Characterizing Surface Charge Density of Solid-State Nanopore Sensors for Improved Biosensing Applications

Solid-state nanopores have shown great potential as single-molecule sensors for various applications, such as DNA sequencing, biomarker detection, and protein identification. The performance of these nanopores can be affected by their surface charge density, which influence the capture and passage of biomolecules through nanopores. Controlled breakdown fabrication [1] has emerged as a reliable approach for creating solid-state nanopores with precise control over pore size, but further research is needed to optimize their design for specific applications. In this study, a pressure control system was designed and developed to characterize the surface charge density of the nanopore walls via streaming current measurements. A 3D printed flow cell housing a solid-state nanopore was used to independently pressurize each side of the membrane up to 0.3 MPa, and the surface charge density of SiN
x
membranes was measured based on the streaming current method. A surface charge density of
$-5.3\pm 0.4$
mC/m
²
was measured in a 0.1 M KCI pH 8 solution for the nanopores tested ranging in size from 10 nm to 11 nm. This study provides valuable insights for further optimizing the design of solid-state nanopores for specific applications.