High-Frequency Artificial Nerve Using Homogeneously Integrated Organic Electrochemical Transistors

Artificial nerves (ANs) are crucial components for nerve repair and brain-machine interfaces, requiring biomimetic capabilities of sensing, processing, and memory at bio-realistic frequencies. A promising building block for ANs, which avoids issues related to heterogeneous integration, is the n-type organic electrochemical transistor (OECT). These devices mimic biological cells due to their positive-potential-triggered potentiation behaviors. However, they are often limited by weak ionic/electronic transport and storage properties, leading to inadequate volatile and non-volatile performance, particularly slow response times. Traditional approaches to enhancing ionic conductivity—such as integrating ion conductors into the channel—often disrupt the continuity of ion/electronic transport pathways, creating a trade-off between ionic and electronic transport. Meanwhile, conventional strategies that focus solely on accelerating ion transport dynamics often overlook the importance of channel morphology, which can disturb molecular stacking and reduce the ion trapping barrier, ultimately resulting in the ion transport-storage trade-off.

Here, we present the development of a vertically stacked, sequentially deposited n-type organic electrochemical transistor (sv-OECT), which significantly improves both volatile and non-volatile performance. The sv-OECT is reconfigurable and achieves record-high response speeds in both volatile and non-volatile modes, making it ideally suited for emulating receptors, somas, and synapses in high-frequency AN circuits, including spiking and non-spiking neurons. Unlike previously reported state-of-the-art OECTs, sv-OECTs are fabricated by sequentially depositing an n-type hydrophilic dopant on top of the semiconducting polymer, creating a gradient-intermixed bicontinuous structure (GIBS) in the vertical channel. This GIBS structure synergistically enhances both ionic and electronic transport, allowing for fast conductance modulation while maintaining long-term ion storage capabilities essential for conductance memory. Importantly, this effect is demonstrated to be universal across a range of semiconducting polymers. By leveraging high-performance sv-OECTs, we demonstrate the design of customized AN circuits and, ultimately, construct a flexible, chemically modulated artificial nerve (CMAN) with integrated sensing, processing, and memory functions operating at bio-realistic frequencies. The behavior of CMAN can be modulated by both external stimuli and internal chemical mediators. Moreover, the integration of CMAN into animal models with impaired neural functions has shown excellent biocompatibility and sophisticated functionalities, demonstrating its potential for advanced bioelectronic applications.

Reference:
[1] S. Wang, B. Wang*, C. Zhao*, W. Ma*, et al. Nat. Electron. (accepted)