Two-dimensional ion channel based soft-matter piezoelectricity

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 [2–4]. 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-