Mechanosensitive ion transport through hexagonal boron nitride nanopores

生物纳米孔是嵌入细胞膜的微小通道，以惊人的精度和速度将离子和小分子穿梭进出细胞，作为控制基本生命过程的高灵敏度筛子。受生物学启发，在薄固态膜中人造纳米孔有望彻底改变DNA传感和水淡化等应用。当膜材料只有一个原子厚时（所谓的2D材料），可以通过选择性地逐个去除原子来制造超精密的纳米孔。在2D材料氮化硼的情况下，其中原子在单层中以六边形图案排列，可以产生三角形纳米孔，这些纳米孔排列有氮原子并携带整体负电荷。形状和化学结构使其能够与孔内的离子和小分子进行独特而精确的相互作用。据预测，通过这些纳米孔的离子通道可以通过将2D材料拉伸到仅百分之几的应变水平来精确控制。该项目将探索在不同应变量下六方氮化硼中这些原子级精确纳米孔的独特传输特性，为与生物系统相媲美的先进可调过滤设备奠定基础。理论和计算机模拟将被用来模拟传输过程，并将进行实验，以调查预测的现象，使用一个专门设计的流体细胞。本科生和研究生将有机会从事纳米科学和工程的前沿研究。在加州中央谷地区，还将有针对性地与K-12 STEM夏季项目参与者进行外展。该项目将探索单层六方氮化硼（h-BN）中冠醚类纳米孔的机械敏感性运输。这些孔将通过在透射电子显微镜/离子显微镜室中进行位置选择性和剂量控制的电子束和离子束钻孔来制造。钻孔后，孔将被安装到定制的流体单元中，该流体单元能够使用流体静压力以及同时的电压偏置应用和电流测量来控制膜应变的应用。该设置将用于表征纳米孔基线电导、孔离子选择性和离子传输活化能，以及这些参数对所施加的膜应变的响应。这些测量还将表征作为施加的应变的函数的孔微分选择性，并将与分析估计和分子动力学模拟应力诱导的离子选择性在一个集成的制造-测量-模型循环。理论和模拟将解释纳米孔上的电荷分布以及离子与孔的极化相互作用。理论和模拟还将产生一个模型，用于预测二元混合物中的孔选择性，该模型将在实验中直接测试。该项目的主要贡献将集中在展示hB-N纳米孔中的机械敏感性传输，探索这些纳米孔中的应变调谐差分离子选择性和离子传输门控，并了解2D材料纳米孔中离子传输的应变敏感性的基本机制。总的来说，这项研究将采取初步的重要步骤，工程精确的界面系统与动态可重构的分离performance.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

Biological nanopores are tiny channels embedded in cell membranes that shuttle ions and small molecules in and out of cells with astonishing precision and speed, serving as highly sensitive sieves that control fundamental life processes. Human-made nanopores in thin solid-state membranes, inspired by biology, promise to revolutionize applications such as DNA sensing and water desalination. When the membrane material is just one atom thick (a so-called 2D material), ultra-precise nanopores can be made by selectively removing atoms one by one. In the case of the 2D material boron nitride, where atoms are arranged in a hexagonal pattern in the single layer, triangular nanopores can be created that are lined with nitrogen atoms and carry an overall negative charge. The shape and chemical structure enables unique and precise interactions with ions and small molecules inside the pore. It is also predicted that the passage of ions through these nanopores can be precisely controlled by stretching the 2D material to a strain level of just a few percent. This project will explore the unique transport properties of these atomically precise nanopores in hexagonal boron nitride under varying amounts of strain, laying the foundations for advanced tunable filtration devices rivaling biological systems. Theory and computer simulations will be used to model the transport processes, and experiments will be conducted to investigate the predicted phenomena using a specially designed fluid cell. Undergraduate and graduate students will be provided opportunities to engage in cutting-edge research in nanoscience and engineering. There will also be targeted outreach with K-12 STEM summer program participants in the California Central Valley region.This project will explore mechanosensitive transport in crown ether-like nanopores in monolayer hexagonal boron nitride (h-BN). These pores will be fabricated by site-selective and dose-controlled electron and ion beam drilling in a transmission electron microscope/ion microscope chamber. After drilling, the pores will be mounted into a custom-built fluid cell that enables the controlled application of membrane strain using hydrostatic pressure as well as simultaneous voltage bias application and current measurements. This setup will be used to characterize the nanopore baseline conductance, pore ion selectivity, and ion transport activation energies, as well as the response of these parameters to the applied membrane strain. These measurements will also characterize pore differential selectivity as a function of applied strain and will be coupled with analytical estimates and molecular dynamics simulations of stress-induced ion selectivity in an integrated make-measure-model cycle. Theory and simulations will account for the charge distribution on the nanopore as well as polarization interactions of the ions with the pore. Theory and simulations will also produce a model for predicting pore selectivity in binary mixtures, which will be directly tested in the experiment. The main contributions of the project will center on demonstrating mechanosensitive transport in hB-N nanopores, exploring strain-tuned differential ion selectivity and ion transport gating in these nanopores, and understanding the fundamental mechanisms of the strain sensitivity of ion transport in 2D material nanopores. Overall, this study will take the initial important steps toward engineering precise interfacial systems with dynamically reconfigurable separation performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.