场效应栅控纳米孔器件的动电输运机理研究

Electrically modulated nanopore devices offer the capabilities of controlling the transport of biomolecules and ions, thus enabling potential applications in bio-chips, genome sequencing, environmental monitoring and water processing. However, complicated electrokinetic transport phenomena of unclear underlying mechanisms usually show up in such devices, resulting in unstable ionic current and seriously obstructing further practical applications of the devices. This project will focus on a new field-effect gated nanopore device recently developed by Stanford, and will study its instability mechanism using both simulation and experiment.In the numerical part, transient simulation method will be developed to couple Poisson-Nerst-Plnack and Navier-Stokes equations. Experimentally, the ALD gate oxide will be optimized，gated nanopore devices fabricated, and the electrical measurement system set up. Based on these works, we will then study the dynamic current-voltage characteristics and low-frequency noise under different biases, pH, ionic strength, ionic species and solvent viscosity conditions. The occurrence of instability and its intrinsic relation with the nonlinear electrokinetic transport of ions and fluids will be explored; its underlying mechanism will be elucidated, giving theoretical support and guide for improving the stability of gated nanopore devices, as well as offering new insight into understanding the instability of nanopore structures in general.

电子调控的纳米孔器件能有效控制生物分子和离子输运，在生物芯片、基因测序、环境监测和水处理方面有重要应用前景。但这类器件常呈现机理不明的、复杂的动电输运现象，导致离子电流不稳定，严重阻碍进一步实用化。本项目将以斯坦福大学最新研制的一种场效应栅控纳米孔器件为研究对象，结合理论仿真与实验测量研究其不稳定性机理。数值方法上将发展耦合Poisson-Nernst-Planck和Navier-Stokes方程的暂态仿真方法。实验上将优化ALD栅极氧化物工艺，制备栅控纳米孔器件，并搭建电测试系统。在此基础上，我们将深入研究不同偏压、pH、离子强度、离子种类、溶液粘度下器件动态电流-电压和低频噪音特性，探究不稳定性出现规律及其与离子流体非线性动电输运过程的内在关联，阐释其产生机理，为进一步提高栅控纳米孔器件的稳定性提供理论支持和指引，也在更大范围内为理解纳米孔结构的动电输运过程提供新思路

纳米孔与纳流道器件在基因测序、DNA/RNA/蛋白质分子检测等生物医疗领域有着重要的应用前景。更清楚地理解器件中离子与流体的耦合输运过程和相应的电学特性，以及更进一步地实现具有更多功能结构的纳米孔与纳流道器件是重要发展方向。在本项目中，我们发展了定态以及暂态建模的方法来对纳米孔与纳流道进行器件层面的数值仿真，并对其数值求解进行了验证。在此基础上，我们深入研究了沟道内离子与流体耦合输运导致的不同电压区间内呈现的层流与涡流现象，并揭示了其分别对应于电导的抑制与恢复。我们也首次揭示了一种输运造成的沟道内离子屏蔽电荷的反转效应，并解释了沟道入口处涡流的产生机理。我们研究了纳流道和纳米孔的瞬态电学响应特性。通过对于具有不同电学参数和几何参数的纳流体器件分析，我们用双极输运解释了暂态过程，并推导了响应时间的数学表达式。在实验方面，我们建立了一套成熟的纳米孔测试平台和封装测试流程，首次开发了以ITO作为栅电极的栅控纳米孔器件工艺，并实现了孔径小于10纳米的栅控纳米孔器件。在栅控纳米孔中我们观测到实时的DNA分子过孔信号，并揭示了栅电压通过场效应对过孔DNA折叠形态的调制作用。另外我们也在这个纳米孔实验平台上制备了二硫化钼纳米孔，并测试到蛋白质过孔信号。