Multi-Stimuli Responsive Angstrom-Scale Two-Dimensional Channels of Natural Layered Materials

Biological ion channels are nature's wonders that regulate complex and multifunctional molecular mechanisms in living things. Emulating such multifunctionality in artificial systems remains a formidable challenge due to the limitations in achieving concurrent multi-stimuli responsiveness. Here, we report biomimetic and multi-responsive two-dimensional (2D) ion channels with Angstrom (Å)-scale channel heights, naturally formed within the interlayer galleries of vermiculite (VM) clay, which inherently possesses negatively charged surfaces. The VM ion channels exhibit electrohydrodynamic ion transport that can be modulated by mechanical (pressure), chemical (pH), and electrical (voltage) stimuli, thereby replicating key gating functions of the biological channels. Under coupled electric field and pressure gradients, the channels display stimulus-dependent polarity inversion of streaming current, governed by surface charge modulation and the redistribution of mobile ions within the confined spaces. To describe this coupled effect, we developed a modified surface charge regulation (mSCR) model that incorporates voltage-, pressure-, and concentration-dependent charge modulation. This study lays the foundation for clay minerals to be utilized as versatile platforms for realizing multi-stimuli responsive nanofluidic systems, opening new avenues for adaptive ionic gating, biosensing, energy conversion, and therapeutic nanofluidics.