Asymmetric Nanopores for Fundamental Studies of Hindered Transport

本研究的目的是开发一种用于大面积制造不对称纳米孔的简单方法，这反过来将用于阻碍传输的基础研究。该研究将采用脉冲等离子体增强化学气相沉积（PECVD）的一种新变体来数字操作模型支架的开口。脉冲PECVD已被设计为原子层沉积（ALD）的替代方案，用于薄膜的自我限制生长（即1 Å/脉冲）。通过控制操作条件，可以设计出符合度，在不牺牲底层支撑的高孔隙度/渗透率的情况下，实现对孔隙闭合的数字控制。由此产生的纳米孔的良好定义的几何结构将作为模型系统的基础研究受阻的运输。表征良好的蛋白质和无机量子点将作为模型溶质进行探索。表面效应通常在所讨论的长度尺度上占主导地位。这个问题将通过使用已建立的自组装技术来系统地操纵孔隙和纳米颗粒的表面终止来研究。使用阳极氧化铝支架的初步工作证明了基本原理。然而，这些研究也表明，这些商业支架的孔径分布不足以在纳米尺度上进行控制。通过与ORNL纳米材料科学中心的合作，采用电子束光刻技术制造的均匀硅支撑将弥补这一限制。这个提议的学术价值在于纳米孔的制造、薄膜的沉积和纳米尺度的传输现象。现有的纳米孔合成方法采用高能束技术，不适合大规模制造。PI的方法采用标准集成电路（IC）制造技术，并在环境温度下进行。将开发特征尺度模型来模拟脉冲PECVD的孔隙闭合，并使用截面显微镜进行验证。由此产生的纳米孔将具有明确的圆柱形几何形状，为阻碍运输的理论模型的严格评估创造了理想的平台。渗透和溶质排斥的实验测量将用于测试和提高对纳米尺度传输的理解。大面积合成定义良好的纳米孔将是生物成分和纳米颗粒分离的有利创新。此外，由此产生的通道将作为纳米流体实验研究的理想平台。纳米流体与带电物质（如离子和DNA）的电操纵的耦合为传统集成电路技术提供了一种潜在的替代方案。硅片作为支撑结构的使用将促进纳米孔阵列与传统电子和微流体元件的集成，用于芯片上的实验室应用。更广泛的影响还包括博士候选人的培训和在重要技术领域的本科生研究人员的参与。PI和他的学生将继续与CSM K-12外展小组合作，为有大量代表性不足的学生的学区开发与膜和水净化有关的教师讲习班材料。

1033203Wolden The objective of this research is to develop a simple approach for large area fabrication of asymmetric nanopores, which in turn will be employed for fundamental studies of hindered transport. The research will employ a new variant of pulsed plasma-enhanced chemical vapor deposition (PECVD) to digitally manipulate the openings of model supports. Pulsed PECVD has been engineered as an alternative to atomic layer deposition (ALD) for self-limiting growth of thin films (i.e. 1 Å/pulse). Through control of operating conditions the degree of conformality may be engineered, enabling digital control over pore closure without sacrificing the high porosity/permeability of the underlying supports. The well-defined geometry of the resulting nanopores will serve as model systems for fundamental studies of hindered transport. Well-characterized proteins and inorganic quantum dots will be explored as model solutes. Surface effects often dominate at the length scales in question. This issue will be investigated by using established self-assembly techniques to systematically manipulate the surface termination of both pores and nanoparticles. The basic precepts have been demonstrated in preliminary work using anodized alumina supports. However, these studies also revealed that the pore size distribution in these commercial supports was inadequate for control at the nanoscale. This limitation will be remedied by employing uniform silicon supports fabricated using e-beam lithography through a collaboration with the Center for Nanophase Materials Sciences at ORNL. Intellectual Merit The intellectual merit of this proposal is in nanopore fabrication, thin film deposition, and nanoscale transport phenomena. Existing approaches for nanopore synthesis employ energetic beam technologies that are not amenable to large scale fabrication. The PI's approach employs standard integrated circuit (IC) fabrication techniques and is performed at ambient temperature. Feature scale models will be developed to simulate pore closure by pulsed PECVD, and validated using cross section microscopy. The resulting nanopores will have well-defined cylindrical geometries, creating an ideal platform for rigorous evaluation of theoretical models of hindered transport. Experimental measurements of permeance and solute rejection will be used to test and improve understanding of transport at the nanoscale. Broader Impacts Large area synthesis of well-defined nanopores would be an enabling innovation for the separation of both biological constituents and nanoparticles. Moreover, the resulting channels will serve as an ideal platform for experimental investigations of nanofluidics. The coupling of nanofluidics with electrical manipulation of charged species such as ions and DNA offers a potential alternative to conventional IC technology. The use of silicon wafers as the support structure will facilitate the integration of nanopore arrays with conventional electronic and microfluidic components for Lab-on-a-Chip applications. The broader impacts also include the training of a PhD candidate and the engagement of undergraduate researchers in areas of great technological importance. The PI and his students will continue their work with the CSM K-12 outreach team, developing teacher workshop materials related to membranes and water purification for school districts with large populations of underrepresented students.