Alternating Current Potentiometric Scanning Ion Conductance Microscopy (Ac-Psicm)

Studies of ion transport at small length scales inform the fundamental understanding of various biophysical processes. Here, we describe a new method, alternating current potentiometric scanning ion conductance microscopy (AC-PSICM), which measures on transport through nanopores as a function of AC perturbations over a range of frequencies (5 Hz to 50 kHz). Phase and amplitude of local potential in the vicinity of nanopores in polymer membranes were Captured with a nanopipet. Phase was found to be sensitive to local conductive pathways (nanopores in this case) and can-be used to quantify single nanopore resistance. Investigation Of phase approach curves and lateral phase distributions with single nanopore samples predicted four distinct frequency ranges, for resolving heterogeneous, conductive pathways within a sample, which were confirmed with line profile measurements of the phase response in samples With different sized nanopores. AC-PSICM is suitable for ion transport studies at the nanometer scale and can be used to access wide ranges of time scales. mapping shows promise for visualization of heterogeneous transport pathways and could be used in future studies to examine conductance at cell and tissue interfaces.