Mar 26, 2007
Scanning nanopipette resolves sample topography and ion conductance simultaneously
During the last couple of decades, scanning probe microscopes sensitive to many different physical quantities on the nanoscale have been developed, but the local measurement of ion conductance has remained a challenge.
A scanning ion-conductance microscope (SICM) records the ionic current through a tapered nanopipette as the nanopipette is scanned over the surface of a sample immersed in electrolyte. Despite the many possible applications of such a microscope, the SICM has been one of the least-developed scanning probe microscopy techniques so far. In a conventional SICM, the measured ion conductance is strongly affected by sample topography. For many applications, however, it is important to measure ion conductance independently of sample topography.
Researchers at the University of Münster, in the BioForce group led by Tilman E Schäffer, recently constructed a SICM with integrated shear-force distance control. They set the nanopipette into transverse vibrations and used mechanical shear forces that arise between nanopipette and sample for topographic feedback. This allowed them to measure the ion conductance independently of and simultaneously with sample topography. Additionally, they developed a new imaging mode that significantly improves image quality. This work will be useful for the investigation of conductive properties of biological samples, such as living cells.
About the author
Tilman E Schäffer and Matthias Böcker are from the Centre for Nanotechnology at the University of Münster, Germany.