Evaluating the Use of Edge Detection in Extracting Feature Size from Scanning Electrochemical Microscopy Images

Abstract

The edge of a reactive or topographical feature is hard to estimate from feedback-based scanning electrochemical microscopy due to diffusional blurring, but is crucial to determining the accurate size and shape of these features. In this work, numerical simulations are used to demonstrate that the inflection point in a 1D line scan corresponds well to the true feature edge. This approach is then applied in 2D using the Canny algorithm to experimental images of two model substrates and a biological sample. This approach circumvents the need for aligning the imaged region between separate microscopy techniques, reveals hidden details embedded in SECM images, and allows individual features to be separated from their background more effectively.

Super-resolution Scanning Electrochemical Microscopy

“…To balance the concept of a “point” conductor with the limitations in the precision of a numerical model, a point conductor with 1/3 the radius of the electrode (1/9 the area) was used. A steady-state solution to Fick’s laws was calculated for various positions of the microelectrode relative to the surface, analogous to the sampling scheme of an experimental scan pattern. , The input model geometry (Point/True) was taken as the true image and the simulated SECM image, as the blurred counterpart. Blind deconvolution was then performed to estimate the PSF for a particular probe–sample distance.…”

“…A 3D finite element model based on our previous work , was built using COMSOL Multiphysics 5.3a to simulate SECM images over point conductors and reactive surface features with complex geometry. A full description of the model geometry and physics is available in the Supporting Information.…”

“…■ METHODS Experimental Section. Optically transparent, topographically smooth (≈45 nm height variation) patterned Au/SiO 2 substrates were fabricated as described previously 44 and used as model experimental substrates. These substrates consisted of photolithographically patterned SiO 2 deposited on a thin layer of Au.…”

Identifying Nanoscale Pinhole Defects in Nitroaryl Layers with Scanning Electrochemical Cell Microscopy

“…As SECM is performed with disk microelectrodes, any small tilt in the surface or electrode, combined with the glass sheath can prevent a probe from approaching a smooth surface, let alone a surface with micron‐scale roughness . In part due to the strong dependence of lateral resolution on tip‐substrate distance and the subsequent diffusional broadening at the SECM tip and in part due the indirect nature of the measurement and the limited mediator regeneration efficiency, sensitivity can be low and there can be a significant uncertainty in the defect size extracted from SECM data especially when the feature is smaller than the probe diameter …”

“…[14][15][16] In part due to the strong dependence of lateral resolution on tip-substrate distance and the subsequent diffusional broadening at the SECM tip and in part due the indirect nature of the measurement and the limited mediator regeneration efficiency, sensitivity can be low and there can be a significant uncertainty in the defect size extracted from SECM data especially when the feature is smaller than the probe diameter. [17,18] Scanning electrochemical cell microscopy (SECCM) is a more recent electrochemical scanning probe method and involves lowering an electrolyte-filled nanopipette onto a substrate of interest to create a nanoscale electrochemical cell. [19,20] By tracking the nanopipette probe across the surface, the local electrochemical activity and topography can be probed simultaneously.…”