Capacitance compensation on a double-barrel nanopipette for improving current detection of scanning ion conductance microscopy

We developed a method to improve the current-detection response of scanning ion conduction microscopy (SICM) using a double-barrel nanopipette. By detecting the difference between the two signals from each channel, capacitive currents can be canceled out, resulting in an improved ion current detection response and reduced imaging time in bias-modulated scanning ion conductance microscopy operated with AC bias voltages (BM-SICM). Furthermore, this method can reduce the synchronized capacitive current noise of two adjacent channels of a double-barrel nanopipette by canceling each other via a differential operation. Therefore, an improved detection signal was achieved even in the SICM operated with a DC bias voltage by reducing the noise from the piezoelectric scanner. As demonstrated by the proposed method, chromosomes that were difficult to observe owing to their strong negative charges were clearly imaged in the BM-SICM operated with an AC bias voltage without artifacts caused by surface charging. Additionally, in SICM operating with a DC bias voltage, dynamic interaction among an intracellular short rod, Listeria monocytogenes, and Caco-2 human enterocyte-like cells was successfully observed.