Abstract
Nanopores have become an important tool for molecule detection at single molecular level. With the development of fabrication technology, synthesized solid-state membranes are promising candidate substrates in respect of their exceptional robustness and controllable size and shape. Here, a 30–60 (tip-base) nm conical nanopore fabricated in 100 nm thick silicon nitride (Si3N4) membrane by focused ion beam (FIB) has been employed for the analysis of λ-DNA translocations at different voltage biases from 200 to 450 mV. The distributions of translocation time and current blockage, as well as the events frequencies as a function of voltage are investigated. Similar to previously published work, the presence and configurations of λ-DNA molecules are characterized, also, we find that greater applied voltages markedly increase the events rate, and stretch the coiled λ-DNA molecules into linear form. However, compared to 6–30 nm ultrathin solid-state nanopores, a threshold voltage of 181 mV is found to be necessary to drive DNA molecules through the nanopore due to conical shape and length of the pore. The speed is slowed down ∼5 times, while the capture radius is ∼2 fold larger. The results show that the large nanopore in thick membrane with an improved stability and throughput also has the ability to detect the molecules at a single molecular level, as well as slows down the velocity of molecules passing through the pore. This work will provide more motivations for the development of nanopores as a Multi-functional sensor for a wide range of biopolymers and nano materials.
Highlights
We show our results about the translocation of l-DNA through a conical nanopore with opening diameters of 30 and 60 nm, fabricated in a 100 nm-thick free-standing Si3N4 membrane by focused ion beam (FIB), which is much larger and longer than the nanopores of sub 5 nm in 6–30 nm ultrathin membranes reported by far. [7,16,17,32] it is more stable and not easy to be blocked. l-DNA molecules were driven through the pore by a set of voltage biases, among which a critical voltage of 181 mV was observed to drive DNA molecules through the pore
Our results show the unique properties of the nanopore with large size in thick membrane and geometrical aspect ratio can provide more information on translocation behaviors of DNA molecules in a new perspective, which can serve as a long lifetime, high throughput, single-molecular biosensor, without the impact of the pore size
The experimental results presented here demonstrate that how a voltage biased solid state nanopore can serve as a high throughput single molecule sensing device, by electrophoretically driven negatively charged l-DNA through a nanopore at a sets of voltage bias (200–450 mV), Our results show that the nanopore fabricated in silicon nitride membrane by FIB with unique
Summary
Over the last several decades, nanopores have been developed into powerful and indispensable devices for the investigation of unlabeled biopolymers at single-molecular level since it was firstly reported by Kasianowicz and co-workers in 1996. [1,2,3] It opens a new possible way to read out the sequence of DNA without amplification and labeling. [4,5] By controlling the velocity, [6] reducing the thickness [7,8,9] and extending the signal bandwidths, [10] both natural and solid-state nanopores have been primarily directed toward low-cost and high-throughput DNA sequencing applications. [11,12,13,14] with the advantages of controllable pore size and shape,[15,16,17] long-term stability and easy integration into detection devices, [17,18] many valuable translocation results about different samples passing through various solid-state nanopores of suitable size have been reported, which shows that the solidstate nanopores can serve as a Multi-functional sensor for detection and characterization of proteins,[19,20,21] DNA/protein [22,23] or DNA/ligand complexes,[24,25,26] nano-materials/nanoparticles. [27,28,29].As a high throughput and label-free sensing tool, nanopores in the range of sub-5 nm and sub-10 nm can unfold and thread DNA molecules into linear fashion,[30,31,32] and offer optimal resolution for the spatial information of DNA molecules at nanometer scale. [11,12,13,14] with the advantages of controllable pore size and shape,[15,16,17] long-term stability and easy integration into detection devices, [17,18] many valuable translocation results about different samples passing through various solid-state nanopores of suitable size have been reported, which shows that the solidstate nanopores can serve as a Multi-functional sensor for detection and characterization of proteins,[19,20,21] DNA/protein [22,23] or DNA/ligand complexes,[24,25,26] nano-materials/nanoparticles. With the advantages of weak DNA–pore interaction and longtime stability, larger nanopores in size of tens to hundreds nanometers are considered for the current DNA analysis with specific characteristics and sensing abilities,[36,37,38] which can ensure free passage of the molecules, suppress the conformational changes of long DNA inside pores and effectively provide a high resolution. The signal-to-noise ratio of the blockade current will conspicuously deteriorate if the pore is too large compared to the size of molecules. [37,38] the choice of nanopores with suitable dimensions is critical for the design of nanopore devices and understanding the physical mechanism of molecules translocating through nanopores
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