The Kai Xiao research group proposed the "ion electron" Coulomb drag effect and applied it to ion energy collection

Recently, the research group led by Kai Xiao from the Department of Biomedical Engineering at Southern University of Science and Technology published an article titled "A nanofluidic chemoelectric generator with enhanced energy harvesting by ion electron Coulomb drag" in the academic journal Nature Communications. Biological systems typically rely on ions or molecules for information transmission, energy exchange, and storage, while current information technology relies on electronic transmission. Although the latter has fast response speed and high transmission efficiency, extreme working environments such as magnetic fields, high temperatures, and high humidity severely limit the usage environment of electronic devices; At the same time, integrated circuits are approaching the limits of Moore's Law based on the von Neumann computing architecture. In recent years, inspired by biological systems, ion electron coupling devices have shown excellent adaptability, mechanical flexibility, and bio like properties, making them a potential bridge for communication between advanced intelligent electronic devices and biological intelligence.

Ionic electron coupling typically occurs at the interface between liquids and solids. Generally, coupling processes can be divided into three basic types: electric double layer (EDL) capacitance processes; Electrochemical oxidation-reduction reaction process and pseudocapacitive process. Unlike the widely studied and applied ion electron coupling process mentioned above, this paper proposes the "ion electron" Coulomb drag effect, which can achieve direct interaction and conversion between ion current and electron current. The Coulomb drag effect refers to the formation of an electrical bilayer structure consisting of two conductive layers that are spatially close but insulated from each other. Applying a driving current to one layer induces an open circuit voltage in the other layer, resulting in interlayer drag effect. The "ion electron" Coulomb drag effect is based on the interaction between ion transport in nanofluids and electron transport in semiconductors, thereby achieving the coupling process of ions and electrons. Specifically, the ion movement behavior at the nanoscale can induce the movement of free electrons in semiconductors. Based on this mechanism, this work developed a nanofluidic chemical generator. As shown in Figure 1, the nanoionic fluid inside the carbon nanotube film is driven by spontaneous redox reactions between metal and oxygen. Due to the huge mass difference between ions and holes in nanoionic fluids (10⁵ to 10⁶), based on the law of conservation of momentum, a large number of free electrons are generated in the carbon nanotube film, thereby achieving an amplified current of 1.2 mA/cm². At the same time, a single nanofluid chemical generator unit can generate a voltage of~0.8 V and has linear scalability up to tens of volts.

Figure 1. NCEG schematic diagram and electrical output characteristics: (a) Schematic diagram of NCEG structure: A highly arranged porous CNTM is sandwiched between a pair of metal electrodes, which are gold foil and conductive carbon ribbon with aluminum substrate, respectively; (b) The morphology of CNTM and XPS characterization of substrate AAO film; (c) Schematic diagram of Coulomb drag effect of ions moving along CNTM and free electrons being dragged in CNTM; (d) The open circuit voltage and short circuit current density generated by NCEG in 0.1 M NaCl electrolyte.

As is well known, intelligent organisms rely on the potential signals (action potentials) generated by ion directed flow (controlled by protein channels on cells) for signal transmission and information exchange; Unlike intelligent organisms, solid-state electronic devices are based on electric potential driven electronic flow and signal transmission. How to construct an ion electron signal interaction system to achieve barrier free interaction between organisms and devices (brain machine) is the most fundamental scientific problem in the future vision of human-computer interaction. The ion electron coupling process based on Coulomb drag effect reported in this work can achieve direct interaction between ion current and electron current, which is expected to build a new high-speed channel for electronic and biological information exchange.

Southern University of Science and Technology is the first unit for this thesis, with Jiang Yisha, a master's student jointly trained by Wenzhou University, as the first author of the thesis, Liu Wenchao, a doctoral student from the Department of Biomedical Engineering of Southern University of Science and Technology in 2022, as the co first author of the thesis, and Dr. Wang Tao from Southern University of Science and Technology, Professor Wang Yude from Yunnan University, Professor Liu Nannan from Wenzhou University, and Associate Professor Xiao Kai from Southern University of Science and Technology as the corresponding authors of the thesis. This work has received support from the National Key R&D Program, the National Natural Science Foundation, the Guangdong Provincial Key Laboratory Project, and the Shenzhen Science and Technology Innovation Committee.

Link: https://www.nature.com/articles/s41467-024-52892-4.

Professor Kai Xiao's research group (Neuro-inspired Materials and Devices Lab) is recruiting postdoctoral fellows, research assistants, and exchange students on a long-term basis. The research group mainly focuses on interdisciplinary research in chemistry, materials, electronics, biology, and other fields related to "neurobiomimetic materials, brain like computing devices, and neural regulation technology". Since its establishment in 2021, the group has independently trained students at Nat, with Southern University of Science and Technology as the first unit Commun., Sci. Adv., Angew. Chem., More than 20 articles have been published in the journal, and several members of the research team have been approved for National Natural Science Foundation projects (2), Youth Fund projects (3), and Postdoctoral Overseas Talent Introduction Special Fund.