ABSTRACT
A three-dimensional (3D) piezo scanner is actuated to translate the sample relative to the micropipette tip in the x-, y-, and z-directions. As the micropipette is made to approach the sample, the ow of ions through the opening of the pipette is reduced at small probe-to-sample separations, resulting in a decrease of the ion conductance between an electrode inside the pipette and an electrode in the electrolyte reservoir. The distance-dependence of ion conductance provides the feedback control to perform noncontact surface proling and is thus less likely to damage the sample surface, which is the advantage of the SICM in comparison with
9.1 Background and principle of operation ............................................. 199 9.2 Improvements in scanning ion conductance microscopy .............. 201
9.2.1 Hopping scanning mode ......................................................... 202 9.2.2 The relationship between pipette resistance and scanning... 202 9.2.3 Pressure: The factor affecting the shape of the pipette tip.... 203
9.3 Scanning ion conductance microscopy and “smart” patch-clamp ... 206 9.4 Applications of scanning ion conductance microscopy to
living cells .............................................................................................. 208 9.5 Conclusion ............................................................................................. 209 References ........................................................................................................ 212
Atomic Force Microscopy (AFM) techniques. To put it briey, the decrease in the ion conductance reduces the ion current (Iion), which is monitored by a feedback control unit (CU), and is also used as a feedback input signal (Vp) on the z-direction of the 3D piezo-stage to keep the probe tip and sample separate during the scanning procedure. Sequentially recording the positions of z-direction piezo at every point of a given x-y plane results in a topographical image of the surface. Positioning of the probe is usually achieved by means of piezoelectric elements or step motors.
