Nanoscale electric polarizability of ultrathin biolayers on insulating substrates by electrostatic force microscopy

摘要: We measured and quantified the local electric polarization properties of ultrathin (∼5 nm) biolayers on mm-thick mica substrates. achieved it by scanning a sharp conductive tip (<10 nm radius) an electrostatic force microscope over quantifying sub-picoNewton forces with sharp-tip model implemented using finite-element numerical calculations. obtained relative dielectric constants er = 3.3, 2.4 1.9 for bacteriorhodopsin, dioleoylphosphatidylcholine (DOPC) cholesterol layers, chosen as representative main cell membrane components, error below 10% spatial resolution down to ∼50 nm. The ability insulating substrates common in biophysics research, such or glass, instead metallic substrates, offers both general platform determine wider compatibility other characterization techniques, optical microscopy. This opens up new possibilities biolayer research at nanoscale, including nanoscale label-free composition mapping.