Nano-BLMs (black lipid membranes) suspending the pores of highly ordered porous silicon substrates have been proven useful for functional investigations of ion channel proteins by electrical readouts. With the aim to monitor the resistive behavior of nano-BLMs spatially resolved in a contact-free manner, we report here on the visualization of nano-BLMs by means of scanning ion conductance microscopy (SICM). Silicon surfaces with highly ordered pore arrays were coated with a gold layer and functionalized with octadecanethiol before a droplet of 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) (2% w/v) dissolved in n-decane was applied. The topography of DPhPC membranes suspending the pores was stably imaged for hours without mechanical contact using SICM. This suggests that SICM provides a significant advantage over atomic force microscopy, where mechanical interactions occur that easily damage the suspended membranes. Dynamic processes such as spreading and rupturing of membranes were spatially and temporally resolved. Furthermore, SICM was used to individually manipulate membranes suspending single pores, thereby writing lithographic patterns into the lipid. The process of local membrane manipulation was correlated to a characteristic signature in the simultaneously recorded ion current. The results show that SICM is well-suited both for contact-free imaging of soft suspended membranes and for local membrane manipulation.

A scanning ion conductance microscope (SICM) is based on a tapered nanopipette as a nanoscale conductance probe that is scanned over a sample submerged in an electrolyte solution. In conventional SICM scanning the ion current through the pipette aperture is at the nano- and picoampere level and is influenced by both sample topography and local conductance. Here we present an SICM with integrated shear-force distance control that allows measuring the ion current independently of sample topography. The nanopipette is hereby transversally vibrated and the shear forces that arise are detected optically with the help of two periscopes that are partially submerged in the electrolyte. We also present a new imaging mode designed to facilitate shear-force imaging of soft samples. This mode is based on a periodic modulation of the pipette–sample distance combined with triggered sampling, reducing the probability for sample and pipette damage and increasing the image quality. We apply this imaging mode to polycarbonate membranes and mammalian cells.