Ion Current Measurements Using SICM
In the words of the research group:
Our studies are mainly focused on scanning probe microscopy, where a nanopipette filled with electrolyte is used to either map the local ion current of a given sample or obtain a current-voltage characteristic over a given surface. Shown in Figure 1 (Left) is our experimental setup for the imaging technique, known as SICM (Scanning Ion Conductance Microscopy), which was specially designed for sub-micrometer resolution imaging of soft and non-conductive materials bathed in electrolyte.
Figure 1: Experimental Setup
During the imaging process we found that our image resolution was limited by background noise. The noise sources include ambient vibration from the floor or pumps, as well as other machinery. Figure 1 (Right) shows the custom instrumentation set-up for characterizing current-voltage response by bringing a nanopipette close to a substrate. Studies based on this setup showed that vibration isolation was required since characterized current-voltage curves obtained when in close proximity to a surface indicate that vibration from a nanopipette probe is not negligible.
We asked Herzan for help with a solution to make our instrument perform better, considering all the above measurements we did are recorded in a mechanically noisy environment. Environmental noise has been significantly curtailed with incorporation of a Herzan active vibration isolation system.
Ion Current Measurement, Utilizing Nanopipettes
Scanning Ion Conductance Microscopy (SICM) and custom instrumentation setup for characterizing current-voltage response by bringing a nanometer scale pipette in close proximity to a surface.
Baker Group, Chemistry Department, Indiana University, Bloomington.
There are three instrumentation setups in the Baker Group that use the AVI-200 active vibration isolation system.
Figure 2 displays an SICM image of a nanopore membrane with improved resolution after stabilization with the AVI-200 vibration isolation system. The first photo in Figure 2(a) shows higher background noise as compared with Figure 2(b).
Figure 2. (a) Image obtained from SICM without AVI-200.
(b) Image obtained with AVI-200 isolation system installed.
A comparison of improved current-voltage curves after addition of the AVI-200 to the experimental setup appears in Figure 3.
Figure 3. (a) Current-voltage curve taken without AVI-200
(b) Current-voltage curve taken with AVI-200 isolation system
All photographs are courtesy of the Lane Baker group, Indiana University, Bloomington, IN, USA
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