Bioinspired Energy Conversion in Nanofluidics: A Paradigm of Material Evolution

Abstract

fly. Many of the well-developed structurefunction relationships in biological systems have become the inspiration for the design and application of innovative materials. [2,3] This bioinspired learning process accelerates the continuous evolution of novel man-made materials, circumventing many of the previously insurmountable challenges in, for example, architecture, aerodynamics, and materials science, etc. [4] More intriguingly, by adopting various design strategies from different natural inspirations, synthetic materials and devices keep on evolving and gaining more functions. Taking the development of aircraft for example, the wing curve of the prototype airplane mimics the streamlined shape of bird wings so as to reduce aerodynamic drag. The bat uses supersonic-based pathfinding to avoid obstacles when flying at night. Learning from this skill, modern aircraft use radar navigation systems as their "eyes". The adaptive surface coatings of aircraft mimic the micro-and nanostructures of shark skin, which greatly reduces frictional resistance, saving fuel and preventing damage from ultraviolet irradiation. As human beings constantly get new inspiration from nature, the evolution of bioinspired materials never stops.Research in nanofluidic energy conversion is enlightened by the electrogenic cells that convert transmembrane ion-concentration gradients into the release of electrical impulses by membrane-protein-regulated ion transport through the hierarchically arranged ion channels and ion pumps. [5] One particular example is electric eels (Electrophorus electricus), which are capable of generating electric shocks up to 600 V for predation and self-defense (Figure 1). Toward this goal, one research direction is to build synthetic nanofluidic devices with a minimum set of components, yet can mimic the biological energyconversion process on the nanoscale. [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.Well-developed structure-function relationships in living systems have become inspirations for the design and application of innovative materials. Building artificial nanofluidic systems for energy conversion undergoes three essential steps of structural and functional development with the uptake of separate biological inspirations. This research field started from the mimicking of the bioelectric function of electric eels, wherein a transmembrane ion concentration gradient is converted into ultrastrong electrical impulses via membrane-protein-regulated ion tran...

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