Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
J Chem Phys. 2021 Mar 14;154(10):105102. doi: 10.1063/5.0044227.
We report ionic current and double-stranded DNA (dsDNA) translocation measurements through solid-state membranes with two TEM-drilled ∼3-nm diameter silicon nitride nanopores in parallel. Nanopores are fabricated with similar diameters but varying in effective thicknesses (from 2.6 to 10 nm) ranging from a thickness ratio of 1:1 to 1:3.75, producing distinct conductance levels. This was made possible by locally thinning the silicon nitride membrane to shape the desired topography with nanoscale precision using electron beam lithography (EBL). Two nanopores are engineered and subsequently drilled in either the EBL-thinned or the surrounding membrane region. By designing the interpore separation a few orders of magnitude larger than the pore diameter (e.g., ∼900 vs 3 nm), we show analytically, numerically, and experimentally that the total conductance of the two pores is the sum of the individual pore conductances. For a two-pore device with similar diameters yet thicknesses in the ratio of 1:3, a ratio of ∼1:2.2 in open-pore conductances and translocation current signals is expected, as if they were measured independently. Introducing dsDNA as analytes to both pores simultaneously, we detect more than 12 000 events within 2 min and trace them back with a high likelihood to which pore the dsDNA translocated through. Moreover, we monitor translocations through one active pore only when the other pore is clogged. This work demonstrates how two-pore devices can fundamentally open up a parallel translocation reading system for solid-state nanopores. This approach could be creatively generalized to more pores with desired parameters given a sufficient signal-to-noise ratio.
我们报告了通过具有两个 TEM 钻制的约 3nm 直径氮化硅纳米孔的固态膜进行离子电流和双链 DNA（dsDNA）转导测量。纳米孔具有相似的直径，但有效厚度不同（从 2.6nm 到 10nm，厚度比为 1:1 到 1:3.75），产生不同的电导水平。这是通过使用电子束光刻（EBL）以纳米级精度局部减薄氮化硅膜来实现的，从而形成所需的形貌。两个纳米孔在 EBL 减薄或周围膜区域中进行设计和随后钻孔。通过将孔间分离设计为比孔径大几个数量级（例如，约 900 与 3nm），我们从理论、数值和实验上证明，两个孔的总电导是各个孔电导的总和。对于具有相似直径但厚度比为 1:3 的两孔器件，预计开放孔电导和转导电流信号的比值约为 1:2.2，就像它们独立测量一样。同时将 dsDNA 作为分析物引入两个孔中，我们在 2 分钟内检测到超过 12000 个事件，并通过高概率将其追溯到 dsDNA 穿过的孔。此外，当另一个孔堵塞时，我们仅监测一个活性孔中的转导。这项工作表明，两孔器件如何从根本上为固态纳米孔开辟并行转导读取系统。如果具有足够的信噪比，可以创造性地将此方法推广到具有所需参数的更多孔。
