Nanometer-scale modification of biological membranes by field emission scanning tunneling microscopy

Manipulation and modification at atomic and nanometer scales of some semiconductor and metallic samples has been made possible by scanning tunneling microscopy (STM). This has generated novel approaches for designing new devices at nanometer scale. The poor electronic conductivity of biological molecules has prevented the extension of those methods to them. Here, it is described how a low current STM operated in the field emission regime allows, reproducible imaging and selective modification of biological membranes. A method is presented (i) to visualize at high-resolution hydrated purple membrane sheets, (ii) to produce nanometer-scale marks on them, and (iii) to image the altered membranes.