Nondestructive thickness measurement of biological layers at the nanoscale by simultaneous topography and capacitance imaging

Nanoscale capacitance images of purple membrane layers are obtained simultaneously to topography in a nondestructive manner by operating alternating current sensing atomic force microscopy in jumping mode. Capacitance images show excellent agreement with theoretical modeling and prove to be a noninvasive method for measuring the thickness of purple membrane layers beyond the single monolayer limit with nanoscale lateral spatial resolution. With the ability of spatially resolving the capacitance while preserving the sample from damaging, this technique can be applied for nanoscale thickness measurement of other biological layers and soft materials in general. © 2007 American Institute of Physics.