionic Signal Processing and Computing

Constructing ion channels to mimic the diode characteristics of protein channels in living organisms is crucial for realizing ionic signal transmission and brain-like computing with logical capabilities. Nonetheless, it is challenging to achieve unidirectional transport of protons due to their high mobility and small volume for the dimensions of most nanochannels (>0.5 nm). Herein, drawing inspiration from the architecture of human skin, composed of dry epidermis and wet dermis that features an inherent electrochemical ion gradient and asymmetric transport routes, we present a quasi-solid-state heterogeneous ionic diode membrane by integrating two layers of poly(vinyl alcohol)-based hydrogels, which synergize the intrinsic electrochemical gradient with asymmetric structure and functional groups. Such membranes exhibit a remarkable proton rectification ratio of 47, which can be further amplified to 65 in response to external pressure, representing the state-of-the-art. Experimental and theoretical results reveal that the difference in proton migration energy barriers at the heterogeneous membrane interface is the key reason for the unidirectional proton transport behavior. With this membrane, we have successfully simulated the signal transmission and computation between neuronal synapses by constructing voltage-adaptive ionic transistor devices. This work demonstrates a general route for designing a high-rectifying proton diode, enabling advanced functionalities in biosensing and neuromorphic computing.