Lipid membrane: inelastic deformation of surface structure by an atomic force microscope

The stability of the 1,2-Dioleoyl-an-Glycero-3-(phospho-rac-1-Glycerol-Na) liposome in the liquid crystalline state have been investigated using an atomic force microscope (AFM). We have observed the inelastic deformation of the sample surface. The AFM tip causes persistent deformation of the surface of the lipid membrane, in which some of the lipid molecules are eventually pushed or dragged by the AFM tip. The experiment shows how the surface structure of the lipid membrane can be created by the interaction between the AFM tip and lipid membrane. When the operating force exceeds 10(-8) N, it leads to large deformations of the surface. A square region of about 1 x 1 mum(2) is created by the scanning probe on the surface. When the operating force is between 10(-11) N and 10(-8) N, it can image the topography of the surface of the lipid membrane. The stability of the sample is related to the concentration of the medium in which the sample is prepared.