Assessment of 1/f noise associated with nanopores fabricated through chemically tuned controlled dielectric breakdown

Recently, we developed a fabrication method—chemically-tuned controlled dielectric breakdown (CT-CDB)—that produces nanopores (through thin silicon nitride membranes) surpassing legacy drawbacks associated with solid-state nanopores (SSNs). However, the noise characteristics of CT-CDB nanopores are largely unexplored. In this work, we investigated the 1/f noise of CT-CDB nanopores of varying solution pH, electrolyte type, electrolyte concentration, applied voltage, and pore diameter. Our findings indicate that the bulk Hooge parameter (α_b) is about an order of magnitude greater than SSNs fabricated by transmission electron microscopy (TEM) while the surface Hooge parameter (α_s) is ∼3 order magnitude greater. Theα_s of CT-CDB nanopores was ∼5 orders of magnitude greater than theirα_b, which suggests that the surface contribution plays a dominant role in 1/f noise. Experiments with DNA exhibited increasing capture rates with pH up to pH ∼8 followed by a drop at pH ∼9 perhaps due to the onset of electroosmotic force acting against the electrophoretic force. The1/f noise was also measured for several electrolytes and LiCl was found to outperform NaCl, KCl, RbCl, and CsCl. The 1/f noise was found to increase with the increasing electrolyte concentration and pore diameter. Taken together, the findings of this work suggest the pH approximate 7–8 range to be optimal for DNA sensing with CT-CDB nanopores.     

Stiffness measurement of nanosized liposomes using solid‐state nanopore sensor with automated recapturing platform

This paper describes a method to gauge the stiffness of nanosized liposomes – a nanoscale vesicle – using a custom‐made recapture platform coupled to a solid‐state nanopore sensor. The recapture platform electrically profiles a given liposome vesicle multiple times through automated reversal of the voltage polarity immediately following a translocation instance to re‐translocate the same analyte through the nanopore – provides better statistical insight at the molecular level by analyzing the same particle multiple times compared to conventional nanopore platforms. The capture frequency depends on the applied voltage with lower voltages (i.e., 100 mV) permitting higher recapture instances than at higher voltages (>200 mV) since the probability of particles exiting the nanopore capture radius increases with voltage. The shape deformation was inferred by comparing the normalized relative current blockade ( at the two voltage polarities to that of a rigid particle, i.e., polystyrene beads. We found that liposomes deform to adopt a prolate shape at higher voltages. This platform can be further applied to investigate the stiffness of other types of soft matters, e.g., virus, exosomes, endosomes, and accelerate the potential studies in pharmaceutics for increasing the drug packing and unpacking mechanism by controlling the stiffness of the drug vesicles.