Two-dimensional ion channel based soft-matter piezoelectricity

Abstract

Hierarchically integrated nanoscale ionic conductors, including ion channels and ion pumps on cell membrane, are the structural and functional basis of the electric organ in many strong bioelectrogenesis systems, such as the electric eel (Electrophorus electricus), which is capable of generating electrical potentials of up to 600 V to stun prey and self-defense [1]. Recently, scientists have built two-dimensional (2D) ion-channel-mimetic piezoelectric systems into graphene-based soft materials to control the mass and charge transportation in the nanosized interlayer spacing as effectively as those natural electrogenic cells [2][3][4]. Being different from existing one-dimensional (1D) nanochannels [5,6], the electrokinetic transport in 2D layered materials is confined only in the normal direction of the channel wall (Fig. 1). One immediate benefit of the layered configuration is the largely reduced fluidic resistance and promoted packing density, without sacrificing the surface-governed properties in the confined dimension [7,8].Moreover, fabrication of the state-of-the-art 1D nano- fluidic devices highly relies on expensive scientific equipments and sophisticated material processing steps [9], which makes the nanofluidic technology far from being economically viable. Towards practical applications, building nanofluidic systems into layered materials provides a straightforward way to control the channel structure by simply tuning the self-assembly process. In addition, compared with other layered nanocomposites, the 2D building blocks provide unparalleled high packing density of the asformed nanochannels [10]. This strategy shows an advance from fabrication of individual nano-sized devices to largescale and low-cost manufacture of 2D yet bulky materials, boosting its application in ultrafiltration, energy storage and conversion, catalysis, and sensing [11,12].The structural inspiration stems from the nacre, an inner layer of mollusc shells, showing excellent mechanical strength and toughness [13,14]. The structural biomaterial consists of alternatively arranged hard matter (aragonite platelets) as backbone, and soft matter (proteins and poly- Figure 1 Fluidic transport in layered graphene membrane is confined only in the normal direction of the channel wall, termed 2D nanofluidics. The nanoscaled channel width (h ~ 0.4-10 nm) and surface-charged properties endow the 2D nanochannels with selective transport of molecular targets, whose size (d) is smaller than h, and counter-ionic species. To date, the layered graphene membrane finds potential for both fundamental and practical research.

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

“…Atomically thin water film was considered as n-type dopant while trapped water droplet acted as p-type dopant [29]. In recent years, 2D nanofluidics consisting of stacked 2D materials have been reported for energy conversion, water treatment and ion transport manipulation [35][36][37][38][39][40]. In the 2D nanofluidics, the charge density and membrane structure asymmetry could be influenced by confined adsorbates between 2D materials, resulting in enhanced ionic current rectification.…”

Bioinspired Energy Conversion in Nanofluidics: A Paradigm of Material Evolution

“…This strategy enables unprecedentedly high modification efficiency, circumventing previous challenges whereby the chemical modification to nanofluidic channels had to be conducted in the already-formed nanoscale confined space. [7] …”

“…[6] Another research direction is the multiscale integration of individual nanofluidic devices into macroscopic materials for practical use. [7] Here, we present an overview of the structural and functional evolution in synthetic one-dimensional (1D) and two-dimensional (2D) nanofluidic systems under the guidance of three different types of biological inspiration: the asymmetric ion-transport behaviors of biological ion channels, the strong bioelectric function of electric eels, and the layered microstructure of nacre. The progress, challenges, and future perspectives in this growing field are highlighted.…”

Barrier Reduction of Lithium Ion Tunneling through Graphene with Hybrid Defects: First‐Principles Calculations

“…Owing to the large specific surface area, DOI: 10.1002/adts.201700009 graphene provides a large amount of adsorption points for Li ions leading to superior storage performance [9][10][11][12] and graphene extensively explored as promising electrode materials for Li-ion battery. [10,[18][19][20] Artificial defects with the desirable tunneling barrier may help to lower the diffusion barriers for some specific ions. The Li ions with a certain direction driving force cannot avoid penetrating the monolayer graphene walls stood in front of them in the bulk electrode materials.…”

“…As an important factor impacting the battery performance, Li ions migration process on the graphene film can be modulated by defects. [10,[18][19][20] Artificial defects with the desirable tunneling barrier may help to lower the diffusion barriers for some specific ions. Thus a good understanding of the influence between Li ions and graphene defects is indispensable to the application of graphene to Li-ion batteries.…”