Scanning ion-conductance microscopy

Instrumentation. A setup has been reviewed [172]. A modified setup using a vibrating micropipette and an AC electronic circuitry that allows better (more precise) position control of the tip and its aperture has been described [174]. Applications reported so far deal with living cells [175, 176] and the internal and external pore structure of membranes [177]. 

Fundamentals. Localized very small variations of the electrode potential that are caused by current flow across the metal/solution interface over the surface of an electrochemically active material (e.g. a corroding metal) can be measured with a scanning reference electrode [178]. The local variations are picked up by a pair of very fine tips about 10 pm above the surface. The response of a twin platinum electrode has been modelled and results could be matched satisfactorily with real 

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Other local probe techniques to be discussed, of an electrochemical nature, which rely on much of the same instrumental technology, are scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM). 

Scanning micropipette microscopy (SMM) Scanning micropipette molecule microscopy (SMMM) Scanning ion conductance microscopy (SICM)... 

SECM associated with scanning ion conductance microscopy (SICM) requires a double tip, on one side of which is a conventional microdisc electrode and on the other side is a narrow pipette filled with electrolyte and an electrode that measures ionic conductance through the mouth of the pipette with respect to another electrode in the bulk solution. When the pipette mouth is within one pipette tip radius away from the sample surface, the conductance varies sufficiently to be used as a control signal to maintain the z-position of the tip during the scans, thereby affording constant-distance SECM operations [133,134]. This methodology is fast and apparently less-challenging to implement than shear force SECM, but it requires the fabrication of double-barrel tips in which one channel is left empty and the other is filled with a conventional microdisc. 

Scanning ion-conductance microscopy (SICM) was initially developed to obtain topographical information on delicate and fragile samples, typically biological samples, immersed in liquid solution in a noncontact and noninvasive way [33]. SICM employs a hollow capillary as scanning probe instead of a microelectrode. 

Comstock DJ, Elam JW, Pellin MJ, Hersam MC (2010) Integrated ultramicroelectrode-nanopipet probe for concurrent scanning electrochemical microscopy and scanning ion conductance microscopy. Anal Chem 82(4) 1270-1276... 

SICM Scanning Ion Conductance Microscopy Surface Roughness Measurement... 

Proksch, R., R. Lai, P. K. Hansma, D. Morse, and G. Stucky, Imaging the internal and external pore structure of membranes in fluid Tappingmode scanning ion conductance microscopy, Biophys. J., Vol. 71, 1996 pp. 2155-2157. 

Bdcker, M., S. Muschter, E. K. Schmitt, C. Steinem, and T. E. Schaffer, Imaging and patterning of pore-suspending membranes with scanning ion conductance microscopy, Langmuir, Vol. 25, 2009 pp. 3022-3028. 

Chen, C.-C., M. A. Derylo, and L. A. Baker, Measurement of ion currents through porous membranes with scanning ion conductance microscopy. Anal. Chem., Vol. 81, 2009 pp. 4742-4751. 

Morris, C. A., C.-C. Chen, and L. A. Baker, Transport of redox probes through single pores measured by scanning electrochemical-scanning ion conductance microscopy (SECM-SICM), Awa/ysr, Vol. 2012 pp. 2933-2938. 

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