Scanning Dielectric Constant Microscopy for imaging single biological cells

A method is developed for obtaining nanoscale dielectric constant maps of any material, using dynamic Electrostatic Force Microscopy (EFM) in conjunction with an analytical model by Hudlet et al for the tip-apex force, modified for dielectric material; and is applied for visualizing dielectric constant variation at sub-cellular level. The method is simple and does not rely on high-end electronics required for sub-attofarad resolution for capacitance measurement or resource intensive computation for specific geometry, but can be applied on available commercial Atomic Force Microscope (AFM). The method is not restricted to obtaining dielectric constant at a single point but it provides the determination of lateral variation in dielectric constant in a sample. The dielectric constant maps obtained using the modified Hudlet tip-apex model are compared with those obtained using the parallel plate and partially-filled parallel plate models. The accuracy of the dielectric constant values depends on the validity of the analytical model used. The dielectric constant values obtained using the modified Hudlet tip-apex model are in agreement with the reported values.