Scaling law to determine peak forces in tapping-mode AFM experiments on finite elastic soft matter systems

Analytical equations to estimate the peak force will facilitate the interpretation and the planning of amplitude-modulation force microscopy (tapping mode) experiments. A closed-form analytical equation to estimate the tip–sample peak forces while imaging soft materials in liquid environment and within an elastic deformation regime has been deduced. We have combined a multivariate regression method with input from the virial–dissipation equations and Tatara’s bidimensional deformation contact mechanics model. The equation enables to estimate the peak force based on the tapping mode observables, probe characteristics and the material properties of the sample. The accuracy of the equation has been verified by comparing it to numerical simulations for the archetypical operating conditions to image soft matter with high spatial resolution in tapping-mode AFM.

Morphology and Orientation in Thin Film of Polystyrene-b-Polylactide Prepared by Solution-Casting

The development of the morphology in asymmetric Polystyrene-b-Polylactide (PS-b-PLA) thin films was investigated by Tapping-mode AFM. The thin films were prepared by solution casting with different evaporation rates. Films were cast onto hydrophobic Si wafers. When PS-b-PLA was dissolved in chloroform, fast evaporation (~110nL/s) produced hexagonally packed perpendicular PLA cylinders in the PS matrix; intermediate evaporation (~25nL/s) generated mixed microstructures of PLA cylinders of either vertical or parallel to the substrate; slow evaporation (~9nL/s) produced the PLA cylinders that were fully parallel to the substrate. This simple one step route is shown where highly oriented, ordered arrays of cylindrical domains of PS-b-PLA can be produced over large distance.